OPERATION GLEN OF CANYON Colorado River DAM Storage Project, Arizona FINAL ENVIRONMENTAL IMPACT STA TEMENT March 1995 Acronyms and Abbreviations AGC Automatic generation control IPP Inland Power Pool AGFD Arizona Game and Fish Department kV Kilovolt kW Kilowatt AMP Adaptive Management Program kWh AMWG Kilowatthour Adaptive Management Work Group LCR Little Colorado River AOP Annual Operating Plan mat Million acre-feet BIA Bureau of Indian Affairs mg/L Milligrams per liter CFR Code of Federal Regulations mm millimeter cfs Cubic feet per second MW u.s. Army Corps of Engineers Megawatt Corps MWh CROD Megawatthour Contract rate of delivery NEPA National Environmental CRSM Colorado River Simulation Model NERC CRSP Colorado River Storage Project North American Electrical Reliability Council CRSS Colorado River Simulation System NHWZ New high water zone DO Dissolved oxygen NOx Nitrogen oxide DOE Department of Energy NPS National Park Service EA Environmental assessment OHWZ Old high water zone EIS Environmental impact statement P.l. Public Law oF Degree Fahrenheit Reclamation Bureau of Reclamation FERC Federal Energy Regulatory Commission AM River mile ROD Record of decision FONSI Finding of no significant impact SLCA/IP FWCA Fish and Wildlife Coordination Act Salt Lake City Area Integrated Projects FWS U.S. Fish and Wildlife Service GCES Glen Canyon Environmental Studies GCPA Grand Canyon Protection Act GLCA Glen Canyon National Recreation Area GRCA Policy Act S02 Sulfur dioxide SAP Salt River Project usc United USGS u.s. Geological Survey WAUC Western Area Upper Colorado Grand Canyon National Park Western Western Area Power Administration GWh Gigawatthour wscc Western Systems Coordinating Council IMPLAN U.S. Forest Service input-output economic model > Greater than Hour < Less than hr States Code As the Nation's principal conservation agency, the Department of the Interior has responsibility for most of our nationally owned public lands and natural resources. This includes fostering sound use of our land and water resources, protecting our fish, wildlife, and biological diversity; preserving the environmental and cultural values of our national parks and historical places; and providing for the enjoyment of life through outdoor recreation. The Department assessesour energy and mineral resourcesand works to ensure that their development is in the best interests of all our people by encouraging stewardship and citizen participation in their care. The Department also has a major responsibility for American Indian reservation communities and for people who live in island territories under U .5. Administration. The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public. Final Environmental Impact Statement Operation 0£ Glen Canyon Dam Colorado River Storage Project Coconino County, Arizona u .S.Department of the rnterior Bureau of Reclamation (lead agency) Bureau of rndian Affairs Fish and Wildlife Service National Park Service U .S.Department of Energy Western Area Power Administration Arizona Game and Fish Department Hopi Tribe Hualapai Tribe Navajo Nation SanJuan Southern Paiute Tribe Southern Paiute Consortium Zuni Pueblo Cooperating Agencies: For Further Information Contact: Mr. Gordon S. Lind Colorado River Studies Office Bureau of Reclamation 125 South State Street, Room 6107 Salt Lake City UT 84138-1102 (801)524-5479 This final environmental impact statement (EIS) analyzes the impacts of operations from 1963to 1990(baselineconditions) and alternative operations of Glen Canyon Dam on downstream environmental and cultural resourcesof Glen and Grand Canyons. Alternative operations evaluated include three that would provide steady flows and six, including no action, that would provide various levels of fluctuating flows. Additional measureshave been combined with the alternative operations, where appropriate, either to mitigate adverse impacts of the alternative or to enhanceresources. The EIS team and the cooperating agenciesattempted to balance benefits to all resourcesin identifying a preferred alternative. As a result of comments on the draft EIS and discussions with the U.S. Fish and Wildlife Service,the preferred alternative described in the draft EIS was modified for the final EIS. The preferred alternative is the Modified Low Fluctuating Flow Alternative. This final EIS was prepared in compliance with the National Environmental Policy Act and Bureau of Reclamation procedures and is intended to serve environmental review and consultation requirements pursuant to Executive Order 11988(Floodplain Management), Executive Order 11990(Wetlands Protection), National Historical Preservation Act (Section 106), Fish and Wildlife Coordination Act, and Endangered SpeciesAct (Section7c). This final EIS will be used by decisionmakers in the Bureau of Reclamation and the Department of the Interior and is provided for public information. A record of decision can be approved 30 days after publication of releaseof the final EIS in the FederalRegister.Any decision regarding the operation of Glen Canyon Dam as well as opportunities for future public involvement will be well publicized. CHAPTERI Purpose of and Need for Action Background Document Organization 2 5 Location and Setting 5 Authorities and Institutional Constraints 8 Glen Canyon Environmental Studies 10 Relationship Between Glen Canyon Dam EIS and Electric Power Marketing EIS Scoping Summary 11 12 CHAPTER I Purpose of and Need for Action The Federal action considered in this environmental impact statement (EIS) is the operation of Glen Canyon Dam, Colorado River StorageProject, Arizona. The Secretaryof the Interior (Secretary)called for a reevaluation of dam operations. The purpose of this reevaluation is to determine specific options that could be implemented to minimize-consistent with law-adverse impacts on the downstream environmental and cultural resourcesand Native American interests in Glen and Grand Canyons. In 1968,Congressenacted the Colorado River Basin Project Act (43 U.S.C. 1501et seq.). This act provided for a program for further comprehensive development of Colorado River Basin water resources. Section 1501(a)states: This program is declared to befor the purposes, among others, of regulating the flow of the Colorado River; controlling flood; improving navigation; providing for the storage and delivery of waters of the Colorado River for reclamation oflands, including The need for this reevaluation stems from impacts to downstream resourcescausedby the operation of Glen Canyon Dam. Such impacts have been identified from scientific studies and have resulted in significant public concern. Analysis of an array of reasonablealternatives is needed to allow the Secretaryto balance and meet statutory responsibilities for protecting downstream resourcesfor future generations and producing hydropower, and to protect affected Native American interests. The underlying project purpose(s) is defined by section 1 of the Colorado River StorageProject Act of 1956(43 United StatesCode (U.S.C.)620), which authorized the Secretaryto "construct, perate, and maintain" Glen Canyon Dam: ...for regulating the flow of the Colorado River , use, making it possible for the States of the Upper Basin to utilize, consistently with the rovisions of the Colorado River Compact, he apportionments made to and among them i the Colorado River Compact and the pper Colorado River Basin Compact, rspectively, providing for the reclamation of rid and semiarid land, for the control of foods, and for the generation ofhydroelectric ower, as an incident of the foregoing municipal, industrial, purposes; improving and other beneficial water quality; providing for basic public outdoor recreation facilities; improving conditions for fish and wildlife, and the generation and sale of electrical power as an incident of the foregoing purposes. In addition, the Criteriafor CoordinatedLongRangeOperationof ColoradoRiver Reservoirs (including Glen Canyon Dam) were mandated by section 1552of the Colorado River Basin Project Act. Article 1.(2) of these criteria requires that the Annual Operating Plan for Colorado River reservoirs: ...shall the purposes, among others, of storing water for beneficial consumptive supplemental water supplies, and for reflect appropriate consideration of the uses of the reservoirs for all purposes, including flood control, river regulation, beneficial consumptive uses, power production, water quality control, recreation, enhancement of fish and wildlife, and other environmental factors. The Colorado River Compact (1922)and the Upper Colorado River Basin Compact (1948)do not affect obligations to Native American intersts. Article VII and Article XD<,part a, 2 Chapter Purpose of and Need for Action respectively ,of the 1922 and 1948 compacts provide that: Nothing in this compact shall be construed as affecting the obligations of the United States of America to Indian Tribes. The Colorado River StorageProject Act of 1956, the Colorado River Basin Project Act of 1968,and the associatedCriteriafor CoordinatedLong-Range Operationof ColoradoRiver Reservoirs(Long-Range Operating Criteria) did not alter these compact GJenCanyon Dam was completed by the Bureau of Reclamation (Reclamation) in 1963,prior to enactment of the National Environmental Policy Act of 1969(NEPA). Consequently, no EIS was filed regarding the construction or operation of Glen Canyon Dam. Since the dam has long been completed, alternatives to the dam itself have been excluded from the scope of the analysis. This EIS is intended to meet the disclosure requirements of the National Environmental Policy Act. provisions. In addition to the Secretary'sdecision calling for a reevaluation, Congress subsequently enacted the Grand Canyon Protection Act of 1992. Section 1802(a) of the act requires the Secretaryto operate Glen Canyon Dam: ...in accordance with the additional criteria and operating plans specified in section 1804 and exercise other authorities under existing law in such a manner as to protect, mitigate adverse impacts to, and improve the values for which Grand Canyon National Park and Glen Canyon National Recreational Area were established, including, but not limited to natural and cultural resources and visitor s. Section 1802(b) of the act further requires that the above mandate be implemented in a manner fully consistent with existing law. Section 1802(c)states that the purposes for which Grand Canyon National Park and Glen Canyon National Recreation Area were established are unchanged by the act. Section 1804(a) of the act requires the Secretaryto complete an EIS no later than October 30, 1994,following which, under section 1804(c), the Secretaryis to "exercise other authorities under existing law, so as to ensure that Glen Canyon Dam is operated in a manner consistent with section 1802." Section 1804(c) also requires that the criteria and operating plans are to be "separate from and in addition to those specified in section 602 (b) of the Colorado River Basin Project Act of 1968." Environmental impacts of the alternatives will be considered, along with other factors, in a separate record of decision (ROD) that will be prepared after filing the final EIS. The ROD will include the type or nature of the decision to be made, the forcing event, background information significant to an understanding of the situation, issues and decision factors, unresolved issues,and a clear description of options. It also will address comments received by Reclamation after filing the final EIS. The Secretaryof the Interior is the responsible decisionmaker. BACKGROUND Sicethe darn was completed, increasing concern hasbeen expressedby the public and Federal and State agenciesabout how Glen Canyon Darn operations may be adversely affecting downstream resources. In responseto these concerns,the Secretarydirected Reclamation to prepare an EIS on Glen Canyon Dam operations. In his July 1989news releaseannouncing the EIS, the Secretarystated: "It is time to gather the facts about this issue, to give all interested parties a hanceto explain their positions, and to do so in ull view of the American people." The Secretary oted that this issue is "an opportunity to balance and environment needs." Gle Canyon Dam-the key feature of the Colorado River StorageProject-is a multipurpose BACKGROUND facility. The Colorado River StorageProject Act directs the Secretaryto operate project powerplants 11...so as to produce the greatest practicable amount of power and energy that can be sold at firm power and energy rates. ..." To this end, the powerplant at Glen Canyon Dam historically has been used primarily for peaking power generation. Fluctuating releasesassociated with peaking power operations have caused concern among State,Federal, and Tribal resource management agencies;river users who fish in Glen Canyon and take white-water raft trips in Grand Canyon; and Native American and environmental groups concerned about detrimental effects on cultural resourcesand downstream plants, animals, and their habitats. Theseconcernswere expressedmost forcefully by the public during two Reclamation studies on possible increasesin peaking power generation at Glen Canyon Dam. The studies were made to dtermine benefits and costs of: 1. Adding one or more generators at the dam (Peaking Power Study) reasing the capacity of the existing generaors (Uprate and Rewind Program) Adverse public reaction to the Peaking Power Study led to its tennination in 1980. Reclamation published an environmental assessment(EA) and a finding of no significant impact (FONSI) on the Oprate and Rewind Program in December 1982. Subsequently,the uprate and rewinduprate and rewind of the generators was completed, but Reclamation agreed not to use the increased powerplant capacity (aspart of the EA and FONSI) until completion of a more comprehensive study on the impacts of historic and current dam operations on environmental resources throughout Glen and Grand Canyons. Therefore, maximum releaseshave been limited to 31;500cubic feet per second (cis) instead of the potential 33,200cfs that resulted from the uprate and rewinduprate and rewind. 3 In December 1982,Reclamation initiated PhaseIof the multiagency Glen Canyon Environmental Studies (GCES)to respond to the concerns of the public and other Federal and State agencies. GCESPhaseI was completed in 1988. Phasen is further defining impacts to the natural environment, associatedpublic uses,cultural resources, non-use value, and power economics. Additional information on the GCESis found later in this chapter. The environmental studies included special researchflows that were conducted from June 1990to July 1991to evaluate resource responsesto a variety of discharge parameters and to provide data for this EIS. To protect downstream resourcesuntil completion of this EIS and the ROD, Reclamation began testing proposed interim flows on August 1, 1991. An EA and a FONSI (Bureau of Reclamation, were completed, and the interim operating ria were implemented on November 1, 1991. ugh the criteria may be modified based on will remain in effect until he EIS and ROD are completed. Theseinterim criteria are essentially the same as those detailed under the Interim Low Fluctuating Flow Alternative in chapter II. Cooperating Agencies The Secretarydesignated Reclamation as lead agency in preparing this EIS. Cooperating agenciesare: Bureau of Indian Affairs (BIA), National Park Service (NPS),U.S. Fish and Wildlife Service (FWS),Department of Energy's Western Area Power Administration {Western), Arizona Game and Fish Department (AGFD), Hopi Tribe, Hualapai Tribe, Navajo Nation, Pueblo of Zuni, SanJuan Southern Paiute Tribe, and Southern Paiute Consortium. Representativesfrom Reclamation, NPS, FWS, Western, AGFD, U.S. Geological Survey (USGS), Hopi and Hualapai Tribes, the Navajo Nation, and a private consulting firm served on the EIS team. The preparation of this EIS required 4 Chapter Purpose of and Need for Action close cooperation among the cooperating agencies,the interagency EIS team, and GCES(see figure 1-1). Figure I-l.-Ongoing interactive communication was essential to the Glen Canyon Dam EIS process. Management Responsibilities Federal agencies,the AGFD, the Hualapai Tribe, and the Navajo Nation have management responsibilities associatedwith Glen and Grand Canyons. Theseagencieshave developed resourcemanagement objectives that describe the desired condition of specific resourcesand outline goals for future management. Federal agencieswith management objectives include Reclamation, NP5, FW5, Western, and BIA the Colorado River Management Plan and other general management plans. Theseplans are prepared with public involvement and in consultation with Indian Tribes and other agencieswith jurisdiction by law. .FWS provides Federal leadership to conserve, protect, and enhancefish and wildlife and their habitats for the continuing benefit of the public. In Glen and Grand Canyons, the fish and wildlife resourceconcerns of FWS include threatened and endangered species,migratory birds, and native and sport fish. Objectives for fish and wildlife resourcesin the Grand Canyon ecosystemare addressedin the Fish and Wildlife Coordination Act Report (see FWS recommendations in attachment 4). Objectives for threatened and endangered speciesare specified in recovery plans, which are required by the Endangered SpeciesAct. .Western's management objectives are based on statutory responsibilities pursuant to the Departmen of Energy Organization Act; section 5 of the Flood Control Act; section 9 of the Reclamation Project Act; and, in the caseof Glen Canyon Dam, the Colorado River Storage Project Act, as well as business,environmental, and other public concerns. .Although BIA has no management role in the proposed action, it has management goals that include fostering the self-determination of Indian Tribes. Its role is to assurethat Indian Tribe interests are coordinated with other Federal agenciesand to provide advice and assistanceto tribes when requested to do so. Reclamation is responsible for operating the Colorado River StorageProject. Water management objectives are based on statutes specific to water storage and delivery (see"Law of the River}. Annual and long-term operating plans are prepared in consultation with the Basin Statesand the public, as well as agencies with jurisdiction by law. AGFD management objectives for the Colorado River fishery are specified in its Arizona Cold Water Sportfishes Strategic Plan, 1991-1995,and on-Game and Endangered Wildlife Program gic Plan,1991-1995. Thesemanagement bjectives are in concert with NPS objectives for te river corridor. NPS managesGrand Canyon National Park and Glen Canyon and Lake Mead National RecreationAreas. NPS management objectives, which are based on the National Park Service Organic Act and the various statutes reserving these lands for park purposes, are described in Th Hualapai Tribe and Navajo Nation manage all ntural and cultural resourceswithin their reervation boundaries, which includes some land along the river corridor downstream of Glen Canyon Dm. fu addition, many sites located on Federal lands hae cultural, ancestral, and LOCATION AND SETTING spiritual significance to Native Americansincluding Havasupai, Hopi, Hualapai, Navajo, Paiute, and Zuni-and these ties must be considered in Federal decisionmaking. .The Hualapai Tribe cooperateswith Federal, State,and local agenciesin managing its resources. Management goals of the tribe are long-term sustainable and balanced multiple use of its resources. The Hualapai Tribe's responsibility in relation to the Colorado River and Grand Canyon is one of stewardship of a sacred trust. The basis for its objectives comes from its Conservation Ordinance 24-70, 1990Revision. The Navajo Nation cooperateswith Federal, State,and local agenciesin managing its resources. The management objectives of the Navajo Nation are expressedin the Tribal regulations and internal policy statementsand position papers. .Management objectives of other Indian Tribes with interest in Glen and Grand Canyons, but whose lands do not border the Colorado River mainstem (Havasupai, Hopi, Paiute, and Zuni), are the preservation of the canyon's natural and cultural resourcesto maintain their values to the tribes. Resourcemanagement objectives and an assessment of how well the various alternatives would sented in chapter II under "Summary Comparison of Alternatives." DOCUMENT ORGANIZATION This EIS document consists of five chapters: Chapter I: describesthe purpose of and need for the proposed Federal action, location and setting, authorities and institutional constraints, Glen Canyon Environmental Studies, the relationship between this EIS and Western's Electric Power Marketing EIS, and a scoping summary. Chapter II: describes the process used to formulate alternatives, the alternatives considered in 5 detail, the alternatives considered but eliminated from detailed study, and a summary comparison of alternatives and impacts. Chapter III: describes the environmental and other resources of the area that would be affected by the alternatives if they were implemented. Chapter IV: describes and analyzes the environmental impacts of each alternative considered in detail. Chapter v: describesthe scoping processand coordination with the public, Federal agencies, Tribal Governments, and private organizations that occurred during preparation of this EIS; and the distribution list. A list of preparers, glossary, conversion tables, and bibliography also are included as part of the document. The attachments in this volume include the environmental commitments, Grand Canyon Protection Act, Long-Range Operating Criteria, fish and wildlife consultation, programmatic agreement on cultural resources,and supporting data on the alternatives. Two separatevolumes accompany this volume. A volume entitled "Summary" contains a brief but complete overview of the contents of the final EIS. The "Comments and Responses"volume summarizes the more than 33,000public comments that were received on the draft EIS, along with the EIS team's responses. n appendix volume was distributed with the ft £15 and contains sections on long-term onitoring and research,hydrology , water uality, sediment, and hydropower. LOCATION AND SETTING The EIS focuseson the Colorado River corridor from Lake Powell, formed by Glen Canyon Dam in northwestern Arizona, southward through Glen and Marble Canyons and westward through Grand Canyon to Lake Mead (seefrontispiece 6 Chapter Purpose of and Need for Action map ). However, this document will disclose all significant impacts of the alternatives wherever they may occur. The uppennost 15 miles of the river are in Glen Canyon, which is part of the Glen Canyon National RecreationArea; the remaining 278 miles of the river flow through Grand Canyon National Park. The Navajo Indian Reservation is immediately east of both park units and comprises the easternpart of Glen and Marble Canyons. The Hopi Indian Reservation is on the plateau farther east of Marble Canyon. The Havasupai Indian Reservation surrounds upper Havasu Creek, immediately south of Grand Canyon National Park. The Hualapai Indian Reservation comprises the southern portion of western Grand Canyon, adjacent to Grand Canyon National Park. Someregional impacts occur outside of the immediate geographic area and are also evaluated. For example, power generated at Glen Canyon Dam is marketed in Wyoming, Utah, Colorado, Arizona, Nevada, and New Mexico. Grand Canyon National Park Grand Canyon National Park, located downstream from Glen Canyon Dam, was first set aside for park purposes as a national monument on January 11,1908, and was expanded and made a national park on February 16, 1919. Additions and boundary changeswere made in 1927and at various other times. The purposes for which these lands were reserved are stated in the various proclamations and acts creating the park. They identify these lands as "an object of unusual scientific interest, being the greatest eroded canyon within the United States" and warned unauthorized persons "not to appropriate, injure or destroy any feature" of the monument. In 1919, Congressdedicated these lands as "a public park for the benefit and enjoyment of the people" (Act f February 16,1919,40 Stat. 1175). In 1975, ongress declared that the entire Grand Canyon is a natural feature of national and international ignificance" (16 U.S.C. 228a). Grand Canyon National Park was dedicated as a World Heritage Site on October 26,1979,joining "a selectlist of protected areasaround the world whose outstanding natural and cultural resources form the common inheritance of all mankind." Historical Perspective Predam Flows The predam period was characterized by large, year-to-year, seasonal,and sometimes daily variability in flow and sediment loads and large seasonalvariation in water temperature. Melting of the Rocky Mountain snowpack typically produced high runoff of long duration during the late spring and early summer. Annual maximum daily flows greater than 80,000cfs were common; in some years they exceeded100,000cfs. fu contrast, flows less than 3,000cfs were typical throughout late summer, fall, and winter. Flows did not fluctuate daily as they do with dam operations, but neither were they steady. During spring snowmelt periods and flash floods from tributaries or side canyons, short duration-but occasionally very high magnitude-changes in flow occurred at intervals of a few days or less. Sediment load increased during the spring runoff and again in late summer from tributary floods. Water temperatures ranged from near freezing in winter to more than 80 degreesFahrenheit (OF)in late summer. Postdam Flows (Historic Operations) Glen Canyon Dam replaced seasonalflow variations with daily fluctuations, greatly reduced sediment load (supplied only by downstream tributaries), and resulted in nearly constant water releasetemperatures year-round-averaging a coo146of. The variability in average daily flows also has been reduced during the postdam period. Mean daily flows have exceeded30,000cfs (approximate powerplant capacity) only about 3 percent of the ime (18 percent, predam) and have been less han 5,000cis only about 10 percent of the time 16 percent, predam). Fluctuations within the day, owever, have increased for power generation urposes. Median (equaled or exceeded50 perent of the time) daily fluctuations (difference LOCATION AND SETTING between minimum and maximum daily release) have ranged from about 12,000cfs in October to about 16,000cfs in January and August. Glen Canyon Dam Operations Glen Canyon Dam operations are affected by physical factors-including reservoir capacity, annual runoff, and discharge capacity-as well as by legal and institutional factors specified in various Federal laws, interstate compacts, international treaties, and Supreme Court decisions. The Criteriafor CoordinatedLong-RangeOperationof ColoradoRiver Reservoirscontains the principal guidelines for annual and monthly operations resulting from the physical, legal, and institutional factors. Thesecriteria are determined by the Secretarywith participation by the Statesand are subject to a formal review at least every 5 years. (Seeattachment 3.) A detailed description of Glen Canyon Dam operations can be found in chapter II under the No Action Alternative. Physical Constraints. Glen Canyon Dam stores and releaseswater from Lake Powell, which has an active capacity of about 24.3 million acre-feet (ma~. Water can be released from Glen Canyon Dam in the following three ways (seefigure 1-2). 1. Powerplant releases. Glen Canyon has eight generators with a maximum Figure 1-2.-Photograph f len Canyon Dam and Powerplant showing water releasecapacities of the powerplant, outlet works, and spillways. Powerplant combined 7 8 Chapter I Purpose of and Need for Action capacity of 1,356,000kilowatts. The maximum combined discharge capacity of the eight turbines is approximately 33,200cfs when Lake Powell is full; however, releasesduring fluctuations are limited to 31,500cfs. When the reservoir is less than full, maximum possible discharge is reduced. Discharge through the turbines is the preferred method of releasebecauseelectricity and its associatedrevenue are produced. 2. River outlet worksreleases.The capacity of the river outlet works is 15,000cfs. The river outlet works are used when there is a need to release more water than can be passed through the powerplant. The outlet works are almost always used in conjunction with powerplant releases, producing combined releasesup to 48,200cis. 3. Spillway releases.Releasesthrough the spillways bypass both the powerplant and the river outlet works. The combined capacity of the right and left spillways is approximately 208,000cis. Spillway releasesare made only when necessary to avoid overtopping the dam or to lower the level of Lake Powell. Spillway releasesare avoided whenever possible, not only to prevent powerplant bypasses,but also becausethe service life of the spillways is shorter than that of the other releasestructures. Although the combined releasecapacity of these facilities is 256,000cis, the maximum combined releasefrom Glen Canyon Dam is expected never to exceed180,000cfs. Grand Canyon Protection Act of 1992 (Public Law 102-575) This act addressesprotection of Grand Canyon National Park, Glen Canyon National Recreation Area, interim operating criteria, long-term monitoring and research,and replacement power, as well as other administrative provisions related to preserving Grand Canyon (seeattachment 2). Law of the River The "Law of the River," as applied to the Colorado River, is a collection of Federal and State statutes, interstate compacts,court decisions and decrees,an international treaty with Mexico, and criteria and regulations determined by the Secretary.Included are (in chronological order): Colorado River Compact of 1922(Wilbur and Ely, 1948) Boulder Canyon Project Act of 1928 (43 U.S.C. 617-617t) California Limitation Act of 1929 (Chapter 16, 48th Session;Statutes and Amendments to the Codes, 1929,pp. 38-39) California Seven-PartyAgreement of 1931 (Nathanson, 1978) Boulder Canyon Project Adjustment Act of 1940 (43 U.S.C. 618-6180) Mexican Water Treaty of 1944,Treaty Series994 (59 Statute (Stat.) 1219) Upper Colorado River Basin Compact of 1948 (Nathanson, 1978) UTHORITIES AND INSTITUTIONAL Colorado River StorageProject Act of 1956 (43 U.S.C. 617) F- General Principles to Govern, and Operating Criteria for, Glen Canyon Reservoir (Lake Powell) and Lake Mead during the Lake Powell Filling Period (FederalRegister, 27 F.R. 6851,July 12,1962) any responsibilities are specifically mandated, whilediscretionary authority is given for dealing with others. Addition Regulation No.1 (FederalRegister, 27 F.R. 6850,July 12, 1962) Arizona v. California et al., 373 U.S. 546 (1963) AUTHORITIES AND Arizona v. California et al., (decree)376 U.S. 340 (1964);(supplemental decree)439 U.S. 419 (1979);(secondsupplemental decree)466 U.S. 144 (1984) Colorado River Basin Project Act of 1968 (43 U.S.C. 1501et seq.) Criteriafor CoordinatedLong-RangeOperation of ColoradoRiver Reservoirs(FederalRegister, 35 F.R. 8951-52,June 10,1970) INSTITUTIONAL CONSTRAINTS 9 Environmental Severallaws and executive orders were designed to restore and protect the natural environment of the United States-air, water, land, and fish and wildlife. Rivers and Harbors Act of 1899(33 U.S.C.401 et seq.) Fish and Wildlife Coordination Act of 1958 (16 U .S.C.661 et seq.) Colorado River Basin Salinity Control Act of 1974 (43 U.S.C. 620d, 1571-1578,1591-1599) Wilderness Act of 1964(16 U.S.C. 1131et seq.) Hoover Dam Flood Control Regulations of 1981 (33 Code of Federal Regulations (CFR) 208.11) Wild and ScenicRivers Act of 1968(16 U.S.C. 1271 et seq.) National Parks National Environmental Policy Act of 1969 (42 U.S.C. 4321et seq.) Severallaws established or added lands to national parks along the river corridor. These park units were established to provide for public outdoor recreation use and enjoyment and to preserve the scenic,scientific, and historic features of the area. Antiquities Act of 1906(16 U.S.C.431 et seq.) National Park ServiceOrganic Act (16 U.S.C.1-4, 22, 43) National Park ServiceGeneral Authorities Act of 1970(16 U.S.C.1a-1) Grand Canyon National Park Establishment Act (16 U.S.C.221,221a,221b) Grand Canyon National Park Enlargement Act (16 U .S.C.227,228a-228j) Lake Mead National Recreation Area Establishment Act (16 U.S.C.46On,46On-1-9) Glen Canyon National Recreation Area Establishment Act (16 U.S.C. 460dd-1-9) Redwood National Park Act of 1978(Public Law (P..L.) 95-250,92-Stat.163as amended) Energy Policy Act of 1992(P.L. 102-486,Sec.2402) Clean Air Act (42 U.S.C. 7401et seq.) Clean Water Act of 1972(33 U.S.C. 1251et seq.) Endangered SpeciesAct of 1973(16 U.S.C. 1532 et seq.) Executive Order 11991,Protection and Enhancement of Environmental Quality, 1977 Executive Order 11988,Floodplain Management, 1977 Executive Order 11990,Protection of Wetlands, 1977 Cultural Preservation Severallaws and executive orders were designed to protect and preserve historic and cultural resourcesunder Federal control in consultation with Indian Tribes. Historic Sites,Buildings, and Antiquities Act (16 U.S.C.461 et seq.) National Historic Preservation Act (16 U.S.C. 470 et seq.) Archaeological ResourcesProtection Act of 1979 .) Chapter 10 Purpose of and Need for Action Native American Severallaws and treaties established reservations and protect the rights of Native Americans to express,believe, and exercisetraditional religious practices. Federal agenciesare responsible for consulting with Indian Tribal Governments and traditional religious leaders to determine appropriate actions necessaryfor protecting and preserving Native American religious cultural rights and practices. American Indian Religious Freedom Act of 1978 (42 U.S.C. 1996) Native American Graves Protection and Repatriation Act of 1990(25 U.S.C.3001et seq.) Religious Freedom Restoration Act of 1993 (P.L.13-141) Laws or treaties establishing Indian Reservations within or adjacent to the study area: Havasupai Indian Reservation: establishedby Executive Orders of November 23, 1880;March 31 1882. Hualapai Indian Reservation: established by Executive Orders of January 4, 1883;June 2, 1911; and May 29,1912. Navajo Indian Reservation: established by treaty of June 1, 1868,15 Stat. 667. Other parcels were set apart as additions to the reservation or for Indian purposes by Executive Orders of October 29, 1878; January 6,1880; May 17,1884; and January 8,1900. Congressadded land to the Western Navajo Indian Reservation and created the Canyon de Chelly National Monument by Act of May 23, 1930,46Stat. 378,Act of February 14, 1931, 46 Stat. 1161(codified at 16 U.S.C.section 445 to 445b);Act of June 14,1934,48 Stat. 960 described the exterior boundaries of the reservation. GLEN CANYON STUDIES ENVIRONMENTAL The Glen Canyon Environmental Studies are an interagency effort to examine short- and long-term effects of historic, current, and alternative dam operations on sediment, vegetation, fish, wildlife, recreation, cultural resources,power economics, and non-use values. Agencies cooperating in the studies are Reclamation, NPS, Western, USGS, FWS, Hopi Tribe, Hualapai Tribe, Navajo Nation, Pueblo of Zuni, SanJuan Southern Paiute Tribe, and the Southern Paiute Consortium with contributions from AGFD, private consultants, universities, and river guides. Funding for these studies has been provided mainly from the sale of hydropower. GCES technical studies are reviewed by the responsible agency , the GCES senior scientist, and the National Research Council. These studies fonn the basis of the effects analysis presented in "Chapter IV , Environmental Consequences." Review of the GCESby a National Research Council committee began in 1986. This Committee to Review Glen Canyon Environmental Studies has provided review and comment on the scientific and technical researchstudies associated with the GCESprogram and advice on alternative operation schemesfor Glen Canyon Dam. In 1987,the committee completed its first report, River and Dam Management:A Reviewof theBureau of Reclamation'sGlen CanyonEnvironmentalStudies (National ResearchCouncil, 1987). When preparation of this EIS was announced, the committee was requested to review the EIS as it developed. In May 1990,the committee conducted a symposium on the application of GCESresults to the management of Glen Canyon Dam. A proceedings of the symposium was published entitled ColoradoRiver Ecologyand Dam Management(National ResearchCouncil, 1991). Phase I (1982-88) The GCES began as an interagency effort to study conditions downstream from the dam related to two major questions: 1. Are current operations of the dam, through control of the flows in the Colorado River, adversely affecting the existing river-related environmental and recreational resourcesof Glen and Grand Canyons? 2. Are there ways to operate the dam, consistent with Colorado River StorageProject water RELATIONSHIP BETWEEN GLEN CANYON DAM EIS AD ELECTRIC POWER MARKETING EIS 11 delivery requirements, that would protect or enhancethe environmental and recreational resources? timetable and researchapproach were adjusted after the Secretaryannounced on July 27, 1989, that an EIS would be prepared. To accomplish the study goals, more than 30 technical studies in the fields of biology , recreation, sedimentation, and hydrology were conducted. A final report integrating the results of all studies (U .5. Department of the Interior, 1988)as well as executive summaries of these reports (U.S. Department of the Interior et al., 1988)were published. Thesestudies were conducted during the wettest 3 years on record (1983-85).While the studies provided considerable information on the effects of floods, they provided only limited information on the effects of powerplant operations. The researchschedule was acceleratedby using special "research flows" to provide more timely data for the EIS. Theseresearchflows were a seriesof carefully designed discharges and data collection programs conducted from June 1990 through July 1991. Each researchflow lasted 14 days arid included 3 days of steady S,O00-cfs flow and 11 days of either steady or fluctuating flow. The researchflows provided a means to evaluate short-term responsesof certain resources to a variety of discharge parameters, including minimum and maximum flows, rate of change in flow, and range of daily fluctuations. Results of Phase I studies indicated the following PhaseII researchis based on an ecological system approach structured around specific hypotheses and researchflows (Bureau of Reclamation, 1990c). Included are 10 primary study components and 2 monitoring components. Certain GCESstudies will extend beyond the EIS schedule; however, sufficient information was available to prepare this EIS. relationships: Glen Canyon Dam and its operation have had an impact on the downstream environment. Changeshave occurred and continue to occur to many ecosystemresources. Somechanges are considered positive and some negative. Operations and management can be modified to minimize lossesof some resourcesand to protect and enhance others. The ecosystemof Glen and Grand Canyons is dynamic and, with careful management, more harmonious environmental relationships may . At the conclusion of these studies (now referred to as GCESPhaseI), Reclamation determined that additional researchwas needed to more fully respond to the initial questions and to provide needed information; therefore, a second group of studies was initiated. II (1988-present) In Jne 1988,the Department of the Interior that the GCESbe continued to gather additional data on specific operational elements. This phase of studies initially was to take place over 4 to 5 years; however, the RELATIONSHIP BETWEEN GLEN CANYON DAM EIS AND ELECTRIC POWER MARKETING EIS Western Area Power Administration is preparing an EIS on its Salt Lake City Area Integrated Projects (SLCA/IP) Electric Power Marketing and Allocation Criteria. The criteria establish the terms used to allocate capacity and energy generated by the dams of the Colorado River Storage,Collbran, and Rio Grande Projects (collectively called the SLCA/IP ). Powerplants in the SLCA/IP operated by Reclamation are Glen Canyon, Flaming Gorge, Blue Mesa, Morrow Point, Crystal, Upper Molina, Lower Molina, Fontenelle, and Elephant Butte. Glen Canyon Dam is the largest power producer within this group. 12 Chapter I Purpose of and Need for Action Although all of thesehydroelectric powerplants are interconnected, Glen Canyon operations by Reclamation and power marketing by Western are appropriately addressed as two separate(but related) matters. The primary focus of the Glen Canyon Dam EIS is the physical environment of the Colorado River downstream from the dam. The primary focus of the Western EIS is systemwide power marketing and allocation. The power marketing EIS looks at possible environmental or operational effects causedby changesin power marketing programs, while the Glen Canyon Dam EIS evaluates the effects of differing modes of dam operations on the humanenvironment. Ultimately, the Glen Canyon Dam EIS identifies a level of power resource available for use by Western to meet its marketing commitments. Western can evaluate different ways of marketing power before knowing the specific operational changesthat may be adopted for Glen Canyon Dam. Similarly I a Department of the Interior decision to change how water is releasedfrom the dam can be made before the Department of Energy decides how to market power. SCOPING SUMMARY The Glen Canyon Dam EIS scoping processwas initiated in early 1990to receive public input on the appropriate scope of the EIS, consistent with NEPA requirements and implementing regulations. Thorough effort was made to notify all potentially interested parties about the Glen Canyon Dam EIS scoping processand opportunities to provide comment. Reclamation increased opportunities for public participation through public meetings, news releases,mailings, legal notices, and contacts with media, organizations, and individuals. egisternotice of environmental Public meetings were held in Salt Lake City , Denver, Phoenix, Flagstaff, Los Angeles, San Francisco,and Washington, DC. More than 17,000comments were received during the scoping period, reflecting national attention and the intense interest of people in the Western States. Public Reclamation contracted with Bear West Consulting Team, a private business,to prepare a detailed content analysis of the oral and written scoping comments. Their methods and analysis were approved by the cooperating agencies. As a result of the analysis, the following were determined to be resourcesor issuesof public concern: beaches,endangered species,ecosystem, fish, power costs,power production, sediment, water conservation, rafting/boating, air quality , the Grand Canyon wilderness, and a category designated as "other" for remaining concerns. Comments regarding interests and values were categorized as: expressionsabout the Grand Canyon, economics,nonquantifiable values, nature versus human use, and the complexity of Glen Canyon Dam issues(Bureau of Reclamation, 1990b). Following the formal public scoping period and review of the comments, representatives from the cooperating agenciesand public interest groups met in July 1990to determine criteria for developing reasonablealternatives for the EIS. Thesecriteria directed that the alternatives: .Be consistent with the scope of the EIS .Be economically and technically feasible .Reflect Have legal considerations general institutional acceptability .Be timely to implement .Be able to be monitored and adjusted Meet .Be Te scoping comment period initially established or March 12 through Apri116, 1990,was extended o May 4,1990, in responseto public comment. Issues and Concerns various agency mandates supported by data .Be multipurpose (integrated) and include all major resources Include mitigation SCOPING SUMMARY A more detailed discussion of scoping can be found in "Chapter V , Consultation and Coordination." Significant Issues Identified Detailed Analysis Tribal Governments, identifying the resourcesand their significant issuesto be analyzed in detail. The following presentation summarizes the issues and the resource indicators that are used to measure impacts of the alternatives. for The EIS team consolidated and refined the issues of concern to the public and Federal, State,and Issue: How do dam operations affect the amount and quality of WA TER available from Lake Powell at specific times? Indicators: Acre-feet of streamflows Frequency and volume of floodflow and other spills Acre-feet reservoir storage in Lakes Powell and Mead Acre-feet of annual water allocation deliveries Acre-feet of Upper Basin yield determination Chemical, physical, and biological characteristics of water quality Issue: How do dam operations affect SEDIMENT resources throughout the study area? Indicators: Probability of net gain in riverbed sancf Active width and height of sandbars Erosion of high terraces Constriction of debris fans and rapids Elevation of deltas Issue: How do dam operations affect FISH-their Indicators: Abundance of Cladophora and associated diatoms for aquatic food base Reproduction, recruitment, and growth of native fish Reproduction, recruitment, and growth of non-native warm water and coo/water fish Level of interactions between native and non-native fish Reproduction, recruitment, and growth of trout Issue: How do dam operations affect VEGETA TION in the river corridor? Indicators: Area of woody plants and species composition Area of emergent marsh plants Issue: How do dam operations affect area "'ILDLIFE AND their HABIT A T? Indicators: Area of woody and emergent marsh plants for wildlife habitat Abundance of aquatic food base for wintering waterfowl Issue: How do dam SPECIAL Indicators: operations STATUS affect the populations SPECIES throughout Reproduction, recruitment, and growth and flannelmouth suckers Trout and aquatic Aquatic Area of woody Maximum food base for bald food base for belted plants life cycles, habitat, and ability to spawn? of ENDANGERED Glen of humpback and ambersnail eagle willow Grand chub kingfisher for southwestern flow for Kanab 13 flycatcher and AND Canyons? razorback OTHER SPECIAL 14 Chapter I Purpose of and Need for Action Issue: How do dam operations affect the continued existence of CUL TURAL RESOURCES in the studyarea? Indicators: Number of archeological sites directly, indirectly, or potentially affected Number of Native American traditional cultural properties and resources directly, indirectly, or potentially affected Issue: How do dam operations affect other electrical production in the area, including those methods that have impacts on AIR QUALITY? Indicators: Sulfates in Grand Canyon air Tons of sulfur dioxide and nitrogen oxides in regional air Issue: How do dam operations Indicators: Fishing trip attributes and angler safety Day rafting trip attributes and access White-water boating trip attributes, camping beaches, safety, and wilderness values Lake activities and facilities Net economic benefits of recreation Issue: How do dam operations affect the ability of Glen Canyon Powerplant to supply HYDROPOWER at the lowest possible cost? Indicators: Power operations flexibility Power marketing resources, costs, and rates Issue: How do changes in Glen Canyon Dam operations affect NON-USE VALUE? Indicators: on-use economic value in dollars Public Review affect RECREA TION in the study area ? of Draft EIS On January 4, 1994,the draft EIS was ffied with the Environmental Protection Agency .The official public comment period began with a January 7 FederalRegisternotice and concluded on April11, 1994. he full three-volume draft EIS was distributed to those listed on the distribution list in chapter V soliciting public comment. In addition, over 17,000interested parties on the newsletter mailing list received the summary volume by itself. Reclamation received over 1,000additional requestsfor either the full draft EIS or summary volume after the initial distribution. To provide the public an opportunity to learn more about the draft EIS, members of the EIS team conducted information sessionsin Salt Lake City , Phoenix, and Flagstaff in March 1994. These sessionswere informational only; public comments were not taken. In addition, two briefings were conducted in Washington, DC. Public hearings were held in the same seven cities as the scoping meetings to receive oral comments on the draft EIS. Over 33,000written comments were received. More than 2,300separateissues and concerns were extracted from the analysis of oral and written comments (Bureau of Reclamation, 1994b) A summary of the comments and responsesis presented in a separatevolume of this document, "Comments and Responses." As a result of comments on the draft EIS and discussions with FWS, the preferred alternative described in the draft EIS was modified for the final EIS. The cooperating agenciesbroadly supported this modification. A more detailed description of the public review of the draft EIS an be found in "Chapter V, Consultation and Cordination." CHAPTER II Description of Alternatives Process Usecj to Formulate Alternatives 15 Altern(]tives Considered in Detail 16 Alternatives Considered and Eliminated From Detailed Study 44 Summary Comparison of Alternatives and Impacts 54 CHAPTER II Description of Alternatives This chapter presents the processused to fonnulate alternatives, the alternatives considered in detail, the alternatives eliminated from detailed study, and a summary comparison of the alternatives and their impacts. PROCESS USED TO FORMULATE ALTERNATIVES Alternatives for the draft Glen Canyon Dam Environmental Impact Statement (EIS)were formulated through a systematic processusing public input, technical information, interdisciplinary discussions,and professional judgment. The processbegan with consideration of Glen Canyon Environmental Studies (GCES)PhaseI recommendations and comments from the 1990public scoping activities. In July 1990, representatives from cooperating agencies and various interest groups participated in a "brainstorming" workshop to fully consider all concepts and suggestions in formulating alternatives (Bureau of Reclamation, 1990a). The interdisciplinary , interagency EIS team then fonnulated 10 preliminary alternatives divided into 3 descriptive categories: fluctuating flows, steady flows, and flows mimicking predam conditions. Some of thesepreliminary alternatives included various structural elements that would provide warmer releasetemperatures in the summer, bypass sediment around the dam, or reregulate releasesto provide steady flows downstream. The team presented these alternatives to the cooperating agenciesand, following their approval, presented them to the public in a newsletter (Bureau of Reclamation, 1991a)and three public meetings held in Salt Lake City , Utah, and Flagstaff and Phoenix, Arizona, during April 1991. Theseoriginal alternatives ranged from providing high, warm, and sediment-laden flows each spring (with relatively low flows the remainder of the year) to providing steady, cool, and clear flows throughout the year. They ranged from steady flows throughout the day to high daily fluctuations. The public was asked to comment on the range of preliminary alternatives as part of the EIS scoping process (Bureau of Reclamation,1991b). The predominant public comment was the need for "operation only" alternatives and/or separate analysis of operational and nonoperational (structural) measures. Other comments most frequently voiced were: .An alternative should be developed that maximizes benefits to endangered speciesand recreation. .Alternative dam operations should be considered to reduce the frequency of floods and daily fluctuations. .The reregulation dam is not a reasonable alternative and should not be considered. .Not only is a reregulation dam a viable alternative, but a powerplant should be added to help pay the cost. .The historic or natural flow patterns should serve as the baseline (No Action Alternative) for comparison of alternatives. .None of the alternatives should include structural elements. .The environmental, social, and economic effects of reduced electrical generation should be evaluated in steady flow alternatives. .A lower fluctuating flow alternative should be formulated with a maximum of 20,000cubic feet per second (cis) and a minimum of 8,000cis. Ramp rates should be 1,000cis per hour up and 500 cis per hour down, with no more than 3,000cis change from day to day. (Many flow regime variations were received.) 16 Chapter II Description of Alternatives Using this additional input, professional judgment, and analysis of interim flows, the EIS team reviewed and revised the preliminary alternatives. Sevenalternatives were then identified for detailed analysis, and others were considered and eliminated from detailed study. Later, to present a full range of reasonable operations, two more alternatives were formulated. As a result of comments on both the draft EIS and draft biological opinion and discussions with the U.S. Fish and Wildlife Service (FWS),the preferred alternative described in the draft EIS was revised with the broad support of the cooperating agencies(seeModified Low Fluctuating Flow Alternative later in this chapter). The EIS team and cooperating agenciesattempted to balance benefits to all resources(physical, biological, cultural, and consumable) in identifying a preferred alternative. Figure 11-1 summarizes the alternatives and their descriptions. ALTERNATIVES DETAIL CONSIDERED IN The nine alternatives considered in detail are described below I beginning with the No Action Alternative (historic operations) to provide a baseline for comparison. Table II-l presents a summary of operating limits under the nine alternatives identified for detailed analysis. All of the restricted fluctuating flow and steady flow alternatives include the following elements designed to provide additional resource protection or enhancement. Thesecommon elements are discussedin detail later in this chapter. .Adaptive management (including monitoring and research) .Monitoring .Flood and protecting cultural resources frequency reduction measures .Beach/habitat-building .New ongoing population .Further flows of humpback chub study of selective withdrawal .Emergency exception criteria Table 11-2.-Percent of days that minimum and maximum releases and daily fluctuations occur under the alternatives Minimum Maximum Daily releases releases fluctuations <8,000 cfs >20,000 cfs >6,000 cfs (percent of days) Altemative No action 90 72 97 Maximum powerplant 90 73 97 High fluctuating flow 79 65 96 Moderate fluctuating flow 41 23 89 Modified low fluctuating flow 29 19 54 Interim low fluctuating flow 29 19 54 capacity The eight action alternatives were designed to provide a broad spectrum of options. One alternative would allow unrestricted fluctuations (within the physical constraints of the powerplant) in flow to maximize the value of power, four would impose varying restrictions on fluctuations, and three others would provide steady flows on a monthly, seasonal,or annual basis. The names of the alternatives reflect the Existing monthly volume steady flow <1 17to18 0 Seasonallyadjusted steady flow <1 15 to 27 0 operational regimes they represent. Year-round steady flow <1 18 to 12 0 Table 11-2shows the frequency of minimum and maximum releasesand daily fluctuations under all Glen Canyon Dam EIS alternatives. 1 Depending on season. (/) - '- .c~ :J", .c~ (.) "C ~.c"' > ~ (.) :;:0 (J) o (J) (J) c: ;n c. .0 E ~ E .-Q) x "' E "' i Q) ... 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(') ~ 000 as as -Jw "' .!. 0) "'iij>w~ o~ 00 O.c -.u 1U'C' ~ :J CoO E o u (/) 0) E~ alu a:~ .c: ~ m Q) >c: >- ~ O ... ~ ="C 10 41 C- (I) O ~ - (1).IO"C 41~ (/) ~ m>~.-.c --1/1 .-a ><-a w~> E "C Q) --J .s -41 e 41 '8 ~ .c Dl ~ la 0 w 8~ Oas .82 j:g "'(') (/) ~ 0 ~ :?:"tU 0 "0 (/) ~ Q) c o -0 ~ .0""asasv ~"(\J oU~ =,,'t; <~~ ~ ~ o ii: >'C 10 0> Ci) (/) ~ o ii: C) c .~ la ~ ... u ~ ii: '0 Q) ... u .~ ... (/I Q) [I: ... E~~ ~ -0EQ.C.) .-~ ><~Q. 1a>1a ~O() 0- ~ 0 ; u cc o z 8:!... o as ...:~ "' ~ ~ u E~ ~ Q) E .-"' x "'~2! ~ 18 !I> .in >""iO c C\1 "C .P. .cu ~ "C ... -0 "C Q) ~ "E Q) :2 !I> Q) .2: rn c ... -Q) ""iO !I> O - ~ C> c ~... Q) c. 9 T"" I Q) :c C\1 1- ~ o ii: CI C ~ IV ~ "G ~ ii: -0 -Q) U .~ ~ C ~ ~ (J E-;;; ;, Q) E (I) .-"' c: Q) ~~ ALTERNATIVES CONSIDERED IN DETAIL Unrestricted No Action Minimum releases (cfs) 1,000 Day Labor to Easter 3,000 Easter to Labor Day Fluctuating Flows Alternative Maximum releases (cfs) 31,500 Daily fluctuations (cfs/24 hrs) 30,500 Day Labor to Ramp rate (cfs/hr) Unrestricted Easter 28,500 Easter to Labor Day The No Action Alternative (historic operations) is presented first to provide an understanding of baseline conditions and operations at Glen Canyon Dam. This alternative provides the basis for impact comparison. Within the overall Colorado River StorageProject purpose, the objective of the No Action Alternative is to produce the greatest amount of firm capacity and energy practicable while adhering to the releasesrequired under the "Law of the River." Under no action, Glen Canyon Dam operations would be the same as they were from 1963-when the dam was placed in operationuntil the researchflows began in June 1990. This alternative would continue operations established under the Criteriafor CoordinatedLong-Range Operationof ColoradoRiver Reservoir:s (Long-Range Operating Criteria) (seeattachment 3) as well as daily fluctuating releases. The maximum allowable discharge during fluctuations is 31,500cfs. Fluctuating releasesoccur when the dam is being operated to follow power system load changes,to produce peaking power, to regulate the power system, or to respond to power system emergencies. Annual Release Volume. The principal factors considered in determining annual release volumes 19 Annual releasevolume is based on inflow and remaining spacein the two reservoirs. Annual releasevolumes vary greatly I but all adhere to the Long-Range Operating Criteria objectives of an 8.23-mafminimum annual releaseand equalized storage between Lake Powell and Lake Mead. Annual releasesgreater than the minimum are permitted to avoid anticipated spills and to equalize storage. From 1966to 1989,annual releasesranged from 8.23maf to 20.4maf (1984). The minimum release has occurred in about half the years since the dam was closed in 1963. Historic predam and postdam annual flows at LeesFerry are shown in figure ll-2(a). This figure shows the reduced variation in annual flows after closure of the dam. Monthly Release Volume. Under the No Action Alternative, the volume of water releasedfrom Lake Powell each month depends on forecasted inflow, existing storage levels, monthly storage targets, and annual releaserequirements. Demands for electrical energyI fish and wildlife needs, and recreation needs also are considered and accommodated as long as the risk of spilling and storage equalization between Lakes Powell and Mead are not affected. Power demand is highest during winter and summer months, and recreation needs are highest during the summer. Therefore, higher volume releasesare scheduled during these months whenever possible to benefit these uses. Spills are excessannual releasesthat cannot be used for project purposes; they usually are the result of inflow forecast changes. Floodflows are the spills of principal concern. Floodflows are releasesgreater than the designed powerplant capacity that are discharged through the river outlet works and spillways. are .Releasing a minimum of 8.23 million acre-feet (maf) (specified in the Long-Range Operating Criteria) .Maintaining .Avoiding .Balancing Mead conservation storage anticipated spills storage between Lakes Powell and Each month during the inflow forecast season Ganuary to July), the volume of water to be releasedfor the rest of the year is recomputed based on updated streamflow forecast information. Scheduled releasesfor the remaining months are adjusted to avoid anticipated spills and maintain conservation storage in accordancewith the Long-Range Operating Criteria. 20 Chapter II Description of Alternatives 50,000. c. Daily Range in Releases (t-Iighest and lowest hourly flows for each day) 1989 (low release year) 40,000 "- 30,000 m 0.. "G) If 20,000 Q :0 8 10,000 ,;i ~;;. 0' , OCr. ,:!~ NOV ;DEC 'JAN ' FEB 'MAR ' APR .MAY' JUN ' JUL ' AUG I SEP 50,000 I 40,000 ~ d. Hourly Releases Wednesday, July 5, 1989 (A day in a low release July) 30,000 0- 10,000 0 4 8 ..~ 24 Figure ll-2.-Historic 16 20 Hours water releases from Glen Canyon Dam. 24 ALTERNATIVES Figure 11-2(b)shows historic monthly release volumes for a low (minimum) releaseyear, which occurs the most frequently. Figure 11-3presents a comparison of historic monthly releasesamong example low, moderate, and high releaseyears. Floodflow A voidance Measures. Methods for providing protection against flood releases under the No Action Alternative are: 1. Storage in Lake Powell exceed 22.6 maf as of January (before the forecast season) in storing and regulating spring is not allowed to 1 of each year preparation for runoff. 2. On the first of eachmonth from January to June, a protection factor (error term) is added to the forecasted inflow so that more water is assumed to be coming into the reservoir than indicated by the forecast. The error terms follow. Figure II -3.-Comparison of monthly volumes released during low, moderate, and high release years. IN DETAIL 21 Additional inflow Date (mat) January 1 February March Under high storage conditions, fall and early winter releasesare designed to meet the January 1 storage target (22.6maf). Under lower storage conditions, releasesare scheduled at a minimum of about 550,000acre-feetper month. January through July releasesare scheduled to create space in the reservoir so that the forecasted runoff will not produce spills but will fill the reservoir in July. July through Septemberreleasesare used to meet the minimum annual releaserequirement and reach the January 1 target of 22.6 maf. CONSIDERED 1 April 1 May 1 June 1 4.98 4.26 3.60 2.97 2.53 2.13 3. Throughout the streamflow forecast season (January 1 to July 1), operations are planned as though Lake Powell has 500,000acre-feetless capacity than it actually has. This provides a storage buffer to further protect against unforecasted inflow. Hourly Operations. Hourly releasesare set to reach the monthly releasevolumes, to maintain established minimum flow rates, and to follow the pattern of energy demand. Emergency conditions-such as searchand rescue operations, generating equipment failures, or power system emergencies-may causeextreme departures from normal operations. Except for search and rescue operations, these departures are short-lived (generally 1 hour or less),and their effects on water releasescan be adjusted in a short time (less than 4 hours). Hourly power operations are most flexible during months with moderate releasevolumes. The need to maintain minimum flows in months with low releasevolumes limits flexibility to accommodate changing hourly power demands. If the reservoir is nearly full and inflow is extremely high, monthly releasesare scheduled at or near maximum capacity most of the time, leaving little flexibility for hourly releasesto change in responseto power demand. Typical hourly releasesfor a sample 24-hour period are shown in figure 11-2(d).Also, figure 11-4compares 24-hour releasesfor typical low, moderate, and high releasevolume days. Fluctuating releasesare made when the generating units are being operated to follow changesin power system load, produce peaking power, regulate the power system, or respond to power system emergencies. To the extent possible 22 Chapter II Description of Alternatives Figure 1I-4.-Hourly releases for typical summer days with low, moderate, and high release volumes. within higher priority operating constraints, the following guidelines are used in producing hydroelectric power: .Maximize water releasesduring the peak energy demand periods, generally Monday through Saturday between 7 a.m. and 11 p.m. .Maximize water releasesduring peak energy demand months and minimize during low demand months .Minimize and, to the extent possible, eliminate powerplant bypasses Historic daily ranges of hourly releasesare shown for an entire minimum releaseyear in figure 11-2(c).During a minimum releaseyear, the greater the daily releasevolume, the greater the daily fluctuation. Minimum Flow.-Figure 1I-5(a)shows the historic distribution of minimum flows. Minimum flows are restricted to no less than 1,000cfs from Labor Day until Easter and 3,000cis from Easteruntil Labor Day (the recreation season). An additional requirement during the recreation season is that weekday releasesaveragenot less than 8,000cfs for the period from 8 a.m. to midnight. The minimum flow for any given hour typically depends on the monthly releasevolume and the magnitude and predictability of electrical load Figure Il-5.-Historic distributions of daily minimums, maximums, and fluctuations in cIs (1965-89). acrossand within the hour. In some cases,dispatcher experiencemay be a factor. For a number of reasons(typically for meeting monthly release volumes), minimum flows are frequently above the objective minimum. Occasionally, power system emergenciesoccur that prevent meeting the minimum releaseobjectives. ALTERNATIVES CONSIDERED IN DETAIL 23 MaximumFlow.-The maximum flow is determined by powerplant capacity, the power demand at the time of release,and the amount of water required and/ or available for releasein a given month. As much as 33,200cis can be discharged through the powerplant if the reservoir is at the appropriate elevation. Flows greater than 33,200cis are discharged through the outlet works first and then through the spillways, as required. Peak dischargesunder normal no action operations do not exceed31,500cfs. Any releasesgreater than 31,500cfs are steady on a daily basis. Figure 11-5(b ) shows the historic distributions of maximum flows. Rangeof FluctuatingFlows.-The range of daily fluctuations under the No Action Alternative is restricted only to between the minimum and maximum flows. Figure 1I-5(c)shows the historic distribution of daily fluctuations. RampRate.-Theramp rate is the rate of change in discharge, integrated acrossthe hour, to meet the electrical load by achieving either higher or lower releases. North American Electric Reliability Council {NERC) operating criteria require Western Area Power Administration {Western) to meet scheduled load changesby ramping up or down beginning at 10 minutes before the hour and ending at 10 minutes after the hour. Any ramping to meet scheduled load changesoccurs during that same 20-minute period. The principal times of change are in the morning, when releases are ramped upward to respond to the peak daytime demand, and at night, when releasesare ramped downward as the electrical demand diminishes. A computerized automatic generation control (AGC) system controls the rate of releaseand generation on an instantaneous basis. It also measuresthe power flow at all electrical interconnections with other control areas. Under historical operations, scheduled ramping has typically resulted in large changesin river stage. However, the continuous small changesin discharge causedby AGC rarely affect river stage by more than a foot. Under the No Action Alternative, the only restriction on ramp rates is the physical capability of the generators. Figure 11-6shows the historic up and down ramp Historic Down Ramp Rates >8,000 ;$.2,000(2%) 6,OOo-B,OOO 4,000-6,000 Figure 1I-6.-Historic (1966-89) distribution of 1-houi ramp rates in cfs per hour. (Maximum daily values for moderate monthly releases of 800,000 acre-feet.) rates. The I-hour up ramp rates have been less than 4,000cfs per hour about 32 percent of the time and greater than 8,000cis about 11 percent of the time. The down ramp rates have been less than 4,000cfs about 29 percent of the time and greater than 8,000cis about 7 percent of the time. 24 Chapter II Description of Alternatives Maximum Powerplant Capacity Alternative Minimum releases Maximum releases (cIs) (cIs) 11,0°° Labor 33,200 Day to Easter I 3,000 Easter to Labor Day Daily fluctuations (cfs/24 hrs) compares operations under these alternatives with historic operations for three different daily water releasesituations in the peak pow~r month of July. Ramp rate (cfs/hr) 32,200 Labor Unrestricted Day to Easter 30,200 to Easter Labor Day This alternative was developed to allow use of the maximum powerplant discharge capacity that resulted from the 1987uprate and rewind (see "Background" in chapter I). Operations under the Maximum Powerplant Capacity Alternative would be the same as under the No Action Alternative except that full powerplant capacity (estimated flows of 33,200cis) would be allowed. Monthly and annual operations, including flood control, would be identical to those described under the No Action Alternative. Releasesin excessof 31,500cis would be possible only when Lake Powell's elevation is greater than 3641 feet. This additional capacity would be used when power demand is high and typically would last 4 hours or less (based on historical operations). Daily and Hourly Operations. Minimum releases would be at least 3,000cfs from Easter to Labor Dayand 1,000cfs for the remainder of the year. The range in daily releasefluctuations and ramp rates would be unrestricted. Restricted Fluctuating Flows The restricted fluctuating flow alternatives were designed to provide a range of downstream resourceprotection measures,while offering varying amounts of flexibility for power operations. All four alternatives-high, moderate, modified low, and interim low fluctuating flowsrestrict daily fluctuations at Glen Canyon Dam as compared to the No Action and Maximum Powerplant Capacity Alternatives. Each alternative also specifies ramp rate restrictions and minimum releaserequirements. Figure 11-7 Within the constraints of the alternatives, maximum water releaseswould be scheduled to coincide with times of peak electrical demand. Low releasesare made at night to maximize the amount of water available for daytime generation and thus minimize expensive daytime power purchases. For any of the restricted fluctuating flow alternatives, the scheduled annual and monthly releasevolumes would be determined using essentially the same considerations described under the No Action Alternative. Beach/habitatbuilding flows would modify monthly release volumes when Lake Powell is drawn down (see "Common Elements"). Habitat maintenance flows-short-term high releasesduring the spring-are included in the Moderate and Modified Low Fluctuating Flow Alternatives to transport and deposit sand for maintaining camping beachesand fish and wildlife habitat. Thesemaintenance flows were not included in the other restricted fluctuating flow alternatives for the following reasons. With habitat maintenance flows, the High Fluctuating Flow Alternative would, over the long term, move more sand than supplied by tributaries and would result in net erosion. Maintenance flows were not included in the Interim Low Fluctuating Flow Alternative becausethis alternative was intended to preserve the current interim flow operations for which nearly 2 years of data have been collected. The common elements that are described later in this chapter apply to all restricted fluctuating flow alternatives. ALTERNATIVES CONSIDERED IN DETAIL Q) c. ~ G) u. u :c ~ () Figure 1I-7.-Example hourly releases under fluctuatingflow alternatives compared to historic operations for low, moderate, and high release days in July. All restricted fluctuating flow alternatives would increase minimum flows and decrease maximum flows when compared to no action. 25 26 Chapter II Description of Alternatives would be constant within a month, the minimum and maximum flows might be different each day. High Fluctuating Flow Alternative Daily and Hourly Operations. Minimum flows would be 3,000,5,000,or 8,000cfs depending on monthly releasevolume, finn load, and market conditions (seetable 11-3).The maximum flow during hourly fluctuating releaseswould be limited to 31,500cis. When high inflow volumes and storage conditions require releasesgreater than 31,500cfs, such releaseswould be steady on a daily basis. The High Fluctuating Flow Alternative was developed to slightly reduce fluctuating flows, with the goal of protecting or enhancing downstream resourceswhile allowing flexibility for power operations. Releaseswould be tied to hydrology and power system demand. This alternative would have the same annual and monthly operation plan as described under the No Action Alternative but would include additional restrictions on daily and hourly operations. Parameterssuch as minimum flows, down ramp rates, and allowable daily fluctuations were designed to provide some resource protection, but without substantial impacts to hydropower. Although daily fluctuation limits The limit on daily fluctuations often would be more restrictive than the minimum and maximum flow rates. Fluctuations would be limited to 15,000,20,000,21,000,or 22,000cfs over any 24-hour period, depending on the monthly release volume. Maximum flows during a minimum releaseyear normally would not exceed25,000cfs. Under this alternative, adverse market conditions (when power demand is relatively high) are assumed to occur during winter and summer: November, December,January, June,July, and August. All other months are considered favorable market condition months (power demand is relatively low). The ramp rate would follow the power load for increasing flows without restriction, but decreasingflows would be limited to 5,000cis per hour in winter and summer and 4,000cis per hour during spring and fall. Table 11-3.-Flow parameters under the High Fluctuating Flow Alternative Minimum flows Monthly release volume Mean (1 ,000 acre-feet) (cfs) flow <650 650-850 850-1 ,000 <1,000 Down ramp rate <11 10,900-1. 14,300-1 >1 D,900 4,300 6,800 6,800 Favorable market conditions Adverse Firm load >500 GWh 1 <500 GWh market conditions Maximum flow (cfs) (cfs) (cfs) (cfs) 3,000 3,000 5,000 8,000 3,000 5,000 8,000 8,000 3,000 3,000 5,000 8,000 31 ,500 31 ,500 31 ,500 15,000 20,000 21 ,000 31,500 22,000 4,000 cfs/hr 5,000 cfs/hr Allowable fluctuation (cfs) ALTERNATIVES CONSIDERED IN DETAIL Moderate Fluctuating Flow Alternative Minimum releases (cIs) Maximum releases 5,000 31,500 (cIs) Daily fluctuations (cfs/24 hrs) I .T. 45% of mean flowforthe month exceed Ramp rate 27 and maximum releaselimits and daily fluctuations are as shown in table 11-4.The equations used to determine minimum and maximum flows are in attachment 6. (cfs/hr) 14,000 2.500 up down Table 11-4.-Flow parameters under the Moderate Fluctuating Flow Altemative not to .T.6,OOO The Moderate Fluctuating Flow Alternative was developed to reduce daily flow fluctuations below no action levels and to provide special high steady releasesof short duration, with the goal of protecting or enhancing downstream resources while allowing intermediate flexibility for power operations. This alternative would have the same annual and essentially the same monthly operating plan as described under no action (except for the addition of habitat maintenance flows) but would restrict daily and hourly operations more than the No Action, Maximum Powerplant Capacity, or High Fluctuating Flow Alternatives. Parameterssuch as minimum flows, ramp rates, and allowable daily fluctuations were designed to provide resource protection through consistent releasepatterns throughout each month Daily and Hourly Operations. Minimum flows for a given month would vary depending on the monthly releasevolume but would be no less than 5,000cis. The maximum releaserate for a given month also would vary depending on the monthly releasevolume but would be no greater than 31,500cfs under normal operations. When high inflow volumes and storage conditions require releasesgreater than 31,500cis, such releaseswould be steady on a daily basis. Maximum flows during a minimum releaseyear normally would not exceed22,300cis. The ramp rate would be limited to 4,000cfs per hour for increasing flows and 2,500cfs per hour for decreasingflows. Allowable Monthly release volume Mean (acre-feet) (cfs) 550,000 800,000 1 ,000,000 1 ,500,000 Minimum Maximum flow flow (cfs) (cis) flow 9,200 13,400 16,800 25,200 5, 100 7,400 10,800 19,200 13,400 19,400 22,800 31,200 daily fluctuation (cIs) :t4,150 :t6,000 :t6,000 :t6,000 Habitat Maintenance Flows. Habitat maintenance flows are included in this alternative to re-form backwaters and maintain sandbars,which are important for camping beachesand fish habitat. Habitat maintenance flows are high, steady releaseswithin powerplant capacity (33,200cis) for 1 to 2 weeks in March, although other months would be considered under adaptive management. A more complete description of habitat maintenance flows can be found under the Modified Low Fluctuating Flow Alternative that follows. The monthly releasevolumes during such flows under this alternative are compared to no action volumes in attachment 6. Modified Low Fluctuating (Preferred Alternative) Minimum releases Maximum releases (cfs) (cfs) 8,000 between 7 a.m. and 7 p.m. 25,000 Flow Alternative Daily fluctuations (cfs/24 hrs) 5,000 6,000 or 8,000 Ramp rate (cfs/hr} 4,000 up 1,500 down 5,000 at night Allowable daily fluctuations as well as minimum and maximum flows would be detennined based on the mean releasesfor the month. The allowable fluctuation would be plus or minus 45 percent of the mean daily flow, not to exceed plus or minus 6,000cfs. Approximate minimum The Modified Low Fluctuating Flow Alternative was developed to reduce daily flow fluctuations well below no action levels and to provide special high steady releasesof short duration, with the 28 Chapter II Description of Alternatives goal of protecting or enhancing downstream resourceswhile allowing limited flexibility for power operations. This alternative would have the same annual and essentially the samemonthly operating plan as described under the No Action Alternative but would restrict daily and hourly operations more than any of the previously described fluctuating flow alternatives. Daily and Hourly Operations. Minimum flows would be no less than 8,000cfs between 7 a.m. and 7 p.m. and 5,000cfs at night. The maximum rate of releasewould be limited to 25,000cfs during fluctuating hourly releases. Any releasesgreater than 25,000cfs (other than for emergencies)would be steady on a daily basis and would be made in responseto high inflow and storage conditions. The limit on daily fluctuations often would be more restrictive than the minimum and maximum flow rates. Fluctuations would be limited during any 24-hour period, depending on monthly releasevolumes (seetable 11-5). Additional information on the effects of dam operations has been gathered since the interim operating criteria were developed. Some of this preferred alternative's parameters have changed since the draft EIS was published based on new information and public comments. To reduce long-term flood frequency, a single method is advanced under this altemativeraising the height of the four spillway gates 4.5 feet to elevation 3704.5feet (see"Flood Frequency Reduction Measures"). However, since other methods are available to accomplish the same goal, a final decision about the method ultimately used would not be made until additional National Environmental Policy Act (NEPA) compliance has been completed to evaluate environmental impacts on Lake Powell shoreline resources. Lake Powell's current elevation is well below the level that would require reserving additional storage space,thus accomplishing the objective of reducing the frequency of flood releases. The lake level is not expected to reach full elevation for another 4 to 5 years. Until the spillway gates would be installed, additional operational measureswould be implemented through the Annual Operating Plan (AOP) processto provide the recommended flood protection. Habitat Maintenance Flows. Maximum releases under the Modified Low Fluctuating Flow Alternative normally would not exceed about 20,000 cis during a minimum release year. Without higher flows: .Portions of sandbars above the normal peak stage could not be rebuilt. .Sediment would accumulate at ~owelevations, including backwaters. .Camping beachesand retum-current channels would likely become filled with sediment and eventually overgrown with vegetation. Although an occasionalfloodflow (greater than 33,200cfs) may rebuild high elevation beachesand re-form backwaters, frequent floodflows would likely transport more sand than could be supplied by the tributaries-resulting in long-term sandbar erosion. Therefore, habitat maintenance flows are included in this alternative to re-form backwaters and maintain sandbars,which are important for camping beachesand wildlife habitat. Table 11-5.-Flow parameters under the Modified Low and Interim Low Fluctuating Flow Alternatives Monthly release volume Allowable Mean flow (acre-feet) (cfs) <10,100 10,100-13,400 >13,400 <600,000 600,000-800,000 >800,000 1 Does not include habitat maintenance flows. Minimum flow Maximum flOW1 daily fluctuation (cfs) (cfs) (cfs) 25,000 25,000 25,000 5,000 6,000 8,000 5,000/8,000 5,000/8,000 5,000/8,000 ALTERNATIVES CONSIDERED IN DETAIL Habitat maintenance flows are high, steady releaseswithin powerplant capacity (33,200cfs1 for 1 to 2 weeks in March, although other months would be considered under the Adaptive Management Program. March was selectedfor the following reasons: Backwater channels could be re-formed prior to the humpback chub spawning period. More sediment is likely to be supplied by tributary flow in March than later in the spring. March is prior to the peak recreation use season. Habitat maintenance flows would not be scheduled when the projected storage in Lake Powell on January 1 is greater than 19 maf. Annual release volumes under such conditions are typically greater than the minimum annual releasevolume (8.23maf), and such flows already may be near or exceedpowerplant capacity. Although habitat maintenance flows are defined as steady, minor fluctuations of up to plus or minus 1,000cfs would be permitted to regulate voltage within the power grid. Maintenance flows would begin by increasing flows at a rate no greater than 4,000cfs per hour and would conclude by decreasingflows back to the normal operating range at a rate no greater than 1,500cfs per hour. The limit on daily change in flow would not apply during these transitions. would be scheduled in a year when there is concern for a sensitive resource-such as sediment or an endangered species. Increasing the flow to 30,000cfs for 10 days would result in the releaseof an additional 412,000acrefeet of water in March, which would require adjusting the releasevolumes in the other months. This scheduling adjustment would be determined during the Annual Operating Plan preparation and may vary from year to year. The monthly releasevolumes under this alternative are compared to no action volumes in attachment 6. Endangered FishResearch. The endangered fish researchdescribed under this alternative in the draft EIS has been moved to the scientifically based Adaptive Management Program (see discussion under "Common Elements" later in this chapter). Interim Low Fluctuating Flow Alternative Minimum releases (cIs) at Maximum releases (cfs) 8,000 between 7 a.m. and 7 p.m. 5,000 Habitat maintenance flows would differ from beach/habitat-building flows (a common element of the restricted fluctuating and steady flow alternatives) becausethey would be within powerplant capacity and would occur nearly every year when the reservoir is low. Beach/ habitat-building flows would be of greater magnitude than habitat maintenance flows and would be less frequent. Habitat maintenance flows would not occur in years when a beach/habitat-building flow is scheduled (see discussion under l'Common Elements" later in this chapter). Neither of these special releases 29 20,000 Daily fluctuations (cfs/24 hrs) 5,000 6,000 or 8,000 Ramp rate (cfs/hr) 2,500 up 1 ,500 down night The Interim Low Fluctuating Flow Alternative was developed to reduce daily flow fluctuations well below no action levels, with the goal of protecting or enhancing downstream resources while allowing limited flexibility for power operations. This alternative would have the same annual and monthly operating plan as the No Action Alternative but would restrict daily and hourly operations as much as or more than under any alternative allowing fluctuating flows. Actual powerplant releasecapacity may be lessunder low reservoir conditions. 30 Chapter II Description of Alternatives This alternative is the same as the interim operating criteria implemented on November 1, 1991 (except for the addition of the common elements). Interim operating criteria were established prior to obtaining results from GCESPhaseII. Parameters such as minimum flows, maximum flows, ramp rates, and allowable daily fluctuations were designed to protect downstream resourcesuntil completion of the final EIS and record of decision (ROD). Daily and Hourly Operations. Minimum flows would be no less than 8,000cfs between 7 a.m. and 7 p.m. and 5,000cis at night. The maximum rate of releasewould be limited to 20,000cis during fluctuating hourly releases. Any releasesgreater than 20,000cfs (other than for emergencies)would be steady on a daily basis and would be made in responseto high inflow and storage conditions. The limit on daily fluctuations often would be more restrictive than the minimum and maximum flow rates. Fluctuations would be limited during any 24-hour period, depending on monthly releasevolumes. Steady Flows The steady flow alternatives were designed to provide a range of downstream resource protection measuresby minimizing daily release fluctuations. Flows would be steady on either a monthly, seasonal,or year-round basis. The monthly distribution of releasevolumes would differ, but daily and hourly operating criteria would be the same for all steady flow alternatives. Flows would be the same each day within the month or season(except during flood control operations). Figure 11-8compares operations under the steady flow alternatives with historic operations for low (8.23maf), moderate (13.6maf), and high (21.1maf) releaseyears. The scheduled annual releasevolume would be determined in accordancewith the Long-Range Operating Criteria. Monthly or seasonalreleasevolumes would be based on the month-to-month pattern specified for the alternative. Although the goal would be to maintain steady (unifonn) water releasesfor selecteddurations, the ability to maintain a steady flow from one period to the next would depend on the accuracy of streamflow forecastsand the spaceavailable in Lake Powell. Minimum or maximum flow rates would be determined by the monthly water volume to be released. The goal would be to hold flows steady to within plus or minus 1,000cis per day and adjust them between months in responseto forecast changes. Ramp rates within this flow range would not be restricted becauseriver stage fluctuations would be within a few inches. The maximum change in releasesbetween months would be 2,000cis per day. Daily variations of plus or minus 1,000cis per day (approximately 42 megawatts) would allow some minor flexibility in dam operations to be used primarily for electrical system regulation. AGC would causeminor fluctuations as the powerplant's computerized regulation system made adjustments every 2 to 6 seconds. Resulting changesin river stage would not be noticeable downstream. Flow fluctuations of this magnitude were measured during steady researchflows, and the corresponding river stagefluctuations were small (seefigure 11-9). Water releasesin excessof powerplant capacity would flow through the outlet works and/ or spillways during high water years or, as necessary, during beach/habitat-building flows. The habitat maintenance flows included in the SeasonallyAdjusted Steady Flow Alternative were not included in the other steady flow alternatives. Such flows would be contrary to the concepts for which thesesteady flow alternatives were developed, i.e., to keep flows steady under the Year-Round Steady Flow Alternative and to retain the pattern of historic monthly releasesunder the Existing Monthly Volume Steady Flow Alternative. The "Common Elements" described later in this chapter apply to all steady flow alternatives. ALTERNATIVES CONSIDERED IN DETAIL 50,000 Low Release Year (1989) e- 40,000 "C 1:= O () Q) (/) , -0) [1. 0) 0) u. Daily range for historic operations Existing monthly volume steady flow Seasonally adjusted steady flow Year round steady flow 30,000 20,000 () ::0 :J () 10,000 0 ocr NOV ' DEC JAN FEB MJ~R APR MAY JUN 50,000 0 Figure ll-8.-Steady flow alternatives compared to no action for low, moderate, and high release years. JUL AUG SEP 31 32 Chapter II Description of Alternatives This alternative would have the same annual and monthly operating plan as the No Action Alternative, but releaseswould be steady within months. Also, beach/habitat-building flows would modify monthly releasevolumes when Lake Powell is drawn down (see"Common Elements"). See figure 1I-8for estimated operations under this alternative, using historic low, moderate, and high annual releasesituations. Below Glen Canyon Dam 11 ~10 "' u & ~ m , 01 !12 ~ .I:. U "' at lees . 011 r Ferry ~-lr-- 10 3 inch , -.~~g~ 17th f!~~u~ti°!:! 18th 19th ...,2Oth December 21st 22nd 1990 Figure 1I-9.-Changes in electrical load during steady research flows caused minor discharge fluctuations that were measured at U.S. Geological Survey gauging stations below the dam and at Lees Ferry. On December 21, the 2,170-cfs fluctuation measured 112mile below the dam was reduced to 1,105 cIs at Lees Ferry. This release fluctuation resulted in a river stage fluctuation of 10 inches at the gauge below the dam and 3 inches at the Lees Ferry gauge. Minimum Flow. Both minimum and maximum flows would be within plus or minus 1,000cfs of the mean monthly release. Basedon analysis of historical releases,minimum flows would rarely be below 8,000cis (476,000-acre-footmonthly volume). Monthly Release Volume. The scheduled monthly releasevolumes would be the same as the monthly volumes under the No Action Alternative. Basedon the period 1963-89, February has the lowest monthly median release volume (556,000acre-ieet-equivalent to 10,000cis), and August has the highest monthly median releasevolume (903,000acre-ieetequivalent to 14,700cis). Seasonally Adjusted Steady Flow Alternative Existing Monthly Volume Steady Flow Alternative Minimum releases (cfs) 8,000 Maximum releases (cfs) Monthly Daily fluctuations (cfs/24 hrs) :t1 1000 Ramp rate (cfs/day) 2,000 volumes between prorated months The Existing Monthly Volume Steady Flow Alternative was developed to provide steady flow on a monthly basis while continuing to maintain flexible monthly releasevolumes to avoid spills and maintain conservation storage. Steady flows were included each month with the goal of protecting or enhancing downstream resources, especially the aquatic ecosystemthat exists downstream from the dam. The SeasonallyAdjusted Steady Flow Alternative was developed to enhancethe aquatic ecosystem by releasing water at a constant rate within defined seasonsand by using habitat maintenance flows. Seasonalvariations in minimum flows and habitat maintenance flows were designed with the goal of protecting and enhancing native fish. See figure 11-8for estimated operations under this ALTERNATIVES CONSIDERED IN DETAIL alternative. Monthly releasepatterns would differ from the No Action Alternative as explained in more detail below. This alternative would provide steady flows on a 1- to 3-month basis, providing seasonalvariations throughout the year to meet downstream resource needs. The highest releaseswould occur in May and June,with relatively low releasesfrom August through December. Minimum Flow. The mffiimum monthly constant releasefor each seasonis shown above. These minimum releaserequirements would be relaxed to avoid spills during high storage or inaccurate forecast situations. Monthly Release Volume. Releaseswithin each month would be steady and would have to equal or exceedthe monthly minimums. Any additional water in excessof the minimum annual release volume would be distributed equally among the 12 months, subject to an 18,OOo-cfs maximum. This 18,OOO-cfs maximum would be exceeded when the annual releaseis more than 13.14maf. If forecastschanged, the volume of water to be releasedduring the remainder of the year would be recomputed monthly based on updated forecasts,and the constant rate of releasewould be adjusted accordingly. Habitat Maintenance Flows. Habitat maintenance flows are included in this alternative to re-form backwaters and maintain sandbars. Habitat maintenance flows are high, steady releases within powerplant capacity (33,200cis) for 1 to 2 weeks in March, although other months would be considered under the Adaptive Management Program. A more detailed discussion of habitat maintenance flows can be found under the Modified Low Fluctuating Flow Alternative. The monthly releasevolumes during habitat maintenance flows under this alternative are compared to no action volumes in attachment 6. 33 Year-Round Steady Flow Alternative Minimum releases Maximum releases (cfs) (cfs) Yearly volume Yearly volume prorated prorated Daily fluctuations (cfs/24 hrs) 11,000 Ramp rate (cfs/day) 2,000 between months The Year-Round Steady Flow Alternative was developed to eliminate fluctuating flows, both daily and seasonal. Year-round steady flows were designed with the goal of protecting or enhancing downstream resourcesby providing the greatest amounts of river-stored sediment and biomass possible in the postdam environment. Minimum Flow. The minimum flow would be determined from the mean monthly releasebut would correspond generally to the minimum annual releasevolume of 8.23maf, which is about 11,400cfs. The minimum releaserequirement would be relaxed to avoid spills during high storage or inaccurate forecast situations. Monthly Release Volume. The monthly volume would be approximately the annual volume divided by 12,except when response to forecast changeswould be required. If forecastschanged, the volume of water to be releasedduring the remainder of the year would be recomputed monthly based on updated forecasts,and the constant rate of releasewould be adjusted accordingly. The ability to maintain a constant rate of releasefor the entire year would depend on the accuracy of streamflow forecastsand the amount of spaceremaining in Lake Powell. Approximately half of the time, lake elevation would be high enough that forecast changes could causesome variations in monthly volumes. Common Elements The elements common to all restricted fluctuating flow and steady flow alternatives are described in detail below. Impact analysesof these alternatives were conducted taking these common elements into account. 34 Chapter II Description of Alternativ'es Adaptive Management The completion of the Glen Canyon Dam EIS processwill result in a decision by the Secretaryof the mterior (Secretary)on the operation of C;len Canyon Dam. It is intended that the ROD ~,ill initiate a processof "adaptive management," whereby the effects of dam operations on downstream resourceswould be assessedaJ1dthe results of those resource assessmentswould form the basis for future modifications of dam operations. Many uncertainties ~til1exist regarding the downstream impacts of water releasesfrom Glen Canyon Dam. The COnCE!pt of adaptive management is based on the recognized need for operational flexibility to respond to future monitoring and researchfindings and varying resource conditions. The Adaptive Management Program (AMP;I was developed and designed to provide an orga:nization and processfor cooperative integration of dam operations, resource protection and management, and monitoring and researchinformation. The program would meet the purpose and strengthen the intent for which this EIS was prepared and ensure that the primary mandate of the Grand Canyon Protection Act of 1992(GCPA) is met through future advancesin information and resource management. The Secretaryof the Interior will issue a ROD outlining criteria and operating plans resulting from this EIS and exerciseother measuresand authorities under existing law, as appropriate, to ensure that Glen Canyon Dam is operated it\ a manner consistent with section 1802of the C;CPA. It is expected that the AMP would be irnple-. mented as an element of the ROD and wouLd provide the basis and processfor developing an annual report to the Congress and Governors of the Colorado River Basin States. The annual report would outline the operations underta.kenin the current and projected years pursuant to the GCPA. The AMP is not intended to satisfy all of the mandates in the GCPA. Likewise, the progr'am is not intended to derogate any agency's statu1tory responsibilities for managing certain resources. For example, operation of Glen Canyon Dam is the Bureau of Reclamation's (Reclamation) responsibility , and Reclamation cannot relegate this authority to any other entity .The AMP would recommend other administrative provisions, but theserecommendations would in no way supersedethe basic management responsibilities of any of the cooperating entities. The purpose of the AMP would be to develop modifications to Glen Canyon Dam operations and to exerciseother authorities under existing laws as provided in the GCPA to protect, mitigate adverse impacts to, and improve the values for which the Glen Canyon National Recreation Area and Grand Canyon National Park were established. Thesevalues include, but are not limited to, natural and cultural resourcesand visitor use. Physical and economic conditions must also be considered in any proposed modification to dam operations. Long-term monitoring and research are essential to adaptive management and would be implemented to measure how well the selected alternative meets resource management objectives (seeAppendix A, Long- Term Monitoring and Research). Authority. The AMP would be implemented consistent with the Grand Canyon Protection Act which requires the Secretary to: (a) Adopt criteria and operating plans separate from and in addition to those specified in section 602(b) of the Colorado River Basin Act of 1968and exerciseother authorities under existing laws, so as to ensure that Glen Canyon Dam is operated consistent with section 1802and to fulfill consultation requirements of section 1804(c)of the GCPA. (b) Establish and implement long-term monitoring and researchprograms and activities that will ensure that Glen Canyon Dam is operated in accordancewith provisions of section 1802and consultation requirements of section 1805(c). In carrying out such provisions, the Secretaryor his designeewould develop, as appropriate, ALTERNATIVES CONSIDERED IN DETAIL modifications to operating criteria or other management actions in consultation with all interested parties and an Adaptive Management Work Group (AMWG). The processwould include coordination of formal consultation required in sections 1804(c)and 1805(c)of tlle GCPA concerning additional operating critE!riafor Glen Canyon Dam and long-term monitorirlg and researchprograms, respectively. In addition, all program activities would comply with applicable laws and permitting requirements. Consultation would be maintained with appropriate agenciesof the Department of the illb~rior, including the U .5. Fish and Wildlife Service,. National Park Service (NPS), Bureau of Reclamation, and Bureau of illdian Affairs; l:he Secretaryof Energy; Governors of Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming; Havasupai Tribe, Hopi Tribe, Hualapai Tribe, Navajo Nation, Pueblo of Zuni, SanJuan Southern Paiute Tribe, Southern Paiute Consortium; and the general public, including representatives of academic and scientific communities, environmental organizations, the recreation industry , and contractors for the purchase of Federal power produced at Glen Canyon Dam. Principles. The principles that guided the design of the AMP organization and process are: Monitoring and researchprograms should be designed by qualified researchersin direct responseto the needs of management agencies. A processis required to coordinate and communicate management agency needs to researchersand to develop recommendations for decisionmaking. A forum is required for the transfer of monitoring and researchinvestigation results to the management agenciesand to develop consensuson management responseto infonnation on affected resource conditions, trends, atld processes. 35 .All monitoring and research programs in Glen and Grand Canyons should be independently reviewed. .Interested parties identified in the GCP A should be provided opportunity for full and timely participation in proposals and recommendations. Specific AMP goals include: .Facilitating management response to monitoring and researchinformation on affected resource conditions, trends, and processes .Ensuring compliance with section 1802of the GCPA and the statutory purposes for Glen Canyon Dam (the "Law of the River"), Grand Canyon National Park, and Glen Canyon National Recreation Area .Assuring resource management obligations are defined and fulfilled in good faith without abridgment of any Federal, State,Tribal, or other legal obligation .providing a mechanism for resolving disputes TransitionPeriod and Funding. Reclamation would continue to provide staff and funding for administering interim flow monitoring and ongoing researchprograms until the ROD is issued and/ or the AMP has been implemented. It is anticipated that monitoring and research functions would be transferred to a monitoring and researchcenter during late fiscal year 1995 and early 1996. The GCESSenior Scientist would direct this transition to assurecontinuity and efficient transfer of the GCESinto the long-term program. Subsequently,Reclamation would continue to allocate funds for administration and monitoring and research as outlined in sections 1807and 1808of the GCPA. The funding of other management actions would be the responsibility of the agency administering the affected resource. Organization. The Adaptive Management Program would be administered through a senior Department of the Interior official (designee)and facilitated through an Adaptive Management Work Group organized as a Federal Advisory 36 Chapter II Description of Alternati\i'es Committee. The AMWG would be chaired by the designeeand supported by a monitoring and researchcenter and technical work group. Independent review panels would provide overview of technical studies and evaluatioJ:ls. Figure II-I0 shows the organizational structure of the AMP . The program would be directed by the designee, who would serve as the Secretary'sprincipal contact for the AMP and as the focal point for issuesand decisions associatedwith the program. Responsibility would include ensuring that the Department of the Interior complies with its obligations under the GCPA and ROD for this EIS. The designeewould review, modify , accept,or remand the recommendations from the AMWG in making decisions about any changesin dam operation and other management actions. designeeand facilitate consultation with all interests. Non-Government representatives would be reimbursed for travel and related expensesfor activities and meetings of the AMWG in accordancewith provisions of the Federal Advisory Committee Act, the AMWG charter, and other existing laws. The work group would: .Provide the framework for AMP policy, goals, and direction .Develop recommendations for modifying operating criteria and other resource management actions .Facilitate coordination and input from interested parties .Review and forward the annual report to the Secretaryand his designee on current and projected year operations .Review AdaptiveManagementWork Group.-The AMWG membership would be appointed by the Secretarywith representation from each of the cooperating agenciesassociatedwith this EIS, each of the Colorado River Basin States,and.two representativeseach from environmental groups, recreation interests, and contractors for Federal power from Glen Canyon Dam. It is recommended that the representation from the latter three interest groups be on a 2-year rotating basis to allow more diverse participation. The AMWG would make recommendations to the Secretary's ~ ecretary of the Interior ~ Adaptive Management "-Work Group / / ~ ~- --"""' ~ ;;:;;;;.~ ~-~~ Figure II-l0.-Drganizational structure of the Adaptive Management Program. and forward annual budget proposals .Ensure coordination of operating criteria changesinto the Annual Operating Plan for Colorado River Reservoirs and other ongoing activities The following organizational elements are proposed. 1. Monitoring and ResearchCenter: To support the designeeand the AMWG, it is recommended that the Secretaryestablish a researchcenter within the U .S.Geological Survey (USGS)and/ or National Biological Service with a small permanent staff in Flagstaff, Arizona. The center would be responsible for developing the annual monitoring and researchplan, managing all adaptive management researchprograms, and managing all data collected as part of those programs. All adaptive management research programs would be coordinated through the center. Long-term monitoring and researchassociated with cultural resourceswould be carried out in accordancewith the approved Programmatic Agreement on Cultural Resources(attachment 5). All provisions as agreed upon by the consulting parties would be implemented through the Monitoring and Remedial Action Plan and the Historic Preservation Plan. Activities outlined in these ALTERNATIVES documents would be coordinated through the center to ensure integration with other facets of the long-term monitoring and researchpro~7am The center's administrative responsibilities would include managing resource data, reporting monitoring and researchresults, administering contracts, and developing annual reports. l1te center would emphasize long-term monitoring and researchdesign, integration, and progriim management. It would be staffed by a research director and a group of program managers responsible for functions such as physical s(jence, biological science,cultural resources,social sciences,engineering and infrastructure operations, and Native American coordination. The researchdirector would be selectedby the Secretaryor his designeefrom a list of candidates provided through Federal hiring authoritie~;with recommendations by the National Academ)r of Sciences,Indian Tribes, and other members of the AMWG. The position would reside with the National Biological Service and/ or the USGSat the GS-14/1Slevel. The Native American coordinator would facilitate and manage monitoring and researchrelated to tribal needs. The coordinator also would ensure integration of tribal concernswith all other monitoring and researchelements. The center's programs associatedwith long--term monitoring and researchwould be funded by power revenues and coordinated through tlle Reclamation budget process. However, professional staffing for the center would be provided by USGS,National Biological Service,and tile participating agenciesin the AMWG. The center would closely coordinate its activities with the Technical Work Group. The following specjlfic duties would be assigned to the Monitoring and ResearchCenter: Develop researchdesigns and proposals for implementing monitoring and research identified by the AMWG Manage all monitoring and researchon resourcesaffected by dam operations CONSIDERED IN DETAIL 37 .Manage and maintain the GCESinfoImation data base,monitoring and researchprograms, and other data sourcesas appropriate .Administer researchproposals through a competitive contract process,as appropriate .Coordinate, prepare, and distribute technical reports and documentation for review and as final products .Coordinate review of the monitoring and researchprogram with the independent review panel(s) .Prepare and forward technical management recommendations and annual reports, as specified in section 1804,to the AMWG 2. TechnicalWork Group: This work group would be comprised of technical representatives from Federal, State,and Tribal Governments, and other interests represented on the AMWG. The Technical Work Group would be appointed by the member agenciesor interests represented on the AMWG. The group would translate AMWG policy and goals into resource management objectives and establish criteria and standards for long-tenn monitoring and researchin responseto the GCPA. Thesewould then be used by the center in developing appropriate monitoring and research. The Technical Work Group would meet two to four times annually, as necessary. It is recommended that the Secretary or his designeeappoint the chair for the group on a 2-year rotating basis, giving consideration to the dominant or most pressing issues. The Technical Work Group would: .Develop criteria and standards for monitoring and researchprograms within 3 months of the formation of the group and provide periodic reviews and updates .Develop resource management questions for the design of monitoring and researchby the center .Provide infonnation as necessaryfor preparing annual resource reports and other reports as required for AMWG 3. IndependentReviewPanel(s):The Independent Review Panel(s)would be comprised of qualified individuals not otherwise participating in the 38 Chapter II Description of Alternati'll'es long-term monitoring and researchstudies. The review panel(s) would be established by the Secretaryof the illterior in consultation with the National Academy of Sciences,the tribes, and other AMWG entities. The review panel(s) would be responsible for periodically reviewing resource specific monitoring and researchprograms and for making recommendations to the AMWC; and the center regarding monitoring, priorities, integration, and management. Responsibilities of this review panel would include: .Annual review of the monitoring and research program .Technical AMWG advice as requested by the center or .Five-year review of monitoring and research protocols Dispute Resolution. Recommendationswould be formulated by the AMWG and forwarded to the Secretary'sdesignee. In the event that one or more entities do not support the recommendation, the views or concerns of the nonconcurring interests would accompany the recommendation for consideration in the decision. Endangered FishResearch. It has been determined through Endangered SpeciesAct consultation with FWS that the studies outlined below are necessaryand would be undertaken through the Adaptive Management Program. Endangered and other native fish in Grand Canyon are commonly thought to be limited by cold, clear water releasesfrom Glen Canyon Dam; large daily flow fluctuations; and non-native fish. However, uncertainty remains regarding the impacts of dam operations on fish. Although a considerable amount of researchon endangered fish has been conducted, there has been no opportunity to study the effects of low, steady flows in summer and fall combined with higher, steady spring flows-which FWS believes are critical to native fish in the Colorado River. Therefore, studies to include endangered fish researchflows would be coordinated with the long-term monitoring and researchunder the AMP. Thesestudies would be carried out in accordancewith the reasonableand prudent alternative developed by FWS in their biological opinion (seeattachment 4). A set of researchhypotheses and specific flows or experiments to test thesehypotheses would be developed. Concurrently I a risk assessmentof the flows would be conducted using existing literature and data and laboratory experiments. Results from the risk assessmentmay lead to reopening Endangered SpeciesAct consultation between Reclamation and FWS. When implemented, the researchflows would require as many as 5 low releaseyears (annual releaseat or near 8.23maf). Sincelow water releaseyears are expected to occur only about half the time, it is uncertain how many total years it would take to complete the researchprogram. However, it is likely that researchflows could be completed within 10 years. The ideal situation would call for uninterrupted researchoccurring during consecutive low releaseyears. Endangered fish researchflows would be between 8,000and 20,000cfs with a spring through fall pattern and monthly releasevolumes similar to the SeasonallyAdjusted Steady Flow Alternative. Results from the researchprogram would be monitored, and corrective action would be taken if adverse effects on endangered specieswere identified. Upon completion of the researchflows and analysis of the data, Reclamation would implement any necessarychangesin operating criteria to comply with the Endangered Species Act through the AMP . Monitoring and Protecting Cultural Resources The existenceand operation of Glen Canyon Dam has had an effect on the historic properties within the Colorado River corridor of Glen and Grand Canyons. Theseproperties include prehistoric and historic archeological sites, along with Native American traditional cultural places and sacred sites. Impacts are likely to occur to some of these historic properties regardless of the EIS alternative chosenfor implementation. ALTERNATIVES CONSIDERED IN DETAIL 39 The National Historic Preservation Act requires Federal agenciesto consider measureswhich would avoid or minimize loss of historic properties resulting from their actions. Due to the potential impact from any dam operation, Federal agency responsibilities for compliance with sections 110 and 106 of the National Historic Preservation Act will be required for each alternative considered in this document. The NPS will prepare agreementswith all of the affected tribes as required by the Native American Graves Protection and Repatriation Act (1990). Reclamation will develop agreementswith the Navajo Nation and Hualapai Tribe for the treatment of human remains that may be affected on their lands. Given the potential impacts of the existence and operation of Glen Canyon Dam, Reclamation and NPS have complied with documentation requirements in established regulations (36 Code of Federal Regulations 800). The Advisory Council on Historic Preservation, Arizona State Historic Preservation Officer, Reclamation, NPS, and Indian Tribes completed a programmatic agreement which ensuresthat both Reclamation's section 106responsibilities and NPS's section 110 responsibilities are satisfied (seeattachment 5). Administration, implementation, and refinement of the program design are detailed in the programmatic agreement and accompanying monitoring and historic preservation plans. Although infrequent floodflows may be considered beneficial to downstream resources, frequent or unscheduled floods, particularly those of long duration, are damaging to downstream resources. Under this common element, the frequency of unscheduled floodflows greater than 45,000cfs would be reduced to no more than 1 year in lOOyears as a long-term average. This would allow for the management of the habitat maintenance flows and beach/habitat-building flows described later in this section. Floodflow frequency of once in 100years is considered rare enough for resourceneeds,while not imposing unreasonablerequirements on Lake Powell water The programmatic agreement and accompanying plans will direct long-term monitoring, which includes continuing consultation, identification, inspection, analysis, evaluation, and remedial protection actions as necessaryto preserve the historic properties within Glen and Grand Canyons. Two separatemethods of reducing flood frequency have been identified. Thesemethods focus on reserving additional storage spacefor flood control. Potential remedial actions would be initiated in consultation with all of the Federal and State agenciesand Indian Tribes involved in the agreement. A range of actions are proposed, which are presented in the Monitoring and Remedial Action Plan in attachment 5. This ongoing consultation processand revision of preservation plans to maintain the integrity and stability of the properties should help to minimize the impacts of Glen Canyon Dam operations on cultural resources. Flood Frequency Reduction Measures storage. 1. Increasethe capacity of Lake Powell 0.75maf by raising the height of the four spillway gates4.5 feet to elevation 3704.5feet (currently, each gate is 40 feet wide and 52.2 feet high). This additional capacity would be nonviolable flood control spaceand would be used only in years when existing flood protection measureswere insufficient. Construction of this project would cost about $3 million. No permits under the Clean Water Act or Rivers and Harbors Act would be required to implement this element. 2. Olange releasesto target a maximum reservoir content of 23.3maf (1 maf less than the current active capacity) in the spring until the runoff peak has clearly passed. This additional spacewould allow improved management of late-seasonforecast errors, the primary causeof flood releasesthat exceed45,000cis. The amount 40 Chapter II Description of Alternatives of required vacant space in the spring months would eventually decrease as Upper Basin depletions increase. water surface to be dry and suitable for wildlife habitat or camping. Consequently, sandbars must be deposited and formed by discharges somewhat higher than the normal operating range. By implementing either flood protection mE!aSUre, additional reserved reservoir spacewould be available from January 1 through July 1 to store any additional unforecasted inflow. Beach/Habitat-Building Flows Under any EIS alternative, Grand Canyon simdbars that exist above the normal peak river stage would continue to erode, and backwater habitat within nonnal stage would tend to fill with sediment. Therefore, beach/habitat-building flows have been incorporated as an element common to all restricted fluctuating and steady flow alternatives. Beach/habitat-building flows would be scheduled high releasesof short duration designed to rebuild high elevation sandbars, deposit nutrients, restore backwater channels, and provide some of the dynamics of a natural system. Magnitude. Replenishing sandbars require:)both an available upstream sand supply and higller than normal flows to deposit sand at high elevalions. Sandbarsmust be several feet above the Table 11-6.-Example beach/habitalt-building Magnitudes would be at least 10,000cfs greater than the allowable peak discharge in a minimum releaseyear for a given alternative but not greater than 45,000cfs (seetable 11-6).Graphs presented by Leopold (1969)show that during the flood of 1948,flows of about 45,000-50,000cis were needed to initiate movement of substantial amounts of sand from the riverbed at LeesFerry .Burkham (1987)provided understanding of the flows necessary to degrade the riverbed and thus initiate movement of sand and coarser sedimentdepending on the amount of sand stored on the riverbed. Andrews (1991b)reported that 40,000-45,000-cisflows would be required in order to rebuild sandbars. Deposition rates calculated by Andrews are about 0.5 centimeter per day at 20,000cfs and about 8 centimeters per day at 40,000cfs. As part of the Adaptive Management Program, a test of a beach/habitat-building flow would be conducted prior to long-term implementation of this element to test the predictions made in peak discharges and monthly volumes Additional volume Beach/ Allowable peak discharge1 Alternative (cfs) habitat- flow Original volume (cfs) (acre-feet) building required (acre-feet per month) Reductions from other months (acre-feet per month) Restricted fluctuating flow High Moderate Modified low Interim low Steady flow Existing monthly volume Seasonally adjusted Year-round , Minimum release year (8.23 mat) 31,500 41,500 30,000 40,000 30,000 40,000 20,000 30,000 607 ,000 607 ,000 607 ,000 607 ,000 14,400 30,000 11 ,400 24,400 40,000 21 ,400 607 ,000 687 ,000 695,000 without a beach/Ihabitat-buildinQ flow. 627, 598, 598, 399, 000 000 000 000 288,000 572,000 200,000 57 ,000 54,300 54,300 36,300 26,200 52,000 18,200 ALTERNATIVES chapter IV .Scheduled flows exceeding powerplant capacity (33,200cis) may require legislation to implement. Ramp Rates. Releases would be increased at a maximum rate of 4,000 cis per hour and decreased at a maximum rate of 1,500 cfs per hour . Seasonand Duration. Beach/habitat-building flows could be scheduled in the spring (to coincide with the May /June peak in the natural hydrologic cycle) or in late summer when, due to local thunderstorms, tributaries are expected to supply large quantities of sediment (especially silt and clay) and nutrients. Initially, beach/habitatbuilding flows would be scheduled in early spring for a duration of 1 to 2 weeks. The duration would be long enough to substantially rebuild sandbars,considering the deposition rates estimated by Andrews (1991b)but would bE! constrained by the volume of water available. The exact seasonand duration would be determined through adaptive management. Releaseswould be curtailed if monitoring showed detrimental impacts to the ecosystem. A 1O-dayflow in March/ April is assumedwhen describing tile environmental consequencesin chapter IV . Water Year and Frequency. A recommendation for a beach/habitat-buildmg flow would come from the AMP I and such a flow would be scheduled as part of the Annual Operating Plan (developed in the summer for the following water year). Such flows would be scheduled only in years when the projected storage in Lake Powell on January 1 is less than 19 ma! (low reservclir condition). Scheduling beach/habitat-building flows during high reservoir conditions would be avoided becauseof the increased risk of unscheduled flows greater than powerplant capacity (seeattachment 6). A beach/habitat-building flow would be reC'ommended during years when sufficient quantities of sediment are available, but not following a year in which a large population of young humpback chub is produced (seechapter III, FISH). A frequency of 1 in 5 years (when the reservoir is low) was assumed for analyzing the environmenl:al consequencespresented in chapter N. Although theseflows would be expected to aggrade many CONSIDERED IN DETAIL 4' sandbars,these sandbars would be subject to natural erosion. How long thesenew deposits would last would be determined through monitoring. Monthly Release Volumes. Additional water would be scheduled in March/ April to support a beach/habitat-building flow. The additional releasevolumes needed in March/ April and the volume to be taken from other months would vary by alternative (seetable 11-6)and would be developed under the AOP . New f'opulation of Humpback Chub The Grand Canyon population of humpback chub useshabitats in both the Colorado River mainstem and the Little Colorado River (LCR). Conditions in the mainstem (principally water temperatures) are not conducive to humpback chub spawning or survival of eggs and young. An aggregation of humpback chub may now be reproducing in the mainstem near river mile 30 (Valdez and Ryel, in preparation); however, the numbers are small and evidence is inconclusive. The only confirmed successfulspawning habitat for that population is in the LCR, with individuals moving between that tributary and the mainstem. Since the only known humpback chub population in the Lower Colorado River Basin depends on the LCR for survival, a catastrophic event or a series of incidents that would reduce the viability of this spawning habitat could causethe loss of this population. This possibility will persist until or unless: 1. At least one more population is established in the mainstem or one or more of the tributaries below Glen Canyon Dam, and/ or 2. Mainstem water temperatures are sufficiently warmed to support spawning and recruitment Therefore, in consultation with FW5, NP5, Arizona Game and Fish Department (AGFD), and other land management entities such as the Havasupai Tribe, Reclamation would make every 42 Chapter II Description of Alternatives effort-through ftmding, facilitating, and technical support-to establish a new population of humpback chub within Grand Canyon. Su<:h efforts will necessitatea feasibility assessmentto report the natural distribution of the fish and the appropriateness of any ecosystemmanipulation being considered. Policy implications for the affected parties would be reviewed as part of consultation. Further Study of Selective Withdrawal Increasing mainstem water temperatures by means of selective withdrawal structures installed at Glen Canyon Dam offers the greatestpotential for creating new spawning populations of humpback chub and other native fish in Grcmd Canyon. Selectivewithdrawal directly addt'esses the thermal constraints on recruitment and growth of endangered and other native fish not addressedby operational changesalone, Prior to the dam, the water quality (including temperature) of the Colorado River was much different than today. Water temperatures varied seasonally,directly influenced by spring snowmelt and summer warming. Seasonalvariations in temperatures ranged from 32 degreesFahrenheit (Of)to 82 Of. Today, the cold water released from the dam varies only a few degrees year-round. Water releasedfrom Glen Canyon Dam to produce hydroelectricity is withdrawn from the cold depths of Lake Powell at an elevation of 3470feet-230 feet below the water surface when the reservoir is full (3700feet). The river water temperature at Lees Ferry, 16 miles downstream, is nearly constant year-round and averagesabout 46 oF. The nearly constant year-round releasetemperatures have resulted in conditions "not unlike those found in a well-balanced aquarium" (Carothers and Brown, 1991). Onlya few speciesof aquatic organisms thrive under these conditions, but those few speciesare abundant. They account for biomass production far exceeding that in more diverse and species-richenvironments. However, many native speciesrequire thermal changesat certain life-cycle stagesand cannot reproduce in theseconstant temperature conditions. Except for draining the reservoir, no operational method would prevent the continued releaseof cold water. Multilevel intake structures (a means of selectivewithdrawal) could be built at Glen Canyon Dam to provide seasonalvariation in water temperature. A structure would be attached to each of the eight existing 15-footdiameter penstocks to selectively withdraw warmer water from upper levels of the reservoir. The structure would include a series of vertically stacked gatesto encloseeachpenstock intake. Different configurations of gates could be opened to mix water of varying temperatures. Gate control would be automated, and adjustments would be made in relation to reservoir elevation, turbine operation, and water temperature. Preliminary studies (ferrari, 1988)indicated that multilevel intake structures on each of the eight existing penstocks could increase the downstream river temperature 5 to 18 opabove present conditions (river temperatures between 54 and 69 of from May to October). This temperature increaseis still 7 to 16 of cooler than predam conditions during the summer months and is the warmest possible temperature (not necessarily the optimum temperature) for native fish or other resources. Withdrawal levels could be seasonally adjusted to meet ecological objectives, although this would involve complex factors. Releasingwanner water during the spring and summer months could possibly raise river temperatures in some downstream reachesto a level that would support spawning by humpback chub and other native fish (Bureau of Reclamation, 1994a). However, increasing the temperature of river water may also create problems for species currently inhabiting the Colorado River below Glen Canyon Dam. The cold river temperatures may act as a barrier to the upstream establishment of non-native predatory fish from Lake Mead. Higher water temperatures may encourage the upstream migration of predatory fish, further ALTERNATIVES endangering humpback chub and other native fish through increased predation or competi,tion. The cost of installing multilevel intake structures at Glen Canyon Dam has been estimated at $60 million. This estimate is based on actual costs for similar structures at Flaming Gorge Dam. Reclamation would implement a selective withdrawal program and determine feasibility by aggressively pursuing and supporting researchon the effects of multilevel intake structures at j::;len Canyon Dam and would use the researchresults to make a firm decision on construction. FW5, in consultation with AGFD, would be responsible for recommending to Reclamation whether or not selective withdrawal should be implemented at Glen Canyon Dam. Reclamation would be responsible for design, NEPA compliance, permits, construction, operation, and maintenance. CONSIDERED IN DETAIL 43 to changesin frequency and load, provided an additional 100megawatts of power. As indicated by records for the USGSgauging station below the dam, the short-duration change in power generation caused a 4,340-cfsincreasein 30 minutes (a stage increaseof 1.6 feet) during a scheduled upramp. The change was undetectable at the Lees Ferry gauging station, where the maximum 30-minute river stage increasewas about 3 inches. Mitigation All environmental mitigation has been incorporated into the alternatives identified for detailed analysis; no other mitigation elements are presently included. Future measuresthat could be considered as mitigation for the loss of power are described below. Power Adjustments Emergency Exception Criteria Normal operations described under any alternative would be altered temporarily to respond to emergencies. NERC has established guidelines for the emergency operations of interconnected power systems. A number of these guidelines apply to Glen Canyon Dam operations (see attachment 6). Thesechangesin operations would be of short duration (usually less than 4 hours) and would be the result of emergenciesat tl1.edam or within the interconnected electrical system. Examples of system emergenciesinclude: .Insufficient generating capacity .Transmission system: overload, voltage control, and frequency .System restoration .Humanitarian situations (search and reSC"Lle) A specific example of implementation of emergency exception criteria is the responseto a magnitude 6.6 earthquake in the vicinity of Los Angeles on January 17,1994. Damage to the Los Angeles transmission system caused a sequenceof power surges and interruptions across most of the Western States. Glen Canyon Dcun, responding more quickly than the thermal plants The Grand Canyon Protection Act directs the Secretaryof Energy to consult with other agencies and the public to identify economically and technically feasible methods of replacing any power generation that is lost through changed operations at Glen Canyon Dam. The Secretaryof Energy must present a report of the findings and draft implementing legislation, if necessary, not later than 2 years after adoption of new operating criteria (ROD). That processshould result in acquisition of permanent replacement power. The manner in which Western markets energy and capacity from Glen Canyon Dam would differ for each alternative (seechapter IV , HYDROPOWER). Somebasic options that exist to replace lost power are listed below: .Purchase .Increase .Change .Build power from alternate sources energy conservation transmission system capability new generating facilities Someof these options may take 5 to 7 years to fully implement. Continuing use of the financial exception criteria allowed under interim operations is a potential short-term (5- to 7-year) mitigation measure. Thesefinancial exception 44 Chapter II Description of Alternativ'es criteria relate to Western's ability to demonstrate that unused generation capacity is available to meet firm (guaranteed) contract commitments at times when nonfirm (nonguaranteed) themlal energy is being used to meet those commitnlents. Under interim operating criteria, operational limits can be exceededfor financial reasonsup to 3 percent of the time (22 hours) in any conSE'cutive 30-day period, with no carryover. Actually exceeding operating criteria for financial reasonsis unlikely. While Western's customers have benefited from having financial exception criteria available during interim operations, Western has not had to exceedoperating criteria for financial reasons. Environmental resourcessuch as fish and wildlife would be protected by avoiding use of finarlcial exception criteria during specific periods of vulnerability (i.e., during breeding and nestjing). If operations to avoid purchases of high-cost power were detennined to be occurring too frequently or at inappropriate times, the Secretary of the Interior could suspend those operations and review the matter, making any necessarychanges. If financial exception criteria are part of the selectedalternative, the availability of capacity and energy would be maintained, and costs to customers would be expected to increaseat a slower rate. Permits and Regulatory Approval~; No permits or regulatory approvals would be immediately necessaryto implement any of the alternatives described in this document. Depending on the results of long-term monitoring and researchunder adaptive management, permits under sections 402 and 404 of the Clean Water Act may be needed in the future. Implementing multilevel intake structures would require additional NEPA compliance, congressional authorization, and permits. A permit from the U.S. Army Corps of Engineers (Corps) under section 10 of the Rivers and Harbors Act and possibly section 404 of the Clean Water Act might be required, depending on the structure design and the amount of fill material used in construction. The Corps would make a decision on issuing a permit only after a public notice and public interest review. Supplementary NEP A documentation might be required, including a section 4O4(b)(1) alternatives analysis, if fill material is involved. ALTE~~NATIVES CONSIDERED AND ELIMINATED FROM DETAILED STUDY During the scoping process,including fonnulation of alternatives, various alternatives and concepts were considered. Somewere detennined not reasonablefor detailed analysis in this EIS, as explained in this section. Run-c,f-the-River Alternative Many comments received during the scoping processexpresseda desire that the dam be operated to mimic predam conditions in Grand Canyon. The natural predam conditions of the Colorado River were characterized by dramatic seasonal fluctuations in flow, sediment, and temperature. Flows typically ranged from less than 3,000cfs in late summer, fall, and winter to over 80,000cfs in spring. The river usually was turbid, and peak sediment loads were carried by spring and late summer floods. Water temperatures ranged from near freezing in winter to more than 80 oFin late summer. Steepsediment deposits were built annually during the sediment-laden spring floods. These deposits later tended to erode following the return to lower flows. Native vegetation existed in the old high water zone above the level of annual scour but was sparseto nonexistent on deposits influenced by seasonalfluctuations. Native plants and animals were well-adapted to this system of strong seasonalfluctuations. Non-native specieswere introduced to Grand Canvon prior to dam construction. Warmwater ALTERNATIVES C:ONSIDERED non-native fish may have been introduced as early as the late 1800's. Tamarisk, a non-native plant that now dominates riparian vegetation, also was present predam. However, tamarisk and other vegetation were uncommon near the river where floodflows annually restructured sediment deposits. Lake Powe1l-formed behind the dam-now inundates all but 16 miles of Glen Canyon. Glen Canyon Dam has replaced seasonalflow fluctuations with daily fluctuations that can range from 1,000cfs to 31,500cis. Sediment is supplied only by downstream tributaries, and water temperatures are nearly constant year-roundaveraging a coo146Of. Speciesand commwuties that were rare or nonexistent before the danl are nowabundant: Cladophora,Gammarus,trout, bald eagles,peregrine falcons, and riparian vegetation and its wildlife in the new high water zone. Native and some speciesof non-native fish have declined. The EIS team responded to scoping commer\ts by formulating the Run-of-the-River Alternative. The objective of this alternative was to mimic, as nearly as possible, the natural predam conditions. This would be achieved through operational changes,sediment augmentation, and selective withdrawal. The historic pattern of high spring flows and low fall and winter flows would be achieved by matching releasesfrom the dam with inflow's to Lake Powell. Spring releaseswould be limited to 48,000cfs (combined capacity of powerplan1:and outlet works), unless the spillway could be tlsed; then releaseswould equal inflow. Under th,~se operating principles and based on predam inflows, flows in May could exceed45,000cis about 40 percent of the time, and June flows could equal or exceed45,000cfs about 60 percent of the time. Low steady inflows and the resulting releasesas low as 1,000cis would occur during late summer and winter . The frequency of high flows needed to simulate predam conditions would scour most of the sediment along the river corridor in Grand Canyon. Tributaries below Glen Canyon Dam cannot supply large amounts of sediment on an AND ELIMINATED FROM DETAILED STUDY 45 annual basis, so the sediment would not be replaced naturally. The scouring of sediment from Grand Canyon would damage environmental, recreational, and cultural resourcesin the canyon. Postdam sediment losseshave been reduced by regulating the frequency of high-flow releasesfrom Glen Canyon Dam. For thesereasons,the Run-of-the-River Alternative would require massive sediment augmentation (1 to 10 million tons annually) in order to replenish sediments transported out of the system. Several technical issuesconcerning sediment augmentation were considered, such as sediment quantity and size (sand, silt, clay), source, and type of delivery system. Potential sediment delivery systems considered included a barge and truck operation and a sediment slurry pipeline to LeesFerry .Sediment would be dredged from a remote source and then continually transported and deposited in the Colorado River. The river would then carry the sediment downstream for deposit in eddies and main channel pools. Any sediment source would have to be renewable in order to indefinitely sustain the sandbars in Grand Canyon under the suggestedwater release regime. Therefore, sediment deltas of Lakes Powell and Mead were considered as possible sourcesfor sediment augmentation. The areasof Lake Powell considered as possible sourcesof sediment were the upstream delta along the mainstem (Cataract Canyon), the SanJuan River, and the Dirty Devil River . To more closely approximate predam seasonal patterns, some type of temperature modification was needed in the Run-of-the-River Alternative. To increaseriver water temperature, multilevel intake structures would be placed on the dam penstocks to draw warmer water from near the reservoir surface for releasedownstream. This approach would raise downstream water temperatures 5 to 18 of above current conditions during spring and summer. 46 Chapter II Description of Alternatives Evaluation of Alternative Evaluation of the Run-of-the-River Alternative focused primarily on flows/ sediment, environmental concerns, and compact and treaty requirements. Flows/Sediment. Sediment augmentation would be required to maintain a sediment balance in the river system when high releasesare frequent. Without sediment augmentation, the Run-of-theRiver Alternative would eventually erode most of the sediment from Grand Canyon-damaging or destroying the canyon's environmental, recreational, and cultural resources. A slurry pipeline would likely take at least 15 to 20 years to implement. This timeframe includes necessaryresearchand data collection, NEPA compliance, design, Federal permitting, congressional authorization, land purchase/ easements,implementing mitigation procedures, and construction. The cost of building a slurry pipeline was estimated at $400,000per mile. For a completed pipeline to the river deltas of the SanJuan, Dirty Devil, or mainstem (Cataract Canyon), costs were estimated at $50,$80, and $85million, respectively. Operational costs could be $10 million per year. Other means of sediment transport (barging and trucking) would be more expensive than a slurry pipeline. EnvironmentalConcerns. Any overland route for sediment transport to the Colorado River below Glen Canyon Dam would cross more than 100miles of high-desert canyon landscape to reach the nearest renewable source of sediment. Construction would causeadverse environmental impacts to fragile resources. Cultural and archeological impacts on tribal lands would be significant and would require additional compliance with the National Historic Preservation Act and other cultural resourcelegislation. A submerged pipeline in Lake Powell would affect recreation during construction and would require an overland route to Lees Ferry . Sediment would be augmented just below Lees Ferry so as not to increaseturbidity in the Glen Canyon reach, which would adversely affect the trout fishery .The high spring flows would scour most of the sand deposits from the river upstream from LeesFerry . Low flows during the winter spawning season would reduce habitat for rainbow trout, and extended low flows at any time would adversely affect the Cladophora-Gammarus segment of the aquatic food chain throughout Grand Canyon. Important unanswered questions exist concerning the types and amounts of contaminants that may be found in some of the sediment sources identified above and their effects on resourcesif added to the aquatic system below the dam. Lastly, modification of water temperature in the Colorado River below Glen Canyon Dam presents both opportunities for enhanced management of some resourcesand risks associatedwith unknown responses. Higher water temperature may benefit humpback chub and other native fish but also may improve habitat conditions for competing non-native speciesand permit an invasion of striped bass from Lake Mead. The current water temperature is below the optimum for rainbow trout growth, but it is unknown how the alga, Cladophora,and the shrimp-like amphipod, Gammarus-which trout depend on-would respond to higher temperatures. Compact and TreatyRequirements. Releasesfrom Glen Canyon Dam under this alternative would not meet the annual water releasepattern requirements of the "Law of the River,1Iespecially the Colorado River Compact, the Colorado River Basin Project Act, the Long-Range Operating Criteria, and the treaty with Mexico. Therefore, this alternative would violate existing laws. Under the Run-of-the-River Alternative, releases from the dam could only match high spring inflows when Lake Powell was full and the spillways could be used. Becauseof the way the dam is designed, the spillways cannot be used unless the reservoir is nearly full. Without using the spillways, releasescannot exceed48,200cis. Inflows to Lake Powell in June typically exceed 45,000cfs, and the excesswould have to be stored ALTERNATIVES CONSIDERED in the reservoir. Lake Powell could be expected to fill and spill at an average frequency of lout of every 4 years under this alternative. Conclusions Restricting releasesto reservoir inflow during prolonged drought periods would prevent Glen Canyon Dam from meeting its statutory purposes. Requirements under the Colorado River Compact and treaty with Mexico could not be met. The natural environment along the river corridor has been forever altered with the introduction of non-native speciesand the construction of Glen Canyon Dam. Under this alternative, the river would be converted into a system very different from existing conditions. Resourcesassociated with the aquatic food chain would be disruptedCladOPhora, Gammarus,aquatic insects, trout, swallows, bats, bald eagles,and peregrine falcons. Most of these impacts would be associatedwith the massive addition of sediment needed to prevent the net loss of sediment and sedimentdependent resources. Sediment augmentation would causesignificant impacts to water quality-most notably increased turbidity .The chemistry of various sediment sourcesand corresponding impacts to Grand Canyon water quality and aquatic resourcesare unknown. The need for sediment augmentation has not been demonstrated under alternatives with reduced daily flow fluctuations. For example, sandbars still exist in Grand Canyon and appear to be stable under the interim operating criteria. A sediment augmentation delivery system would causeenvironmental damage along the route during construction and operation and would be expensive to build and maintain. Somepeople consider sediment augmentation the ultimate solution for Grand Canyon becausea portion of the natural sediment supply could be restored and the life of Lake Powell could be extended (there would be a corresponding decreasein the life of Lake Mead). However, others doubt the wisdom of using a major AND ELIMINATED FROM DETAILED STUDY 47 construction project to solve the environmental problems of a previous construction project. ill either case,sediment augmentation would take a long time to implement-perhaps 15 to 20 yearsand a plan to operate Glen Canyon Dam would still be needed in the interim. Sediment augmentation would require data collection; researchand analysis; an EIS addressing alternate sediment sourcesand delivery systems; congressional authorization and funding; Federal, State,and tribal permits; land purchases and easements;and construction. A project of this magnitude is beyond the scope of dam operations and would be better addressedin a separate NEPA document. Without sediment augmentation, the volumes of clear-water releasesdefined in this alternative would eventually eliminate most sediment deposits along the Colorado River in Glen and Grand Canyons. This loss would affect recreational opportunities, cultural resources, backwaters, marshes, and riparian vegetation. Mitigating theseimpacts by reducing seasonally high flows createsa flow regime incorporated into the SeasonallyAdjusted Steady Flow Alternative. In conclusion, the EIS team recognized the desire of some to return riverflows to a more historic (predam) pattern. A return to a seasonal streamflow pattern emulating the magnitude of historic spring flows would, however, be very destructive to downstream resourcesunless a large-scale,long-term sediment augmentation program were added. This program would have significant impacts-all of which are not yet known. If sediment augmentation is desired in the future, this action should be the subject of a separateEIS. The Run-of-the-River Alternative was therefore eliminated from further consideration in this document. Historic Pattern Alternative Comments received during the scoping process indicated that many respondents wished to alter dam releasesto return to predam flow patterns. The Historic Pattern Alternative attempted to 48 Chapter II Description of Alternatives follow predam water flow patterns more closely while still managing flows within current powerplant capacity. This alternative was a modification of the Run-of-the-River Alternative. Minimum annual releasesof 8.23maf would be met, and all scheduled releaseswould be within powerplant capacity.Flows would be steady each month while following a seasonalpattern of higher spring/ summer and lower fall/ winter flows. Maximum flows would be limited to 33,200cfs, and minimum flows would be determined by the forecasted annual releaseremaining after high spring/ summer flows were allocated. The Historic Pattern Alternative also included a sediment slurry pipeline and multilevel intake structures for the reasonsdiscussedunder the Run-of-the-River Alternative. Evaluation of Alternative Although the high flows under the Historic Pattern Alternative would be of less magnitude and perhaps of shorter duration than under the Run-of-the-River Alternative, sediment augmentation would still be required to prevent long-term adverse impacts to downstream resources. Without sediment augmentation, the sediment resourcesalong the Colorado River would be more subject to erosion under the Historic Pattern Alternative than under any of the steady or fluctuating flow alternatives, including the No Action Alternative. The Historic Pattern Alternative was not expected to conflict with the "Law of the River ." Conclusions This alternative was eliminated from detailed study for most of the reasonsgiven for the Run-of-the-River Alternative. Specifically, sediment augmentation would causean increase in turbidity and disrupt the aquatic food chain below LeesFerry, and high and low flows would adversely affect resourcesabove Lees Ferry . Other potentially adverse impacts are unknown. Sediment augmentation would require 15 to 20 years to implement, and a plan to operate the dam in the interim still would be needed. Without sediment augmentation, the flows under this alternative would causemore erosion to sediment deposits below Glen Canyon Dam than other steady or fluctuating flow alternatives, including no action operations. Mitigating these impacts by reducing seasonallyhigh flows creates a flow regime incorporated into the Seasonally Adjusted Steady Flow Alternative. For these reasons,the Historic Pattern Alternative was eliminated from further consideration in this document. Reregulated Flow Alternative The EIS team responded to scoping comments requesting full use of Glen Canyon Dam Powerplant's generating capacity by developing the Reregulated Flow Alternative. The objective of this alternative was to initiate operational changesto fully use the powerplant's generating capacity (flows of 33,200cis) while reducing, to the extent possible, existing adverse impacts to downstream resourcesby constructing a reregulation dam. Releasesfrom Glen Canyon Dam under this alternative would be similar to those described under the No Action Alternative, with maximum flows increased to 33,200cis and minimum flows of no less than 1,000cis year-round. Annual and monthly releaseswould be based on the following factors: meeting water deliveries to the Lower Basin States,maintaining conservation storage in Lake Powell, avoiding anticipated spills, balancing storagebetween Lakes Powell and Mead, and seasonalpower demand patterns. Daily releaseswould be patterned to meet power demand within the limits of the required monthly releasevolume. Ramp rates would be constrained only by physical limitations of the powerplant. An increasein the magnitude of daily fluctuations would causeadditional impacts to downstream resourcesat levels above those documented for the No Action Alternative at 31,500cfs. To reduce new and existing impacts, a reregulation dam would be constructed approximately onehalf mile upstream of the gauge at Lees Ferry to ALTERNATIVES CONSIDERED provide steady flows downstream of the reregulation dam. The top of the dam would extend about 20 feet above the downstream water surface. Flows below the reregulation dam would follow a daily pattern of steady flows but would be adjusted daily and monthly. Minimum steady flows would be about 8,000cfs, and maximums would be dictated by the monthly and daily volume to be released. Downstream of the reregulation dam, changesin river stagebetween weekdays and weekend days would likely occur becausethe average daily releasemay be lower on a weekend day than on a weekday; however, the transition between flows would be gradual. Effects of ramping would be virtually unnoticeable below the reregulation dam. Between Glen Canyon Dam and the reregulation dam (Glen Canyon reach), the river would be converted to a fluctuating reservoir storing water during the day for releaselater at night. Minimum water elevation at the upstream face of the reregulating dam would increase4 feet, and the water level would fluctuate up to 17 feet daily. This fluctuating reservoir would act as the damper to accept the fluctuating releasesof Glen Canyon Dam and would convert them to nearly steady releasesbelow the reregulation dam. Evaluation of Alternative The Reregulated Flow Alternative would provide complete flexibility in power operations at Glen Canyon Dam while providing a mechanism for protecting physical and biological resources downstream from Lees Ferry (260miles). However, the river reach between Glen Canyon Dam and the reregulation dam (15 miles) would be altered by increased fluctuations. Flowsand Sediment Resources. Steady flows below a reregulation dam would virtually eliminate rapid changesin flows and would reduce the capability of the river to transport sediment. Under these conditions, natural input of sediments from tributaries (Paria and Little Colorado Rivers) would allow sediment to accumulate in the river corridor at relatively low elevations. AND ELIMINATED FROM DETAILED STUDY 49 Fluctuations in flow above the reregulation dam would be considerably higher than under historic operations. In the Glen Canyon reach, sediment exposed to thesehigher releasefluctuations would continue to be lost. Further, becauseriver stages would be from 4 feet to 20 feet higher in elevation, sediment deposited above historic normal operational ranges would be subject to fluctuations and loss. Becausethis reach lacks a source of sediment input, these operations eventually would eliminate most of the sand and finegrained sediment from sandbars and banks in the Glen Canyon reach. Riparian and TerrestrialResources. Stabilized flows downstream from the reregulation dam would promote further development of riparian resourceson stabilized sandbars in Grand Canyon. Terrestrial wildlife linked to riparian resourceswould benefit from the stabilized riparian corridor . The AGFD categorizesthe riparian habitat found in the Glen Canyon reach as ResourceCategory I habitat (of the highest value to wildlife) and recommends that all potential lossesof existing habitat values be prevented. Riparian habitat associatedwith perennial streams in Arizona is considered unique and irreplaceable on a statewide basis. The loss of sandbars through inundation in the reach above the reregulation dam would result in the direct loss of riparian resources. Riparian vegetation near the reregulation dam would be immediately inundated, and virtually all riparian resourcesin this reach would be eliminated as sandbars eroded due to rapid fluctuations in water level. Aquatic Resources. The placement of the reregulation dam would not directly disturb habitat used by the endangered humpback chub. Reregulated flow to the river reachesbelow the LCR could stabilize backwaters and promote warming that would provide rearing habitat for larval or juvenile chub. River temperatures would remain cold, thus limiting the movement of larval humpback chub out of the LCR. Stabilized flows would not guarantee that backwaters would be 50 Chapter II Description of Alternatives maintained through time. As backwaters developed into riparian areasover time, they would eventually lose their value as fish-rearing habitat. Reregulated flows would not create additional spawning habitat for humpback chub in the main channel nor would they encourage establishment of new spawning populations in tributaries. The aquatic system above the reregulation dam would be altered. Accelerated sandbar erosion causedby increased fluctuations-<:ombined with lake-like conditions in the reach above the reregulation dam-would favor planktonic algal forms, which could decreasewater clarity . Changesin water clarity , combined with wL"ekend minimum stages,could reduce the zone occupied by the alga, Cladophora.Reduced Cladophora and/ or reductions in its transport out of the reregulating reservoir could result in the entire food chain being restructured throughout the river in Grand Canyon. Restructuring the food chain above and below the reregulation dam would affect the existing trout fishery .This resource would change from a "stream" to a "lake" fishery above the reregulation structure, with very different management needs and expectations. Natural reproduction would be reduced. Impacts to Cladophoraand the algal/ invertebrate community associatedwith it would reduce the probability of maintaining a blue ribbon trout fishery within the Glen Canyon reach. Seechapter III for more information concerning fish needs. Cultural Resources.More than 40 cultural sites have been documented within the Glen Canyon reach. In addition, two locations currently under evaluation could be Hopi spiritual sites. Greater fluctuations would increasethe erosion affecting these sites. Someimpacts to cultural sites could be mitigated by collecting data during excavation, but impacts to others cannot be mitigated because of their complexity or traditional nature. If these sites are determined to be sacred to Native Americans, by their very nature they cannot be moved, transferred, or excavated. The reregulation dam would be built within the historic district of Glen Canyon National Recreation Area. Increasedbeach erosion and the inundation of additional areasof the Glen Canyon reach would affect the cultural heritage associated with the last remaining miles of Glen Canyon. This National Register Historic District contains one individually listed property, the Charles H. SpencerSteamboat,downstream from the potential damsite. Activities that may impact sites listed on the National RegisterofHistoric Places, especially those that would alter the setting that justified registration, are considered adverse effects. Recreation. White-water boating would not be inhibited by the near-steady flows below a reregulation dam; steady flows above 8,000cfs are considered desirable conditions. However, recreation above a reregulation dam would change dramatically. The Glen Canyon reach typically is used by day rafters and fishermen. Under the Reregulated Flow Alternative, accessto this reach was an unresolved issue. However, the type of accessand the recreational fishery undoubtedly would change. Safety would be a major concern for those using the reregulating reservoir. A policy decision on safety would be required from the NPS. If boating were permitted, a ramp would provide access upstream from the reregulation dam. Sustained high flows above powerplant capacity would overtop the reregulation dam spillway. Therefore, boat launching or operation near the reregulation dam under high flow conditions would be dangerous. Recreationaluse of this segment of Glen Canyon would likely be prevented for extended periods. Such closures would have exceeded 24 months as a result of the 1983-86high flows. Economics. Construction cost of a reregulating dam is estimated at $60 to $110million. A reregulation dam would permit the powerplant to operate at maximum capacity whenever enough water was available (Lake Powell elevation greater than 3641feet) and electrical demand was high. Estimates show that, under these criteria, the powerplant would operate at maximum capacity about 25 days per year (7 percent of the time) for less than 4 hours at a time. ALTERNATIVES CONSIDERED Existing Legislation. The Grand Canyon Protection Act directs the Secretary to operate Glen Canyon Dam ...and exerciseother authorities under existing law in such a manner as to protect, mitigate adverse impacts to, and improve the valuesfor which Grand Canyon National Park and Glen Canyon National Recreation Area were established. .. The 1916act establishing the National Park Service defined those purposes generally as being ...to conserve the scenery and the natural and historic objects and the wildlife therein and to provide for the enjoyment of the same in such manner and by such means as wiIlleave AND ELIMINATED FROM DETAILED STUDY 51 NEPA compliance, design, Federal permitting, consultation with the Arizona StateHistoric Preservation Officer and the Advisory Council on Historic Preservation, excavation of cultural sites, consultation under the Endangered SpeciesAct, congressional authorization, implementation of mitigation procedures, and construction. Construction impacts would be irreversible. Conclusions Construction of a reregulation dam in Glen Canyon National Recreation Area would require a change in existing law. While most downstream resources would experience improved conditions over the No Action Alternative, resources in the Glen Canyon reach would experience negative impacts under the Reregulated Flow Alternative. them unimpaired for the enjoyment of .future generations. Section3 of the Colorado River StorageProject Act (1956)states: "It is the intention of Congressthat no dam or reservoir constructed under the authorization of this Act shall be within any national park or monument," Congressdeclared in 1970and reemphasized in 1978that all National Park Service areas,including Glen Canyon National RecreationalArea, are interrelated and part of one national park system, Public Acceptance. Planning and constructing a reregulating dam would be guided by the Federal Government's Economicand Environmental Principlesand Guidelinesfor Waterand RelatedLand Resources ImplementationStudies(Water Resources Council, 1983)that govern all implementation studies. Theseprinciples and guidelines apply the four tests of completeness,effectiveness, efficiency, and acceptability to all project alternatives that are considered reasonable. Although some segments of the public would find a reregulation dam acceptable,diverse groups have expressedstrong opposition to placing a dam in the last remaining reach of the Colorado River in Glen Canyon. Administrative Clearance. A reregulation dam would take at least 5 to 15 years to construct after the ROD. This estimate includes such activities as researchand data collection, additional Resourcesin the Glen Canyon reach that would be adversely impacted include sandbars, riparian vegetation and associatedterrestrial wildlife, Cladophoraand associatedalgal and invertebrate communities, a regionally important trout fishery , recreation potential, Native American cultural and sacredsites, and archeological and historic areas/sites. Impacts to the Cladophora-based aquatic food chain could have effects throughout Grand Canyon. Most of theseimpacts would result from the greater frequency and magnitude of fluctuations behind the reregulating dam constructed to protect downstream resourcesfrom those same fluctuations. A reregulating dam would require $60 to $110million to construct and 5 to 15 years to implement without any opposition. Impacts in the Glen Canyon reach could be mitigated by reducing the frequency and magnitude of daily river fluctuations. However, without maximum fluctuations, there would be no need for a reregulation dam. Reduced fluctuations and elimination of the reregulation dam create conditions identical to those evaluated under other fluctuating flow alternatives, including no action. In summary , predicted impacts to resources, required changes in existing law, acceptability 52 Chapter II Description of Alternatives problems under the principles and guidelines, and the scrutiny required under section 404 of the Clean Water Act combine to render this alternative unreasonable at this time. Concepts Study Eliminated From Detail,~d Somecomments received during the scoping processsuggestedconcepts that were not formulated into detailed alternatives. A short discussion of those conceptsfollows. Although sand pumping and beach protection were eliminated from detailed study in this EIS, both could be considered during long-term monitoring under adaptive management. Sand Pumping Pumping sand from the river channel to rebuild eroded sandbars on a systemwide basis currently is not necessaryand may not be in the future. Also, such an operation is not compatible with NPS management policies for reasonsof visitor use and potential wilderness designation. In the future, NPS might decide to consider sand pumping on a site-specific basis, if needed. If so, NPS would be responsible for obtaining any required permits and NEPA compliance. Description of Concept. Sandbarscould be built by pumping sand from the river channel to a nearby site during low or normal flow. This could be done at specific locations identified by NPS to protect the base of slopes containing prehistoric or historic resourcesor to enhancesites for recreational purposes. This action could be taken only where channel sand deposits are available. A source of river channel sand nearest each selectedsite would be located. Small portable pumping equipment would be transported downstream by raft, and a temporary, small barrier or berm to contain the pumped sand would be constructed on a site. A sand-water mixture would be pumped into the contained area. Water would then drain back to the river through the barrier or underlying sandbar, and the pumped sand would remain. The barrier would be removed at the end of the pumping operation. The newly deposited sand would form a more natural slope after being reworked by wind and water. The sand pumping operation would most likely take place during January or February when recreation use is lowest. This concept would be flexible becauseboth the number of beaches targeted and the frequency of sand pumping could be varied, assuming channel-stored sand is available. Cost estimatesfor pumping river bottom sand range from $30,000to $150,000per year. Evaluation of Concept. Grand Canyon sandbars are scarcestin narrow reaches. However, sand pumping in these reacheswould be difficult becauseof strong river currents and may not be possible due to scarcity of riverbed sand. If long-term net erosion of low elevation sandbars were to occur, it would likely be due to a shortage of sand in the river channel, and sand pumping would not be a feasible method of sandbar restoration becauseof lack of supply. Results from the long-term monitoring program may identify sites where sand pumping should be considered. The feasibility of sand pumping would have to be evaluated on a case-by-case basis. Beachmanagement by sand pumping would be a minor project involving only a few beachesbut would require a permit from the Corps under section 10 of the Rivers and Harbors Act and section 404 of the Clean Water Act. A formal application must be submitted to the Corps by the agency proposing such work. A separate NEPA document also would be required, which would establish a site-specific project purpose and include a section 404(b)(1)analysis to identify the least-damaging practicable alternative in terms of cost, logistics, and available technology . Beach Protection Beachprotection on a systemwide basis is not currently necessaryand likely will not be needed. NPS will determine if beach protection at certain ALTERNATIVES CONSIDERED sites is feasible and appropriate and, if so, obtain any required permits and NEPA compliance. Description of Concept. Rock jetties or riprap lining (layer of rock) could be placed to protect or rehabilitate existing sandbars. A jetty would be used to divert high velocity flow away from a sandbar and create a small eddy on the downstream side of the structure. Riprap lining of the channel bank would help prevent sandbar erosion by high water velocities and recreational activity. Either of theseprotection measures would work well in conjunction with a sand pumping operation. All structures would consist of native rock and vegetation and would be designed to blend with the natural environment. No steel, wires, or concrete would be used. Rock would be obtained from nearby tributary debris fans and not from talus slopes or canyon walls. All rock would be placed by hand or with small mechanized equipment. Becauseof logistical difficulties, only sites that are within a few hundred yards of a debris fan could be protected this way. Any necessaryequipment and personnel would be transported by raft from LeesFerry .These sh"uctureswould require a maintenance program with accessby raft. Cost estimates for beach protection have not been determined. Evaluation of Concept. Grand Canyon sandbars are scarcestin narrow reaches. However, beach protection in these reacheswould be difficult due to strong river currents and may not be possible due to the scarcity of nearby debris fans (source of rock). Due to the unique logistical problems in Grand Canyon, sandbars could be protected with rip rap only above the low river stage. High water velocities could scour the sandbar below the riprap and causethe entire beachfaceto fail. Sandbar erosion due to a rapid drop in river stage during fluctuating flows has been documented (Beusand A very , 1992). However, rip rap would not be effective against this type of erosion. Results from the long-term monitoring program may identify sites where beach protection should AND ELIMINATED FROM DETAILED STUDY 53 be considered. The feasibility of beach protection would have to be evaluated on a case-by-case basis. Beachmanagement by bank protection would be a minor project involving only a few beachesbut would require a permit from the Corps under section 10 of the Rivers and Harbors Act and section 404 of the Clean Water Act. A formal application must be submitted to the Corps by the agency proposing such work. A separate NEPA document would be required that would establish a site-specific project purpose and include a section 404(b)(1)analysis to identify the least damaging practicable alternative in terms of cost, logistics, and available technology . Remove Glen Canyon Dam Removal of the dam is considered unreasonable in viewof: .The many establishedbeneficial uses that it now serves .The legal framework ("Law of the River") that now exists, including the Grand Canyon Protection Act of 1992 .The investment that the dam represents .The adverse social, economic, and other impacts to the existing human environment that would result from its removal Most importantly, Reclamation was directed by the Secretaryto evaluate alternative operations for Glen Canyon Dam. The concept of removal is an alternative to operating the dam and, thus, does not address dam operations. Since dam removal is outside the scopeof dam operations, it violates the Secretary'scharge to Reclamation. As a result, this concept was eliminated from further study. Move Hydropower Peaking From Glen Canyon Dam to Hoover Dam Both Glen Canyon and Hoover Powerplants already are operated as hydroelectric power peaking plants. No excesscapacity or energy is available at Hoover to substitute for reduced 54 Chapter II Description of Alternatives peaking at Glen Canyon, as all of the capacity and energy at Hoover is allocated by existing contracts. It has been suggestedthat more units could be added at Hoover to increasecapacity and to supply the peaking that now occurs at Glen Canyon. However, Hoover modification is already being considered by the Arizona Power Authority and the Colorado River Commission of Nevada to augment their peaking needs. Therefore, power produced at Hoover may not be available for use in the area served by Glen Canyon power. It may be possible in the future to apply additional computer tedmology on a regional or system basis to refine and enhance the efficiency of the power network, including Glen Canyon and Hoover Powerplants. This could facilitate some peaking and spinning reserve adjustments between the two projects. SUMMARY COMPARISON OF ALTERNATIVES AND IMPACTS Table 11-7,presented at the end of this section, summarizes the impacts of the alternatives considered in detail on the affected environment. Impacts of the Maximum Powerplant Capacity and High Fluctuating Flow Alternatives would be very similar to those of the No Action Alternative. Impacts under the Moderate and Modified Low Fluctuating Flow and SeasonallyAdjusted Steady Flow Alternatives would be similar for most resources(becausethey include habitat maintenanceflows) except hydropower. The habitat maintenance flows of these three alternatives would provide some ecosystemvariability that was characteristic of the predam environment. Impacts under the Interim Low Fluctuating Flow and Existing Monthly Volume and Year-Round Steady Flow Alternatives would be similar for most downstream resources and result in a relatively static environment. The impacts on each of the affected resourcesare described in more detail in "Chapter IV , Environmental Consequences." Theseresourcesinclude: water, sediment, fish, vegetation, wildlife and habitat, endangered and other special status species,cultural resources,air quality , recreation, hydropower, and non-use value. Resource Management Objectives Federal, State,and Tribal Governments develop management objectives to define the desired condition of specific resources. The attainment or nonattainment of these objectives drive the implementation of management actions intended to maintain or reestablish the resource condition. In some cases,objectives must be reevaluated if they are not achieved. As outlined in the Grand Canyon Protection Act of 1992,the actions considered in this EIS are intended to protect and mitigate adverse impacts to and improve the natural and cultural resource values for which Grand Canyon National Park and Glen Canyon National Recreation Area were established. Many resourcesin Glen and Grand Canyons developed in responseto conditions created by the dam. Reasonableobjectives, developed by the management agencies,are goals for future management of these resourcesand provide meaning to the terms "protect," "mitigate," and "improve." Reclamation, NPS, FWS,Western, AGFD, Hualapai Tribe, and Navajo Nation have management responsibilities associatedwith Glen and Grand Canyons and have developed resource management objectives. The agency resource management objectives and the potential for the alternatives to meet those objectives are assessedbelow. Attainment of objectives for all resourceswill require complex interagency planning and management. Some issueswould remain unresolved under any alternative. WATER: Reclamation's water management objectives are to use Colorado River Storage Project (CRSP) reservoirs for the statutory SUMMARY COMPARISON purposes of flood control, river regulation, beneficial consumptive uses,water quality control, enhancement of fish and wildlife, other environmental factors, and power production. This is to be accomplished consistent with other applicable Federal laws, the Mexican Water Treaty, interstate compacts, and decrees. The Navajo Nation seeksto ensure that dam operations will not affect existing or future water rights or the use of those rights. NPS objectives are for releasesthat have a degree of variability to sustain sediment deposits and promote a dynamic ecosystem. Water released from the dam should meet or exceedState of Arizona standards for full-body contact use. The Hualapai Tribe's objective for water releases is to establish a flow pattern that maintains long-term sustainable and balanced multiple use of its resourceswhich include: cultural resources, fish, wildlife, vegetation, water supply and quality , and recreation enterprises. Assessment: All of the alternatives would likely accomplish Reclamation objectives for CRSP reservoirs. Raising the height of the spillway gatesto reduce flood frequency would meet Navajo Nation objectives. The other flood frequency reduction measure (increasing exclusive flood control space) would decreaseUpper Basin yield. NPS and Hualapai objectives would be accomplished under the Moderate Fluctuating, Modified Low Fluctuating, and SeasonallyAdjusted Steady Flow Alternatives. Water quality objectives would likely be attained under all alternatives. SEDIMENT: NPS, Hualapai, and Navajo seekto maintain a long-tenn balance of river-stored sediment and the entire range of predam sediment deposits-including an annually flooded baresand active zone, a less frequently flooded vegetation zone, and predam terraces. They prefer a diversity of dynamic, higher-elevation sediment deposits over stable, low elevation deposits. OF ALTERNATIVES AND IMPACTS 55 Someactions taken to benefit Grand Canyon may have negative consequencesin the Glen Canyon reach, and such consequencesmust be considered. Assessment:All management objectives for sediment (except high terraces)in Grand Canyon would be accomplished under the Moderate and Modified Low Fluctuating Flow Alternatives and the SeasonallyAdjusted Steady Flow Alternative. Thesealternatives provide the greatest cycles of deposition and erosion and maintain sandbars at the highest elevations, since daily releasefluctuations would be restricted and seasonalvariability would be added-primarily through habitat maintenance flows. However, high terraces would continue to erode under any alternative. Glen Canyon sediment would be subject to long-term net erosion under any alternative. FISH: NPS, Hualapai, and AGFD objectives for native fish are to ensure viable populations in Grand Canyon. The Hualapai seek to completely eliminate carp from Glen and Grand Canyons. FWS objectives for native fish are to closely mimic the natural, predam ecosystemprocessunder which native fish evolved. NP5, AGFD, Hualapai, and Navajo objectives for the trout fishery are to provide a recreational resource while maintaining and recovering native fish in Grand Canyon. In the Glen Canyon reach, their objective is to encouragenatural reproduction, survival, and growth of trout to blue ribbon quality sizes. In Grand Canyon, the objective is to sustain a wild trout fishery . Assessment:To assurefuture accomplishment of agency objectives for native fish, additional researchis needed on native and non-native fish interaction, the feasibility of selective withdrawal, the potential for reintroduction of extirpated native fish, and potential for eliminating carp. Achievement of objectives for native fish vary by species. None of the alternatives appear to increasespawning habitat for native fish in the mainstem. Selectivewithdrawal may be required to allow warmer releases. Reproduction and recruitment of razorback sucker in Grand Canyon 56 Chapter II Description of Alternatives is virtually unknown; it is unlikely that any of the alternatives in and of themselveswill reverse this trend. Flannelmouth sucker appear to be favored by those alternatives that create or maintain rearing habitats in the mainstem (i.e., Modified Low Fluctuating and SeasonallyAdjusted Steady Flow Alternatives). All steady flow alternatives and the Modified Low and Interim Low Fluctuating Flow Alternatives would likely meet AGFD, NP5, Hualapai, and Navajo objectives for the trout fishery and its food base. VEGETATION: NP5, Hualapai, and Navajo objectives for vegetation in the river corridor are to maintain a dynamic ecosystemmade up of diverse groups of native, riparian plant speciesat different stagesof successionand at different elevations above the water line. Emergent marsh vegetation should be sustained as a functioning, dynamic resourceproviding wildlife habitat that changesin location and extent in responseto flow and sedimentation processes. The Hualapai Tribe seeksto remove non-native vegetation, as necessary,to maintain campsites. Assessment:Habitat maintenance flows, which are components of the Moderate Fluctuating, Modified Low Fluctuating, and Seasonally Adjusted Steady Flow Alternatives, provide the greatestpotential for accomplishing the NPS, Hualapai, and Navajo objective for sustaining a dynamic ecosystem. Other alternatives result in system stability or eventual loss of ecosystemcomponents. Becauseof the regulated flows, it would be difficult under any alternative to achieve the NPS objective of maintaining dynamic marshes. However, alternatives with habitat maintenance flows and variable water releasesamong years should maintain some marsh dynamics. WILDLIFE AND HABITAT: NP5, Hualapai, and Navajo objectives are to provide for diversity of wildlife species,giving priority to native species and associatednatural processes. Assessment:Objectives for vegetation-and thus aquatic and terrestrial habitat-would be best met under the Moderate and Modified Low Fluctuating Flow Alternatives and the Seasonally Adjusted Steady Flow Alternative, therefore providing the greatestpotential for accomplishing wildlife objectives. ENDANGERED AND OTHER SPECIAL STATUS SPECIES: NPS, FWS,AGFD, Hualapai Tribe, and Navajo Nation objectives are to monitor, protect, and recover populations of endangered species,candidate species,and Statelisted species. Recovery plans developed for threatened and endangered speciesspecify FWS and AGFD objectives. Final recovery plans have been approved for the bald eagle,peregrine falcon, and humpback chub; a recovery plan for the razorback sucker is being developed. FWS and Navajo Nation objectives specific to the humpback chub and other native fish are to protect the LCR and restore mainstem populations. Assessment:It may not be possible to accomplish theseobjectives for some native fish under any of the alternatives without adopting other measures such as selective withdrawal. Objectives for terrestrial species,including bald eagle, peregrine falcon, and willow flycatcher, would likely be met by sustaining the processesneeded to accomplish sediment and ecosystemobjectives (i.e., Moderate Fluctuating, Modified Low Fluctuating, and SeasonallyAdjusted Steady Flow Alternatives). However, dam operations alone cannot meet some objectives for endangered fish over the long term. The entire Grand Canyon humpback chub population is in jeopardy, partly becauseof the limited distribution of the fish. Establishment of a second spawning population of the humpback chub is an expressobjective of AGFD, FW5, Hualapai Tribe, and Reclamation. This objective may be met by establishing a spawning population either in another tributary or in the mainstem, which is a common element under all restricted fluctuating and steady flow alternatives. Humpback chub SUMMARY COMPARISON OF ALTERNATIVES AND IMPACTS would appear to be able to maintain a viable population under all alternatives but only because the LCR provides spawning habitat. FWSbelieves that their management objectives can best be accomplished under the Seasonally Adjusted Steady Flow Alternative during low releaseyears (seeattachment 4). CUL TURAL RESOURCES: NPS and cooperating tribe objectives are to maintain the integrity of all cultural resourceswithin the river corridor, with site preservation as the optimal condition, and to maintain biological and spiritual resources important in preserving Native American values. For the cooperating tribes, preserving traditional cultural properties-including accessto cultural properties and perpetuation of cultural practices within Glen and Grand Canyons-is the highest 57 ribbon angling opportunity and to provide safe boating and accessfor boaters, waders, and campers. AGFD seeksto provide accessfor hunting waterfowl in this reach. The Hualapai Tribe also promotes motorized white-water boating, hunting, camping, and sightseeing in lower Grand Canyon. The Navajo Nation also seeksto provide recreational opportunities for Navajo people and to support and enhancerecreation and tourism industries in northern Arizona. Assessment:The steady flow alternatives would offer the most immediate benefits for recreation activities and attributes. However, the Moderate Fluctuating, Modified Low Fluctuating, and SeasonallyAdjusted Steady Flow Alternatives would best meet the long-term recreation objectives of NPS, Hualapai, and Navajo. priority. Assessment:Moderate Fluctuating, Modified Low Fluctuating, and SeasonallyAdjusted Steady Flow Alternatives would contribute most toward preserving sites in place. However, management actions other than dam operations may be required to meet NPS and cooperating tribe objectives over the long term. The same three alternatives would most likely preserve and maintain biological and spiritual resourcesimportant to Native Americans. Objectives for biological resourceswould not be as well met under the other steady flow alternatives and Interim Low Fluctuating Flow Alternative. Cultural resource objectives, in general, would not be met under the unrestricted fluctuating flows or the High Fluctuating Flow Alternative. RECREATION: NPS, Hualapai, and Navajo objectives are to provide opportunities for recreational experiencesalong the river corridor that do not diminish natural or cultural resource values and to protect and preserve environmental and wilderness conditions that contribute to quality recreation experiences. Flows should allow navigation by white-water boats in Grand Canyon and power boats in Glen Canyon. In Glen Canyon, AGFD and NPS seek to maintain a blue All alternatives except the Maximum Powerplant Capacity Alternative would improve boating accessand navigation over no action. AGFD and Hualapai objectives for fishing, hunting, and safety would be realized most under the steady flow alternatives and, to a somewhat lesserdegree,under the Modified Low and Interim Low Fluctuating Flow Alternatives. HYDROPOWER: Western's objective is to serve the public interest by marketing and delivering the greatestamount of long-term firm power and energy from Glen Canyon Dam Powerplant while striving to protect and enhanceenvironmental values both downstream of Glen Canyon Dam and throughout the marketing area. Assessment:Western's objective is most readily accomplished under the Moderate Fluctuating Flow Alternative. The Interim Low and Modified Low Fluctuating Flow Alternatives offer approachesto achieving a balance between enhancing benefits to natural resourcesand reducing impacts to hydropower. 58 Table 11-7.-Summary Comparis.on of Alternatives Maximum No Action Powerplant Capacity and Impacts High Fluctuating Flow Moderate Fluctuating Flow WATER Streamflows (1,000 Annual acre-feet) streamflows Median annual release 8,573 Monthly streamflows (median) Fall (October) Winter (January) Spring (May) Summer (July) Hourly streamflows can be found 8,573 8,559 8,559 587 568 899 592 592 1 ,045 1,045 1,045 50 41 49 36 53 45 61 44 to 74 47 to 77 33 to 53 10t015 10 to 16 28 to 47 41 to 66 6 to 10 9 to 14 Limited by reliable wetted perimeter Same as no action Minor increase Moderate increase Stable to Same as no action Same as no action Same as no action Same as no action Same as no action no action Same Same as no action Same as no action 568 568 899 899 587 1 ,045 568 899 in table 11-2 SEDIMENT Riverbed sand probability (percent of net gain) After 20 years After 50 years Sandbars Active 70 (feet) width With habitat Potential maintenance flows maintenance flows height With habitat 7to 1 FISH Aquatic food base Native fish declining Non-native warmwater coolwater fish and Interactions between native and non-native fish Trout Stable to declining Some predation and competition by non-natives Stockin!~dependent as no action Same as no action Same as no action Same as Increased growth potential, stockingdependent 59 Modified Low Fluctuating Flow Interim Low Fluctuating Flow Existing Monthly Volume Steady Flow Seasonally Adjusted Steady Flow 8,559 8,559 8,559 8,554 8,578 568 899 592 568 899 592 568 899 592 492 688 1,045 1,045 1,045 699 703 699 699 64 73 69 76 24 to 41 24 to 41 1,106 768 Year-Round Steady Flow 71 71 74 82 82 100 10 to 19 41 to 66 16 to 29 37 to 60 4to7 8 to 13 0 6 to 9 3toS Potential major increase Major increase Major increase Major increase Potential minor increase Potential minor increase Uncer1ain potential minor increase Uncer1ain potential major increase Uncertain potential minor increase Potential minor increase Potential minor increase Potential minor increase Potential minor increase Potential minor increase Potential minor increase in warm, stable microhabitats Potential minor increase in warm, stable microhabitats Potential minor increase in warm, stable microhabitats Potential minor increase in warm, stable microhabitats Potential minor increase in warm, stable microhabitats 6 to 9 9 to 14 Potential major increase O to 1 Increased growth Increased growth Increased growth Increased growth Increased growth potential, stockingdependent potential, stockingdependent potential, possibly self-sustaining potential, possibly self-sustaining potential, possibly self-sustaining 60 Table 11-7.-Summary Comparison of Alternatives Maximum Powerplant Capacity No Action and Impacts-Continued Moderate High Fluctuating Flow Fluctuating Flow VEGETATION Woody plants New high (area) water zone No net change O to 9% 15 to 35% reduction 23 to 40% increase increase With habitat maintenance flows Species composition O to 12% increase Tamarisk and others dominate Tamarisk and others dominate T amarisk, willow, and coyote arrowweed, camelthom dominate Emergent marsh Tamarisk, coyote willow, arrow weed, and camelthorn dominate plants New high water Aggregate zone area of No net change Same as no action Same as or less than no action Same as or less than no action Same as no action Same as no action Potential increase Same as no action Same as no action Same as no action Same as no action Same as no action no action Same as no action Same as no action Same Stable Same as no action Same as no action Potential increase Peregrine falcon No effect No effect No effect No effect Kanab ambersnail No effect wet marsh plants WILDLIFE AND HABITAT Riparian See vegetation. habitat Wintering waterfowl (aquatic food base) ENDANGERED Humpback Stable AND OTHER SPECIAL STATUS SPECIES chub Stable to declining Razorback sucker Stable to declining Flannelmouth sucker Stable to declining Bald eagle Some incidental Southwestern willow flycatcher Undetermined increase Some take Same as no action incidental Same as as no action Some take Same as no action incidental take Same as no action 61 Modified Low Fluctuating Flow Interim Low Fluctuating Flow Existing Monthly VOIIJme Steady Flow Seasonally Adjusted Steady Flow 30 to 47% increase 30 to 47% increase 45 to 65% increase 38 to 58% increase O to 12% increase O to Tamarisk, coyote willow, arrow weed, and camelthorn dominate Tamarisk, coyote willow, arrow weed, and camelthorn dominate Same as or less than no action Same as or less than no action Potential increase Potential increase Tamarisk, coyote willow, arrow weed, and camelthorn dominate 12% Year-Round Steady Flow 63 to 94% increase increase Tamarisk, coyote willow, arrowweed, and camelthorn dominate Tamarisk, coyote willow, arrow weed, and camelthorn dominate Less than no action Less than no action Potential increase Potential increase Potential increase Less no than action Potential minor increase Potential minor increase Uncertain potential minor increase Uncertain potential major increase Uncertain potential minor increase Potential minor increase Potential minor increase Uncertain potential minor increase Uncertain potential minor increase Uncertain potential minor increase Potential minor increase Potential minor increase Uncertain potential minor increase Uncertain potential major increase Uncertain potential minor increase Potential increase Potential increase Potential increase Potential increase Potential increase No effect No effect No effect No effect No effect Some incidental Some take Same as no action incidental Some take Same as no action incidental Some take Same as no action incidental Some take Same as no action incidental take Same as no action 62 Table 11-7.-Summary Comparis;on No of Alternatives Action Maximum Powerplant Capacity and Impacts-Continued High Fluctuating Flow Moderate Fluctuating Flow CULTURAL RESOURCES Archeological sites (Number Major affected) (336) Major (336) Potential to become major Moderate (Less than 157) (263) Traditional cultural properties Major Same as no action Potential to become major Moderate Traditional cultural resources Major Same as no action Same as no action Increased protection 1,960 1 ,954 Same as no action Slight reduction Slight reduction Potential danger Same as no action Same as no action improvement Difficult at low flows Same as no action Negligible improvement Major improvement High risk at very high and very low flows Same as no action Negligible improvement improvement Less than 7,720 square feet Same as no action Same as no action Minor increase AIR QUALITY Regional air quality Total emissions Sulfur (thousand tons) dioxide Nitrogen oxides RECREATION Fishing Angler Day safety Moderate rafting Navigation past White-water 3-Mile Bar boating Safety Camping beaches (average area at normal peak stage) Wilderness values Economic Change Influenced by range of daily fluctuations Same Minor as Minor Moderate no action increase Increase benefits in equivalent annual net benefits (1991 nominal Present value (1991 $ million) 0 0 0 +0.4 0 0 0 +4.6 $ million) 63 Modified Low Fluctuating Flow Moderate (Less than 157) Moderate Interim Low Fluctuating Flow Existing Month Iy Volume Steady Flow Seasonally Adjusted Year-Round Steady Steady Flow Flow Moderate (Less than 157) Moderate (Less than 157) Moderate Moderate (Less than 157) (Less than 157) Moderate Moderate Moderate Moderate Increased Increased Increased Increased Increased protection protection protection protection protection Slight reduction Slight reduction Slight reduction Slight reduction Slight reduction Moderate Moderate improvement improvement Major improvement Major improvement Major improvement Major improvement Major improvement Major improvement Major improvement Major improvement Potential to become major improvement Major improvement Potential to become major increase Major increase Major increase Major increase Minor Minor improvement improvement Minor increase Minor increase Moderate to potential to become major increase Moderate to potential to become major increase +3.7 +3.9 +3.9 +4.8 +2.9 +43.3 +45.6 +45.6 +55.0 +23.5 Moderate improvement Major increase Major increase 64 Table 11-7.-Summary Comparison of Alternatives No Action Maximum Powerplant Capacity o o -1.5 O and Impacts-Continued High Fluctuating Flow Moderate Fluctuating Flow POWER Annual economic 1991 nominal cost $ million Hydrology Contract rate of delivery Present value (1991 $ million) Hydrology Contract rate of delivery Wholesale Retail O 18.78 (1991 of end end 28.9 19.38 54.0 36.7 624.5 424.5 22.82 (+21.5%) mills/kWh) users users (weighted 24.3 [+3.2%) 23% of end users 7% -17.3 mills/kWh) rate 70% 18.78 rate (1991 o o 2.1 2.5 No change No change No change to slight decrease No change to slight decrease No change No change Slight decrease to moderate increase Slight decrease to moderate increase 64, mean) NON-USE VALUE No data. 64.1 64.6 69.7 (+0.8%) (+8.8%) 65 Modified Low Fluctuating Flow Interim Low Fluctuating Flow Existing Monthly Volume Steady Flow Seasonally Adjusted Steady Flow 15.1 44.2 36.3 35.6 65.9 68.7 88.3 123.5 69.7 85.7 174.6 511.2 418.7 411.7 761.4 794.6 1 ,021.2 1 ,428.4 805.0 991.2 Year-Round Steady Flow 23.16 23.18 25.22 28.20 26.78 (+23.3%) (+23.4%) (+34.3%) (+50.2%) ~+42.6%) No change to slight decrease No change to slight decrease No change to slight decrease No change to slight decrease No change to slight decrease Slight decrease to mode rage increase Slight decrease to mode rage increase Slight decrease to moderate increase Slight Slight 70.5 70.2 (+9.6%) 72.9 75.8 74.5 (+13.8%) (+18.4%) (+16.3%) (+10.0%) decrease to moderate increase decrease to moderate increase CHAPTER III Affected Environment This chapter describesthe general setting, Colorado River system resource linkages, and resourcesin the study area that would be affected by any of the alternatives if implemented. The conditions described are those that existed in 1990, prior to the Glen Canyon Environmental Studies (GCES)researchflows, under the water and power operating regimes that existed at that time. Theseconditions establish the baseline for analysis of effects,found in chapter IV .The resources presented are: water, sediment, fish, vegetation, wildlife and habitat, endangered and other special status species,cultural resources,air quality , recreation, hydropower, and non-use value. SEnlNG The affected environment includes two areas: (1) the immediate or Glen Canyon Dam area and (2) the region. The immediate area is the Colorado River corridor through Glen, Marble, and Grand Canyons in Coconino and Mohave Counties in northwestern Arizona. This area extends from Lake Powell downstream into Lake Mead. While the focus of the environmental impact statement (EIS) is on this river corridor, some alternatives may lead to regional impacts outside of the immediate geographic area. The following map shows the regional extent of the Colorado River Basin. Immediate Area (seefrontispiece) Lake Powell and the first 15.5miles of the Colorado River downstream of Glen Canyon Dam are part of Glen Canyon National Recreation Area (GLCA). The river flows another 278 miles through Grand Canyon National Park (GRCA) 1 River mile designates distance downstream into Lake Mead, part of Lake Mead National Recreation Area. All of these areasare administered by the National Park Service (NPS). The Navajo Indian Reservation is adjacent to GRCA and GLCA. Kaibab National Forest, administered by the Forest Service of the U .5. Department of Agriculture, adjoins GRCA on the north and south. The Hualapai Reservation includes 108miles of Grand Canyon south of the river from National Canyon (river milel (RM) 166.5)to RM 273. The Havasupai Reservation adjoins GRCA south of the river and west of the Kaibab National Forest. Between Glen Canyon Dam and Lake Mead, the Colorado River falls about 1,900feet, or from approximately 3100to 1200feet above sea level. More than 100 rapids, some having drops of up to 40 feet, account for most of this elevation loss. Numerous tributaries enter this stretch of river, the principal onesbeing the Paria and Little Colorado Rivers, and Bright Angel, Tapeats, Kanab, Havasu, Diamond, and SpencerCreeks. The Colorado River can be reached by two highways: u.s. 89 crossesthe river immediately below Glen Canyon Dam, and u.s. 89 Alternate crossesabout 20 miles downstream near the community of Marble Canyon (near RM 4). Yearround accessto the south rim of Grand Canyon is provided by U .S.180 and Arizona 64. Accessto the north rim is provided by Arizona 67, but the part of that road between the GRCA boundary and the north rim is open only from about mid-May to rnid-October. Accessto the south and north rims and the river at other locations is provided by a few unimproved roads and several trails. Some of the unimproved roads and trails accessthe canyon via the Navajo Indian Reservation, and permits for their use must from Lees Ferry (RM 0), which is located 15.5 miles downstream Dam. Negative numbers (i.e., RM -9) indicate distance upstream between Lees Ferry and the dam. from Glen Canyon be obtained from the Navajo Nation in Cameron or Window Rock, Arizona. Accessto the river is also available from Supai via a hiking trail through the Havasupai Reservation and from PeachSprings to Diamond Creek via the Hualapai Indian Reservation. An NPS road provides access to LeesFerry from Marble Canyon. division between the two basins is at Lee Ferry, a referencepoint in the mainstream of the Colorado River 1 mile below the mouth of the Paria River (not to be confused with LeesFerry, which is the site of the u.s. Geological Survey (USGS)stream gauge above the Paria River confluence). Two cities in the area are Flagstaff, Arizona, about 80 miles south of the south rim of Grand Canyon, and Page,Arizona, about 2 miles southeast of Glen Canyon Dam. Commercial air service is available at both cities and near Grand Canyon Village on the south rim. Commercial boat trips on the Colorado River begin immediately below Glen Canyon Dam and at Lees Ferry (RM 0); private trips begin only at LeesFerry. Also, the Hualapai Tribe provides commercial river trips from Diamond Creek to Lake Mead. Mule trips are conducted from Grand Canyon Village and the north rim. Geology Colorado For more than 5 million years, the Colorado River and its tributaries-along with geologic uplift and weathering-have carved the Grand Canyon. The canyon is about a mile deep and varies in width from a few hundred feet at river level to as much as 18 miles at the rim. The river cut only a narrow gorge; running water from the canyon walls, freezing and thawing, and abrasion of rock against rock excavated most of the canyon. The Colorado River is like a huge conveyor belt for transporting finer particles to the ocean, temporarily (geologically speaking) dropping its load into Lake Mead. River Region The Colorado River has its headwaters in the mountains of Colorado and flows southwestward to its mouth at the Gulf of California. It drains an area of approximately 244,000square miles, of which 242,000are in the United Statesand 2,000 are in northern Mexico. The basin extends from the Wind River Mountains in Wyoming to south of the United states-Mexico border, a straight line distance of approximately 900 miles. Basin width varies from about 300 miles in the upper reaches to more than 500 miles in the lower reaches. It is bounded on the north and east by the Continental Divide in the Rocky Mountains, on the west by the Wasatch Mountains, and on the southwest by the SanJacinto Mountains. Colorado River tributaries drain parts of seven Western States: Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming. The Upper Colorado River Basin drains an area of 108,000square miles; its tributaries include the Upper Colorado, Green, Gunnison, SanJuan, and Paria Rivers. The Lower Colorado River Basin drains an area of 136,000square miles, and its tributary basins include the Lower Colorado, Little Colorado, Virgin, and Gila Rivers. The In cutting the canyon, the river has exposed rocks of all geologic eras, covering a span of nearly 2 billion years. The rocks of Grand Canyon are part of the Colorado Plateau, a 130,000-squaremile area covering most of the Colorado River Basin. The elevation of the canyon rim varies between about 5000 and 8000feet above sealevel, with the north rim about 1,000feet higher than the south rim. A river trip starting at Glen Canyon Dam is a trip backward through geologic time (Beusand Morales, 1990). Glen Canyon is cut through the massive Navajo Sandstoneof the Mesozoic era-about 200 million years old. Downstream from LeesFerry, the great sequenceof nearly horizontal sedimentary rocks of the Paleozoic era appear at river level in descending order, beginning with the Kaibab Formation that caps much of the canyon rim. In Marble Canyon, river runners pass through the cavernous Redwall Limestone. The river is narrower here and in other places where the Paleozoic rocks are relatively hard and wider through more easily eroded formations. The shelves of the Tapeats Sandstone(more than 500 million years old) at the base of the Paleozoicsappear near the mouth of COLORADO RIVERSYSTEMRESOURCELINKAGES the Little Colorado River (LCR). For the rest of the trip, the narrowest reachesare cut through the dense,dark-colored Vishnu Schist of the Proterozoic era (about 1.7billion years old). In the Toroweap area,river runners are greeted wj.th a spectacular display of the youngest rocks in the canyon-remnants of lava flows that poured over the north rim about 1 million years ago during the Cenozoic era. The hardened lava still clings to the canyon walls, and basalt boulders still affect riverflow-providing thrills for river runneJ~at Lava Falls Rapid. The trip ends in Lake Mead at Grand Wash Cliffs, the southwestern edge of the Colorado Plateau and the mouth of Grand 69 mountains and arid in the lower southern areas. Annual precipitation in the higher mountains occurs mostly as snow, which results in as much as 60 inches of precipitation per year. Thousands of square miles in the lower part of the basin are sparsely vegetated becauseof low rainfall and poor soil conditions. Rainfall in this area averages from 6 to 8 inches, mostly from cloudburst storms during the late summer and early fall. COLORADO RESOURCE RIVER SYSTEM LINKAGES Canyon. Climate Climatic conditions in the area vary considerably with elevation. At Bright Angel Campground (elevation 2400feet) near Phantom Ranch, tile climate is characterized by mild winters, hot summers, and low rainfall. Average high temperatures range from about 59 degrees Fahrenheit (OF)in winter to 103 oFin summer. Low temperatures range from about 39 to 7lj oF. Average annual precipitation-mostly in the form of rain-is about 11.2inches. Precipitation occurs uniformly in summer, fall, and winter and is somewhat less in spring. In contrast, the climate at the north rim (elevation 7800to 8800feet) is characterized by cold winters, cool summers, and abundant precipitation with snowfall. Average high temperatures range from 39 oFin winter to 75 oFin summer; low temperatures range from about 18 to 43 OP.Average annual precipitation is 33.6inches. The south rim (elevation 7000feet) receives about 16 inches of precipitation annually. Average high temperatures range from 41 oFin winter to 84 opin summer; averagelow temperatures range from 18 oFin winter to 54 oFin summer. The Upper Colorado River Basin can be generally classified as semiarid and the Lower Basin a:sarid. The climate varies from cold-humid at the headwaters in the high mountains of Colorado, New Mexico, Utah, and Wyoming to drytemperate in the northern areasbelow the Resourcesdownstream from Glen Canyon Dam through Grand Canyon are interrelated, or linked, since virtually all of them are associatedwith or dependent on water and sediment. This section gives an overview of linkages to better illustrate the interdependence of processesand resourcesin the study area. A detailed description of resources follows this overview. This resourcelinkage overview specifically responds to the EIS scoping process. Many comments from the public called for consideration of the "Grand Canyon ecosystem:' showing public awarenessof the interrelationships among resources. The term " ecosystemII refers to the system formed by interactions between communities of organisms and their environment. A IIsystemll is based on the concept that resources and the processesthat drive them are linked. In an ecosystem,changesin a single processcan affect resourcesthroughout the entire system. This EIS emphasizesthe holistic pattern of system behavior rather than impacts on separate elements. However, it cannot provide a complete, scientific study of the Grand Canyon ecosystem becausesuch an approach is too technically detailed for the purpose and scope of this document. Also, all the linkages among resources of the Grand Canyon ecosystemare not fully understood at this time. As discussed in chapter II, a program of monitoring and adaptive management is required to expand our understanding of how changesin processesaffect this system. The Glen Canyon Dam EIS focuseson the following processes,resources,and their linkages: Water releaseand sediment transport patterns Aquatic and terrestrial "indicator resources" within the system The system of concern in this study is the Colorado River corridor-from Glen Canyon Dam through Grand Canyon to Lake Mead-and includes resourceslocated in the river channel and in a narrow band of adjacent land (figure 111-1). Resourceswithin this system depend on factors outside these operationally defined boundaries, including the physical and biological constraints of Lake Powell and, to a lesserextent, Lake Mead and tributaries such as the LCR. The Grand Canyon ecosystemoriginally developed in a sediment-laden, seasonally fluctuating environment. The construction of Glen Canyon Dam altered the natural dynamics of the Colorado River. Today, the ecological resourcesof Grand Canyon depend on the water releasesfrom the dam and variable sediment input from tributaries. The alternatives evaluated through this EIS must take into account not only the short-term needs of the environment but also the long-term requirements for maintaining and supporting the ecological elements of Grand Canyon. Lake Powell traps water, sediment, and associated nutrients that previously traveled down the Colorado River. mterruption of riverflow and regulated releaseof lake water now support aquatic and terrestrial systemsthat did not exist before Glen Canyon Dam. Somechangesare lamented while others are valued. The following discussion addressesthe current systems,their resources,and how dam operations affect them either directly or through linkages among resources. The present interactions among water volume and releasepatterns, sediment transport, and downstream resourceshave created and support a complex system much different from predam conditions. Water Volume and Pattern of Release The major function of Glen Canyon Dam (and Lake Powell) is water storage. The dam is managed to releaseat least 8.23million acre-feet (maf) of water annually to the Lower Basin. In this EIS, riverflows below the dam are referred to as releasesor discharge. The measure of riverflow is in cubic feet per second (cis). Annual and monthly volumes are measured in acre-feet. To put theserelationships in perspective, Glen Canyon Dam would have to releaseapproximately 11,400cis, 24 hours per day, every day of the year to release8.23maf. The amount of water and its pattern of releasedirectly or indirectly affect physical, biological, cultural, and recreational resourceswithin the river corridor. Predam flows ranged seasonally from spring peaks sometimes greater than 100,000cfs to winter lows of 1,000to 3,000cfs. During spring snowmelt periods and flash floods, significant daily and hourly flow fluctuations often occurred. While annual variability in water volume was high, a generally consistent pattern of high spring flows followed by lower summer flows provided an important environmental cue to plants and animals in the river and along its shoreline. The frequency of daily and hourly fluctuations has increased since the dam was completed. Water is releasedto maximize the value of generated power by providing peaking power during high-demand periods. More power is produced by releasing more water through the dam's generators. Daily releasescan range from 1,000to 31,500cfs, but actual daily fluctuations have been less than this maximum range. These fluctuations result in a downstream "fluctuating zone" between low and high river stages(water level associatedwith a given discharge) that is inundated and exposed on a daily basis. For purposes of this analysis, flows are defined as fluctuating if they both increaseand decrease more than 2,000cfs in a 24-hour period. Hydropower conservesnonrenewable fuel resourcesand is cleaner, more flexible, and more responsive than other forms of electrical COLORADO RIVERSYSTEMRESOURCELINKAGES Figure III-l.-Photograph of Colorado River corridor looking downstream from Nankoweap Creek. Photo by Gary Ladd 71 72 Chapter III Affected Environment generation. Glen Canyon Powerplant is an important component of the electrical power system of the Western United States. The powerplant has eight generating units with a maximum combined capacity of 1,356megawatts. When possible, higher releasesare scheduled in high-demand winter and summer months to generatemore electricity. Glen Canyon Powerplant historically has produced about $55 million in revenue in a minimum water release(8.23-maf)year. Glen Canyon Dam also affects downstream water temperature and clarity. Historically, the Colorado River and its larger tributaries were characterizedby heavy sediment loads, variable water temperatures, large seasonalflow fluctuations, extreme turbulence, and a wide range of dissolved solids concentrations. The dam has altered these characteristics. Before the dam, water temperature varied on a seasonalbasis from highs around 80 opto lows near freezing. Now, water releasedfrom Glen Canyon Dam averages 46 of year round. Very little warming occurs downstream. Lake Powell traps sediment that historically was transported downstream. The dam releasesclear water, and the river becomes muddy only when downstream tributaries contribute sediment. Sediment Transport and Its Effect on Other Resources Sediment can be considered a basic resource', linked in some way to most of the resources within Glen and Grand Canyons. The discussions in this document deal mainly with sand-sized particles, although all sizes of sediment-from the smallest clays and silts to the largest bouldersare important system components. Sediment occurs both above and below the river's surj:ace, and its transport and deposition are important considerations in many resource analyses. Exposed and submerged sediment deposits throughout Glen and Grand Canyons are very important for cultural, recreational, and biological resources. Sediment is critical for stabilizing archeological sites and camping beaches,for developing and maintaining backwater fish habitats, for transporting nutrients, and for supporting vegetation that provides wildlife habitat. Large annual floodflows-sometimes greater than lOO,OOO cfs-historically transported tremendous quantities of sediment that accumulated in high deposits and sometimes formed terraces. Wind and water eroded these deposits after the return to lower flows. Natural cycles of deposition and erosion generally prevented establishment of vegetation near the river. Sediment supply and the river's capacity to transport sediment (especially sand and larger particles) both have been reduced. Maximum water releases(31,500cfs) are much lower than the peak flows that occurred before Glen Canyon Dam. During normal operations, the riverbed and low elevation sandbars tend to build up (aggrade), and high elevation sandbars tend to erode. The only sourcesfor resupplying sediment to the river below the dam are tributaries-primarily the Paria River, LCR, and Kanab Creek. The 1983-86floodflows (similar to predam spring peaks) transported sand stored within the river channel, eroded low elevation sandbars, and aggraded high elevation sandbars in wide reaches. In many places,vegetation that had developed since darn construction was scoured, drowned, or buried. Somearcheological sites also were damaged. The high elevation sandbars eroded following the return to lower flows (as they did predam). Becausefloods of predam magnitude and sediment concentration can no longer occur, erosion of high terraceswill continue. The future existenceof Grand Canyon sandbars depends on sand supplied from tributaries, daily water releasepatterns, and the long-term frequency and magnitude of flood releasesfrom the dam. Cycles of sediment deposition and erosion are a natural processfor rivers in the Southwestern United States. High flowswhether daily or annual-are necessaryto replenish sand deposits, but high flows occurring too frequently in the dam-altered river will lead to long-term net erosion. COLORADO RIVERSYSTEMRESOURCELINKAGES Flows, Sediment, Resources and Downstreann The Colorado River is the main influence in this dynamic ecosystem: changesin its flow ripple outward to affect both aquatic (water) and terrestrial (land) resourcesdownstream. The system now contains a mixture of native and non-native plant and animal communities that began developing prior to the dam, with the introduction of non-native fish and vegetation. Dam construction and operation further modified this mixture and created the current system that is supported by postdam conditions. The river is forever changed. That change-brought about by Glen Canyon Dam-permitted this ecosystemto develop and establish itself. Aquatic Resources The predam aquatic system supported an array of native and non-native fish. Non-native caq>and channel catfish have probably been present since the late 18{)()'s.Channel catfish comprised 90 percent of fish captures in Glen Canyon in the late 1950's. At the time of the dam closure in 1963, at least eight speciesof non-native fish also were present in the system. During the 4 years following dam closure, when water temperature still varied seasonally from 45 to 70 oF,relative abundance of native fish increased over non-natives in the Glen Canyon area. By 1968,non-native fish once again becamemore abundant than natives, with trout dominating the now cold water system immediately below the dam. The biological foundation of the aquatic system in the postdam Colorado River below Glen Canyon Dam is Cladophoraglomerata,a filamentous g;reen alga. River conditions created by the dam--low temperatures, nutrients from Lake Powell, and clear water-make possible the abundant growth of Cladophora.Cladophorafilaments provide attachment sites for diatoms and hiding places for insect larvae. The non-native small crustacean, Gammaruslacustris,feeds on diatoms and uses Cladophoraas a refuge. Together, Cladophora, diatoms, and associatedinvertebrates (Gammarus and insects)provide an important food source for other organisms in the aquatic food chain. 73 Severalspeciesof fish, including trout, were stocked in the Colorado River and some of its tributaries before construction of Glen Canyon Dam. Trout could not survive in the seasonally warm, muddy river. The postdam conditions described above, including the Cladophoradiatom-Gammarusfood chain, now support a blue ribbon rainbow trout fishery in the Glen Canyon reach below the dam. However, water quality changeswith distance from the dam, and aquatic communities change in response. While water temperature increasesonly slightly downstream, sediment from tributaries accumulates,turbidity increases,and the abundance of food-chain organisms decreases.The sediment particles' abrasive action also decreasesthe abundance of food organisms. As their food supply decreases downstream, trout decreasein abundance and condition (figure 111-2). Before the dam, eight native and several non-native fish speciesinhabited the river. Today, three native specieshave been extirpated, two are listed as endangered, and one is a candidate for listing under the Endangered SpeciesAct. Two natives remain relatively common in tributaries and certain sections of the river. Non-native carp and channel catfish also have declined, while trout have increased. The reasonsfor extirpations or declines are undoubtedly complex, but principal known factors are competition and predation by Figure 1II-2.-As the river's sediment load increases downstream, the abundance of Cladophora, aquatic macroinvertebrates, and rainbow trout decreases. 74 Chapter III Affected Environment non-native fish and habitat changes brought about by construction and operation of Glen Canyon Dam. The following linkages are believed related to changes in water quality . .Low water temperature prevents mainstem spawning and threatens survival of young fish, .Low water temperature may affect food consumed during certain fish life stages. .Increased water clarity may make some native fish more vulnerable to competition and predation from non-native fish. Becauseof cold water temperatures, suitable habitats for young native and non-native fish in Grand Canyon are confined to tributaries, tributary mouths, and backwaters. Reproduction of warmwater fish speciesis restricted to within the tributaries, which are mostly outside the influence of the dam. The slow-moving water in backwaters and nearshore areasprotects young fish from the stressand dangers of the main channel. Under the proper conditions, backwaters have higher water temperatures than the main channel and better food conditions for young fish. Flow fluctuations affect the spawning attempts of all fish. Although the trout fishery is maintained by stocking, mature trout attempt to spawn at suitable river sites and in certain tributaries. Rapid decreasesin disdlarge can strand spawning trout, and low river stagescan exposetheir nests and limit their accessto tributaries. Fluctuating releasesalso may affect fish accessto tributaries and backwater habitat. Flow fluctuations destabilize backwaters and nearshore areasand may force fish out of these more favorable habitats into the harsher conditions of the mainstem. Bald eagles-which only passed through Grand Canyon before the dam-now stop during winter at sites along the river to feed on spawning trout and fish stranded by fluctuating flows (figure 111-3). Water releasepatterns also affect recreation. Three groups account for almost all recreational use of the Colorado River corridor: anglers, day Thosenative fish populations that remain iJ1 Grand Canyon may derive some indirect protection from cold water releases. Year-round releasesof uniformly cold water may discourage further invasion and reproduction of warm water non-native fish that prey on native fish or compete with them for food or other resources. Not only do the physical characteristicsof water .affectaquatic resources,but how water is released from the dam also affects them. For example, periods of exposure can adversely affect Cladophoraand its associatedinvertebrates through drying, freezing, or ultraviolet light. Fluctuating dischargesmay dislodge segmentsof Cladophoraand temporarily increasedrifting clumps of this important food-bearing resource downstream for trout and other organisms. The fluctuating zone supports fewer aquatic invertebrates than those sites that remain continuously inundated. Insect larvae are uncommon in the fluctuating zone. Figure IlI-3.-The effects of dam operations on linkages behveen aquatic and terrestrial resources are exemplified by the trout fishery. Fluctuating flows can affect food abundance, trout spawning in the river and tributaries, the availability of trout as prey for eagles, and the sport fishery. These resources were not found in the Colorado River corridor through Grand Canyon before construction of Glen Canyon Dam. COLORADO RIVERSYSTEMRESOURCELINKAGES rafters, and white-water boaters. Most trout fishing occurs in the 15-mile Glen Canyon reach below the dam. While some bank fishing occurs, most anglers are also boaters who motor upstream from LeesFerry .Low flows can expose submerged cobble bars and make navigation difficult. Terrestrial Resources Riparian (near water) vegetation is a major terrestrial "indicator resource" below the dam. Before Glen Canyon Dam, seasonallyhigh riverflows reworked sediment deposits and scoured most vegetation from the river corri.dor below the 100,000- to 125,OOO-cfs river stage elevation. The only riparian vegetation present along the river developed above this scour 2:onein what is known as the old high water zone (OHWZ). Dominant plants in the OHWZ include acacia,mesquite, and hackberry . Following dam construction, protection from annual high flows permitted riparian vegetation to develop below the OHWZ in what has become known as the new high water zone (NHWZ). Today, this new zone of vegetation provides over 1,000acresof additional habitat for native wildlife A mixture of native and non-native plant species provides habitat for numerous speciesof mammals, birds, amphibians and reptiles, and terrestrial invertebrates. Many of theseplants and animals have cultural significance to Native Americans. Riparian vegetation reflects water flow patterns and sediment dynamics and is an excellent example of how system processesaffect linked resources. High flows transport available sediments. Somesediments are deposited and becomesandbars after flows recede,while other sediments are carried out of the system to bE!COme part of Lake Mead's delta. Before the dam, annual high flows carried large sediment loads through Glen and Grand Canyons, scouring or burying any vegetation below the OHWZ. With the dam, flows are regulated, sediment supplies are limited, and riparian vegetation has established in the NHWZ. 75 Riparian vegetation in the NHWZ grows on sediment deposits. While high flows can rapidly and dramatically restructure sandbars and associatedriparian vegetation, daily dam release patterns influence the distribution of plants on sediment deposits. Below the level of maximum flow, sediment deposits are unstable and generally unsuitable for the establishment of woody vegetation. NHWZ plants grow in the area between the river's maximum stage and the level where limited ground water no longer supports growth. Emergent marsh vegetation, such as cattails, often develops in areaswith low water velocity , high concentrations of silt and clay, and a reliable water supply-typically backwaters. Under fluctuating dam releases,these important sites are periodically flooded and dewatered, allowing patches of emergent marsh plants to become establish'ed. Marshes probably did not occur in Glen and Grand Canyons before dam construction. Even though emergent marsh vegetation now makes up less than 2 percent of the total riparian vegetation, it greatly enhancesplant diversity in the river corridor. While riparian vegetation supports its own insect populations, it also provides habitat for insects emerging from the river. Structural diversity of the riparian plant communities and abundant invertebrates make the riparian zone-especially the NHWZ vegetation resulting from damregulated flow&-valuable wildlife habitat. The riparian zone is attractive to mammals becauseit provides them with cover and food, and some mammals-like bats-eat the abundant insects in the river corridor. Birds are more dependent than mammals on riparian vegetation for cover, specifically nesting cover. Over half of the bird speciesnesting along the river corridor nest in riparian vegetation. Many birds eat insects or feed insects to their young, relying on the river and riparian vegetation for this important food. Somebreeding bird densities in the riparian zone are among the highest recorded for their species. One of the highest known densities of peregrine falcons in North 76 Chapter III Affected Environment America resides in Grand Canyon, feeding on the swallows, swifts, and bats there (figure 111-4). The importance of riparian zone resourcesas wildlife habitat is easily demonstrated by the distribution of four common lizards. These speciesare most abundant near the shoreline where invertebrates, including insects,are common. Densities of lizards in some Colorado Riyer corridor locations are higher than anywhere elsein the Southwest. Summary As described above, the processes(water releases and sediment transport) that control downstream resourcesand the resourcesthemselves (water, sediment, fish, vegetation, and wildlife and their habitat) are interconnected within a system operationally defined as the Grand Canyon The reader should keep in mind that this system exists within the boundaries of conditions dictated by Glen Canyon Dam. None of the alternatives considered in this EIS has the potential to return the system to predam conditions. Well-defined volumes of cold, clear water annually pass through Glen and Grand Canyons. Native and non-native fish that could not tolerate these conditions have declined or disappeared from the canyon. Other speciesand communities that were rare or nonexistent before the dam are now abundant: Cladophora,Gammarus,trout, bald eagles,peregrine falcons, and riparian vegetation and its wildlife in the NHWZ. The following discussions present the details surrounding the affected resourcesnecessaryto understand and evaluate the effects of each alternative. WATER ecosystem. Swifts and ~ Figure 1II-4.-Insects are an important linkage between aquatic and terrestrial systems in Grand Canyon. Some insects emerge from the river as adults and become food for various wildlife species using the river corridor. For example, swallows, swifts, and bats feed on emerging insects; peregrine falcons, an endangered species, feed on these foraging species. Most of the Colorado River water flowing into Lake Powell and ultimately releasedinto Glen Canyon originates in the Rocky Mountains. Runoff from spring snowmelt in the Rockies is high during April through July, and flow in the Colorado River above Lake Powell reachesits annual maximum, then recedesfor the remainder of the year. During the summer and fall, thunderstorms causeflooding in tributaries originating on the Colorado Plateau, producing additional peaks in the river, but usually smaller than the snowmelt peaks and of much shorter duration. SinceGlen Canyon Dam was completed in 1963,flows immediately below the dam have consisted almost entirely of water releasedfrom Lake Powell. Downstream, the river gains additional water from the few perennial tributaries, ground-water discharge, and occasionalflash floods from side canyons. Flow regulation by the dam has resulted in a slight increase in median flows and a large decrease in the magnitude and frequency of major floods in the Colorado River, although flash floods in tributaries continue to produce temporary uncontrolled peak flows in the river. Because demands for hydroelectric power determine the WATER hourly schedule of discharges,water releasesvary over a 24-hour cycle. The peak daily discharge below the dam generally occurs in the daytime, and the minimum discharge occurs at night. The times at which the peak and minimum occur downstream vary with distance from the dam. In addition to reservoir capacity, annual runoff, and discharge capacity, Glen Canyon Dam operations also are affected by legal and institutional constraints specified in various Federal laws, interstate compacts, international treaties, and Supreme Court decisions-the "Law of the River." 77 additional resource management agenciesand organizations were invited and becameinvolved. This section provides historic perspectives on the following water issues: .Streamflows .Floodflows .Reservoir and other spills storage .Water allocation deliveries .Upper Basin yield determination .Water quality Streamflows Section 602 of the Colorado River Basin Project Act (Public Law 90-537)directed the Secretaryof the Interior to develop operating criteria to comply with and carry out the provisions of the Colorado River Compact, the Upper Colorado River Basin Compact, and the Mexican Water Treaty. This resulted in the 1970Criteria for Coordinated Long-Range Operation of Colorado River Reservoirs (Long-RangeOperating Criteria). TheseLong-Range Operating Criteria cover the coordinated operations of the Upper Basin reservoirs and Lake Mead and are reproduced in attachment C. The Long-Range Operating Criteria are subject to review at least every 5 years. The most recent review was completed in 1993. As part of the review process,comments are invited and received from numerous individuals and groups. In 1985,the Colorado River Management Work Group was formed to "seek consensusregarding operating flexibility available in the existing operating criteria and to develop procedures and analytical tools to be used for formulating future annual operating plans'l (Bureau of Reclamation, 1986). Sinceformation, the work group has met several times each year to develop annual operating plans and to conduct studies with the objective of improving overall operations. Until recently, the work group has consisted principally of representativesof the Basin States,Bureau of Reclamation (Reclamation), and the Western Area Power Administration (Western). In 1991, The closure and water releasemanagement of Glen Canyon Dam have affected Colorado River flows in Glen and Grand Canyons. Figure 111-5 illustrates the changesin the pattern of annual flows at LeesFerry for the predam period (from 1922,when continuous records began, through 1962)and postdam period (1963-89). Predam Streamflows Predam flows were characterized by large year-to-year and seasonalvariability (figure 111-6). Melting of the mountain snowpack typically produced high runoff of long duration during the late spring and early summer. Spring flows often were characterized by double peaks. Annual maximum daily flows greater than 80,000cfs were not uncommon; in some years they exceeded 100,000cfs. In contrast, flows less than 3,000cfs were typical throughout late summer, fall, and winter. Figure 111-7illustrates the occurrence of predam and postdam daily flows for 4 representative months (the higher flows are shaded darker) and shows that spring flows were much higher and winter flows much lower predam than postdam. Throughout most years, an additional variability pattern was superimposed on the general seasonal pattern of predam flows, particularly during the summer-fall monsoon season. Increasesand decreasesof short duration, but occasionally very high magnitude, commonly occurred (and still do) 78 Chapter III Affected Environment at intervals of a few days or less due to floods from tributaries-perennial tributaries such as the Paria River and LCR and hundreds of usually dry side canyons. Thus, while predam flow did not resemblethe daily fluctuations of dam operations, neither was it steady, as shown in figure III-6. Before closure of Glen Canyon Dam, flows below the damsite typically exceeded33,200cis (powerplant capacity) during April through July. Occasionally, flows exceeded33,200cfs in August and into the fall in responseto floods from tributaries-mainly the Paria River and LCR (a few of the largest floods in the LCR have occurred in mid-winter). Table 111-1summarizes maximum predam and postdam flows and the frequency with which powerplant capacity was exceeded. Thesedata show that high flows were larger and more frequent before the dam was built. Table 111-1.-High predam and postdam Colorado River flows below Glen Canyon Dam (daily values) Percent of days 33,200 cfs exceeded Month Predam (1922-62) Postdam (1963-89) Maximum flows (cfs) Predam (1922-62) Postdam (1963-89) April 16 0 75,000 May 61 9 119,000 48,000 June 77 13 124,000 93,000 July 17 7 119,000 88,000 3 2 August 65,000 45,000 22 20 18 16 6 4 2 0 1920 1930 1940 1950 1900 1970 1980 Figure IlI-5.-The pattern of annual flows at Lees Ferry changed with completion of Glen Canyon Dam in 1963. 1900 WATER 79 Lake Powell began storing water in March 1963 and filled in June 1980. Very little water was releasedthrough Grand Canyon for the first 2 years after dam closure (about 2.5 maf each year). In 1964,Lake Powell achieved the minimum elevation necessaryfor power production (3490feet). Since 1965,the minimum annual releasefrom Glen Canyon Dam has been about 8.23maf, and variability in annual releases has been reduced. Figure 111-7compares the postdam daily flows with predam flows. Of particular note is the substantial reduction of high spring flows in the postdam period. Monthly Streamflow. Predam monthly flow volumes reflect high spring flows and low winter flows. Table 111-2 presents predam and postdam median monthly volumes for representative months of the four seasons. Postdam volumes have been much less extreme than predam volumes. Table 111-2.-Median predam and postdam monthly flows at Lees Ferry (1 ,000 acre-feet) Predam (1922-62) Figure Ill-6.-Predam stage hydrographs at Phantom Ranch. Day-to-day variations caused by tributary floods are superimposed on the seasonal variation caused by snowmelt in the Rocky Mountains. Postdam Streamflows Historic operations (prior to existing interim flows) are described under the No Action Alternative, chapter II. Additional historical perspective on monthly and hourly releasesis provided here. Postdam (1963-89) Fall (October) 412 609 Winter (January) 319 745 Spring (May) 2,805 845 Summer (July) 1,357 827 Hourly Streamflow. Figure 111-8shows the daily range in flows for low, moderate, and high water releaseyears. The range is represented by a plotting of the lowest and highest hourly releasesfor each day of the water year. Greater fluctuations occur in years with low and moderate release volumes. Seechapter II (figure II-4) for typical daily fluctuations during 24-hour periods with high, moderate, and low daily releasevolumes. Daily flow maximums, minimums, and fluctuations are important when comparing EIS alternatives. Figure 1I-5in chapter II shows postdam daily occurrencesof these parameters by month. Table 111-3 provides such postdam daily occurrencesby season. 80 Chapter III Affected Environment Daily c=:J <5 Flows (1000 , ,-':~~::~~~~~~: 1().20 Season :",:,,:,",,::,:::-,:: 5-1O I Predam I 3.4% 2()-40 -40-60 >60 (1922-62) 19.9% Fall (October) 54.5% 0.5% Winter 54.4% 45.1% (January) 0.6% Spring (May) 1% Summer (July) Figure 1II-7.-Predam and postdam daily flows at Lees Ferry (percent of days that the specified flows occu"ed). Rate of Change in Streamflow (Ramp Rate). The ramp rate is the rate of change in instantaneous discharge to achieve either higher or lower releasesin responding to electrical load. The principal times of changeare in the morning, when the releasesare ramped upward to respond to the peak daytime demand, and at night, when releasesare ramped downward as the electrical demand diminishes. Ramp rates are of concern becauseof their effects on sediment, aquatic resources,rafting, and fishing downstream of the dam. The historic down and up ramp rates are shown in chapter II (figure II-6). WATER Table 111-3.-Historic minimum and maximum hourly releases and daily fluctuations. 1965-89 (percent of days) Minimum hourly releases <5,000 cfs <8,000 cfs Fall (October) 70 81 Winter (January) 54 76 Spring (May) 44 64 Summer (July) 49 66 Maximum hourly releases >20,000 cfs >25,000 cfs Fall {October) 32 11 Winter {January) 64 39 Spring {May) 99 96 Summer {July) 70 47 Daily fluctuations >8,000 cfs >12,000 cfs >20,000 cfs Fall (October) 77 49 7 Winter (January) 83 69 23 Spring (May) 74 49 10 Summer (July) 83 67 22 Downstream Releases Transformation of Fluctuating Daily fluctuations in releasesfrom Glen Canyon Dam produce long waves that travel the length of the canyon. To an observer at a fixed location, thesewaves resemble ocean tides. The waves produced by fluctuating releasestransfer the energy of the releasedwater downstream by continuously displacing an equivalent amount of water. As a wave passesa fixed location, an observer seesdisplaced water, not the released water that initially formed the wave. height) decreases.The rising limb of the flow fluctuation, or wave, becomessteeper,and the falling limb becomesflatter. Such changesare important considerations for determining impacts on sediment resources,fish habitat, riparian habitat, and recreation. SeeAppendix B, Hydrology, for additional information about wave transformation. , Travel Time of Water Information about travel time of water released from the dam to sites of interest downstream is important for assessingwater quality and sediment transport. Travel time is determined by water velocity, which varies with discharge. Dissolved materials, such as oxygen or a tracer dye, travel at the same velocities as the water in which they are mixed. Suspended materials, such as silt, tend to travel at slightly lower velocities, and floating materials-when not trapped in an eddy-travel at the highest water velocities at the water surface. The energy waves produced by fluctuating releasesfrom the dam, however, travel at substantially greater velocities than the water that initially forms them, so wave travel times through a given reach are much shorter than travel times of the releasedwater. Additional information about travel time of water is provided in appendix B. Tributary Flows Principal tributaries to the Colorado River below Glen Canyon Dam are the Paria and Little Colorado Rivers, and Bright Angel, Tapeats, Kanab, and Havasu Creeks. Streamflow records are available for the Paria River (at Lees Ferry), the LCR (near Cameron, Arizona), and Bright Angel Creek (near Grand Canyon). Table 111-4presents USGSwater records for maximum and minimum flows by day, month, and year for each of these tributaries. Floodflows and Other Spills The size and shape of the waves change as the waves travel downstream. Minimum flows at wave troughs increasewith distance below the dam, and the range in flow fluctuation (wave 81 Floodflows are defined in this EIS as flows in excessof the powerplant capacity of 33,200cfs 82 Chapter III Affected Environment 80,000 60,000 "(;;' u ; 40,000 o ii: 20,000 0 Figure 1II-8.-The magnitude of daily fluctuations has been greater for low to moderate release years than for high release years. Spills other than floodflows are excessannual releasevolumes greater than legally required owing to scheduling difficulties. The ideal operating plan would enable Lake Powell to fill each year without risking floodflows. Floodflows are undesirable because they move sediment out of the system, they bypass the powerplant, and they exceed diversion capacities (often causing loss of downstream water uses). Unfortunately, inflow forecasts have a large degree of uncertainty , which increases the risks of WATER 83 Table 111-4.-Recorded flows of principal tributaries to the Colorado River in Grand Canyon through 1990 Little Paria River (1924-90) Minimum day (cfs) Maximum day (cfs) Bright Angel Creek (1923-74) Colorado River (1947-90) 0 6,750 18,400 10 2,500 Minimum month (acre-feet) Maximum month (acre-feet) 24,596 257,766 30,019 Minimum year (acre-feet) Maximum year (acre-feet) 8,280 45,900 16,873 815,855 62,845 O 119 either flood releasesor not filling the reservoir. Since the closure of Glen Canyon Dam, floodflows (releasesin excessof powerplant capacity33,200cfs) have occurred almost exclusively in the months of May, June,July, and August. The present methods of scheduling releasesto avoid floodflows are discussedunder the No Action Alternative in chapter II. These operating measuresare thought to provide protection against floodflows for all years except those with extreme inflows compounded with a high forecast error. If the reservoir was near full when such hydrologic events occurred, floodflows would be difficult, if not impossible, to avoid. Reservoir Storage 795 10,562 begirming in 1976and a more recent one that started in 1988. Lake Powell first filled in 1980 and, under historic and present operations, is not allowed to exceed22.6 maf on January 1 to allow receiving spring inflows. A typical storage pattern is to draw the reservoir down begirming in July or August through February or March of the next water year. With spring inflow beginning in March or April, Lake Powell begins to rise to its maximum storage in June or July. During drought periods, its annual increasein storage is very slight or nonexistent. Lake Mead is somewhat insulated against dramatic drawdowns due to drought becauseof the minimum annual releaserequirement from Lake Powell under the Long-Range Operating Criteria. Also, annual fluctuations at Lake Mead are smaller than those at Lake Powell. Storagein Lake Mead rises and falls as a result of scheduled releasesfrom Lake Powell and Lake Mead to meet downstream demands or to comply with flood control regulations. If monthly releasevolumes were altered, storage patterns at Lake Powell within the year could be affected. Further, if annual releasevolumes were changed (such as by increasing or decreasing spills), carryover storage from one year to the next could be affected. Storageamounts in Lakes Powell and Mead are operationally tied together becausethe Long-Range Operating Criteria require storage equalization between the two reservoirs under certain conditions. Figure 111-9 presents the end-of-month storage in the two reservoirs since 1963. Water allocation deliveries are the deliveries of Colorado River water to entities in the seven Colorado River Basin Statesand Mexico, in accordancewith the "Law of the River ." Sincefirst reaching storage equalization with Lake Mead in 1974,Lake Powell has had two significant periods of drawdown due to drought-one In recent years, Lower Basin water demands have approached their 7.5-maf entitlement, thus requiring rationing and innovative solutions to Water Allocation Deliveries WATER Table 111-5. -Historic Colorado River consumptive water use, Lower 85 Basin 1 (in 1 ,000 acre-feet) Mexico Year Arizona California 2,800 4,400 4,804 4,891 5,040 5,144 5,219 5,006 Nevada Total Basic 7,500 6,273 6,734 7,092 7,530 7,657 7,050 1,500 1,700 1,700 1 ,700 Excess2 Basic apportion ment 1986 1,357 1987 1988 1,734 1 ,923 1989 2,230 1990 2,260 1991 1 ,864 300 112 109 129 156 178 180 1,500 1,542 1,521 9,224 3,044 759 228 134 141 1 Published in accordance with the Supreme Cour1 decree in Arizona v. California. 2 Includes amounts ranging from 98,000 to 148,000 acre-feet per year pursuant to minute No.242 of the Mexican Water Treaty. Table 111-6.-Colorado River consumptive water use, Upper Basin (in 1 ,000 acre-feet) Year Basic apportionment Arizona Colorado 50 42 40 42 44 44 3,079.5 2,086 2, 106 1 1981 1982 1983 1984 1985 1 In accordance with 1988 hydrologic 1,920 1 ,865 1 ,994 New Mexico 669.5 342 425 426 417 401 Utah 1,368 782 746 718 762 879 Wyoming 833 341 330 346 307 336 Total 6,000 3,551 3,607 3,410 3,351 3,610 determination. The determination concluded that annual water depletion for the Upper Basin reasonably can be allowed to increaseto 6 maf. The determination further certifies the availability of interim excess supplies of 69,000acre-feetannually through year 2039for marketing in New Mexico. Subsection (b) of article II of the Upper Colorado River Basin Compact permits New Mexico (or any other Upper Basin State)to use water in excessof its percentageallotment, provided such excessdoes not prohibit any of the remaining Statesfrom using their allotment. Any reduction in the 6-maf determination (as a result of implementation of an alternative or otherwise) would causea corresponding reduction in the 69,000acre-feetdetermined to be available to New Mexico through 2039. Water Quality The study area for evaluation of water quality includes Lake Powell and the Colorado River and its tributaries between Glen Canyon Dam and the inflow area of Lake Mead. This section describes chemical, physical, and biological characteristics of the study area and their influence on river system water quality .More detailed information can be found in Appendix C, Water Quality. Lake Powell Lake Powelllimnology-Qr water quality and aquatic ecology-is a story of change,both over years and seasons. Changesinclude: 86 Chapter III Affected Environment .The reservoir's stagesof development, from initial filling to a full reservoir, and subsequent stagesof drawdown and refilling .Seasonal changesin climate .Variable quality and quantity of inflow Lake Powell was filling nearly continuously from 1963unti11980. Through 1982,the reservoir periodically stratified into chemical layers through most of the year and thermal layers from spring through early fall. The depth of stratification was to about the penstocks. The reservoir completely filled and spilled for the first time in 1980and remained full through 1987. Releases through the river outlets and spillways during the 1983-84high flows helped flush out the reservoir and mix the layers, forestalling stratification for over a year. The major drought in the Southwest that began in 1987causedthe elevation of Lake Powell to drop over 80 feet from full pool between 1988to 1992. Lake Powell has reestablishedits stratifications, but winter vertical mixing has not been strong enough to mix as thoroughly. Thus, winter inflows travel primarily along the bottom of Lake Powell, pushing oxygen-poor, saline water up toward the penstock intakes. Late summer inflows are intermediate in density and travel about mid-depth in Lake Powell. Figure 111-10 illustrates these general current patterns. § 3700 ~ 3600 (/) ~ 3500 Q) ~ Q) 3400 > 0 ~ 3300 c O ~ 3200 > Q) w 25 50 River Miles 75 Upstream April 100 125 From Lees Ferry, 150 175 200 Arizona -July Long-term hydrologic cycles causelarge changes in reservoir depth and volume which influence vertical mixing, nutrient distribution, sedimentation patterns, and circulation in the reservoir. Inflows. The Colorado River is the major tributary to Lake Powell, followed by the Green Riverwhich joins the Colorado River upstream of Lake Powell-and the SanJuan River. Together, the three tributaries contribute about 95 percent of the total reservoir inflow. Each tributary has a unique chemical, physical, and biological composition stemming from diverse basin geology, development, and seasonaland annual hydrologic variations, among other factors. 25 River 50 Miles 75 100 125 From Lees Ferry, Upstream Aug ~ 150 175 200 Arizona -act 3700 ..J m cn 3600 ~ 0) 3500 ~ Three distinct seasonalinflows from the Colorado River form currents which travel in different ways through Lake Powell. Spring inflows are warm and less densethan the cold reservoir water, allowing the inflow to flow over the top of the reservoir surface. Theseinflows may reach the dam in 2 to 7 months, depending on the volume of water in the reservoir and amount of spring inflow. In contrast, winter inflows are cold and saline, so they are denser than reservoir water. ~ o 3400 ~ 3300 3200 0 I I I I 25 50 75 100 125 From Lees Ferry, River Miles Upstream Nov- I I I 150 175 Arizona Mar Figure 1II-10.-Generalized seasonal circulation patterns in Lake Powell (modified from Merritt and Johnson, 1977). I 200 WATER When reservoir water is drawn through the penstock intakes at elevation 3470feet--0r about 230 feet below full pool-a withdrawal current forms, which further influences other currents in Lake Powell. The vertical extent of the withdrawal current increaseswith the amount of discharge and reachesa maximum of about 100 feet above and below the intakes Oohnson and Merritt, 1979). The intakes usually withdraw water from within the bottom layer of the lake, the hypolimnion, which is discussedlater in greater detail. Studies. Lake Powelllimnology has been studied at various levels of detail since about 1968, providing a basic background of some limnological components and processesat particular stagesof reservoir development. Reservoir fisheries have been studied in greatest detail. Since about 1972,Reclamation's water quality data collection program has focused on salinity and temperature; dissolved oxygen (DO), circulation, and other data also were collected. Recently, the Lake Powell Monitoring Program has been gathering data at more regular intervals. Short-term and single-event studies, often not conducted reservoir wide, have provided additional information on nutrients, plankton, sediment chemistry , pH, and trace elements such as mercury, selenium, and lead. The U.S. Fish and Wildlife Service(FWS) also has collected fish samples for trace chemical analysis, and NPS conducts bacteriological studies in recreation areasfor human health concerns. Since data was not collected at regular intervals, limited comparisons may be made between seasonsand years. Accordingly, general statementscharacterizing all components and processesof reservoir limnology and quantitative predictions of future changescannot be made with confidence. In the absenceof a complete data history, alternate means were used to assess past and future conditions, such as comparing the characteristicsof Lake Powell with other reservoirs and lakes. Temperature. Most of Lake Powell is extremely clear; sunlight penetrates to depths of 82 to 113 feet. Sunlight's ability to warm water 87 decreaseswith depth, so Lake Powell is thermally stratified through much of the year. The epilimnion is the topmost and warmest layer, ranging from 30 to as much as 80 feet in depth (Johnson and Merritt, 1979). However, the thickness varies with seasonsand location (Hammer and MacKichan,1981). Although temperatures within this layer vary slightly with depth, summer temperatures reach about 80 of, and winter temperatures may drop to 45 Of. Temperatures of 45 of or less can be lethal to the threadfin shad, which comprise much of the prey base for the Lake Powell sport fishery .The metalimnion, or the middle layer, often ranges from 30 to as much as 80 feet in depth. Here sunlight is limited, and water temperatures decreasewith depth. The hypolimnion, or bottom layer, is too deep for sunlight to reach, and water temperatures remain nearly constant at about 46 of. This uneven heat distribution also createscirculation in the reservoir. Nutrients. Most of the incoming nutrients to Lake Powell are associatedwith or attached to sediments, and essentially all sediment settles to the reservoir bottom. Lake Powell retains over 97 percent of the inflowing phosphorus, primarily with sediments (Miller et al., 1983). Algae cannot readily consume nutrients attached to sediments. Nutrient concentrations near the surface are highest during June and July, stimulating growth of plankton. As plankton populations grow, the nutrient supply diminishes. Typically, planktonic algal blooms occur in the summer, mainly in shallow, sunny inflow areaswhere tributaries enter the reservoir carrying nutrient-rich sediments. Other Characteristics. Other water quality characteristicsalso vary with reservoir depth. Atmospheric reaeration and wind-induced mixing of reservoir water is limited to the epilimnion, thus restricting reaeration of deeper water throughout the summer. The shallow epilimnion is generally well oxygenated, averaging over 8 milligrams per liter (mg/L). 00 concentrations in the metalimnion may range from 5 to 10 mg/L, except when associatedwith the summer development of the minimum DO layer, described below. Concentrations of 00 deep in the 88 Chapter III Affected Environment hypolimnion can be as low as 2 to 3 mg/L, and overall water quality remains nearly constant in this layer. Salinity, nutrients, selenium, and mercury concentrations are highest in the hypolimnion and lowest in the epilimnion. A 00 minimum layer periodically develops in the metalimnion between 45 and 60 feet below the reservoir surface during the summer with concentrations as low as 2 mg/L (Johnsonand Page,1981). Its formation results from DO consumption by algae,bacteria, zooplankton, fish respiration, and the chemical processesof organic decay. The DO minimum layer typically begins forming in tributary inflow bays and may extend over most of the reservoir by September. A water quality inventory conducted for Lake Powell analyzed tributary delta sediments and surface and bottom waters for lead, mercury , selenium, and other trace elementsprimarily associatedwith sediments (Kidd and Potter, 1978). This study concluded that Lake Powell traps most of the elements investigated, except lead. More dissolved lead left the reservoir than came in, attributable to gas spills from boating. Mercury and selenium occur naturally in the Colorado River Basin and accumulate in tissues of living organisms in the lake (Wood and Kimball, 1987). Lake Powell also traps sediment. It is estimated that within about 300 to 500 years, sediment will fill the reservoir to near the elevation of the penstocks. As the lake fills with sediment, the reservoir will shrink-affecting changesin temperature distribution, DO and nutrient content, circulation, plankton communities, and other reservoir components. Colorado River Below Glen Canyon j~am Two major influences on Lake Powell and downstream water quality are: Reservoir elevation (the amount of water in Lake Powell) The intake level where water is withdrawn The intakes withdraw water mostly from the hypolimnion when Lake Powell's elevation is above about 3590feet. As Lake Powell is drawn down (below 3590feet), the reservoir surface drops, and water may be withdrawn from'the metalimnion and epilimnion, where reservoir water differs in quality . Most of Lake Powell's influences on the Colorado River below the dam center on flow, sediment, and water quality .Reservoir releaseshave changed variation and magnitude of downstream riverflow, turbidity, temperature, salinity , nutrients, and other water quality characteristics. Below the dam, both temperature and salinity change little with the seasons. Salinity fluctuations downstream now vary less over several years than the predam cycles changed in months. Downstream salinity is of major economic significance to water users in the Lower Colorado River Basin becausehigh salinity causesproblems, such as damage to irrigated crops and municipal water systems. River temperatures at Lees Ferry are inversely related to Lake Powell water surface elevations. Releases from Glen Canyon Dam have ranged from 43 to 54 OFand average about 46 oF. River temperatures increase slowly downstream of the dam but seldom exceed 60 op at Diamond Creek, about 240 miles downstream (Sartoris, 1990). The greatest warming occurs during June through August. The average annual downstream river temperature is about 55 OF(48 to 62 OF),and actual river temperatures have deviated very little in recent years (Sartoris, 1990). As the reservoir surface elevation falls below 3590 feet, release temperatures, and thus river temperatures, begin to rise measurably. Releasesfrom Glen Canyon Dam are relatively clear, lacking nutrient-rich sediments or any algae, and are resultingly low in nutrients. The clear water allows greater sunlight penetration, enhancing productivity in spite of low nutrient concentrations. Tributaries below the dam have somewhat higher nutrient concentrations than the mainstem, yet contribute little to overall main stem nutrient concentrations. 90 Chapter III Affected Environment as campsitesby boaters and are substrate for vegetation and wildlife habitat. Next in size are the gravels and cobbles,which-together with small boulders-armor the streambed in some places. Some fish speciesuse shallow gravel beds for spawning. The largest particles are boulders, some larger than automobiles, which fall from the canyon walls or reach the river in debris flows from steep tributary canyons. Boulders create and modify most of the major rapids and are a major factor in the creation of sandbars. Although its riverbed is bedrock in some places, the Colorado River generally is a cobble- and gravel-bed stream, through which sand is transported. Sand is stored throughout Grand Canyon in "patches" on the riverbed and in eddies (Graf et al., 1993). The river's capacity to transport sediment increasesexponentially with the amount of water flowing in the river. All sediment particles weigh more than water, so they tend to settle to the bottom. The turbulence of flowing water is the uplifting force that causessediment particles to be carried in suspension or roll along the strearnbed. The greater the river's flow, the greater the velocity and the greater the turbulence. Clayand silt particles commonly are carried in suspension by nearly all dam releases. Flows in the river often are large enough to carry sand grains in suspension or to roll them along the riverbed, depositing the grains temporarily in areaswhere water velocity is insufficient to move them. Even larger flows and velocities are needed to move gravel and cobbles. The largest boulders remain Riverbed Sand The decreasedannual peak flows reduced the river's capacity to transport sand (figure lII-l1). Measured suspended sediment loads (sand, silt, and clay) at Phantom Ranch averaged 85.9million tons per year during 1941-57.Sinceconstru(iion of Glen Canyon Dam, this averagehas been reduced to an estimated 11 million tons per :year, approximately 70 percent of which comes fr,Dm the Paria River and the LCR. Together these rivers have delivered an average of 12 million tons per year of sediment to Grand Canyon since 1941 (Andrews,1991a). Most of the sediment delivered to and transported by the Colorado River is silt and clay. Because thesefiner particles can be carried in suspension by most dam releases,the quantity of silt and clay transported depends mainly on tributary supply. Although sandbars along the banks of the Colorado River contain some silt and clay, their existence primarily depends on the transport of sand. As bed-materialload (mainly sand and gravel) enters the Colorado River from the tributaries, it begins the long and slow journey to Lake Mead. During the course of this journey, sand particles may go through numerous cycles of temporary transport and deposition. The riverbed is made up of bedrock, boulders, cobbles,gravel, and sand. The location of thesematerials depends on the local geology, river velocity, and the supply of incoming sediment. The riverbed is highly irregular and contains many deep pools, rapids, and eddies, where sands, gravels, and cobbles are stored during periods of low discharge (Graf et al., 1993). Becauseof reduced capacity to transport sand, the Colorado River now can store more sand and larger-sized sediments in low velocity areas. The amount of sand stored within the riverbed each year depends on the tributary sand supply (which is highly variable), the pattern of water release, source for building sandbars during periods of high releases. The probability of net increasein sand stored in the river channel is used as an indicator of impacts of the alternatives. Delivery to the Colorado River The quantity of sand stored in a given reach-and thus available for deposition on sandbarsdepends upon the supply of sand from the upstream channel and tributaries and the rate at which sand is removed from the reach by transport downstream. SEDIMENT 8. 91 150,000 25,000 0 e;. .0 [ o -.t 0> ~ 0 11) m ..- 0 <0 0) 0 N 0> .- 0 (') m o v 0) .- O In 0} ~ o (0 0) O ,... m ~ o 00 0> .- o 0) 0) ..- 0 0> .- 20 III ()~ ~ ~ O O 00- ~O U= C O M 0) .- 25 b. III '1- 0 (\I m .- U) C O 15 10 .III E (/)~ ""iU :1 1:= C « 5 0 O 0) .- Figure III-11.-Annual peak flows (a) ana' estimated sand transport capacity (b) for the Colorado River at Lees Ferry from 1922 to 1990, both of which have been substantially reduced since dam closure. Sand transport capacity wa:; estimated from an accumulation of daily sand loads. Daily loads (both predam and postdtjim) were determined from mean daily flow at Lees Ferry, using the Pemberton (1987) sand loaa' equation for Phantom Ranch. Actual predam loads may have been greater than those computed, and actual postdam loads much smaller than computed. Postdam transport capac1!ty at Lees Ferry is much greater than sand supply. Many tributaries supply sediment, including sand, to the Colorado River downstream from Glen Canyon Dam. The Paria and LCR are estimated to supply over 70 percent of the total sediment (sand, silt, and clay) entering Grand Canyon. Other tributaries typically deliver sediment during flash floods or debris flows. There are no tributaries that deliver substantial quantities of sediment between the dam and the Paria River, although sediment occasionally is delivered to that reach by side-canyon flash floods. Gauged Tributaries. Sand contribution from the Paria and Little Colorado Rivers and Kanab Creek, estimated at USGS gauging stations, varies greatly from year to year (see figure 111-12)but 92 Chapter III Affected Environment generally has decreasedin the 20th century .Sand delivery is subject to long-term climate variations that affect sediment storage in the flood plains of these streams (Hereford and Webb, 1992;Graf et al., 1991). Paria River at Lees Ferry 10 I o " ~ o g 16 3 " " ~ 8 In spite of the reduced sand-transport capacity of the Colorado River, there has been a net decrease in sand storagebetween the dam (RM -15.5)and the LCR (RM 61) since closure of the dam. Most of the decreasehas occurred since the floods of 1983-86.Also, annual sand deliveries from the Paria River (RM 1) have been below average since 1980(figure 1II-12;also seeGraf et al., 1991);however, Topping and Smith (1993)are reevaluating the flood history and transport capacity of the Paria. A well-documented large flood on the LCR during interim flows delivered large quantities of sand and silt to the river (Beuset al., 1993;Hazel et at., 1993;Kaplinski et al., 1994). Downstream from the LCR, there has been a net increasein sand storage. 6 4 2 0 Little Colorado "ii)' c .9 o I/) c ~ "E 16 o -J "0 c tU (/) River near Camleron 10 8 6 Under normal fluctuating flows, a long-term sand balance is likely downstream from the LCR but may not be achieved upstream. However, future long-term changesin the sand supply from tributaries could alter this conclusion. Smilie, Jackson,and Tucker (1993)analyzed the frequency of annual sand delivery from the Paria River (1949-76)in relation to Colorado River transport capacity. Their results for a minimum releaseyear (8.23maf) suggestthat, when the range in daily flow fluctuations exceedsabout 18,000cfs on an annual basis, transport capacity exceedsthe long-term supply from the Paria River (about 790,000tons) in the reach between the Paria River and LCR .Even when transport capacity and long-term sand supply are in balance,however, there would be periods of fairly substantial short-term lossesand gains in sand storage between the Paria River and LCR. 4 2 ""(U :3 c c 80 280 24 5.2 42 210 27 7.4 81 220 24 7.9 72 350 18 5.3 36 Wide 390 15 11.1 30 12.1 62 4 5 61.5-77.4 6 77.4-117.8 Narrow 190 27 7 117.8-125.5 Narrow 230 21 8 125.5-140 Narrow 210 26 140-160 Narrow 180 23 6.3 78 Wide 310 19 6.9 32 Narrow 240 30 8.4 58 9 10 160-213.8 11 5213.8-236 12 , 2 3 4 5 Channel Percentage of bed composed of bedrock and boulders4 236-278 10.6 48 68 [No data] See figure 111-14. Average of cross-section data at about 1-mile intervals at 24,000 cfs (Randle and Pemberton, Based on predicted water-surface elevations at 24,000 cfs (Randle and Pemberton, 1987). From channel-bed material maps (Wilson, written communication,1987). Results from miles 213.9-225. The narrowest, steepest,and shallowest places of all are the rapids, which account for about 90 percent of the river elevation drop through the canyon but only about 10 percent of the length (Leopold,1969). Water velocities typically are 10 times greater in the largest rapids than in the long pools that extend upstream from the rapids (Kieffer, 1988,1990). Thus, while nearly all sediment particles but the largest boulders can be transported quickly through high velocity rapids, much of the sand is stored temporarily in low velocity pools and eddies. 9.0 1987). Essentially all sand in the main channel between Glen Canyon Dam and Lees Ferry was deposited before the dam was closed. Since closure, the channel has degraded (Pemberton, 1976; Burkham,1987). Loss of sand from this reach is irreversible without artificial resupply of sand becausecontribution from tributaries is very small, and transport capacity of the river is large. During the initial filling of Lake Powell, sand scoured upstream from Lees Ferry and sand contributed by tributaries downstream from Lees Ferry accumulated in the river channel. The 96 Chapter III Affected Environment 30 25 0 c: 20 ..9 c: ~ g 15 Q) CI tIS ~ 0 W 10 U c: tIS W 5 I Net gain 0 \ Net loSS Lees Ferry to Uttle Colorado -5 ~\ River ., -10 1964 1968 1972 1976 1980 1984 1988 Figure 1II-15.-Cumulative sand storage betweenLeesFerry and Phantom Ranch. Sand accumulated in the river during the relatively low releaseswhile Lake Powell was filling, coupled with large sand contributions from the Paria and Little Colorado Rivers in 1972,1979,and 1980. Sand was erodedfrom the channel during the 1983-86high water years. Computation method is describedin text. so degradation stops. This process,called annoring, has happened in the Glen Canyon reach (Pemberton, 1976). If the supply of sand is sufficient, the amount transported by the river is exponentially proportional to the riverflow (i.e., the rate of increasein sand load is much greater than the rate of increasein flow). Fluctuating flows, therefore, will transport more sediment than steady flows of the samevolume becausethe fluctuating flows are higher than steady flows during part of each day. As the wave shape changesdownstream (see WATER in this chapter), sediment transport capacity is reduced. Computed sand loads at the gauge above the LCR for steady and fluctuating water releasesof the samevolume for 1 day are compared in figure m-16. Computed sand loads are based on the river's transport capacity.Actual sand loads may be smaller than computed loads when the tributary supply is less than transport capacity. As the bed elevation continues to increase,the annual transport through Grand Canyon will approach the amount delivered annually by tributaries. The sand that accumulates during low releaseyears may be available to build sandbars during periods of sufficiently high discharge. SEDIMENT 97 30 , 000 -- Fluctuating 20,000 $' ..2. ~ o iI 10,000 Flov'J -~ '-Steady J I I Flow I o Kearsley and Warren,1993). Sandbarsare important for vegetation, riparian habitat for fish and wildlife, and recreation. Beachesare sandbars that have recreational value. Backwaters are low velocity areasformed by low elevation sandbars (seeFISH, this chapter). Sandbar deposition and erosion, both predarn and postdam, are natural processes. Ratesand amounts of deposition and erosion vary with: .Flow magnitude and duration .Tributary sediment supply .Amount of sand stored in river channel pools and in eddies .Local Figure 1II-16.-Comparison of riverflow and computed sand load at the gauge above the LCR under steady and fluctuating flouls within a 24-hour period. Cumulative sand loads in this example are 1,500 tons for the steady flow and 2,500 tons for the fluctuating flow. At Phantom Ranch, the cumulative loads increased to 3,100 tons for the steady flow and 5,100 tons for the fluctuating flow. - Sandbars (Beaches and Backwa'ters) Sandbarscommonly found along the banks of the Colorado River in Grand Canyon are dynamic. Sandbarsare derived from sand transported by the river and exchangesand with the river. These bars are composed mainly of sand; however, they may contain some silt, clay, or gravel. In this EIS, the term "sandbar" is used to mean any of the fine-grained alluvial deposits that intermittently form the banks of this otherwise talus- and bedrock-lined river (at low flows, some sandbars may appear to be separated from the main riverbank). There are more sandbars used as campsitesin wider reachesthan in narrower reaches(U.S. Department of the Interior, 1988; channel hydraulics The pattern of sandbar deposition and erosion has been altered by Glen Canyon Dam. Before completion of the dam in 1963,sandbars in Glen and Grand Canyons were aggraded and eroded cyclically by seasonaland long-term variation in flow and sand transport (V .S.Department of the Interior, 1988;Howard and Dolan, 1981). During 1965-82(following the flood releaseof 1965),high elevation sandbars generally eroded and low elevation sandbars generally aggraded; erosion rates decreasedwith time (Schmidt, 1992). During the floods and prolonged high releasesof 1983-86, sand was deposited on higher sandbars but removed from lower sandbars. Generally, high rates of erosion were observed during the nearly steady high releasesand during the return to normal fluctuating releasesbetween October 1985 and January 1986(Schmidt and Graf, 1990). Between 1987and 1991,aggradation and erosion patterns were similar to those of 1965-82,but erosion rates were greater (Schmidt, 1992). Since implementation of interim flows, sandbars have cyclically aggraded and eroded, with negligible net change overall (Beusand Avery , 1992). Also, sandbarsbetween the 20,000-and 30,000-dslevels have eroded and not been rebuilt, riparian vegetation is encroaching into the 20,000to 30,000-cfszone, and backwater habitats have filled with silt (Patten, written communication,1993). Floods in the LCR during JanuaryFebruary 1993added much sand to the system and substantially aggraded many sandbars downstream; however, postflood erosion removed 98 Chapter III Affected Environment much of the newly deposited sand from higher to lower elevations (Hazel et al., 1993;Kaplinski et al., 1994). Recirculation main channel and the riverbank. The location of the reattachment point and length of the recirculation zone vary with riverflow. The recirculation zone lengthens with increasing discharge and shortens with decreasingdischarge. Zones (Eddies) There is great potential for deposition of sand, silt, and clay within a recirculation zone, where water velocities are much lower than velocities in the main channel (Schmidt, 1990). Figure 111-18 shows that water with relatively high sand concentration moves into the eddy near the streambed, and water with relatively low sand concentration moves out of the eddy near the surface (Nelson, 1991). Sandbarsform in low velocity areasat the downstream and upstream ends of the recirculation zone. Thesesandbars usually are continuous deposits, although the retum-current channel connecting them may be submerged at most riverflows. Sand deposition and erosion in Nearly all sandbars in Grand Canyon are associatedwith recirculation zones that consist of one or more eddies. As the river flows around an obstruction, such as protruding bedrock or a debris fan, the flow becomesconstricted, and the downstream-directed current becomesseparated from the riverbank (figure 111-17).Downstream from the constriction, the channel is wider, the main current reattachesto the riverbank, and some of the water is redirected upstream. This change in flow direction forms a zone of recirculating water and sand between the points of separation and reattachment and between the Rapid or Riffle \/\I\r~ Separation £' Flow , Reattachment r,} ~J~ "0, ,,: ,...:0;(;:,. ~ :-t»$1 "m~ Reattachment ':~!:::!~:,: ~ Bar Intermittently Submerged Reattachment Bar , Return-Current Channel (backwater) Tributary Figure 1II-17.-Relationship of sandbars and flow patterns. Riverflow is constricted in a rapid, causing an eddy downstream. Sand is suspended in the highly turbulent currents of the rapid and deposited on sandbars associated with the relatively tranquil eddy currents. SEDIMENT Figure 1II-18.-Cross section of the Colorado River. Eddies are very efficient sediment traps. Water with relatively high sand concentration (near the streambed) moves toward the eddy and builds a sandbar. Water with relatively low sand concentration (near the surface) moves from the eddy back to the main channel. recirculation zones is dynamic, varying with changesin riverflows and the dimensions of debris fans. Sandbars are classified as reattachment bars, separation bars, or channel margin bars, according to their position in a recirculation zone or location along the river (Schmidt, 1990; Schmidt and Graf, 1990). Reattachmentbars, formed in low velocity areas near the downstream end of recirculation zones, extend upstream from the point of flow reattachment and typically are broader but lower than the other types of sandbars (figure 111-17).Theyare inundated more frequently and have been subjectedto a greater range of aggradation and degradation (Schmidt and Graf, 1990). Reattachment bars and the retum-current channels directly associatedwith them are important for backwaters and emergent marshes. Boatersuse these sandbars for campsiteswhere they are high enough to avoid inundation-mostly in wide reaches. In the narrowest gorges, reattachment bars may be submerged by all but the lowest flows. Retum-current channels,whether submerged or exposed,are components of reattachment bars. Retum-current channels are excavatedwhen the velocity of recirculating flow is strong enough to transport more sand from behind the reattachment bar than is being transported acrossthe bar face. Responsesof retum-current channels to various flow-release patterns are not well understood; however, there is general agreement that they are destined to fill with sand and silt unless flushed occasionally by high flows-probably greater than powerplant capacity. Backwatersare open retum-current channels connected to the river that have little or no velocity and have potential for warming by exposure to the sun (seeFISH in this chapter). The channel must be inundated, but the crest of the reattachment bar must be above water. Suitable backwaters are formed within certain ranges of riverflow; higher flows inundate the reattachment bar, and lower flows may leave the channel dry or disconnected from the river. According to Schmidt (verbal communication, 1992),floods increasethe number of backwaters by removing vegetation and scouring the retumcurrent channels; the number of backwaters decreasesbetween floods as they fill with 99 100 Chapter III Affected Environment sediment (figure 111-19).The effects of a flood of given magnitude and duration could vary considerably, depending on antecedent conditions-especially riverbed sand storage. Deposition of silt and other fine sediment is important for establishment and maintenance of marshes (seeVEGETAnON in this chapter). Marshes becameestablished along wide reachesof the Colorado River in Grand Canyon after flow regulation began in 1963,developing where large reattachment bars becameovergrown by cattails and other marsh vegetation. The 1983-86floods scoured the marsh vegetation and probably eroded several vertical feet of sand from these reattachment bars (Stevenset al., 1991). Since that time, emergent marsh vegetation has reestablished on many new reattachment bars. Vegetation becomesestablished on stable sandbars;however, the vegetation apparently does not prevent erosion (Stevensand Ayers, 1993). Separation bars (typically high elevation bars) are formed in the low velocity areasnear the upstream ends of recirculation zones and commonly mantle the downstream surface of debris fans ~~~~~lIcfj'li9Q (figure 111-17).They generally are steeper and higher than reattachment bars; many extend above the level of 30,000cfs. Usuallyassociated with eddies, separation bars are built with sand transported upstream from the reattachment point. Therefore, separation bars are composed of finer-grained sand than reattachment bars. They are preferred as campsitesbecausethey are less likely to be inundated by rising river levels, and becausethe low velocities in the upper ends of eddies make it easier to moor boats (see REcREAnoN in this chapter). Channel margin bars are elongated sand deposits along the margins of the Colorado River that have the form of terraces. Channel margin bars are not directly associatedwith large eddies; instead, they typically form in small eddies related to some sort of flow obstruction, such as a large boulder (Schmidt and Graf, 1990). Typically, channel margin bars cover bedrock or talus. In some reaches, particularly where the channel is wide, thesebars line the channel from a few hundred feet to nearly a mile and often are heavily vegetated. Downstream from RM 236, riverflow and deposition and erosion of sand and silt are affected by the level of Lake Mead (seediscussion of Lake Mead delta later in this section). Silt and Clay (/) 0) ca ~ O IG m O 0) .0 E ~ z ~ ~ "Q) a: 1965 1970 1980 1990 Figure 1II-19.-Conceptual change in relative number of backwaters (open return-current channels) during low flow seasons since the 1965 flood release, based on interpretation of aerial photographs (source: Schmidt, verbal communication, 1992). Although most of the silt and clay delivered to the river is transported directly through the canyon, an important fraction is carried by currents into low velocity areassuch as retum-current channels, where silt and clay are deposited. Silt and clay add nutrients to the slackwater environment. Clay contributes to cohesion of sand on sandbars. The presenceof silt and clay in sandbars can reduce permeability and make them more susceptible to seepage-inducederosion. Like that of sand, the only source of silt and clay in the canyon is the tributaries. Unlike sand, however, transport of silt and clay is not a function of the magnitude of dam releases. Silt and clay particles are readily transported by almost any discharge in the Colorado River, but the height of deposition in eddies depends on river stage-a result of both dam releaseand tributary inflow. SEDIMENT Little silt or clay would be deposited, however, when the riverflow is high and the supply of silt/ clay entering from tributaries is small. In fact, previously deposited silt and clay are susceptible to being washed out of an eddy by any high, turbulent flow. Thus, the likelihood of deposition of fine sediment in the eddies would be greatest during the tributary flood season,coupled with higher-than-average dam releases. Sandbar Deposition and Erosion Deposition requires high flows, whether annual or daily; erosion occurs following the return to lower flows (Schmidt and Graf, 1990;Schmidt, 1992; Hazel et al., 1993;Kaplinski et al., 1994). Without occasionalperiods of sustained high releases (above powerplant capacity), high elevation sandbars eventually will erode and not rebuild (Andrews,1991a). Sandbarstypically were not vegetated prior to the dam. Unvegetated sandbars are dependent on cycles of deposition and erosion. Active erosion is a part of this natural process. Comparison of photographs taken of the same sites in 1890and in 1990provides some information about the long-term change of sandbars (Webb, in press). In eastern Grand Canyon (RM 0-126),a relatively high percentageof sandbarshad eroded between 1890and 1990. In western Grand Canyon (downstream from RM 126),more sandbars were about the same size or had aggraded than had eroded. This comparison, however, does not take into account the short-term variability of sandbars,which could affect the conclusions. Short-term changesin sandbarshave been documented since completion of the dam. During periods of low releases(1966-82and 1987-90), channel banks in wide reachesaggraded while high elevation sandbars used as campsites eroded. Erosion rates decreasedwith time. During periods of relatively high discharge (1983-86), reattachment bars eroded, but high elevation sandbars aggraded. Aggradation rates during 1987-91were equivalent to those of 1966-82,but erosion rates during 1987-91were about twice as great as those of 1966-82(Schmidt, 1992). 101 Normal Operations. Sandbarsexperience cycles of deposition and subsequenterosion during normal operations. Generally, net erosion decreases downstream, with the attenuation of the daily extremes in river stageand the addition of sand from tributaries. Sandbar erosion can result from any of three mechanisms: main-current erosion, seepageinduced erosion, and wave-induced erosion. At a particular sandbar and at a particular time, one of thesemechanismsmay be predominant. Up ramp rates have not been linked to sandbar erosion. Main-current erosion is causedwhen the main channel current is in direct contact with part of a sandbar. Exposure of sandbars to this type of erosion may be increasedby the contraction of the recirculating zones during periods of low discharge or when debris fans are overtopped during periods of high flow. Main-current erosion is believed to causegreater net loss of sand from recirculation zones to the river than the other types of erosion, but this has not been documented quantitatively. Seepage-inducederosion affects most sandbars in Grand Canyon and is responsible for rivulet formation, slope failures, bank cuts, and piping and tunneling (Budhu, 1992). Seepage-induced erosion is affected by fluctuations in river stage, down ramp rates, and the duration of minimum flow. Erosion causedby rapid upramping has not been documented. Wave-induced erosion is causedby turbulence in nearby rapids, wakes from motor boats, and wind. At each sandbar, effects of wave-induced erosion are concentrated at a specific river stage under steady flow but are distributed over the range of river stagesunder fluctuating flow. There is some evidence that waves agitate bottom sediments, enhancing the possibility of sand transport (Bauer and Schmidt, 1991,1993). During increasing flow, eddies expand downstream, and sand deposition rates within the eddy systems increase(Andrews,1991b). During decreasingflow, the downstream areasof eddies shift upstream (contract), and sand deposition 102 Chapter III Affected Environment rates within the eddy system decrease. Sand deposited near the reattachment point during higher flows is subjectedto main-current erosion by the river. Water stored within the sandbars begins to flow toward the river. Ground-water processesoccur on every sandbar during daily and hourly fluctuations. Groundwater levels within exposed sandbars rise and fall with increasesand decreasesin river stage (Werrell et al., 1993;Carpenter et al., 1991;Budhu, 1992). If river stagedecreasesrapidly, seepageinduced erosion may occur. Water table fluctuations within sandbars attached to the bank are greatestnear the river and decreasewith distance from the river. When river stage declines faster than ground water can drain from the sandbar, the exposedbarface becomessaturated. Water seeping from the saturated barface forms rills that move sand particles toward the river (Werrell et al., 1993). When the rate of river stagedecline is equal to or less than the rate at which ground water naturally drains from the barface,a seepage face will not form. The sandbar slope stability model of Budhu (1992) is applied in this EIS (seefigure 111-20).Sandbars are initially deposited at angles ranging from 20 to 45 degreeswith an average of 26 degrees. As the river stage recedes,this slope may be unstable. Seepage-inducederosion tends to reduce the slope of new deposited sands to about 11 degrees. On some sandbars,a rapid decreasein river stagesets up conditions for bar failure. The next rising river stage (at almost any ramp rate) could easily cause a failure to occur. Sandbarheight and active width for the range of daily and annual flow fluctuations are used as indicators of impacts of the alternatives. These are the height and width of the inundated zone (figure 1II-20). Unanticipated Floods. Large unanticipated floods of sediment-free water generally have a much greater effect on sandbars than releasesunder nonnal operations. The magnitude and extent of the effects depend on the magnitude and duration of the flood and the supply of sand in eddies and the main channel prior to the flood. Floods may be beneficial to backwaters by removing vegetation and re-fonning retum-current channels. Floods occurring when sand storage in the main channel is low probably would causemore extensive loss of sand-dependent resourcesthan when pools and eddies are relatively full of sand. The 1983flood, with plenty of stored sand available, aggraded many sandbars. However, Schmidt and Graf (1990)reported evidence that the floods of 1984-86did not deposit as much as the flood of 1983and caused greater erosion. If sand contribution from tributaries is sufficient to balance the sand removed from Grand Canyon over the long term, the net change in sandbars would be small. Figure 1II-20.-Conceptual cross section of a sandbar affected by fluctuating flows. Daily fluctuations create an unstable zone within the sandbar. The minimum stage determines the boundary between the stable and unstable zones. SEDIMENT The number of sandbars used as campsites increasedbetween the inventories of 1973and 1983in both narrow and wide reachesas a result of the 1983flood (Kearsley and Warren, 1993). The floods and prolonged high releasesof 1984-86, followed by fluctuating releasesin 1985-86,caused net erosion of many campsites. The 1991inventory indicated that erosion has reduced the number of campsites to slightly more than the 1973count in wide reachesand less than the 1973count in narrow reaches(seefigure 111-21). Vegetative overgrowth further reduced the number of campsites in all reaches. Other Factors. Sandbarsalso are eroded by natural forces not influenced by dam operations, such as wind, waves, rainfall, flash floods, and debris flows. Sandbarsthat are not inundated by dam releasesare susceptible to erosion by wind and the effects of camping use. Recreation causessandbar erosion, but this erosion is primarily limited to camping beaches. 300 ~ 01973 250 01983 ~ .~200 .1991 Beaches 01991 Beaches suitable for camping overgrown ~ 0150 ~ ,.1.59. -11L 100 50 0 Narrow Reaches Wide Reaches Figure 1II-21.-Comparison of sandbars used as campsites based on inventories conducted in 1973, 1983, and 1991. The number of campsites increased in both narrow and wide reaches as a result of the 1983.flood. By 1991, erosion reduced the number of campsites to slightly above 1973 levels in wide reaches and below 1973 levels in narrow reaches; vegetative overgrowth further reduced the number of campsites (source: Kearsley and Warren, 1993). 103 The amount of erosion is thought to be small in comparison with other causesof erosion. Valentine and Dolan (1979)estimated that on a typical camping beach,human foot traffic moves about 4 cubic yards of sand (lessthan 1 percent) per year into the river. Sand eroded from elevations above maximum flow would be permanently lost; sand eroded from lower elevations could be replaced by subsequenthigh flows. High Terraces High elevation alluvial terracesin wide reachesof Grand Canyon support native vegetation and may contain buried or partly buried archeological remains. The archeological remains are susceptible to exposure and loss by erosion. Most of this discussion of high terracesis based on the work of Hereford et al. (1993). The high terraceswere deposited by large floodflows (100,000cfs and greater) prior to the dam and commonly have been reworked by wind and runoff from local rainfall. The larger the floodflow, the higher the terrace and the older the deposit (seefigure III-22). The highest terraces are more than 1,000years old, while the lowest terrace is about 30 years old. Many high terracesare eroded by runoff from local rainfall resulting in networks of deep water-carved gullies (arroyos). Such erosion was extensive during the heavy rainfall of 1978-85,one of the wettest periods on record. This erosion does not occur if runoff filters into the ground before draining to the next lower terrace. However, if runoff drains to the next lower terrace, arroyos will erode to that level, exposing or eroding archeological remains, if present. Arroyo-cutting of even the lowest terraces indirectly causeserosion of higher terraces. In some cases,windblown sand may refill the arroyo. The oldest and highest terraceseroded prior to the dam and will continue to erode. However, predam annual floodflows maintained the lowest high terrace and prevented some arroyos from cutting all the way to the Colorado River (see figure 111-22).The lower peak discharges and SEDIMENT temporary storage of substantial amounts of riverbed material-mostly sand and gravel. As discussedin the section on riverbed sand, debris fans that constrict the river channel also create downstream eddies in which most of the camping beachesused by river runners are deposited. For a given flow, the constriction width and riverbed elevation at a rapid control the velocity and water surface elevation of the upstream pool, which in turn control the amount of sand and gravel that can be deposited in the pool. Aggraded debris fans will allow the channel to store more sand in the associated pools and eddies. More than 100 rapids and numerous riffles between LeesFerry (RM 0) and Bridge Canyon (RM 235) were documented by Stevens(1983). The debris fans that form rapids will continue to be replenished and enlarged by infrequent debris flows, but Glen Canyon Dam has greatly reduced the magnitude and frequency of floodflows and, thereby, the capability of the river to move boulders from the rapids. In fact, many debris fans are accumulating sediment finer than boulders (Melis and Webb, 1993). Formation of new rapids and steepening of existing ones will continue. Debris flows created rapids at RM 127.6 in 1989 and at RM 62.5 in 1990, and recent debris flows steepened 24-Mile, Specter, and Bedrock Rapids (Webb, in press). In the absenceof floods, there will be a continuing buildup of boulders and smaller particles on many rapids (Graf, 1980;Melis and Webb, 1993). The channel will become more constricted, resulting in steeperrapids. Such rapids could becomemore dangerous to navigate. Constriction ratios and elevation drops at rapids can be used as measuresof long-term hydraulic effects of changesin debris fans that intersect the river. The constriction ratio described by Kieffer (1985,1987, 1990)is the ratio of channel width at the narrow part of the rapid to the channel width of the pool upstream. Many rapids have a constriction ratio of 0.5, which may be an indicator of equilibrium (Kieffer, 1985,1987,1990). 105 As future debris flows deposit new material in a rapid, riverflows within the operational range of Glen Canyon Dam Powerplant will remove some of the new material. However, floods of 100,000 to 200,000cfs or more probably would be necessaryto remove the largest boulders from some debris fans, to increasethe constriction ratio, and to decreasethe elevation drop (Kieffer, 1985). For example, the 1966debris flow on Bright Angel Creek (Cooley et al., 1977)deposited material in Bright Angel Rapid (RM 87.9) that could not be reworked completely by riverflows in the range of powerplant releases. The 1983-86floods and sustained high releasesreturned this rapid to its pre-1966condition but could not do the same at Crystal Rapid. In 1966,a debris flow in Crystal Creek (RM 98.1) changed this previously minor rapid to one of the largest in the canyon. The debris fan temporarily dammed the river completely, and the channel that subsequently was cut through the debris fan was constricted to 25 percent of the upstream width. The 1983flood releaseof nearly 100,000cfs increased the constriction ratio to about 40 percent (Kieffer,1985). Thus, Crystal Rapid will remain a fonnidable obstaclefor river runners in the foreseeablefuture. It serves as an example of what may happen at other rapids when they aggrade with new debris flows in the absenceof large floods in the Colorado River. For purposes of this EIS, relative capacity to move boulders from debris fans will be used as an indicator of impacts. Lake Deltas The ultimate destiny of all reservoirs is to be filled with sediment. The coarserparticles (mostly sand) carried into the reservoirs by tributaries are deposited as deltas in the tributary arms. Most of the finer particles (silt and clay) are carried far into the reservoir, where they settle out as lakebed deposits. Deltas fill the upstream parts of the tributary arms first, building toward the submerged mainstem channel and eventually the dam. Somesediment deposited in upstream parts of deltas may be transported downstream by floodflow when the reservoir is low. FISH relatively high is exposed to erosion during subsequent periods when the lake level is lower. Exposed deposits tend to have steep faces(many nearly vertical), which are more susceptible to erosion; bank caving is common. Without replenishing flood releases,predam flood deposits of sand and finer sediment above high lake level are subject to long-term erosion by wind and local runoff. The shape of the Colorado River delta profile is affected mainly by lake level. The delta surface in Lower Granite Gorge and upper Lake Mead is relatively flat and is mostly sand. The delta face dips steeply, constantly building towards Hoover Dam as new sediment arrives. The elevation of the delta crest where the slope changesfrom relatively flat to relatively steep (seefigure 111-25) can be used as an indicator of changesin the delta. According to a 1948-49survey of the delta deposits (Smith et al., 1960),the delta crest was at RM 278;by 1963-64(Lara and Sanders,1970),it had progressed to RM 286. In 1963-64,the maximum thickness (depth) of the delta was about 250 feet. The lakebed deposits consisted of 12 percent sand, 28 percent silt, and 60 percent clay (Lara and Sanders,1970). The delta contains a much higher percentageof sand. Lara and Sanders(1970)estimated that the closure of Glen Canyon Dam extended the life of Lake Mead to about 500 years. Average accumulation of sediment in Lake Mead was estimated by Smith et al. (1960)to be about 100,000acre-feetper year during the first 14 years after closure of Hoover Dam in 1936. Lara and Sanders(1970)estimated about 91,000acre-feetper year during the first 30 years, for a total accumulation of about 2.72maf. Sinceconstruction of the dam, the rate of accumulation has declined substantially. FISH The present Colorado River aquatic ecosystem downstream of Glen Canyon Dam differs from the "natural" system that predated human influence. The natural ecosystemcontained communities of native speciesthat evolved in 109 a heavily sedimented river subject to extreme seasonalvariability in flow and temperature. This ecosystemwas characterized by relatively low productivity and speciesdiversity .Eight native fish specieswere known to have inhabited Glen and Grand Canyons. Human influence began when wannwater non-native fish specieswere introduced, possibly as early as the late 1800's(Carothers and Brown, 1991). Thesespecieswould have affected the abundance of native fish through competition and predation. However, due to the very limited data collected prior to construction of Glen Canyon Dam, the predam distribution and relative abundance of native and late non-native fish is largely unknown and subject to much speculation. Limited sampling in Glen Canyon by Woodbury et al. (1959)and McDonald and Dotson (1960) resulted in only two fish speciesreported from the Colorado River mainstem: channel catfish, a non-native (about 90 percent), and flannelmouth sucker, a native (about 10 percent). Tributaries had a more diverse fish assemblage,including 20 species: 14 non-native, 6 native. Flannelmouth sucker and speckled dace,both native species, dominated. Construction of the dam permanently altered the Colorado River downstream, creating a relatively clear river with near constant year-round cold temperatures and daily fluctuating, but seasonally modulated, flows. The result has been a more productive aquatic ecosystemwith a higher speciesdiversity than existed before the dam. The dam shifted the basis for river productivity from material of terrestrial origin to predominantly algal production. This river ecosystemis a mixture of native and non-native plant and animal communities. It is characterized by a food base (the Cladophoradiatom-Gammarusfood chain) and by introduced coldwater fish (predominantly rainbow trout) that were only present in cold tributaries before the dam. Thesedam-induced river conditions are most evident in the upstream reachesof the mainstem closestto the dam. With distance downstream, the river tends to become more turbid and slightly warmer, productivity 112 Chapter III Affected Environment Cladophorais the dominant alga in the reach below the dam (Blinn et al., 1992). Algal production is maintained becauseof the clear, cold releasesfrom the dam. Downstream, a blue-green alga (Oscillatoriasp.) becomescodominant in the middle canyon and dominant in the lower canyon (figure m-26), likely becauseof its tolerance of exposure and lower light levels (Blinn et al. 1992). Inundation with cold, nutrient-carrying water permits abundant growth of Cladophora,while exposure can causemortality (Angradi and Kubly, 1993). For example, Pinney (1991)recorded highest biomass of Cladophorafrom areasbeneath the fluctuation zone and lessbiomass from areas exposed by large daily fluctuations. Usher and Blinn (1990)reported that exposure of more than 12 hours can causedecreasesin Cladophora biomass from drying (summer), freezing (winter), or ultraviolet light damage. Angradi found that even 6 to 8 hours of exposure causedsignificant decreasesin Cladophorabiomass (Angradi and Kubly, 1993;Arizona Game and Fish Department, 1993). Once affected, Cladophorais not very resilient. Pinney (1991)suggested recovery times of 2 weeks to 1 month under steady flow conditions. Other researchershave suggested that "disturbances severeenough to destroy the periphyton (Cladophora)will have protracted (several months to greater than 1 year) ecosystemlevel effects under fluctuating flows" (Angradi et al., 1992; Figure lll-26.-Cladophora declines with distance from the dam and Oscillatoria becomescodominant (source: Blinn et al., 1992). Angradi and Kubly, 1993). Angradi and Kubly (1993)reported that gross primary productivity of pennanently inundated Cladophorawas 10 times that of the surviving algae in the zone subject to daily fluctuation. In summary , Cladophoradepends on and is susceptible to influences of dam operations. The cold, clear water releasedfrom the dam promotes its establishment, but fluctuating river stages result in stranding of some Cladophorafor varying periods. The GCES(Leibfried and Blinn, 1987; Usher et al., 1988;Blinn et al., 1992;Angradi et al., 1992;Angradi and Kubly, 1993)showed that Cladophoraisolated out of the water for more than 12 hours (and perhaps as little as 6 hours) would dry out and die. Much of the drift that feeds fish and other aquatic organisms is Cladophora-either dead from drying or scoured loose by water flow-and invertebrates forced to move to avoid drying. That drift also settles to the bottom in eddies and backwater areaswhere it is fed on by organisms and recycled through the food chain. Other Aquatic Food Sources The drift also contains zooplankton that originate from Lake Powell (Haury , 1988)and consequently may reflect the level at which water is withdrawn from the reservoir .Years in which the reservoir is quite low may seeshifts in the composition and density of these plankton as waters are withdrawn from layers closer to the surface. Thesemicroscopic animals are important food sourcesfor fish and other aquatic organisms. They typically are important to recently hatched larval or juvenile fish (trout, flannelmouth sucker, and bluehead sucker) (Haury,1988;Maddux etal.,1987;Arizona Game and Fish Department, 1994). Larger aquatic invertebrate organisms (macroinvertebrates) are extremely important members of the aquatic community (and aquatic food base) of the Colorado River and may even bridge the gap into the terrestrial community. Gammaruslacustris has become an important member of the macroinvertebrate community .Gammarus was first introduced into Bright Angel Creek during the 1930'sby the NPS and began colonizing the river FISH shortly thereafter (Carothers and Minckley, 1981). Gammarusand a speciesof snail (Physasp.) were also introduced to the river below Glen Canyon Dam by the Arizona Game and Fish Department (AGFD) during 1967-68as a food source for the developing trout fishery (Arizona Game and Fish Department, 1968). Other important species probably already resided in the Colorado River, including aquatic worms (oligochaetes), chironomid midges, and buffalo gnats (Carothers and Minckley,1981). Researchershave found that wide canyon reaches (Blinn et al., 1992),eddies, and backwater areas are very important to the production of aquatic invertebrates (Carothers and Minckley, 1981). These areasof slower current tend to accumulate organic material from the drift (detritus ) that forms the basis for their food source. fu addition to habitat, the constant cold water temperature influences the diversity and density of these invertebrates. wetted perimeter together become an important index of algal biomass and reflect the strength of the aquatic food base. Algal colonization experiments by Angradi (Angradi et al., 1992)illustrated the concept of reliable minimum flow by anchoring sandstone tiles in the river to measure the accumulation of growing Cladophoraat different river stages. Figure 1II-27shows the accumulation of algae at different river stagelevels (-10.5-mile bar above LeesFerry) during the spring of 1991. The figure illustrates the ability of the aquatic food base to develop in responseto minimum flow. Even tiles that were dewatered only 20 to 30 percent of the time showed less accumulation of attached algae than tiles that were always inundated. Aquatic invertebrate drift appears to be controlled by discharge from Glen Canyon Dam. Valdez et al. (1992)observed little drift of invertebrates during steady flows under interim operations. Significantly lower drift density for macroinvertebrates was found in samples collected around the LCR during interim operations than before (Valdez et al., 1992). At Lees Ferry, Blinn et al. (1992)found significantly greater drift densities for macroinvertebrates during fluctuating flows than during steady flows. In total, the aquatic food base of the Colorado River below Glen Canyon Dam is a community of algae and invertebrate animals that fonns the powerhouse for the aquatic ecosystemand, in some cases,an energy transfer route between the aquatic and terrestrial ecosystems. Solar energy, captured by CladopJiora and the diatoms that encrust it, is transmitted through the food chain to many invertebrate and vertebrate species. The amount of energy that can be captured and made available to the food chain appears to be determined by the area of cobble bars inundated on a reliable basis (Blinn et al., 1992). Reliable minimum stage (the river stage that can be relied upon over extended periods of time) and reliable 113 Figure 1II-27.-Accumulation of Cladophora measured as (a) Chlorophyll a, and (b) in biomass. Tiles placed below 5,000 cfs were always inundated (modified from Angradi et al., 1992). FISH identity of the humpback chub throughout the Grand Canyon is being investigated in a basinwide study of the genus Gila (U.S.Fish and Wildlife Service,1991a). The humpback chub evolved under seasonally variable environment with seasonally changing temperatures, large annual spring-summer floods, and short-term rainfall flood events. Sincethe closure of Glen Canyon Dam, the specieshas experienced daily stage fluctuations in a consistently cold environment. Habitats of adult and juvenile humpback chub in the Colorado River mainstem have not been satisfactorily determined, and responseof adult humpback chub to daily fluctuations is the subject of an ongoing radio tracking researchstudy in the Grand Canyon (Valdez, Masslich, and Leibfried, 1992). Preliminary information from that study and from studies conducted in the upper Colorado River (Valdez and Nilson,1982; Kaeding et al., 1990)found humpback chub have an affinity for specific locations and use habitats such as eddies, retum-current channels, and runs. In Grand Canyon, 48 humpback chub moved an average of 0.8 mile over a period of 5 to 149days (Valdez, Masslich, and Leibfried,1992). Daily habitat use and movement of adult humpback chub are influenced by time of day, riverflow and fluctuations, and turbidity. Movements of humpback chub in responseto changesin flow may be due to increased availability of food or to changesin the above habitats (Valdez, Masslich, and Leibfried, 1992). In February, adults were found to form aggregations in eddies and deep pools, while in March through May they moved toward the mouth of the LCR, apparently to stage for spawning (Valdez and Hugentobler, 1993). Valdez and Hugentobler (1993)hypothesized that thesemovements were triggered by daylight length. The lower 9 miles of the LCR are important habitat for the humpback chub (Kaeding and Zirnrnerman, 1983). Razorback Sucker (Federally Endangered). The razorback sucker is rare in the Grand Canyon reach of the Colorado River, with only a few 115 captured during recent surveys (1984-90). It is uncertain whether they reproduce in the area. While the historical status of the speciesis unknown, the canyons may have been refuges from high water temperatures or droughts that occasionally plagued the basin (Minckley, 1991). Historic habitat for the speciesmay have included large backwaters and oxbows of the Colorado River and its large tributaries. While successful natural reproduction and recruitment in riverine habitats has not been documented recently, the speciesdoes reproduce and recruit in ponds and other similar habitats where there are no fish predators (Minckley et al., 1991). Razorback suckers, like other "big river" endangered fish, are long-lived. Ages of individuals from Lake Mohave (downstream from Lake Mead), determined from polished and sectioned ear bones, range from 24 to 44 years (McCarthy and Minckley,1987). Many of these fish would have hatched at or prior to reservoir impoundment. Adult razorback suckers are found in the Colorado River above Lake Powell and in the lower SanJuan River. Recentcollections of razorback suckers from the western portion of Lake Mead (sjoberg, written communication, 1990)have renewed investigations and interest in increasing this limited population in Lake Mead. An enhanced Lake Mead population would have accessto over 250 miles of habitat in Grand and Marble Canyons. FlannelmoufhSucker (Federal Candidate). The £1annelmouthsucker is now listed as a category 2 speciesunder the Endangered SpeciesAct. The speciesis found in the Paria and Little Colorado Rivers; Shinumo, Bright Angel, Kanab, and Havasu Creeks; as well as in various locations in the mainstem (Arizona Game and Fish Department,1993). During GCESPhaseI, most juvenile and larval £1annelmouthsuckers were collected in the lower reachesof the river, while larger adults were found in the upper reachesincluding the reach above LeesFerry (Maddux et al., 1987). Recentcollections in the Paria River have found £1annelmouthsuckers in reproductive condition, but survival of young-of-year life stages 116 Chapter III Affected Environment has not been documented (Gorman et al., 1993; S.J.Weiss, 1993). Larval through adult-size £1annelmouthsuckers are found in the LCR (Arizona Game and Fish Department, 1993). and the chapter on management of the razorback sucker by Minckley et al. (1991). This last referencealso includes information on native and endangered fish in the Western United States. Other Native Fish Mainstem Reproduction Other native fish of the Colorado River through Glen and Grand Canyons include the speckled dace and bluehead sucker. Bluehead sucker and speckled dace are most common in the lower reachesof the river (Maddux et al., 1988)and use tributaries extensively (Maddux et al., 1988;Allen, 1993;Gorman et al., 1993;Otis, 1993;Mattes, 1993). Native fish depend on the diversity of habitats available in the river system. Backwaters,eddies, tributaries, and the mouths of tributaries appear to be essentialto their life cycles,particularly reproduction and recruitment. Water temperatures in the river are too low to allow development of eggs spawned there, which Water temperature is an overriding constramt for native fish in the Colorado River mamstem (figure 111-28).Minckley (1991)indicated that "water temperature too low for reproduction or larval development clearly results in loss of populations and is the culprit excluding natives from Marble/Grand Canyons." In discussing the larger causesof collapse of native fish populations throughout the basin, he indicates that "introduction and enhancementof non-native fishes as a result of river alterations forced the native species to extinction." At the same time, the "cold water of today is as large a deterrent for non-native warmwater speciesas for natives" (Minckley, 1991). Becausethe temperature of dam releasesis not altered by any of the alternatives, other factors becomeimportant, including 1) accessto tributaries for reproduction and 2) availability of warmer, low velocity environments in the main channel for rearing of young fish flushed from the tributaries. General information on the biology and habitat requirements for the humpback chub, razorback sucker, and other native fish of the Grand Canyon can be found in the individual speciesaccountsby Minckley (1991);the HumpbackChubRecoveryPlan (U.S.Fish and Wildlife Service,1990b);a compendium of existing information on the four "big river" endangered fish (Miller and Hubert, 1990); Figure III-28.-Spawning and egg incubation temperatures for native and non-native fish. Shaded area denotes current temperature range. FISH directly limits successfulreproduction to tributaries (Hamman, 1982;Marsh, 1985;Valdez, 1991;and Maddux et al., 1987). Under extended drought conditions when the elevation of Lake Powell is very low (approximately 5 percent of the time), the releasedwater may be slightly warmer than under normal conditions. Therefore, access to tributaries and tributary mouths for spawning is of primary importance to these species. Major tributaries (primarily the Paria and Little Colorado Rivers and Kanab Creek, but also Shinumo, Bright Angel, Diamond, Havasu, and SpencerCreeks)appear to contribute to native fish productivity . Besideswater temperature, other environmental conditions important to spawning and egg development include streamflow and habitat (Valdez, Masslich, and Leibfried, 1992);however, quantities or measuresof these conditions have not been verified. Tributary Reproduction Low flows of 1,000cfs (Labor Day until Easter)or 3,000cis (Easteruntil Labor Day) may limit access to tributaries (except perhaps the LCR), especially at night, when adult spawners likely would be moving. Indirectly, this fluctuation pattern may further limit reproduction of native fish. Evaluation of aerial videography indicates that flows above 5,000cfs are clearly sufficient to allow accessto major tributaries for spawning (with the exception of Havasu Creek, which is inaccessible under all normal operational flows due to the presenceof a prominent physical barrier) (Arizona Game and Fish Department, written communication,1993). Other detailed accessibility surveys have not been performed on any major tributary . Reliable minimum flow is used as the indicator for accessibility to tributaries for reproduction. The cold water releasedfrom the dam limits egg and larvae survival of most native fish in the mainstem, and successfulreproduction and development of early life stagesof humpback chub in the Grand Canyon is known only in the LCR. Under interim operations, there has been some evidence of limited chub reproduction in the mainstem in the vicinity of RM 30 in association 117 with warm springs (Valdez and Ryel, in preparation; Arizona Game and Fish Department,1994). Eggs and larval fish can be flushed into the mainstem by periodic floodflows in the tributaries. Angradiet al. (1992)reported measurable drift of native fish eggs and larvae from the LCR near its mouth. Temperature shock to these flushed eggs and larval fish may be lethal (Hamman, 1982; Marsh, 1985;Maddux et al., 1987;Hendrickson, 1993;Lupher and Clarkson, 1993). Researchwith larval humpback chub demonstrated that coma or reduced activity was induced by cold shock (from 68 of to 50 Of),with potentially severeimplications for survival (Lupher and Clarkson, 1993). It was further demonstrated that growth of larval and juvenile chub was markedly reduced at 50 of and 58 of. Thus, there is some dependenceon tributaries to accommodate the earliest life stages of native fish, and mainstem rearing habitats would be limited to relatively warm refuge areas (backwaters). Very young native fish are found in specialized mainstem habitats, suggesting that refuge areas playa role in recruitment of native fish. Humpback chub hatched in the LCR in the spring grow to sufficient size to be able to withstand the cold temperatures of the mainstem by October (Maddux et al., 1987). This life stage and 1-yearold humpback chubs have been found in the mainstem in backwater eddies, connected backwaters, and nearshore channel margins (Angradi et al., 1992;Valdez, Masslich, and Leibfried, 1992). Backwaters,eddies, and nearshore areasare the habitats used by early life stagesof humpback chub in the Upper Colorado River Basin (Holden and Stalnaker, 1975;Tyus et al., 1982). The AGFD (Maddux et al., 1987;Angradi et al., 1992)found similar habitats important to early life stagesof native fish, particularly backwaters connected to the mainstem during June through September. Compared to mainstem eddy habitats, backwaters offer higher zooplankton and benthic invertebrate densities (Kubley, 1990;Arizona Game and Fish Department, 1994), lower current velocities, and refuge from predatory fish. Other mainstem nearshore habitats, adjacent to riffles and runs with cobble and gravel substrates,are very productive. Data reported by Leibfried and Blinn FISH Mainstem Recruitment and Growth Growth of wannwater non-natives is limited by temperature, as is growth of native fish. The aquatic food baseis used as the indicator for growth potential of non-native wannwater and coolwater fish. Interactions Non-Native Between Native and Fish The presenceof warmwater, coolwater, and coldwater speciesis an issue of considerable importance. Competition from and predation by non-native fish has been cited along with habitat modification as causesof the decline of native fish in the Colorado River system (Holden and Stalnaker, 1975;U.S. Fish and Wildlife Service, 1990b;Minckley, 1991). The cold waters released from Glen Canyon Dam not only put some of the warmwater native fish at risk by limiting natural reproduction but also may benefit them by limiting the numbers and activities of non-native predators and competitors. 121 seasonality in their collections of striped bassin Grand Canyon (April through July). Primary concernsof this researchinclude whether operational changeswould encourage greater movement of striped bassupstream into Grand Canyon, whether bassmight become resident in the river, and whether they might feed on native fish. Predation by striped basshas been an issue of some concern. The level of that concern has been tempered somewhat by recent findings. Of 21 striped bassstomachs examined, only one contained a fish (rainbow trout) (Valdez and Hugentobler,1993). One way that non-native fish directly influence native fish is through predation upon one or more of their life stages. Becauseof its position in the large lakes above and below Glen and Grand Canyons and its reputation as a voracious predator, the striped basscould become an important influence on native fish populations. Generally, striped bass are found in the lower reachesof Grand Canyon below Lava Falls, but in recent years isolated individuals have been captured near the mouth of the LCR. The striped bassis not the only predator of native fish. Other non-native wannwater fish are already established in the river. Perhaps prime among those established is the channel catfish. The channel catfish is an omnivore by nature and can compete with as well as prey upon native fish Channel catfish are established in and around the LCR and are potential predators of native fish, including the endangered humpback chub. Their numbers appear to increasewith distance from the dam, reaching peak abundance below Lava Falls at the western end of Grand Canyon (Haden, 1991). Examinations of channel catfish and striped bass stomachsreported by Valdez and Hugentobler (1993)revealed fish remains, but no humpback chub were identified. Severalnative suckers were found in the stomachs of channel catfish near the LCR. Largemouth bass and green sunfish, currently restricted to the lower river reaches,also are potential predators of native fish. Recentwork in Grand Canyon (Valdez and Hugentobler, 1993)documented little predation on native fish by these species. They have been implicated as significant predators elsewhere in the basin. Striped bassin the Southwest are far from their native range on the Atlantic coast, where they typically reside at seabut ascend rivers along the coastal plain to spawn. After spawning, they exit the riverine spawning areas(Crance, 1984),but some individuals stay in cool tailwater areas (Coutant, 1985). Striped bassappear to display this ascentand retreat spawning behavior in the Southwest, and recent researchby Valdez and Hugentobler (1993)has recorded a definite Trout, among the most numerous fish in Glen and Grand Canyons, also have the potential to act as predators of native fish. Brown trout, usually concentrated between Clear and Bright Angel Creeks (Valdez, 1991),typically feed on fish (piscivorous) at larger sizes. Rainbow trout, though generally not considered piscivores, also have been implicated as possible predators on young native fish and fish eggs (Maddux et at., 1987;Haden, 1991;Angradi et al., 1992;Valdez, Striped Bass and Other Predators 122 Chapter III Affected Environment 1991). Rainbow trout stomachs examined by Maddux et al. (1988)and BIO/WEST, Inc. (Valdez and Hugentobler, 1993)did not contain any evidence of predation on native fish. Following exceptional production of humpback chub in the spring of 1993,an examination of rainbow trout stomachscollected near the LCR's confluence with the main stem found very small but identifiable bones of humpback chub, suggesting some predation (Paul Marsh, written communication). Brown trout, more piscivorous than rainbow trout, have been implicated as an important predator upon humpback chub (Valdez and Hugentobler,1993). The only documented predation on humpback chubs during 1991and 1992in the mainstem was by brown trout (Valdez and Hugentobler, 1993). Thirteen percent (3 fish) of the 23 brown trout collected near the mouth of the Little Colorado River contained identifiable chub remains. Coldwater fish speciessuch as brown trout, cutthroat trout, and brook trout usually prey on other fish, and the recovery plan for the humpback chub recommends against stocking predatory or competitive non-native fish into waters occupied by threatened and endangered species. Other coolwater fish also could be introduced accidentally from Lake Powell. The walleye and smallmouth bass (both piscivores), currently expanding their distribution in Lake Powell, could reside in reachesin Glen and Grand Canyons. One walleye has recently been collected in Grand Canyon (Valdez and Hugentobler, 1993). Establishment and Expansion of Other Competitors While predation has a very direct effect on the abundance of native fish, competition has an indirect-but no less important-effect on their abundance and well-being. Fish life requirements include both the physical characteristicsof where they live and reproduce, as well as the food resourcesthey depend on for energy and growth. When accessto food resourcesand shelter is limited through competition, the abundance of the disadvantaged competitor is often reduced. While competition is difficult to document, its results usually are striking. Native fish living in altered habitats and/ or competing with non-native fish for limited resourcesmost often have been restricted, or even excluded, in their native range. Potential competitors with native fish include carp, fathead minnow, killifish, rainbow trout, and red shiner and may include some of the omnivorous speciesthat also prey on native fish. Thesecompetitors may share rearing habitats in backwater areasand eddies, on which native fish appear to be dependent. Native fish speciesdominate over non-native speciesin tributaries. Of nine tributaries sampled by Angradi et al. (1992)in Marble and Grand Canyons, seven were found to be dominated by native species,and only two were found to be dominated by non-native species(the coldwater rainbow trout). Trout populations use some of the same tributaries for spawning as native fish. It was suggestedby Maddux et al. (1987)that trout and native fish use tributaries in different seasons,and thus partition the habitat seasonally. Native fish rely on the tributaries during spring months for spawning and during summer months for rearing, while trout rely on tributaries during winter months for spawning and spring months for rearing. Carothers and Minckley (1981)characterized the overlapping use of tributaries by native fish and trout as an example of competition. In the mainstem, cold water releasesfrom the dam-and possibly daily fluctuations and flood events-have considerably reduced the numbers of individuals and kinds of non-native speciesthat are currently resident (Minckley, 1991). Main channel habitat conditions for all warmwater non-natives are marginal. Channel catfish, carp, and fathead minnow persist and probably rely upon tributary spawning (and backwater spawning in the caseof fathead minnow) to maintain their populations. Trout The issuesdefined for detailed analysis under this topic include trout spawning and recruitment and VEGETATION percentage)is used as the indicator. Ultimately, this proportion may determine whether the fishery must be maintained by stocking or could become self-sustaining (a condition desired by the angling public). Downstream Reproduction and Recruitment While the trout in Glen Canyon spawn in the main channel, it is assumed that downstream populations in Grand Canyon are largely maintained by tributary spawning. It is unknown whether main channel spawning significantly contributes to the population. Tributary populations may have persisted for many years with limited use of the main channel. NPS and the U.S. Forest Servicebegan stocking tributaries in the 1920's(Carothers and Minckley, 1981),and trout use of the mainstem was likely limited in summer months when water temperatures were unsuitable. Tributary populations have persisted without augmentation since stocking ended in 1964. Accessibility to tributaries is the prime issue for maintaining these populations. It is assumedthat trout accesshas been sufficient under pre-1989operational criteria, since trout dominate in theseupper river reaches. Only extremely low flow in the mainstem, especially when coupled with low discharge from the tributary, would preclude its use. Growth and Condition Trout tend to be opportunistic feedersand often consume foods based on their size. In Glen and Grand Canyons, trout fry appear to be rather dependent on zooplankton in the mainstem (Haury, 1988;Maddux et al., 1988). Adults, on the other hand, feed on chironomid midge larvae, Cladophora,Gammarus,and decaying organic material. Fish material appeared in less than 1 percent of stomach samples (Maddux et al., 1988). Rainbow trout usually are not considered herbivores, but some researchershave indicated that the occurrence of Cladophorain their stomachsis no accident, or at least that they have benefited 125 considerably from consuming it. It can be argued that Cladophorais consumed coincidentally when trout forage for bottom dwelling invertebrates like Gammarus.It also has been argued that trout benefit directly from feeding on Cladophoraas well as indirectly by consuming the invertebrates that depend upon it (Pinney,1991). Montgomery et al. (1986)and Leibfried (1988)proposed that the high fat content of the diatoms encrusting Cladophora provide a ready energy source and may be partially responsible for the enhanced growth of trout in the tailwater area. The amount of Cladophorain the diet of adult rainbow trout generally declines from upstream populations at Lees Ferry to downstream populations in the lower Grand Canyon, which probably reflects availability (Maddux et al., 1988). The aquatic food base is used as the indicator for growth and condition of trout. VEGET A TION Plant communities found in north central Arizona reflect the influences of climate, topography, soil, and elevations that characterize the area. For example, the uplands surrounding Grand Canyon support a unique blend of plants influenced by three adjacent deserts: the Mohave to the west, the Sonoran to the south, and the Great Basin to the east and north (Carothers and Brown, 1991). However, the Colorado River and operation of Glen Canyon Dam have little effect on the majority of plant life surrounding Grand Canyon. The river, as influenced by dam operations, affects a narrow band of vegetation along the river corridor known as the riparian zone. The riparian zone will be the focus of this discussion and chapter IV analyses. Riparian Vegetation Plant communities affected by releasesfrom Glen Canyon Dam exist in a restricted zone at the juncture between the river's aquatic communities and upland plants adapted to desert conditions. Riparian zones are supported by inflowing water-either perennial, intermittent, or ephemeral-and occur in a continuous area VEGETATION Daily fluctuations not only affect area coverage of vegetation but also speciescomposition to some degree. At many sites, tamarisk marks the 30,OOO-cfs stage-unable to expand to higher elevations without the disturbances of higher flows and unable to expand to lower elevations becauseof daily fluctuations. Sediment deposited by the high flows of 1983is no longer wetted and is being colonized by coyote willow and arrowweed via rhizomes or underground running shoots from adjacent stands. Plant speciescomposition also depends on location in Grand Canyon. River elevation decreases almost 2,000feet from LeesFerry to Lake Mead, and the accompanying climatic changesaffect plant community composition. For example, coyote willow is more common in the upper canyon, while arrow weed and horsetail are more common in the lower canyon. While various herbaceousplants form a ground cover near the high water stagebelow woody plants in the upper canyon, bermuda grassbecomesthe dominant ground cover at many sites below Havasu Creek. LakesPowell and Mead. Woody riparian vegetation also is associatedwith Lakes Powell and Mead. Lake levels have declined since the high floodflows of 1983-86becauseof a regional drought. Riparian vegetation has increased on sediment exposedby declining water levels, and woody vegetation has become abundant below Separation Canyon into Lake Mead. Emergent Marsh Plants Common emergent marsh plants found in the study area include cattails, bulrushes, and giant reed. Another plant-horsetail-is not generally considered emergent marsh vegetation but is included in this discussion becauseit develops and grows under conditions similar to the other specieslisted. Theseconditions include a reliable water source and sediment properties found only at certain sites. Deposits containing clay/ silt sediments are necessaryfor development of emergent marsh vegetation (Stevensand Ayers, 1993). Low water velocity sites, such as eddies and retum-current channels along the river (seefigure 111-16) and the 129 deltas of Lakes Powell and Mead, permit clay / silt particles to settle from suspension. Thesedeposits provide a higher quality substrate for seed germination and seedling establishment than underlying sand becauseof their greater nutrient levels and moisture-holding capacity.With an appropriate water regime, these are the sites that support emergent marsh vegetation. Marsh plants were selectedas one of the indicators of riparian vegetation becausetheir requirements place them between the aquatic and terrestrial systems at the aquatic end of the riparian zone. Together with woody plants (which require drier conditions), these indicators are assumedto represent the range of riparian system responsesto dam operations. Marsh PlantsAlong the Colorado River. Patchesof marsh vegetation can be found in backwaters, channel margins, seepsand the mouths of tributary streams,and in other isolated sites within the fluctuating zone located between the NHWZ and the rninirnum discharge stage. Prior to closure of Glen Canyon Dam, annual floodflows prevented the establishment of marsh plants along the Colorado River in Grand Canyon (Stevensand Ayers, 1993). By 1976,65 distinct sites supported about 12 acresof marsh vegetation. Further expansion occurred until 1983-86,when floodflows eliminated cattails and bulrushes from all but 17 sites. Stevensand Ayers (1991)identify two types of marsh plant associations. Wet marsh plants include cattails, bulrushes, and some less common emergent plants. Theseassociationsdevelop on sediment deposits containing about half clay / silt and half sand, at sites between 10,000-and 20,000-cfsstagesthat are inundated once every 1.1 to 2.5 days (figure 1II-31). Patchesof dry marsh plants (horsetail, giant reed) occur between discharge stagesof about 20,000to over 31,500cfs that are inundated once every 3 days. Emergent marsh plants commonly occur in small patches along the river between the dam and Lees Ferry (Stevensand Ayers, 1991). The average size ranges from 0.05(dry) to 0.1 (wet) acre, with the largest (CardenasMarsh), just over 1 acre in size. WILDLIFE AND It is reasonable to assume that, as riparian vegetation increased, wildlife also increased to the levels observed today. Riparian vegetation, and particularly that in the NHWZ, is among the most important wildlife habitat in the region. The structural diversity of the plant speciesand thick growth found in the riparian zone provides many habitat resourcesin a relatively small area. Riparian plants provide food and cover for insects emerging from the river, as well as providing habitat for its own resident invertebrate populations. The plants, insects,and other resourcesfound in the riparian zone, in turn, support numerous mammals, birds, reptiles and amphibians, and other invertebrates. Wintering waterfowl found along the river corridor cannot be directly linked to riparian vegetation, but they are attracted to and use the clear open water of the Colorado River within Glen and Grand Canyons. Although no predam survey data are available, the turbid river water was probably not very attractive to waterfowl. Dam construction resulted in clear, cold water that now supports an abundant green alga, Cladophora glomerata,and the aquatic food chain associated with it. Increasedwaterfowl numbers are probablya responseto this increasedaquatic productivity (Stevensand Kline, written communication,1991). The variety of animals present in the river corridor, their habitats, and how they use their habitats result in a complex system that would be difficult to evaluate in detail. However, like other resourcesin the study area, this system is linked to the river and ultimately to Glen Canyon Dam operations. Theselinkages and anticipated changesform the basis for analysesin the remainder of this document. Two resourceswere selectedfor detailed evaluation to serve as indicators of wildlife: riparian habitat (woody and emergent marsh plants), to represent terrestrial wildlife, and the aquatic food base,to represent wintering waterfowl requirements. The following discussion explores existing wildlife and habitat and how they reflect predam conditions and dam operations. HABITAT 131 Riparian Habitat (Woody and Emergent Marsh Plants) Mammals Some26 speciesof mammals are considered uncommon to abundant along the Colorado River corridor in Grand Canyon (Carothers and Brown, 1991). Of thesespecies,only the deer mouse depends directly on the riparian zone for its existence. Deer mice were not found along the river prior to construction of Glen Canyon Dam. Riparian vegetation may have provided a competitive edge for deer mice over cactus mice along the river's banks. Both the brush mouse and pinyon mouse have increased in numbers since closure of the dam and subsequent development of the NHWZ. Small mammals use all types of vegetation, from densepatches of marsh plants to scattered desert shrubs. The beaver is a large aquatic rodent that lives in dens in stable deposits above the fluctuating zone and feeds on riparian vegetation. Although the river corridor through Grand Canyon may not appear to be beaver habitat, Stevens(written communication, 1992)developed a conservative 1991estimate of 200beavers between LeesFerry and Diamond Creek (225miles). Beaverscan affect plant speciescomposition and coverageby their feeding activities. Cuttings and drag marks from these animals are common on beaches supporting stands of coyote willow. Six bat speciesare uncommon to abundant along the river corridor (Carothers and Brown, 1991). While thesespeciesalso inhabit desert habitats, they may be attracted to the river corridor by the insects associatedwith the river and riparian vegetation. Bats are important prey for peregrine falcons (B.T. Brown, 1991b). There is one record of the spotted bat in the river corridor. This speciesis mentioned here because it is a candidate speciesunder the Endangered SpeciesAct. Very little is known about the spotted bat or its habitat requirements. The single record indicates that it is rare, and this specieswill not be treated in detail in this document. 132 Chapter III Affected Environment Ringtail and the western spotted skunk are among the most common small mammals in the study area. Thesespeciesmay have become more abundant since construction of the dam. Whether riparian vegetation has contributed to this increaseor human use at beach campsiteshas increasedtheir food supply is unknown (Carothers and Brown, 1991). Desert bighorn sheep and mule deer are the largest mammals that use sectionsof the river corridor. Bighorn sheep come to the river to drink and feed during the heat of summer (Carothers and Brown, 1991). Although rapidly increasing dischargesmay occasionally strand individual animals, the size, strength, and mobility of these two speciesmake it unlikely that river discharge causesdirect effects. Birds The importance of riparian vegetation as wildlife habitat, specifically in the NHWZ, is exemplified by bird use. Some303 speciesof birds have been recorded in the Grand Canyon region, with 250 (83 percent) of these in the river corridor Gohnson,1991). Most birds use the corridor as a travel lane through the desert and are not affected by dam operations. However, birds that nest in the riparian zone along the river corridor are directly and indirectly affected by flows. Some48 speciesof birds nest along the river (modified from Carothers and Brown, 1991). Fifteen speciesnest in both the OHWZ and NHWZ, with an additional 14 speciesnesting exclusively in the NHWZ (figure 111-32).One speciesnests primarily in the OHWZ. The number of nests at some sample sites in the riparian zone exceededdensities comparable to 800 pairs per 100acres,among the highest ever recorded in North America (Brown and Johnson, 1988). Bell's vireo, summer tanager, hooded oriole, and great-tailed grackle have expanded their nesting ranges into Grand Canyon in responseto riparian vegetation development (Carothers and Brown, 1991). Riparian vegetation supplies both cover and food to birds and to a principal prey: insects. Of the 30 bird speciesthat nest exclusively in the OHWZ, NHWZ, or both, 13 are insectivors; and at least 10 more bird speciesfeed insects to their young. Other speciesthat may not nest in riparian vegetation-such as phoebes,swifts, and swallowsfeed on the insects associatedwith this zone. Little direct effect has been recorded on birds nesting along the river corridor under historic dam operations. Bird populations were studied during the flood years of the 1980'swhen segmentsof riparian vegetation were inundated for long periods. Brown and Johnson (1988) recorded only one nest lost at flows up to 31,000cfs. At higher discharges,bird nests located near water or on the ground risk inundation. Discharges of 40,000cis inundated 90 percent of common yellowthroat nests. Above 40,000cfs, nests of Bell's vireo, yellow-breasted chat, black and Say'sphoebe, and violet-green swallow were affected. Mallards nest in dense vegetation-such as patches of emergent marsh plants-above the high water stage. Dense vegetation provides cover and abundant insects for foraging young. Mallard pairs were observed in almost every large eddy in Marble Canyon and upper Grand Canyon reachesin the summer of 1991(Stevens,written communication,1992). Vegetation within the riparian zone is not continuous but rather occurs in disconnected blocks or patches. Factors that affect the patch sizes of vegetation-such as disease,fire, beach erosion, or colonization of barren sites---can indirectly affect habitat use by breeding birds. For example, patches of vegetation in the NHWZ must be at least 1.2 acresin size before blackchinned hummingbirds will use them for nesting (B.T. Brown, 1991c). Habitat patch size also is important to other species. Factors that decrease patch size would limit subsequent habitat use, while factors that permit increasesin area would promote increaseduse by some nesting birds. Amphibians and Reptiles Some27 speciesof amphibians and reptiles (herpetofauna) inhabit the river corridor 134 Chapter III Affected Environment and open tamarisk sites, support lizard densities equal to or higher than any other sites reported in the Southwest (Warren and Schwalbe, 1988). The river is the source of abundant invertebrate food, while riparian vegetation-together with various other substratesincluding cliff faces-provides structural diversity. Together, these features createhabitat conditions for some speciesof herpetofauna that may be unique in southwestern riparian zones. While mammals and birds use riparian vegetation primarily for cover and secondarily for insect food, amphibians and reptiles focus their feeding activities on the many insects associatedwith riparian vegetation (Carothers and Brown, 1991). . The importance of insects to herpetofauna is illustrated by the distribution of four common species: the side-blotched, the western whiptail, the desert spiny, and the tree lizard. Individuals of thesespeciesare most abundant within 16 feet of the water's edge, moderately abundant in the NHWZ and OHWZ, and least abundant at upland sites adjacent to the riparian zone (Warren and Schwalbe,1988). The NHWZ fluctuating zone is a particularly important source of food. The western whiptail commonly feeds in the fluctuating zone on harvester ants, stranded Gammarus,and black flies (Carothers and Brown, 1991). Warren and Schwalbe (1988)observed eight western whip tails and five desert spiny lizards feeding along a section of shoreline at CardenasMarsh. Some speciesselectspecific substrate within the riparian zone. For example, side-blotched lizards are most commonly observed in open areaswith rocks or bare soil, western whiptails on bare soil or litter, desert spiny lizards on large boulders or large tree trunks, and tree lizards on vertical cliff facesalong eddies and quiet shorelinesjust above the splash zone (Warren and Schwalbe, 1988). Numbers of lizards observed in the NHWZ were lowest in dense tamarisk sites (Warren and Schwalbe,1988). Along the Gila River-a similar desert habitat with dense tamarisk-only desert spiny and tree lizards were captured in dense tamarisk Gakle and Gatz, 1985). Jakle and Gatz speculated that densestands of tamarisk do not provide suitable habitat for lizards. Terresfriallnverfebrafes Invertebrates playa major role in both aquatic and terrestrial food chains in Grand Canyon. Some insectshatching and emerging from the river may swarm into the NHWZ and land on riparian vegetation, rocks, and other substrates,supplying abundant food for various forms of mammals, birds, and herpetofauna. Vegetation within the riparian zone also supports resident insect populations that are independent of the river. To date, several thousand speciesof insects, representing 260 families, have been identified along the river corridor (Stevensand Waring, 1986). Spiders, scorpions, and other invertebrates also are present in the varied substrates of the riparian zone. Aquatic/ Aerial Forms. The Colorado River mainstem supports a relatively low diversity of invertebrates, but these few specieshave high populations and produce a high biomass (see discussion of macroinvertebrates under FISH in this chapter). In contrast, the tributaries support high speciesdiversity, with each tributary and spring supporting a different assemblageof species. Chironomid midges, simuliid black flies, and amphipod crustaceansdominate the aquatic food chain in the river (Carothers and Brown, 1991). Speciesthat develop in the clear, cold river water and then emerge to live in the air above are often important in terrestrial food chains. For example, black flies develop as larvae attached to underwater rocks. Instead of emerging directly from the water as adults like chironomid midges, black flies must first reach land and dry their wings (Carothers and Brown, 1991). Thesevulnerable emerging flies are an important source of food for numerous speciesthat forage in the zone of fluctuating discharge. Adult chironomid midges are a significant food resource available to predacious insects, amphibians, reptiles, and birds in this system (Stevens and Waring, 1986). Following emergence,chironomids prefer to alight on willows rather than on tamarisk. Adult chironomid populations were lowest during years of high flood discharges and large fluctuations. ENDANGERED Leibfried and Blinn (1987)noted a lack of invertebrates at sample sites exposed to fluctuating flows. More recently, Blinn et al. (1992)found a total of only 33 invertebrates in 900 samples from 10 sites in the fluctuating zone between LeesFerry and Diamond Creek. Ground-Dwel/ingForms. Another group of insects important in terrestrial food chains are species that live just below or on the ground. One of these speciesbest known to campers is the harvester ant. Before Glen Canyon Dam, annual flooding removed colonizing harvester ants from the scour zone. Populations rose to 2.4 nests per 100 square yards after closure of Glen Canyon Dam but were reduced to predam levels by the 1983-86floods (Carothers and Brown, 1991). Current population levels,have stabilized at about 0.35nest per 100square yards. Harvester ants feed on vegetation or other insects,human food debris, and black flies. They are in turn fed upon by predacious insects,herpetofauna, birds, and mammals. Vegetation-UsingForms. Although most terrestrial insects use plants to some extent, several forms exhibit important relationships with riparian vegetation. While tamarisk is the most abundant woody plant along the Colorado River in Grand Canyon, it supports only four or five speciesof insects. Among these are leafhoppers and armored scalesrestricted to tamarisk, a lady bug that preys on the armored scales,and Apache cicadas (Carothers and Brown, 1991). In contrast, coyote willow-second only to tamarisk in abundance-supports many different speciesof insects. Tamarisk produces a much greater amount of insect biomass primarily due to large outbreaks of leafhoppers (Carothers and Brown, 1991). Leafhopper outbreaks provide food that may be used by native predacious insects, amphibians and reptiles, birds, and mammals. The insect community continues to develop as riparian vegetation becomesestablished. Tributaries support different insect speciesthan the river corridor and may serve as population reservoirs for mainstem colonization. AND OTHER SPECIAL STATUS SPECIES Wintering Waterfowl Base) (Aquatic 135 Food The numbers of waterfowl using Grand Canyon increasein late November, peak in late December and early January, and then decreasein February, March, and April (Stevensand Kline, written communication,1991). During peak winter concentrations in 1990-91,some 19 different speciesof waterfowl used the river between Lees Ferry and Soap Creek at a denSity of 136 ducks per mile. An average density of 18 ducks per mile occurred over the entire upper Grand Canyon (RM 0-77). It is assumed that the birds are attracted to and use the river becauseof the open water and abundant food resourcesavailable. No specific information on feeding is available for wintering waterfowl in Grand Canyon. However, the diets of individual speciesare well known from other studies and indicate that foods taken from the river would range from plants through invertebrates to small fish. The variety and abundance of waterfowl using the river during winter indicate that a productive aquatic system exists below the dam. As described in the section on aquatic resourcesunder FISH in this chapter, this system is supported by clear, cold releases from the dam and is based on the linkages between Cladophora,diatoms, Gammarus,and larval insects. ENDANGERED AND OTHER SPECIAL STA TUS SPECIES The Federal endangered speciesconsidered in this report include the humpback chub, razorback sucker, bald eagle,peregrine falcon, and Kanab ambersnail. The southwestern willow flycatcher has been proposed for listing as endangered, and the flannelmouth sucker is a candidate species being considered for listing. Other Arizona speciesof concern in Grand Canyon are the southwestern river otter, osprey, and belted kingfisher. 136 Chapter III Affected Environment An "endangered species" is defined as a speciesin danger of extinction throughout all or a significant portion of its range. Candidate speciesinclude category l-a speciesfor which there is substantial information to support listing as threatened or endangered-and category 2-a speciesfor which some information indicates that listing is possibly appropriate, but biological data on vulnerability and threat are not currently available. Endangered Species Humpback Chub The humpback chub evolved in the Colorado River system 3 to 5 million years ago but was not described as a speciesunti11946 (Miller, 1946). It was on the origina11967 Federal list of endangered speciesand remains endangered today. The Grand Canyon population of humpback chub is considered especially important to the recovery of the species(U.S.fish and Wildlife Service,1990b). fu 1978,a FWS biological opinion found that Glen Canyon Dam operations had an adverse affect on essentialhumpback chub habitat and were jeopardizing the continued existenceof this speciesby limiting its distribution and population size. The opinion also stated that dam operations were modifying major portions of humpback chub and Colorado squawfish habitat and were limiting recovery of both species. A jeopardy biological opinion was not included for the Colorado squawfish since it was considered extirpated from Grand Canyon in 1978and remains in that status today. The opinion suggestedReclamation fund long-term studies on: .Impacts of warming the release water .Ecological needs of endangered species below Glen Canyon Dam .Reducing known factors constraining humpback chub populations .The relationship between mainstem and tributary habitats Following GCESPhaseI, Reclamation in 1987 requested formal consultation on the existing operation of Glen Canyon Dam. A draft biological opinion was prepared but not made final. Discussionsbetween FWS and Reclamation resulted in an agreement for Reclamation to fund seven conservation measuresthat would identify actions to assistin removing jeopardy for the humpback chub. AGFD, FWS, Hualapai Tribe, NPS, Navajo Nation, and Reclamation have been working cooperatively to implement the conservation recommendations. With the announcement of the preparation of this EIS, FWS recommended that a biological opinion, including the seven conservation measures,be prepared for the preferred alternative. The draft biological opinion was submitted to Reclamation in October 1993. The preferred alternative was revised to be consistent with the reasonableand prudent alternative contained in the draft biological opinion. Comments on the draft EIS and the draft biological opinion led to further refinements of both documents. FWS issued a final biological opinion with a jeopardy finding for humpback chub and razorback sucker (see chapters IV and V). The final reasonableand prudent alternative can be found in attachment 4. Information on designation of critical habitat for the humpback chub is included in the next section on the razorback sucker. Humpback chub habitat requirements and general biology are described in the FISH section of this chapter. ENDANGERED Razorback Sucker AND OTHER SPECIAL STATUS SPECIES 137 The limited information on razorback sucker habitat requirements is presented in the FISH section of this chapter. Bald Eagle The razorback sucker was listed as an endangered speciesthroughout its range on October 23, 1991 (U.S.Fish and Wildlife Service,1991b). Specific habitat requirements for the speciesare not well known and are the subject of several research programs. However, two major causesfor its decline throughout its range were cited in the listing rule: 1. Modification of the natural riverine habitats (including impoundment of rivers), modification of historic hydrologic patterns, and cold water from bottom releasedarns 2. Predation by and competition with nonnative fish introduced into the razorback's native range FWShas completed the processof determining critical habitat for all of the "big river II endangered fish species. Critical habitat is defined by the Endangered SpeciesAct as habitat containing the physical and biological features essentialto the conservation of a listed speciesand may include occupied or unoccupied habitat. A proposed rule was published in January 1993and the final rule in March 1994. Critical habitat for the humpback chub includes the lower 8 miles of the LCR and Colorado River from RM 34 to RM 208. For the razorback sucker, critical habitat includes the Colorado River from the confluence with the Paria River (RM 0) to and including Lake Mead. The bald eagle was listed as endangered in 1978 and retains that status in 42 states. On July 12, 1994, FWS proposed to reclassify the bald eagle as threatened. The Colorado River corridor through Grand Canyon is used by migrating bald eaglesin the winter. While eaglesare capable of taking fish from a river system with characteristics identical to the Colorado River before Glen Canyon Dam, they were not often observed in Grand Canyon until after the rainbow trout fishery was established. Eagleswere first recorded in the winter of 1985-86(4 birds) and have increased to a high of 26 birds counted in a single day at Nankoweap Creek in the winter of 1989-90. Some 70 to 100bald eaglesmoved through the area in February and March of 1990(National Park Service,1992). Bald eagle use of the river corridor is opportunistic and currently concentrated around Nankoweap Creek, where the birds exploit an abundant food source in the form of winter-spawning trout. Use of the river by eaglesmay increaseand eventually expand to other locations. For example, bald eaglesare regularly located along the river corridor above the LCR and occur around Lake Powell (National Park Service,1992), 138 Chapter III Affected Environment Bald eagleshave been recorded wintering on Lake Powell in numbers ranging from 30 to 50 individuals since the early 1980's(Stevens, written communication, 1993). They are present from November through March, apparently using the recreation area both as a migration route and as a winter stopover. Eagleseat trout stranded in isolated pools along the river near the creek mouth, but the main feeding activity is in Nankoweap Creek itself (National Park Service, 1992). Eaglesappear to shift foraging strategiesin responseto food availability .At low riverflows, foraging is concentrated at the creek mouth and the lower 150 feet of stream. Bald eagle foraging locations appeared to be flow dependent. Increasing riverflows are directly related to an increasein bald eagle foraging attempts more than 150 feet above the creek mouth. However, the successrate for prey capture is the same at the creek mouth or 150 feet above it. It appears that the number of eaglesat Nankoweap Creek is related to the number of spawning trout. More than 500 trout have been recorded at Nankoweap Creek during recent years, with the spawning run peaking at 1,500fish in 1990(National Park Service,1992). The number of trout attempting to ascendand spawn depends on the number of spawning trout in the river and conditions in Nankoweap Creek. Eagle numbers at Nankoweap Creek were down in 1990-91,as were the numbers of spawning trout. Low discharges in Nankoweap Creek, low water temperature, and ice may have limited the number of trout attempting to ascendand spawn in the creek. Peregrine falcons were 1isted as endangered in 1970but have generally increased nationwide since the prohibition on use of certain pesticides. Grand Canyon and surrounding areassupport the largest known breeding population of peregrine falcons in the contiguous United States(Carothers and Brown, 1991). Between 1988and 1990, 71 different breeding areaswere identified in Grand Canyon National Park. Extrapolation estimatesindicate that 96 pairs of peregrine falcon may exist in the study area (B.T. Brown, 1991b). The birds using Grand Canyon appear to be part of an increasing Colorado Plateau peregrine falcon population. For example, more than 60 territories around Lake Powell have been geographically defined and confirmed to be occupied, within which about 50 peregrine breeding areashave been specifically located (Stevens,written communication,1993). Although relationships are still under investigation, it is assumed that the peregrine falcon's successin the area is at least partially due to the abundant prey: violet-green swallows, white-throated swifts, several speciesof bats, ducks, and other prey. Prey speciesare plentiful becauseof large insect populations produced in the clear river water. The relationships between aquatic productivity, insects,prey species,and peregrine falcons are largely speculative. No specific data are available that could be used to refute or confinn the above relationships, and no data are available on peregrine falcons in Grand Canyon before Glen Canyon Dam. Swifts and swallows make up a ENDANGERED significant part of the diets of peregrine falcons elsewherein the Southwest where falcon densities are identical to those in Grand Canyon (Hays and Tibbitts, 1989;Tibbitts and Ward, 1990;Bemer and Mannan,1992). At those sites, surface water is often unregulated, limited (small perennial streams),or virtually absent (ephemeral streams). Kanab Ambersnail AND OTHER SPECIAL STATUS SPECIES Other Special Status Species FJanneJmouth Sucker The £1annelmouthsucker is listed as a category 2 speciesunder the Endangered SpeciesAct. The speciesis found in the Paria and Little Colorado Rivers; shinumo, Kanab, and Havasu Creeks; as well as various locations in the mainstern, especially western Grand Canyon (Arizona Game and Fish Department, 1993). Habitat requirements and general biology of the £1annelmouthsucker are discussedin this chapter under FISH. Southwestern The Kanab ambersnail was designated an endangered speciesin 1992. Only three known populations exist-two near Kanab, Utah, and one in Grand Canyon on land around a perennial stream that plunges from the canyon wall to the Colorado River (Spamer and Bogan, 1993). Since the listing of this speciesin 1992,one of the Utah populations is believed extirpated. The Kanab ambersnail is a terrestrial snail in the family Succineidae. It has a mottled grayish to yellowish-amber shell and lives in marshes and seepslocated at basesof sandstonecliffs. Vegetative cover is necessaryfor this mollusk. Inclividuals in Grand Canyon are associatedwith cardinal monkey flower and water cress. The assumedhabitat is a densely vegetated, wetted area of about 340 square yards. The availability of cardinal monkey flower or other vegetation and the presenceof rock ledges influence the distribution of this speciestowards the river. Sinceimplementation of interim flows in 1991, Kanab ambersnail habitat has increased down to an elevation equivalent to the 20,OOO-cfs river stage. 139 Willow Flycatcher Nesting pairs of the southwestern willow flycatcher in Grand Canyon increased following closure of Glen Canyon Dam. In the 1980's,the population along the Colorado River in Grand Canyon was believed to be no more than a few dozen pair but represented the largest population of willow flycatchers in Arizona (Unitt, 1987). Carothers and Brown (1991)attribute this responseto increasesin riparian vegetation following reduced high flood discharges. In a 1991survey conducted in Glen Canyon and the upper portion of Grand Canyon to Cardenas Creek, only two pair of nesting birds were detected. It has been speculated that changesin the numbers of nesting pairs may be related to brown-headed cowbird parasitism and habitat fragmentation (B.T .Brown, 1991a). On July 23, 1993,this bird specieswas proposed to be listed as endangered (seediscussion under "Consultation" in chapter V). Arizona Species of Concern The Stateof Arizona lists three speciesof concern that may use the river corridor and tributaries in Grand Canyon: the southwestern river otter, belted kingfisher, and osprey. The southwestern river otter is considered an endangered species by the State of Arizona. River otters have always been considered rare in Grand Canyon, with the last sighting reported in 1983 (Bravo, verbal communication, 1991). The 140 Chapter III Affected Environment southwestern river otter is listed as a category 2 speciesunder the Endangered SpeciesAct but generally is believed to be extinct. .Havasupai .Hopi .Hualapai The osprey is a rare fall, spring, or accidental transient in the canyon listed by the State as a "State threatened" species(Arizona Game and Fish Department, 1988). The belted kingfisher is a "State candidate" speciesfound in low numbers year round in the canyon and its tributaries. Both birds are rare or uncommon in Grand Canyon. CULTURAL RESOURCES Cultural resourcesinclude prehistoric and historic archeological sites, traditional cultural properties, sacredsites, collection areas,and other resources that are important to Native Americans in maintaining their cultural heritage, lifeways, and practices. Both archeological sites and Native American traditional cultural properties exist in the corridor of the Colorado River between Glen Canyon Dam and Separation Canyon, a 255-mile section of the Colorado River within Grand Canyon and Glen Canyon. The affected area also includes lands adjacent to the Navajo Nation, the Havasupai and Hualapai Reservations,and Lake Mead National Recreation Area. Both historic and prehistoric resourcesrelate to cultural traditions beginning with the Archaic peoples (ca.2500B.C.), continuing through the Puebloan and Cohonina peoples (ca.AD. 500-1200),the Cerbat tradition (ca.AD. 1300-1700),and Paiute groups (possibly Archaic through historic times). Apachean occupation of the Grand Canyon region is documented by the late 17th century, and use by numerous groups continues to the present. Historic Angle-American use of the area began in 1869with the first attempt to explore the Colorado River and subsequent exploration and economic exploitation of the area. The following Native American groups have ancestral claims to the canyon and continue to use the area today: .Navajo .Southern Paiute .Zuni Archeological Sites Archeological researchin Grand Canyon began in 1869with the first report of "Moqui" ruins by John Wesley Powell, the first Anglo-American to travel the length of the Colorado River (Powell, 1875). Professional archeological work was begun in the Lees Ferry area by Julian Steward in the early 1930's(Steward, 1941)and by Walter Taylor along the Colorado River in Grand Canyon in 1953(Taylor, 1958). Site reporting over the years and limited surveys of the rims and the inner canyon have recorded over 2,600sites in Grand Canyon and 2,300sites in Glen Canyon. A complete archeological inventory of the river corridor, encompassing all traversible terrain from the river up to and including predam river terraces,was completed for this EIS. A total of 475 prehistoric and historic sites were located within the affected environment, many representing use by Puebloan people including the Hopi and Zuni, Pai and Paiute, and the Navajo and Anglo-Americans. A total of 323 sites have been determined eligible for inclusion on the National Registerof Historic Places(National Register) as contributing elements to the Grand Canyon River Corridor Historic District. One site has been recommended for archeological testing before the determination of eligibility is made. The remaining sites either were ineligible or were not evaluated becausethey are outside the zone of potential impact. Anglo-American historic resourceswithin the affected area total 71 sites or components and represent use of the area between 1869and 1940. One historic resource located in the Colorado River, the Charles H. SpencerSteamboat,was listed on the National Register in 1974as part of the LeesFerry Historic District. A separate nomination was prepared for the steamboat, and 142 Chapter III Affected Environment locations of medicinal herbs, and other sacred places in Grand Canyon are important becauseof their role in perpetuating Hopi life and culture. Theseplaces provide a vital spiritual and physical link between the past, the present, and the future. Hopi culture begins with the emergenceof the people into this present world from the Sipapu,a travertine cone in Grand Canyon. After their emergence,Hopi people migrated around the Southwest until all clans came back together at the center of their universe: the Hopi Mesas. For many clans, these migrations included residence in Grand Canyon. This is well documented in the archeological record (Fairley et al., 1994). Of the 475 cultural resource sites identified by the NPS during its survey of the canyon bottom, at least 180 consisted of the remains left by a prehistoric Puebloan people. Conventional archeological theory , as well as Hopi oral history , holds that thesesites were produced by the ancestors (Hisatsinomin the Hopi language) of the present day Hopi people. Evidence shows that use of Grand Canyon by the Hisatsinom began around AD. 700-800. These people increased in number and began to use all portions of the northern and eastern canyon bottom, as well as both the north and south rims. By the lOth century, small pueblos dotted much of the arable land in the canyon bottom. Associated with some of thesepueblos were kivas,ceremonial structures found in every modern Hopi village and centers of religious life. By AD. 1200,the Hisatsinom had largely moved from Grand Canyon, migrating to areasnearer to the present day Hopi Mesas. Ties to the Grand Canyon region were not severed,however, as evidenced by Hopi ceramics dating to post-AD. 1300found throughout the canyon. Similarly, ritual pilgrimagesto Grand Canyon for salt, minerals, and other resources-as well as to visit shrines-have continued into the 20th century. Just as modem Hopi villages have shrines associatedwith them, so do their prehistoric counterparts. Any pueblo that contains a kiva can be assumed to have shrines. While people may no longer regularly deposit offerings at theseshrines, they are still sacred areas. Hopi people have a number of concerns about their ancestralhomesites being damaged by erosion. The Hopis value these sites as markers on the landscape that serve to physically document their cultural claim to the land. Many of these sites contain the remains of Hopi ancestors. Proper respect for and treatment of the dead are extremely important values in Hopi culture. Hopi people feel that human graves should not be excavatedsolely to satisfy scientific curiosity. When graves are disturbed by erosion, however, most Hopis believe these graves should be reburied away from danger, not taken out of the canyon. Nondestructive study of human remains during the processof relocating graves is acceptableto most Hopi people. Like ruins, rock art ties modem Hopi people to land inhabited by their ancestors. The Hopis have a rich interpretive schemefor assigning meaning to rock art. Their oral history records a number of clans residing in Grand Canyon. Hopi elders have observed the symbols of the Fire, Strap, Spider, Kachina, Lizard, Turkey, Bow, Water, Bear, Greasewood, and Badger Clans immortalized in petroglyphs in the canyon. The many handprints at rock art sites are interpreted as the markings left by clan leaders during Hopi migrations. All of the springs in Grand Canyon have spiritual importance to the Hopi people. One of these springs, Vasey's Paradise,was specified by Spanish priests as the location from which the Hopi people were to collect holy water and drinking water for the Catholic missions. It is important to the Hopi that these springs are not damaged in any way by the Glen Canyon Dam operations. Hopi people continue to use Grand Canyon for important ceremonial and ritual purposes. The Hopi Salt Mines on the Colorado River are the focus of an arduous pilgrimage associatedwith initiation rites of Hopis. The Twin War Gods established the steep trail down the walls of Grand Canyon for this salt pilgrimage and identified many shrines where offerings and rituals are conducted along the way. Hopis continue to us~ theseplaces for prayer and make offerings at them during winter ceremonies 144 Chapter III Affected Environment bands of the Pai but also with neighboring tribes such as the Hopi, Paiutes, Mohaves, and Navajos The Hualapai Indians have occupied and used the lands and waters lying within their ancestral territory , as well as within the present reservation, for more than 1,000years-long before the records and history of white society in the area. Evidence of their occupancy, use, and ownership of the territory is contained in their family and tribal records, traditions, and legends-unwritten, but faithfully transmitted from parent and leader to offspring and follower, from a people that lived in the distant past to the present. Navajo Nation The Navajo Reservation borders part of the affected environment, from Glen Canyon Dam to the confluence of the LCR-a distance of 76.5miles. Throughout the Colorado River corridor are places of historical, cultural, and religious importance to Navajo people. Archeological and linguistic evidence suggests that the Apacheans (Athabaskan-speaking ancestorsof the modem Navajos and Apaches) entered the North American Southwest sometime between A.D. 1000and the 1400's(Brugge, 1983; G.M. Brown, 1991). During this time, the Apacheans traded and intermarried with neighboring Puebloan and other groups. Traditional Navajo culture of today is the result of these interactions (Brugge, 1983;Kelley et al., 1991). Historical accounts refer to ancestral Navajo interactions with Havasupais in the Grand Canyon region by the 1600's(Navajo Nation, 1962). Evidence clearly establishesNavajo settlement on the plateaus surrounding Grand Canyon by the 1700's(Navajo Nation, no date). By at least the mid-1800's, Navajos were fully using resourcesin and around Grand Canyon for farming,livestock grazing, plant gathering, hunting, and religious purposes, as well as seeking refuge from Mexican slave raiders and non-Navajo Indian Tribes. During the 1860's, when Navajos were conquered by the U.S. Anny and incarcerated at Fort Sumner, New Mexico, many Navajo families escapedinto the canyon and lived there for several years. The canyon continued to provide protection to Navajos and their herds of sheep,goats, and horses during the federally imposed livestock reduction program of the 1930'sand 1940's. The boundary of the traditional Navajo homeland is symbolized by the four sacred mountains (although the aboriginal use area extends beyond thesemountains): SisNaajinii on the east (Blanca Peak near Alamosa, Colorado), TsooDzil on the south (Mount Taylor near Grants, New Mexico), Dook'o'oosliidon the west (SanFrancisco Peaks near Flagstaff, Arizona), and DibeNtsaaon the north (La Plata Mountains near Durango, Colorado). Navajos believe they originated from three underworlds and emerged through a seriesof events into this, the fourth world. Theseworlds were given to the Navajo people by the Holy People. Water is the basis for the origins of many Navajo clans and is important in oral tradition and many ceremonies. The Colorado River is a sacred female being to the Navajo's, forming a protective boundary on the western border of Navajo land. It is inseparable from the larger sacredlandscape of which it is an integral part. Oral traditions and physical places connect Grand Canyon to its tributaries and the landforms that surround it. Prayers are offered to all theseplaces. The LCR is considered a sacred male being. Theserivers provide protection to the Navajo people, not only in the water that is ceremonially used, but in the refuge the canyons have provided to Navajos throughout history . Theseare among the many sacred and secular resourcesthesecanyons, collectively called Grand Canyon, provide to the Navajo people. In addition to ceremonial uses of water, the Colorado River and its tributaries have provided water for both people and livestock for many generations. The beachesprovided arable land for corn fields, and the river terracesprovided habitat for the deer, bighorn sheep,and other game that Navajos hunted. The beachesand terraces also support the vegetation that continues to be used for medicinal, ceremonial, and daily domestic CULTURALRESOURCES 145 purposes. The salt mines also provide salt that is still used ceremonially and was historically used for seasoningfood. The many trails used to access the canyons also serve both sacred and secular refuge. Thus, Grand Canyon becamethe final refuge for traditional Southern Paiute life and, as such, assumed additional cultural significance. purposes. Modern Southern Paiute people continue to use Grand Canyon and the Colorado River in traditional ways becausethey believe the Creator requires them to do so. If a land and its resources are not used in an appropriate manner, the Creator becomesdisappointed or angry and withholds food, health, and power from humans. For this reason,Paiute people continue to visit the canyon and river to harvest plants and fish and to conduct ceremonies-even though accessto these areasis now limited. Any effects on Grand Canyon and its resources from the operation of Glen Canyon Dam ultimately affect the stories that are told about them. Thesestories are the most irreplaceable of Navajo cultural resources. Southern Paiute Tribe The traditional lands of the Southern Paiute people are bounded by more than 600 miles of Colorado River from Kaiparowits Plateau in the north to Blythe, California, in the south. According to traditional beliefs, Southern Paiute people were created in this traditional land. Through this creation, the Creator gave Paiute people a special supernatural responsibility to protect and manage this land, including its water and natural resources. PuaxantTuvip (sacredland) is the term that refers to traditional ethnic territory. Southern Paiute people expressa preservation philosophy regarding PuaxantTuvip and the water, minerals, animals, plants, artifacts, and burials existing there. Natural resourcesare perceived as having their own human-like life force. The Colorado River is one of the most powerful of all natural resourceswithin traditional lands. Elders tell children about its power and the gifts it provides when talked to and treated with great respect. Traditionally, Southern Paiutes lived, farmed, collected plants, and hunted along the Colorado River where it passed through their land. For this reason,the riverbanks are full of culturally meaningful human artifacts and natural elements. Historically, most Southern Paiute people died when Europeans encroachedupon PuaxantTuvip, bringing domestic animals and diseases. Paiute people soon lost control over most of the tributaries of the Colorado River, including the Santa Clara River, the Virgin River, and Kanab Creek. As Paiute people were forced out of these riverine oases,they retreated to Grand Canyon to live in Zuni Tribe The traditional territory of the Zuni Tribe is bounded by the San FranciscoPeaks on the northwest corner and by portions of the LCR and the Pueblo Colorado Wash on the far northern boundary .Although they do not reside in the directly affected environment, Zunis have close ties to the Colorado River and Grand Canyon. The area of Zuni traditional use extends considerably beyond their traditional territorial boundaries and includes Grand Canyon. Archeological sites, traditional cultural properties, and other sacred locations along the Colorado River corridor and the LCR are important to Zuni traditional and cultural values, providing important spiritual linkages to the place of emergencefor the Zuni Tribe. Areas where soil, water, plants, and rocks are collected for ceremonies,as well as a portion of the Zuni Grand Canyon Trail, are located within the affected environment of the Colorado River. From the moment that the Zunis arrived on the surface of the earth, Grand Canyon and the Colorado River have been sacred. Creation narratives describe the emergenceof the Zuni people from Earth Mother's fourth womb, coming out into the sunlight at the bottom of Grand Canyon. The narratives also describe the Zunis' subsequent searchfor the center of the world, the Middle Place. The people moved up the Colorado River and then up the LCR, periodically stopping SO2is now a regulated pollutant associatedwith adversehealth effects. Nitrogen oxide (NOx} emissions also are produced from burning fossil fuels and react in the atmosphere to form ozone and acid aerosols. Most utilities presently concentrate their efforts on reducing SO2and NOx emissions, so changesin these emissions will be tracked under this analysis. RECREATION Figure 1II-35.-Sources of sulfates at Grand Canyon, 1981-85. year to year as well. For example, during 1980-85, there was a 50-percentincreasein summer sulfate levels measured at the canyon (Maim, 1989). One source of sulfate in Grand Canyon is Navajo Generating Station, identified as a major 502 contributor by an NPS study. In responseto the study, the Environmental Protection Agency mandated modifications to reduce emissions beginning in 1995. Thesemodifications are scheduled to be in service for all three powerplant units by August 1999. Regional Air Quality Changesin dam operations may affect regional air quality. Glen Canyon Powerplant is integrated into a regional power system (chapter III, HYDROPOWER). Although the total annual generation would not vary significantly if power production at Glen Canyon Dam was shifted from daytime to nighttime (or from peak to off-peak months), power for those periods would have to be replaced elsewhere in the system. This replacement power could be generatedby new, cleaner-buming powerplants, which would result in less emissions than generation by existing powerplants. This change could be apparent either in the region, or elsewhere in the marketing area served by the Salt Lake City Area Integrated Projects. Dam operations affect the experience of recreationists using the Colorado River in Glen Canyon and Grand Canyon, as well as those using Lake Powell and Lake Mead. The recreationists most affected by different flows are anglers, day rafters, and white-water boaters. The 15-mile segment of the Colorado River below Glen Canyon Dam, located within the Glen Canyon National RecreationArea, is the last remaining riverine section of the 189-mile rivercarved channel that was once Glen Canyon. This segment, the Glen Canyon reach, is used by a variety of recreationists including fishermen, boaters, day rafters, campers, and hikers. The Colorado River through Marble and Grand Canyons is the longest stretch of river (278miles long, with over 160recognized rapids) for recreational use entirely within a national park. The river is surrounded by more than 1 million acres of land with little human development. Some of the world's most challenging and exciting white water occurs here. The river's isolation in the mile-deep gorge of Grand Canyon gives it primitive recreational qualities and enhances off-river hiking, climbing, and sightseeing. Hoover Dam impounds the water of the Colorado River, forming Lake Mead-the largest reservoir in the Western United States. About lOO,OOO boaters annually use the stretch of Lake Mead and Grand Canyon from South Cove to Separation Canyon for scenicboating, camping, fishing, water-skiing, and other recreational pursuits. 150 Chapter III Affected Environment fish. Blue ribbon fishery management limits the harvest of fish through special regulations that encourage "catch and release" by implementing low daily bag limits, size limits, and gear restrictions. The fishery in Glen Canyon is one of only two blue ribbon stream fisheries in Arizona, which increasesits importance to anglers and AGFD. Blue ribbon fishery waters can be maintained through natural reproduction or by stocking. Under historic dam operations and current fishing regulations, supplemental stocking is necessaryin order to maintain catch and harvest rates. Rainbow trout spawning occurs on gravel bars in Glen Canyon, and naturally reproduced fish represent about 28 percent of the average trout harvest (U.S.Department of the Interior, 1988). ]anisch summarized the history of the Glen Canyon fishery in four stages(Bishop et a1.,1987). .Put-and-take era (1964-71) .Trophyera (1972-78) .Quality era (1978-84) .Something less than quality but not put-and-take (1985-present) From 1964to 1971,the "put-and-take" era, catchable-sizedtrout were stocked and most were caught within a few months. The averageweight of the rainbow trout taken was less than 0.75pound during this period, and fishing pressure was relatively light. Around 1971,Gammarusbecamea major part of the trout's diet, and the trout growth rate apparently increased. This resulted in the "trophy" fishery era from 1972through 1978. Bag limits of 10 fish weighing a total of 40 pounds were not unusual during this period. In response,the number of angler days rapidly increased. Water temperature and habitat seemedconducive to natural reproduction, so the AGFD fish stocking strategy shifted from introducing catchable-sized trout (as practiced during the put-and-take era) to stocking fingerlings. Researchsubsequently showed that the fishery heavily depends on stocking and that only limited natural reproduction is taking place (Personset al., 1985). In 1978,the bag limit was reduced from 10 to 4 trout in an attempt to protect the resource from ever-increasing fishing pressure. In 1980,a rule was enforced requiring that trout either be releasedor killed immediately after being caught. This rule was an attempt to discourage people from keeping fish alive for extended periods and then releasing them if a larger fish was taken, a practice resulting in high mortality rates for the releasedfish. Even though the fishery has declined in productivity since 1978,fishing pressure continued to escalateunti11984. Janisch termed the period 1978-84the "quality" fishery era. Creel censusreports still showed a very respectableaverageweight of 2.79pounds for fish caught and kept through this period. However, the days of the trophy fishery were ending, and the averageweight of fish taken steadily declined. Bishop et al. (1987)stated that Janisch characterized the current era (beginning in 1985)as "something less than quality but not put-andtake." Further, catch rates are still relatively high and some large fish are taken, but most fish are small in comparison to the trophy era (Bishop et al., 1987). Management strategy is to reduce fishing pressure and stock trout so the fishery can be restored to the quality , if not trophy, level. Fish over 20 inches long made up about 25 percent of the harvest in the period 1979-83and less than 10 percent during 1985-88. In 1984-85,fish less than 15 inches long accounted for about 50 percent of the harvest; this decreasedto about 20 percent in 1986. However, the harvest percentageof fish less than 15 inches long has been increasing ever since (Reger et al., 1989). Angler Safety. This flat water section of river is fished predominantly from boats launched at Lees Ferry .Bank fishing, including fly fishing by wading fishermen, occurs in the area around Lees Ferry .They wade out into the channel to the depth their wading gear permits. The rate of increasein flow directly affects the safety of fishermen, in terms of their ability to move toward shore once they notice changing water levels. Lee and Grover (1992)found that anglers believe high flows (30,000cfs or more) reduce the potential for RECREA TION safely wading in the river. At least three drownings in the past 12 years possibly are related to river stage or stage change. Camping and Day UseSites. Within the Glen Canyon reach are six designated camping areas above the high water zone, generally on terraces. There are up to three campsites per camping area, designated by pit toilets and fire grates. Beaches in this reach are used mainly by anglers and day rafters, with over 50,000visitors each year. Although the camping surfacesgenerally are located well above the river, discharge and its influence on sediment deposits and sedimentation processesultimately will influence the size and distribution of these sites. Other flow-related problems include accessibility to sites and physical spacefor mooring boats at campsites. 151 and mainstem fisheries (table III-ll) for rainbow and brown trout in Grand Canyon are managed under the wild:fish concept. Table 111-11.-Wild trout fishery designations in Grand Canyon (AGFD, 1990) Bright Angel Creek (12.9 miles) Clear Creek (4.1 miles) Colorado River (229.0 miles) Crystal Creek (5.2 miles) Deer Creek (0.1 mile) Havasu Creek (3.5 miles) Nankoweap Creek (0.1 mile) Phantom Creek (3.9 miles) Pipe Creek (0.5 mile) Royal Arch Creek (0.7 mile) Kearsley and Warren (1993)inventoried sites available in the Glen Canyon reach for camping and day use. Of the potential 18 camping and day-use sites in this reach, only 12 normally are available. The other 6 are low water sites available only when flows are 15,000cfs or less. Shinumo Creek (0.1 mile) Stone Creek (5.0 miles) Tapeats Creek (4.5 miles) Thunder River (0.4 mile) Vishnu Creek (1.8 mile) Fishing in Grand Canyon Fishing in Grand Canyon is largely an activity incidental to white-water boating or backpacking. The exceptions are found mostly in the vicinity of JackassCanyon and in other side canyons around Marble Canyon. NPS controls most accessto these wild trout fisheries by issuing backcountry and river permits. Commercial river companies are not allowed to offer trips that are primarily for fishing within Grand Canyon; however, fishing is allowed as an incidental activity on river trips. The only restrictions on anglers are localized closures to protect endangered speciesand a required fishing license from the State of Arizona. Wild Trout Fishery. The Arizona Coldwater Sportfisheries Plan uses a wildfish concept to "provide anglers the opportunity to catch fish that are naturally reproduced in the wild." The tributary Wild fisheries are sustained entirely by natural reproduction. Since most of the waters within Grand Canyon are accessedby trail or raft, angler density is limited, thus protecting the fishery from overharvest. The daily limit is four fish for the Colorado River from the Marble Canyon Bridge through Grand Canyon to Separation Canyon, including all tributaries. Trout taken from these areasmust be either immediately releasedor killed and retained as part of the bag limit. Angler Safety. Most Grand Canyon fishing is conducted from either a raft or the riverbank; few anglers wade into the river to fish. As a result, angler safety is not considered a major issue. Day Rafting A Glen Canyon raft trip is a leisurely 15-mile, 1-day float trip. In 1991,more than 33,000visitors took ha1f-dayraft tours of the Glen Canyon reach. All Glen Canyon raft trips have professional guides to run the rafts and explain the river 152 Chapter III Affected Environment attractions. Wilderness River Adventures is the only concessionaireauthorized to provide commercial Glen Canyon raft trips. Severaltour companies support these trips by busing raft passengersfrom Grand Canyon south rim and other areasto Glen Canyon. Trip Attributes Bishop et al. (1987)found that the only flowsensitive attribute of a Glen Canyon day-raft trip may be its origin. At low to moderate flow levels (generally less than 29,500cis), the 2o-persontours depart from a dock near Glen Canyon Dam and float or motor downstream to LeesFerry. When releasesare above 29,500cfs and outlet works are in use, departure from the base of the dam is unsafe due to the volume and turbulence of the water. In these cases,rafts normally depart from LeesFerry carrying fewer people (10) and motor part way upstream before floating back downstream. The decreasedraft capacity occurs becausethe pontoons are removed to reduce water resistancewhile motoring upstream, which reduces stability. Most trips departing from Lees Ferry do not go all the way up the river, and passengersdo not get a view of Glen Canyon Dam from the river. Lee and Grover (1992)found that-at low flowsday rafters were more likely to feel that the water was too low and slow, more likely to wait longer to launch, or more likely to experienceminor motor or raft damage. At high flows, rafters were more likely to notice beach erosion at shore stops. Overall trip satisfaction remained high and not significantly different at all flow levels. Raft trips stop at channel margin sediment deposits for day-use and lunch stops. Thesesites are beach-like in character and likely to be influenced by discharge from the dam. Navigability, Access, and Boating Safety Individuals who boat in the Glen Canyon reach must launch at LeesFerry and motor upstream. The narrow constrictions and riffles within the reach causethe greatest difficulties during periods of low flow. Certain types of equipment, such as jet boats, can better negotiate the river during periods of low discharge. During flows of 3,000cfs and less, few boaters are able to go upriver past 3-Mile Bar (RM -3), a shallow riffle (Welsh, verbal communication, 1991). Damage to boats and motors is more frequent than at higher water levels. In addition, fishing activities at flows less than 3,000cfs are concentrated within the 3 miles above Lees Ferry, especially on weekends and other high-density days; some boats are stranded upstream of 3-Mile Bar following lowering of flows. If tied too tightly to banks, boats are left "high and dry" above water stage,only to become swamped when discharge increases. During 5,000-cfsflows, about 75 percent of boaters are able to negotiate 3-Mile Bar, while nearly all boaters can do so during 8,000-cfsor greater flows. Up to 23 rafts are launched daily by the rafting concession. Discharge from the dam becomesan influence on theserafts at constrictions in the channel, causing the most problems during periods of flows less than 5,000cfs (O'Mary , verbal communication, 1993). White-Water Boating The history of nmning the Colorado River in Grand Canyon can be traced back to 1869,when John Wesley Powell led the first expedition down the Colorado River through Grand Canyon. Commercial river trips began in 1938. Today, white-water boating in Grand Canyon is a major industry , with 17 companies having permits to conduct commercial raft trips in the park. Also, the Hualapai Tribe conducts river trips from Diamond Creek to Lake Mead. Prior to the early 1960's,there was little concern about resource impacts along the river. Glen Canyon Dam was yet to be completed, and few visitors entered the canyon or ran the river. From 1960to 1972,the number of boaters annually running the river grew from 205 to 16,432persons, paralleling a dramatic increasein white-water boating nationwide. In 1972,increasing problems with management of campfires, human waste, RECREATION and trash along the river; damage to fragile soils and vegetation; unofficial trails; and destruction of prehistoric sites prompted NPS to regulate river use more closely. Approximately 15,000to 20,000commercial and private boaters annually run the river. This range reflects the changing trends in the length of commercial trips-presently, short duration trips. The number of user days is restricted to 115,500for commercial trips and 54,450for private parties. Motorized trips are allowed to launch from midDecember through mid-September. Oar-powered craft can be used throughout the year and exclusively during the "oar-only" period from September15 to December 15. Noncommercial group size averagesbelow the limit of 16, while commercial group size usually is 36 people. The Lower Gorge, beginning at Diamond Creek, is used for the Hualapai Tribe concessionas well as by other commercial and private rafters. The number of visitors on the river is not solely a reflection of increasedpopularity of white-water sporting nationwide. Before the dam, riverflows were highly variable and ranged from low flows frequently less than 3,000cfs to peak flows occasionally in excessof 100,000cfs in spring and early summer. Now, riverflows are within a much narrower range-from 3,000to 31,500cfs-and show less seasonalvariation, making it possible to raft during all months of the year becauseof the reduced high and low water risks. However, many people have rafted the river through Grand Canyon (predam) at and below 1,500cfs. Most commercial and private raft trips take place during May through October. Commercial trip passengerscontract with an outfitter to provide a boat, other rafting equipment, food, and a guide. Commercial trips use both oar- and motor-powered rafts and typically run from 3 to 4 days for a motor trip (only the upper stretch of the river from Lees Ferry to Phantom Ranch) to 20 days for an oar-powered trip (the ful1255 river miles through the park). One- to 2-day trips launch from Diamond Creek. 153 Private parties furnish their own boats, rafting equipment, food, and guides or boat operators. Individuals must apply for private permits, which are awarded in the order that applications are received. Currently, the waiting list for private permits is about 10 to 12 years, although 40 percent of the individuals on the list are able to take trips sooner due to cancellations. River Trip Attributes Bishop et al. (1987)asked white-water boaters, including commercial passengers,to report the attributes that contribute most to an excellent Grand Canyon trip. Good weather, good social interaction, good guides, an unrushed pace (time for layovers and stops at attraction sites), and a wilderness experiencewere the attributes mentioned most often by respondents. Of the attributes listed by at least 15 percent of all respondents, four are potentially affected by discharges: .Time for layovers and stops at attraction sites .Good/ exciting rapids .A wilderness experience .Not feeling crowded Bishop et al. (1987)asked white-water boaters and commercial white-water guides to provide self reports on the quality of Grand Canyon whitewater trips. Both the guides and the passengers reported that the quality of trips was highest during periods of constant flows in the range of 25,000cfs to 30,000cfs. Rapids are important attributes of white-water boating trips (Bishop et al., 1987). Rapids are flow related since a number of small to medium rapids become "washed out" at relatively high flows, while other larger rapids become more exciting to run. Constant daily flows affect trip procedures at major rapids differently for commercial motor, commercial oar, and private trips. Most commercial oar guides stop to scout major rapids no matter what the flow level. In contrast, commercial motor guides are more likely to stop when flows are below 10,000cfs and above 50,000cfs. (Releaseshigher than 31,500cfs are rare and unscheduled.) Private trip leaders are most likely to scout rapids at moderately high 154 Chapter III Affected Environment levels of 25,000to 35,000cis. Guides and trip leaders also are more likely to have passengers walk around major rapids at flows above 35,000cfs. At low flows (5,000cfs or less),it often becomesnecessaryto either walk passengers around some rapids or wait for higher water. Flow levels also can affect trip schedules. Commercial guides are more likely than private trip leaders to attempt to compensatefor the speed of the current at high or low constant flows. Nearlyall commercial guides will row or motor more at flows of 10,000cis or lower, while most will row or motor less at flows higher than 35,000cis. Numerous attractions are found along the tributaries and side canyons of the Colorado River . River trips make planned stops at many of these and schedule short or extended dayhikes. These stops are important attributes of white-water trips. During low flows, both commercial and private trip passengersmay have to miss one or more attraction sites becauseof the additional time needed on the river to maintain a trip schedule. Finally, white-water boaters may feel more crowded at high flows becausethe number and size of beachesfor camping are significantly reduced. In addition, during daily fluctuations in flows, boaters may congregate above rapids as they wait for the water level to rise. Jalbert (1992) found no relationship between flows and the incidence of on-river contacts between river rafters, probably becauseother factors-such as launch dates and itineraries-have a greater influence. Wilderness Values Studies of wilderness values in Grand Canyon were begun in the early 1970'sbut postponed due to the controversy over motorized raft use on the Colorado River. An amendment (Public Law 94-31)to the Grand Canyon Enlargement Act of 1975called for completion of a wilderness study within 2 years. NPS releasedfor public comment a draft environmental impact statement (DES 76-28)and a preliminary wilderness recommendation in 1976. The preliminary recommendation was for designating 82 percent of the park area as wilderness and an additional 10 percent as potential wilderness. Following incorporation of comments, a final EIS was completed in August of 1980and forwarded to the Department of the Interior. In August 1993,NPS updated this wilderness recommendation, and action by the Congressis pending. NPS is mandated by the Wilderness Act to protect wilderness values in the park, including those along the river, and to take no action that would potentially compromise future wilderness suitability. Motorized rafts are still in use on the river, and it is anticipated that the Congress,if it enacts a wilderness designation for the park, will stipulate the conditions under which motor use will or will not continue (under the direction of the Secretaryof the Interior) on the Colorado River within Grand Canyon. Wilderness is both a legal and philosophical concept-an area that appears to be influenced primarily by the forces of nature. The presence of Glen Canyon Dam does not preclude wilderness designation for the Colorado River through Grand Canyon, but dam operations can have an influence on the wilderness setting. The feeling of being in a wilderness area can be affected by fluctuations in daily flows since changesin releasesfrom the dam would continually remind boaters of human control over riverflow and thus the recreational environment. It should be noted that short duration, sometimes high magnitude changesin flow occurred predam-commonly at intervals of a few days or less-due to floods from tributaries and side canyons. Thus, while predam flow did not resemble the daily fluctuations of dam operations, neither was it steady (seeWATER in this chapter). However, predam fluctuations did not detract from the wilderness value in that they were "forces of nature" and evidently not "the hand of man." One of the attributes of an excellent or perfect river trip most often identified by river runners is a wilderness experience. Enjoying a "wilderness experience" is more important to private RECREATION 155 (noncommercial) rafters and oar trip passengers and least important to motor passengers. Most river runners are aware of wide daily fluctuations, and most feel that the fluctuations make the trip seem less like a natural setting (Bishop et al., 1987) Safety Riverflow levels affect accident rates (although the element of risk is a factor that attracts rafters to Grand Canyon); floodflows and low flows are believed to be the most hazardous. Fluctuating flows are not considered a significant factor in river safety.At low flows, major rapids (such as Hance) become difficult to navigate. Depending on the craft being used and the skill of the boatman, it often is necessaryto camp above a rapid to wait for the river to rise. As the average daily flow increases,boaters become more tolerant of wider fluctuation ranges (Bishop et al., 1987). Commercial guides believe that minimum constant flows must be over 8,000cfs to safely run river trips with passengers. Commercial motor guides prefer flows around 20,000cis, while commercial oar guides and private trip leaders prefer higher mean discharges of 25,000to 26,000cis. The preferred mean maximum flow for commercial guides is over 50,000cis, while a great number of private trip leaders prefer 40,000cis or less (Bishop et al., 1987). Accident Occurrence. Although the actual boating accident rate is not high, the very nature of the Colorado River in Grand Canyon presents an unusually severehazard for white-water boaters since rapids are difficult to navigate and people might fall into the water. In addition to the high water velocities and turbulence, the cold water is life threatening. Flows in the range of 10,000to 17,000cfs appear to be the safest (Brown and Hahn, 1987). The chance of hitting rocks generally decreasesas flow increases. The chanceof going overboard, flipping boats, and sustaining injuries increases with higher flows. Actions taken to avoid rapids-such as walking passengersaround a rapid and portaging-increase at extremely high (above 31,000cfs) and low (below 5,000cis) flows. Taking into account a boatman's judgment of risk and the actions taken to avoid accidents,high flows (16,000to 31,500cfs) are safestfor both private and commercial trips, with medium and low flows presenting increased hazard for both. During flows less than 5,000cfs, commercial motor trips have the highest rate of all types of accidents,but private oar-powered trips sustain more equipment damage and more frequently have their passengerswalk around rapids (Jalbert, 1992). During floodflows, accident risk is much greater for private than for commercial trips. The risk of accidentsvaries by the type of boat employed. At extremely low flows (lessthan 5,000cfs), motor rigs have the highest incidence of accidents,followed by small (typically private group) rafts (Jalbert,1992). At flows higher than powerplant capacity, smaller craft-such as small rafts, dories, kayaks, and canoes/inflatableshave more accidents (Brown and Hahn, 1987). It appears the large, oar-powered rafts had the lowest incidence of accidents over the range of flows (Brown and Hahn, 1987;Jalbert, 1992). Handicapped Accessibility White-water boating in Grand Canyon-though a rigorous activity-is in demand by many, including handicapped individuals. Federallaw ensuresthat special populations with mobility difficulties can take white-water trips. Since 1991, two such trips annually have been chartered specifically for special populations. It is likely that many commercial and private rafters could accommodatehandicapped individuals for a raft trip down the Colorado River. Potential inconveniencesmight include steeppitched beachfacesand poor mooring sites (for example, a highly armored beachface). Where a party might otherwise be required to carry gear around a rapid, it might be necessaryto alter an itinerary, set up camp, and wait for more suitable flows. The greatest risk to disabled populations occurs during flows that have the highest incidence of accidents resulting in persons going overboard. This risk is compounded by the probability that 156 Chapter III Affected Environment another person will go into the water to help rescuethe disabled individual. Dam operations have the greatestinfluence on handicapped accessibility during low flows, especially those below 5,000cis, when passengers(possibly handicapped) need to walk around a potentially unsafe rapid. Camping Beaches Sandbarsform the camping beachesused by river runners (seeSEDIMENT in this chapter). Camping is possible in only a limited number of locations along the river between Glen Canyon Dam and Lake Mead becausemost of the shoreline is unsuitable. An inventory of these camping beachesin 19751istedabout 333 campsites within the river corridor, but thesewere unevenly distributed in size and location. These beacheswere resurveyed to assesshow high flows influence individual beaches(Brian and Thomas, 1984). At least 227 were verified as being inventoried in both surveys. A survey of the Lower Gorge (Ross,written communication, 1992) inventoried 14 camping beaches. encroachment accounted for nearly 50 percent of the campsite degradation in wider (noncritical) reaches(figure 111-36). Eroded Other Overgrown Eroded/Overgrown 7% (3} Non-Critical Reaches The 1983-84flood releasescausednumerous changesin camping beaches. Of inventoried beaches,30 percent increasedin size, 28 percent decreasedin size, and 42 percent remained the same. Beachdegradation occurred in narrow, upstream reaches,while aggradation occurred mostly in wide, downstream reaches. The result was 24 beachesremoved or nearly eliminated and 50 new campsites deposited. Brian and Thomas (1984)hypothesized that the system was not in equilibrium after the 1983floods and that the number, size, and distribution of beacheswould change depending on the stability of the sediment deposited at the new beaches. While flood releasesmay dramatically impact the size and number of camping beaches,normal dam operations also can affect the long-term characteristics of beaches. Sand storage, erosion, and transport vary with pattern and magnitude of dam releases,as discussedin the SEDIMENT section of this chapter. At a given time, however, campable area depends on the local stage (height) of the river, which is determined by the magnitude of releasesand local topography. A survey by Kearsley and Warren (1993)revealed that the total number of suitable camping beaches above the new high water zone had declined to 226 sites,a 48-percentdecline in the number of sites considered usable. This reduced number of usable camping beachescan be attributed to erosion and vegetation growth. In narrow (critical) reachesof the river, erosion was the primary causeof campsite degradation. Vegetation Campable Beach Area. Flows affect the usable area of a camping beach. The rise and fall of water levels, as a result of fluctuating discharges, inundates portions of the beaches,strands boats, and influences the wild character of the setting. Daily fluctuations influence campsite selection; many river runners will not choose a campsite that does not offer protection against water level changes(Bishop et al., 1987). Figure 1II-36.-Number of camps degraded by reach type and type of degradation. RECREATION Kearsley and Warren (1993)evaluated the average area for small, medium, and large campsites (basedon size of group accommodated) at several discharges. They concluded that campable areas differed significantly under the discharges evaluated. Table 111-12 shows the average area of camping beachesby size class and discharge, while figure 111-37 shows the percent of beach area changebetween evaluated discharges. Although large campsites lose more area at higher levels of discharge, this loss is not important in terms of carrying capacity for many camps. The campable area of most large camps far exceedsthat needed for the maximum trip size of 36 people. The percent change in area of campsitesbetween dischargesfor critical reacheswas not significantly different than that for noncritical reachesat any discharge level. 157 An average of 35 percent of potential campsite area is inundated when releasesincrease from 5,000to 25,000cfs. About 36 percent of the small and medium sites available at 25,000cfs become large enough to change size classwhen dam releasesare reduced to 15,000cfs or less (Kearsley and Warren, 1993). Beach Availability and Distribution. The location and distribution of beaches,by reach, set the absolute limits on visitor carrying capacity; i.e., the numbers of groups in a critical reach must be equal to or less than the number of campsites available in that reach. The distribution of camping beachesby reach is shown in table 111-13. The number of campsites averages1.0 per mile, with campsitesin critical reachesaveraging 0.7 per mile and campsitesin noncritical reaches averaging 1.1 per mile (Kearsley and Warren, 1993)(figure 111-38).Campsite availability is critically limited in four narrow sections of the river: .Supai and Redwall Gorge .Upper Granite Gorge above and below Phantom Ranch (RM 76-117) .Muav Gorge above and below Havasu (RM 140-165) .Lower Granite Gorge and Lake Mead (RM 226-270) Critical reacheshave disproportionately fewer large campsites per mile at 0.20per mile compared to 0.51large site per mile in noncritical reaches. Deer Creek reach (RM 131-139)has more sites per mile than any other river reach at 2.3 sites per mile. However, becauseof the popularity of attractions in the area, it is not uncommon for 5-8 5-15 15-25 5-25 Change in Riverflow (in thousand cis) Figure III-37.-Percentage inundated between Table of beach area discharges. 111-12, -Average area in square feet of campsites by size class and discharge for 1991 Small 2,660 3,560 6,490 Medium 4,950 4,940 Large 1,720 13,980 All 7,720 9,200 Note: Low water campsites not included. 7,210 ,660 19,340 11,740 12,910 17 160 Chapter III Affected Environment thus, the number of suitable campsites. Competition for prime camping areasmay result in unavoidable crowding, which in turn may influence the recreational experience. Canyon. Also, the channel changeswith fluctuating flows, making it hard for even small boats to stay in the channel. Lake Level and RiverRafting. Lake levels have an influence on commercial raft trips taken on the SanJuan River and on the Colorado River through Cataract Canyon. The lake is considered a takeout point for raft trips, and most operators are more concerned about lack of water volume in the SanJuan and through Cataract Canyon than they are about low lake levels. Lake levels do have an influence on operating costs (in the form of wear and tear on equipment and increased labor costs) and on trip duration. Economics Navigability of Upper Lake Mead Boats usually are launched at Piercebasin, South Cove, or Temple Bar for excursions into Grand Canyon. Rental houseboatsalso travel to the Grand Wash Cliffs area on their week-long trips. Becausethere are no gas facilities on the lake upstream from Temple Bar, boaters must carry enough fuel to complete a round trip to their destination. Sightseeingin the Lower Gorge is a popular activity for boaters on upper Lake Mead. Popular points of interest on these trips are Columbine Falls, Bat Cave, SpencerCreek, and Separation Canyon. Overnight beach camping is often a part of the itinerary for people enjoying the lower Grand Canyon by powerboat. Use This section describesthe existing quantity, distribution, and economic impact of recreation in the study area. Two economic measures-the net economic value of recreation and the regional economic impact of recreation-are introduced. Thesemeasuresare used to illustrate the national and regional economic impacts of the proposed alternatives. The net economic value of an activity is the net addition to the Nation's output of goods and servicesmeasured in dollar terms. The term "net economic value" is used to emphasize that it is a measure of the value over and above the costs of participating in a recreational activity. The costs of participation in a recreational activity are simply the expenditures made by recreationists. Regional economic impact is a measure of the importance to the local economy of the expenditures made by recreators. Since such expenditures reflect the costs of participation, they are not considered benefits from the national point of view and are excluded from the calculation of net economic value. Recreation Before construction of Glen Canyon Dam, spring runoff carried heavy loads of sediment down the Colorado River to Lake Mead, where the sediment dropped out and settled at the lake bottom in the vicinity of Grand Wash to Piercebasin. After the dam was completed, sediment continued to be transported down the river, but in smaller quantities from side canyons and the beachesbelow the dam. Over the years, thesesediment deposits have built up and are now exposed as broad mud flats in the vicinity of Piercebasin when lake levels fall below 1180feet. Becauseno welldefined river channel has been established through theseflats, the river is too shallow at low flows for boaters to navigate up to the Grand Wash Cliffs and into the lower reachesof Grand of Recreational Use The amount and distribution of recreational use in the study area have important implications both for estimating regional economic impact and for estimating the net economic value of recreation. The distribution of visitation during calendar year 1991by recreational activity is shown in figure III-40. As shown, much of the white-water boating use occurs during the summer months when most Americans take their vacations. Most of the angling use occurs during the spring and fall. This pattern of use has an important effect on the generation of net economic benefits. To the extent that net economic benefits are directly determined by flow, changesin flow during periods of high recreational use produce larger RECREATION 163 from other individuals and local businesses. Theseindividuals and businesses,in turn, spend a portion of their revenue in the region, and so on. A portion of each dollar spent by nonresident recreators is re-spent over and over in the region, and the impact of each dollar of direct expenditure by visitors is greater than $1. An example can be used to demonstrate this concept more clearly. Supposethat all of the businesses,government agencies,and households in a hypothetical county spent 40 percent of the money they receive from nonresident expenditures on goods and servicesin the local area. They spent the other 60 percent of the money to buy goods and servicesoutside of the region. Each dollar spent by nonresident visitors will stimulate an initial $1 worth of local economic activity. That $1 is re-spent by businesses,government agencies, and households. Of that $1, $0.60is spent outside the county and $0.40is spent inside the county. Of that $0.40,$0.40x 40 percent = $0.16is re-spent in the region and $0.40x 60 percent = $0.24is spent outside of the county. After six successive re-spendings, the money that circulates inside the hypothetical county is less than $0.01. In this example, the effect of each $1 of direct expenditures by nonresident visitors is: Initial expenditure = $1.00 $1.00 x40% $0.40 x 40% $0.16 x 400;0 $0.06 x 400;0 = $0.40 $0.03 x 40% Total impact = $0.16 of nonresident expenditure. Multipliers allow the impact of nonresident expenditures to be more fully assessed.For instance, suppose that a nonresident visitor spent a total of $101.00in the hypothetical county discussedpreviously. Using the multiplier of 1.66,this direct expenditure would create $101.00x 1.66= $167.77in local economic activity . The u.s. Forest Service'sImpact Analysis for Planillng (IMPLAN) model (Taylor et al., 1992),a sophisticated framework for assessingregional impacts, was used to estimate multipliers for this analysis. Thesemultipliers are based on the concept described above. However, unlike the example discussed,IMPLAN multipliers are disaggregated into business sectors. Two Arizona counties, Coconino and Mohave, were assumed to capture the bulk of the local economic impacts generatedby river-based recreation in Glen and Grand Canyons. Riverbased recreators who reside outside of these two counties are described as nonresidents for the purposes of this analysis. River-based recreators who reside in either Coconino or Mohave Counties were classified as residents. Using IMPLAN, multipliers were developed for the local impact region and were used to develop the results reported in table 1II-16. = $0.06 = $0.03 =$Q..Q.1 = $1.66 This example illustrates that each additional dollar of direct expenditure by a nonresident visitor produces $1.66 in local economic activity. A simple multiplier is calculated from this result: ($1.66/$1.00) = $1.66. A multiplier relates the amount of direct nonresident expenditure to the total amount of local economic activity produced by the visitor's spending. The size of a multiplier differs depending on the economic structure of the region. In general, the more complex the economy, the larger the multiplier and the more the impact on the local economy from each dollar Estimates of averageexpenditures by anglers and white-water boaters were obtained by Bishop et al. (1987). Expenditures by white-water boaters below Diamond Creek are unknown. Estimates of their expenditures were derived by apportioning the trip costs found in Bishop et al. (1987)on a daily basis and by substituting their commercial trip fees as appropriate. As shown, commercial white-water boaters generate most of the economic activity in the region. In total, river-based recreational users generated approximately $23 million in local economic activity in 1991. Chapter III Affected Environment 164 Table 111-16.-Number of nonresident trips. direct expenditures by nonresident river-based recreators, and estimated local economic activity generated in the region in 1991 Estimated trips by nonresidents regional expenditures per trip (1991 $) Glen Canyon (scenic) rafting 32,816 72 Glen Canyon anglers 10,270 2,926 Number of 1991 Private white-water boating in Grand Canyon Commercial white-water boating in Grand Canyon 13,478 Commercial white-water boating below Diamond Creek 1 ,504 467 Private white-water boating below Diamond Creek Total 61 ,461 Total direct expenditures by nonresidents Local economic (1991 $) activity generated (1991 $) 122 1,252,000 ,833,000 255 747,000 124,000 71 9,581,000 15,420,000 299 450,000 735,000 103 48,000 75,000 14,452,000 23, 115,000 Recreation, Economics, and Indian Tribes Hualapai Tribe. Recreationaccessfees and commercial recreation enterprises generatea significant percentageof the total revenue earned by the Hualapai Tribe. This revenue supports the reservation's economy and createsemployment for tribal members. Recreationaluse of Hualapai resourcesin Grand Canyon has increased in the past decadeand is anticipated to increaseover time. Figure 111-41 illustrates this trend. As shown, recreational use has increasedsubstantially over the period that data is available. The revenues generatedby recreational activities on the Hualapai Reservation are earned by tribally owned enterprises. The Hualapai Tribe's recreational enterprises can be classified into two types: .River-based .River-related recreational activities recreational activities Figure IIl-41.- Total recreation permits sold by Hualapai Tribe, 1985-91. RECREATION River-based recreational enterprises are those that are directly flow dependent, including such activities as fishing and white-water boating. Conversely, river-related activities such as sightseeing and camping take place in the river corridor but are not directly influenced by flow. Commercial white-water boating below Diamond Creek may have net economic value and regional economic impact. However, Bishop et al. (1987) did not investigate the net economic value of white-water boating in this reach. Basedon use data provided by the Hualapai Tribe and several assumptions about boater expenditure patterns, estimates of the regional economic impact of boating below Diamond Creek were developed. Theseestimated impacts are shown in table 111-16. River-Based Recreation.-A substantial portion of the Hualapai Tribe's gross revenue is derived from river-based recreational activities. The largest of these activities is white-water boating. The Hualapai Tribe owns and operates Hualapai River Runners, a commercial whitewater boating company. Hualapai River Runners is one of four tribal enterprises and was the major source of tribal income in the 1980's. In addition to offering white-water boating trips, Hualapai River Runners provides shuttle services,tows acrossLake Mead, and accessfor river takeouts at Diamond Creek. In 1987,Hualapai River Runners earned 49 percent or approximately half of the Hualapai's total gross income. The tribe has diversified its business interests and now depends less on river-based recreation activities than it did in the past. Nevertheless, the tribe earned about 33 percent of its total 1991income from such activities. River-Related Recreation.-The Hualapai Tribe also owns and operates Grand Canyon West, an enterprise based on the natural beauty of Grand Canyon and the Colorado River. This enterprise offers guided tours of the Hualapai Reservation at the west end of the canyon. 165 Currently, Grand Canyon West only provides river-related activities that are not directly flow dependent. The Hualapais sell permits for sightseeing and camping on the reservation. Much of this river-related use is concentrated along the river corridor. In addition, the Hualapai Tribe derives approximately one-fourth of its gross revenue from the sale of permits to hunt desert bighorn sheep. Someof these sheep are known to use riparian zones in Grand Canyon. Navajo Nation. The Navajo Reservation borders portions of Glen Canyon National Recreation Area and Grand Canyon National Park. There has been little development of business enterprises in this region due largely to the "Bennett Freeze." Imposed by the Federal Government in 1966,this statutory freeze precluded construction or development on this portion of the reservation pending resolution of a territorial dispute. The Bennett Freezehas recently been lifted, and river-based enterprises may develop in the near future. At the present time, however, no river-based enterprises owned or operated by the Navajo Nation have been documented. At various times, the Navajo Nation has planned to construct a marina at Antelope Point on Lake Powell. Should such a marina be constructed, it would be subject to the same impacts as existing NPS facilities on the lake. These impacts are described under "Lake Activities and Facilities." A number of tribally owned or operated businessesin Cameron, Tuba City, Grey Mountain, and elsewhere on the reservation are dependent on Grand Canyon visitors. The many jewelry stands along Arizona Highway 89 and other approachesto the park are especially prominent examples. Owned and operated by individual Navajo families, these small enterprises are frequented by visitors to the region. Other Tribes.Portions of the Havasupai Reservation border Grand Canyon National Park. No river-based enterprises owned or operated by the Havasupai Tribe have been documented. The Hopi Tribe, Pueblo of Zuni, and Southern Paiute HYDROPOWER 169 Emergenciesand Outage Assistance. Western's operating procedures meet North American Electric Reliability Council guidelines for emergency operating criteria. NERC guidelines state that under emergencies,generation must be available to quickly restore the transmission system and start the return to normal operating conditions within 10 minutes. Generally, emergency servicesare needed only for short periods (1 hour or less). Glen Canyon Powerplant is important in responding to interconnected transmission system emergencies. Western has existing contractual agreementsto use Glen Canyon capacity to restart thermal powerplants in the area in the unlikely event of a widespread power outage. Emergency assistanceis similar to emergency operations, but generally involves smaller outages that last longer. Under this service, each IPP member utility is obligated to provide up to its spinning reserve amount of capacity and energy for 72 hours if an unplanned outage occurs. Western's ability to supply IPP emergency assistanceis limited by two factors: available transmission capacity and generation capability . Western's ability to deliver emergency assistance varies on an hourly basis, depending on firm load obligations and available generation from project resources. Under historic operations, with a full reservoir and average loads, Glen Canyon Powerplant has provided emergency assistance beyond its required reserves. When an unplanned outage extends beyond 72 hours, the affected utility may arrange to purchase or exchangefirm capacity and/ or energy with another utility. SLCA/IP often provides scheduled outage assistancedue to its central location within IPP and the flexibility of its hydroelectric resources. TransmissionSystem. The CRSP/W AUC transmission system has approximately 2,300miles of transmission lines. The following map shows the CRSPInterconnected Transmission System. The CRSPtransmission system stretchesfrom southern Wyoming through western Colorado and eastern Utah, down to northern New Mexico, acrossnorthern Arizona, and finally into the south-central Arizona area. The WAUC is interconnected with six other Federal and private load control areas: .Public Service Company of Colorado .PacifiCorp .Public (including Utah Power and Light) Service Company of New Mexico .Western Area-Lower Missouri .Arizona Public Service Company .Western Area-Lower Colorado Western's transmission lines transport electricity from Glen Canyon Dam and other generating sourcesto customer utilities that serve end users, such as residential, irrigation district, and commercial and industrial consumers. Both hydroelectric and thermal generation are affected by transmission limitations when lines do not have enough capacity to transport electricity from the point of generation to the point of demand. At times, Western can mitigate existing limitations on Glen Canyon's eastern transmission line by exchanging power with the Salt River Project (SRP),as explained later in this section. The amount of power scheduled for transmission varies from seasonto season,day to day, and hour to hour. Scheduling limits are derived from physical limits and determine how many transactions may occur. Actual transmission refers to the actual measured flow of power on the line. NERC requires monitoring of the actual and schedule power flow for system operation. Transmission Service.-Western,like many utilities, offers both firm and nonfirm transmission service. Firm transmission service is contractually guaranteed for the term of the agreement. Nonfirm transmission service is provided as available and is not guaranteed. Western participates in electricity transfers through "wheeling," which occurs when two indirectly connected utilities agree to purchase or sell power to each other. The purchaser or seller must make arrangements to use the transmission system that electrically connectsthem. Western offers HYDROPOWER commitments, either through generation alone or by generation combined with purchases. Longterm firm commitments vary seasonally according to project loads and customer requirements. Sevenof SLCA/IP's customers are considered to be "large" systems-utilities that buy capacity and energy to supplement their own generating resources. The rest of Western's customers are "small" systems that have little or no generating capacity and rely on purchasesfor most or all of their capacity and energy needs. Almost all SLCA/IP customers have supplemental suppliers to meet additional capacity needs. The SLCA/IP marketing area and some of the many customers are shown on customer service maps in appendix E, along with a detailed listing of their firm capacity and energy allocations. Short-Term Firm Power Short-tenn finn salesof capacity or energy can be made seasonallyor monthly. Short-term firm salesare based on resource availability projections that exceedlong-tenn finn commitments. Prior to each 6-month marketing season,Western determines whether excesscapacity or energy will be available for a seasonor a month. This shortterm firm resourceis made available first to Reclamation for project needs, then to preference customers (municipalities, public corporations, cooperatives, and other nonprofit organizations). Any remaining resourcesare offered to nonpreferencecustomers. Prices are based on long-tenn finn power rates. Nonfirm Energy Nonfirm salesare short duration energy transactions, always less than 1 year. Normally scheduled 1 day in advance, they can be determined up to the hour of transaction. The flexibility of hydropower operations allows actual deliveries to be modified hourly, as system conditions warrant. Western may market nonfirm 171 energy and arrange for interchange transactions, depending on revised water releaseestimates. Nonfirm energy salesare not guaranteed and may be interrupted with advance notice. The price for this service is based on market conditions. Nonfirm salesalso are known as economy energy or fuel replacement sales,terms related to substitution of hydroelectric generation for oil- and gasfueled generation. The fuel replacement program began in the early 1980'sto encourage this substitution. Economy energy salesare scheduled as market and hydrologic conditions allow. SLCA/IP Post-1989 Power Marketing Criteria In 1980,Western began to review and modify its marketing and allocation criteria becauseexisting power contracts were due to expire on September30,1989. The associatedpublic process in 1986resulted in the post-1989marketing criteria. Western is preparing an EIS on the post-1989marketing criteria (Western Area Power Administration, 1994). Marketable Resources The SLCA/IP hydropower resourcessupply the marketable energy and capacity under the post-1989power marketing criteria. Capacity and energy are marketed on a seasonalbasiswinter season(October-March) and summer season(April-September). Under the post-1989 marketing plan, SLCA/IP has contractual commitments for 1,407MW of capacity and 3,105,848megawatthours (MWh) of energy in the winter seasonand 1,315MW of capacity and 2,904,403MWh of energy in the summer season. Theseamounts are explained in greater detail in the following sections. Capacity. The CRSP and Fontenelle Powerplant components of the SLCA/IP totallong-term firm capacity values are based on the amount of capacity available 9 of every 10 years.3 Critical 3Marketable firm capacity and energy are based on attempts to ensure a reliable level of capacity and energy, while maintaining an acceptablelevel of risk. This level of acceptablerisk was approved by Western's customers following review of the September 1984 "Revised Proposed General Power Marketing and Allocation Criteria " (U.5. Department of Energy, 1985). NON-USEV ALUE Retail Rates. Approximately 180public power utilities currently purchase electric power from the SLCA/IP. Most of theseutilities are located in Arizona, Colorado, Nevada, New Mexico, Utah, and Wyoming (figure I11-43),though some extend into California, Nebraska, and Texas. 173 indirectly from Glen Canyon Dam (Electric World, 1993). The power rates paid by theseusers potentially could increaseas a result of changesin dam operations. Regional Economic Activity All (or the vast majority) in the region is consumed of the power produced in the region. As the supply of peaking power falls, for any given level of demand the price of electricity rises. Supply-induced price changesmay affect the production of final goods and services and the demand for many other goods in the impact region. To further complicate matters, loss of capacity at Glen Canyon Dam is likely to result in the construction of new powerplants in the region earlier than would otherwise be the case. Largescaleconstruction projects may create employment and stimulate local economic activity. NON-USE V ALUE Figure IlI-43.- The SLCAIIP markets power to approximately 180 utilities, mostly in six States. The retail rates charged by thesepublic power entities normally are set to cover system operation and capital costs. The largest portion of these obligations, in the caseof Glen Canyon, is attributed to operating expenses. As costs of these individual components change,the retail rates are adjusted to ensure enough revenue is collected to meet the utility's financial obligations. There are approximately 5.6 million residential industrial, and commercial power customers in the six-Statearea where power from Glen Canyon Dam is sold (U .S.Department of Energy, 1994). The majority of these end users, approximately 3.9 million (70 percent), do not receive power from the dam. The remaining 1.7 million (30 percent) end-use customers receive power directly or The previous sections on recreation and hydropower focused on the human usesfor Colorado River flows in Grand Canyon. These usesinclude fishing, white-water boating, and the production of electric power. Analyses of the impact of riverflows on all of these usesare presented in chapter IV .Until recently, most descriptions of theseusesof resourcesprobably would have ended there. However, social scientists have long acknowledged the possibility that humans could be affected by changesin the status of features of the natural environment even if they never visit or otherwise use these features, Theseindividuals may be classified as non-users, and expression of their preferencesregarding the status of the natural environment may be termed "non-use value," Non-use value is the term used in this EIS to describe the monetary value non-users place on the status of the natural environment, CHAPTER IV Environmental Consequences This chapter describesand analyzes the impacts of alternatives considered in detail on the affected resources. The analysesare organized by resource: water, sediment, fish, vegetation, wildlife and habitat, endangered and other special status species,cultural resources,air quality, recreation, hydropower, and non-use value. sections on FISH and HYDROPOWER. Potential impacts on the other resources,which are expected to be minimal, are addressed later in this chapter under "Cumulative Impacts." WATER The linkages among these Colorado River system resourcesare described in chapter III. Where possible, the impacts described for each resource take into account the impacts on other related resources. For example, each alternative affects streamflows, which in turn affect sediment. Sediment affects vegetation, which in turn affects wildlife and habitat-al1 of which affect recreation. The conditions that existed in 1990,prior to the Glen Canyon Environmental Studies (GCES) researchflows and the subsequentinterim operations, establish the baseline for analysesof effects (see"Chapter III, Affected Environment"). Some anticipated impacts are a result of the existenceof Glen Canyon Dam and will occur in the future regardless of which alternative is implemented. Existing information was used to develop the detailed impact assessmentsof the alternatives that follow. However, existing information is limited for some resources,as is knowledge of how changesin Glen Canyon Dam operations would affect theseresources. For example, limited data permit opinions to vary concerning interactions between native and non-native fish and how operational changeswould affect these interactions and ultimately resident fish populations. Endangered fish research,which may include experimental flows, would be developed through the adaptive management processto address these uncertainties. Endangered fish researchmay have additional consequences,and these potential impacts are evaluated in the summaries of the following The area of potential impacts on water includes the Colorado River downstream from Glen Canyon Dam, Lakes Powell and Mead, and the Upper and Lower Basin States. Computer modeling studies projected operations for 50 years to determine long-term impacts and for 20 years to determine short-term impacts. Analysis Methods The Colorado River Simulation System (CRSS) was used in analyzing impacts on annual and monthly streamflows, floodflows and other spills, water storage, water allocation deliveries, and Upper Basin yield determinations for this environmental impact statement (EIS). CRSSis a package of computer programs and data bases designed to assistwater resource managers in ;: . 'CQ) mC')mm momm <0!'-<0<0 II) In I!) II) U) . I -;n"6 o~ 0!!? 0onQ) ,,~ -.I-> 1/1 ~>- ~ o o ~ .5 ';-; o o .s v o o .- .= ';; o o .- .s v c c .s ';i 9 .5 v o o " I a: 0ca GI-J U)o ~o v~ ~a>" ~o 00 ~~ ~ai CX) Lno 00 <0- r-~. 00"' C .-ID E Q)Q)c. c.c.Q):;) ::)'C c. 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It). m (') t-II: "' U) s: .2 E "' Q) ~ -"'-") 10 '(;) C:I C-.:-"' '>. :)~- >- :) .aQ) C .-"' "C E :) 0- "C ~ c o joU. a:>, "C - ~ ...~ GJ ~ GJ>- tl' >="co IQGIc-u. o~>U) .-"c IQ"CIQ GI-Q.Q;O)E --c .I: = c .~ -"' .-c. §\L~(/)(/) ~ '- -Q) > w~>~ ~~ ;;- 4) iE m ~ c: ... 2 ~ ~ >- 0g'.?;-4)..Q .c E u. .D -U)c~> U> °)( o O "C .~ ~ c: ~ ~ .~ .c:~3' OI:1C ~uLL :1 u: ~~ aI c -0M (U-~ ..(U~ aI :1 O '0-oUU. 0) O 0) .= "C I E .Q .~ ~ "iU~ Q; GlO~o c uU. c. --J-... -~ u: m~ £ 'C°~ O..J- O C> c: .i: :J "C a: w ~ c: 0 U> u "' a; «' m U) m tf) m :J c c as ~ .x 0) ~ 0) 0) "' "' .5 Q) .£ 0 tJ ~ 0) z (3 0> ~ o 7 u (1) ~ O 7 u 0) ~ ~ o z u Q) == Q) o c::o: u 0> ~ 0 ~ u 0) ::: 0) 0 ~ u Q) ~ O 7 ""Qi~ > c: <1> O -:; .-11! 0 > <1> ?:~ <1> <1> (1)><1><1> -~ 'i"iO; ~Em C"~Ll) ..gt') <1>--6 "iU~ ~ -" .~ ~~Q) >-- "C.o C"C 179 Q) -0 Q) u Q) = "' "'" "' O Q) ~ E Q) g~ "-.0 >- ~ "' . = "' c.:E <~ C O O .c ~ ~s "' Q) ~ E Q) e -III -§o. ° Q) "C.c >-""QjO -ca Q) E C .-O Xz e 0. o.~ III .-O ~ ~ Q) "~:5 C""~~~ Q)O.c -ca~~.c" Q)O"cO " .-Q) ..= - U O "C".o >-C(/)111 UI11 ~ C C .~ C'-ca"C", Q) C " ~ .-U "' Q) III ~ C "' Q) U C .C ." "' Q) :5 ~ C O "8~::~ ~O-OQ) Q) C "C C>~Q)~ C ~ .-"Q; 9 .-"' "C>-Q) ~.~E§5 -:a.:2.c O[DO~ > "C o ~>-~ ~o ."'.- ~ Q)-.c 0. .c -0.-Q) Q):Jc>- O E ~ E U-OQ) III 0. O.Q)",~ "' U Q) E " C ~ O UXOO. Q)~~O C>"'Q)e=UO O"C-"'!UU1 "' Q) E- .III "C--Q) ~ -> III E Q) ~ E ~ Q)Q)c"C "' III O u C O .-Q) ->Q)'5:C:C .CO.!UE -E.Co "(/)~:5 ~a:=o C>oC u .-"' E(/)-Q) «)wQ) u " "C @ 180 Chapter IV Environmental Consequences level of Lake Powell to increaseby 4.5 feet (to elevation 3704.5feet) over no action. This increase would inundate an additiona13,710 acres (2-percentincrease)for about lor 2 months at an expectedfrequency of once in 20 to 40 years. Since the 8-foot increasein 1983did not affect Rainbow Bridge National Monument, this increasewould not affect the monument. Potential impacts on water quality were assessed based on analysis of existing limited data on chemical, physical, and biological processes influencing water quality in Lake Powell. Under normal hydrologic conditions, changing releasepatterns under any alternative would not affect reservoir or releasewater quality .Under any alternative, greater amounts of certain constituents (salinity, nutrients, sediment, selenium, and mercury) enter Lake Powell than are discharged. Therefore, theseconstituents would tend to increasein concentration, primarily in sediment and deep reservoir waters that rarely circulate. Lead concentrations also would continue to increase,as a result of leaded fuels used in motorized recreation on the lake. Other factors, such as future Upper Colorado River Basin depletions, development, and land use, may also influence water quality in Lake Powell and downstream. Extended droughts causelow reservoir conditions (Lake Powell storage at or below half its capacity, or less than elevation 3590feet) 5 percent or less of the time. When this does occur, intakes may draw water from nearer the reservoir surface, and large areasof delta may be exposed. As a result of these events: .Release temperatures may increase by 3 degrees Fahrenheit or less .Release lead and dissolved oxygen concentrations may increase .Release salinity, nutrient, mercury, and selenium concentrations may decrease compared to hypolimnetic release concentrations Unrestricted Fluctuating Flows No Action Alternative Streamflow. Annual, monthly, and hourly streamflows, daily fluctuations, and ramp rates would remain as defined in chapter II under the No Action Alternative and chapter Ill, WATER. Projected annual releasepatterns are similar to the historic patterns summarized in chapter II. The average annual releasewould be 10.16million acre-feet(maf), and the projected median would be 9.37maf. The minimum releaseof 8.23maf would be expected to occur about 30 percent of the time in the next 20 years and 46 percent of the time in the next 50 years. Projected monthly releasevolumes, presented in table IV-2, are similar to the historic patterns discussed in chapters II and III. Table IV-2.-Projected median monthly release volumes under the No Action Alternative in 1 ,000 acre-feet 20-year Fall (October) Winter (January) 1,045 Spring (May) Summer (July) 1,032 568 715 50-year 568 899 587 1,045 The median monthly releaseswould range from 568,000acre-feetin October to 1,045,000acre-feet in July for the 50-year analysis. Figure IV -1 showl the 50-year projected distribution of monthly flows under all alternatives. Effects of habitat maintenance flows are not included in this figure. The results of the peak-shaving model 20-year projections of daily minimum and daily maximum flows and daily fluctuations are shown in figures IV-2, IV-3, and IV-4, respectively, along with projections for the restricted fluctuating flow alternatives. Effects of habitat maintenance flows are not included in these figures. Under the No Action Alternative, the minimum releasesare projected to be less than 3,000cubic feet per second (cis) about 26 percent of the days and less than 8,000cis about 90 percent of the days. WATER 181 annual releasesfrom Lake Powell (greater than legally required) causedby scheduling difficulties-usually a substantial decreasein actual inflow from the initial forecasts. Under the No Action Alternative, frequencies of floodflows in excessof 45,000cis are projected to be once in 30 years for the 20-year period and once in 40 years for the 50-year period of analysis. 1,000 to 2,999 cIs 3,000 to 4,999 cIs 5,000 to 7 ,999 cIs 8,000 cIs and greater No Action -Fall (October) E::] Winter (January) -Spring (May) D Summer (July) High Fluctuating Flow Alternative Figure IV-l.-Fifty-year projected distribution of monthly volume releases (flood frequency reduced by increasing height of spillway gates), Maximum flows are projected to be greater than 25,000cfs 14 percent of the days and greater than 20,000cfs about 72 percent of the days. Daily fluctuations would be greater than 20,000cfs about 13 percent of the days and greater than 8,000cfs about 95 percent of the days. Floodnows and Other Spills. Floodflows are releases in excess of the powerplant capacity of 33,200 cfs. Spills other than floodflows are excess Modified Low and Interim Low Fluctuating Flow Alternatives Figure IV-2.-Projected 20-year minimum hourly releases under the fluctuating flow alternatives (percentage of days that the minimums would occur). (Frequenciesof floodflows in excessof 33,200cfs would be about once in 20 years for both the 20- and 50-year periods of analysis.) Median annual water releasepatterns are used as indicators of the extent to which spills other than floodflows may be of concern under each of the alternatives. The expectedno action median 20- and 50-year annual releaseswould be 9.4 and 8.6 maf, respectively. Greater than 20,000 cfs 16,000 to 20,000 cfs 12,100 to 15,999cfs 8,000 to 12,099 cfs """""' 6,000 to 7,999 cfs 5,000 to 5,999 cfs E:=] Less than 5,000 cfs 52. 2.6% 23. No Action Maximum Powerplant Capacity Alternative 1 3.3% 0.9% 4% 41 High Fluctuating Flow Alternative 26.7% 1 Moderate Fluctuating Flow Alternative "'"C"CCC C":'",; 23.5% 1 The model-estimated flows in this range are just slightly over 8,000 cfs (the limit for these alternatives). Figure IV-3.-Projected 20-year maximum hourly releases under the fluctuating flow alternatives (percentage of days that the maximums would occur). "cc cc..,c ,,"~C""'19.6% Modified Low and Interim Low Fluctuating Flow Alternative Figure IV-4.-Projected daily fluctuations under the fluctuating flow alternatives (percentage of days that the specified fluctuation would occur). 184 Chapter IV Environmental Consequences Extended droughts (a natural hydrologic variation) that causelow reservoir conditions are expected to occur less than 5 percent of the time. The magnitude of such drought-related water quality changeswould depend on the amount of reservoir drawdown and inflow, circulation, and other factors. As the reservoir refills and reaches normal levels, changesare expected to diminish. Under low reservoir conditions, the intakes may withdraw water from nearer the surface in the middle layer, the metalimnion, or even the top layer, the epilimnion. Sincewater quality in the upper layers differs from that in the hypolimnion, changesin reservoir and releasewater quality would result. A complete discussion of the effects of abnormally low reservoir conditions on water quality can be found in Appendix C, Water Quality. Maximum Powerplant Capacity Alternative Annual and monthly streamflow patterns under this alternative would be the same as under the No Action Alternative. The results of the peak-shaving model projections of daily minimum and daily maximum flows and daily fluctuations are shown in figures IV-2,IV-3, and IV -4, respectively. Thesehourly minimums, maximums, and fluctuations would differ little from no action. Effects on floodflows and other spills, reservoir storage patterns, water allocation deliveries, Upper Basin yield determination, and water quality would all be the same as under the No Action Alternative. Restricted Fluctuating Flows The four restricted fluctuating flow alternatives would result in some common impacts, which are discussedin this section. Differences among alternatives are described under the individual alternatives that follow this section. Hourly streamflow patterns under each of the restricted fluctuating flow alternatives would differ from those of the No Action Alternative (and those of each other) and are therefore discussedindividually below. The annual patterns would be essentially the same as no action; monthly patterns would differ negligibly from no action, since the manner of scheduling monthly volumes would be the same. However, habitat maintenance flows (under the Moderate and Modified Low Fluctuating Flow Alternatives) and beach/habitat-building flows would about double March or April releasesin years when the reservoir is low. Other monthly volumes would be reduced by about 5 to 10 percent under such circumstances. Figure IV -1 shows the projected monthly patterns for the SO-yearanalysis without habitat maintenanceor beach/habitat-building flows. Further, as shown in table IV-1, the projected median annual and monthly volumes are similar to those of no action. Tools are not available for projecting the frequencies of ramp rates,but ramp rates for all alternatives would be limited as defined in chapter II. The expected frequency and magnitude of floodflows under the restricted fluctuating flow alternatives would be reduced to less than 1 in 100years due to the addition of flood frequency reduction measures. Reclamation, in consultation with the Colorado River Management Work Group, would devise specific operating methods to achieve frequencies no greater than once in 100years. Annual water releasepatterns from Lake Powell have been used as an indicator of the extent to which spills other than floodflows may be of concern when flood frequency reduction measuresare added. The projected median annual releaseswould be essentially the same as under no action for both the 20- and 50-year analysesusing either method of reducing flood frequency. Therefore, the alternatives would have a negligible effect on spills other than floodflows. Long-term monthly and annual reservoir storage would be the same under the restricted fluctuating flow alternatives as under the No Action Alternative for both Lakes Powell and Mead, WATER except for slight differences due to addition of flood frequency reduction measuresand habitat maintenance and beach/habitat-building flows. The lowest storage projected for the next 50 years would be the same as under the No Action Alternative for all restricted fluctuating flow alternatives. The end-of-analysis storageswould be very nearly the same as no action (table IV-l). GenerallyI storage effects would be negligible to minor. Water allocation deliveries under the restricted fluctuating flow alternatives would be essentially the same as under no action. CRSSanalysesindicated that under projected depletion levels, water allocation deliveries in the Upper Basin for the next 20 and 50 years would be affected negligibly by either of the methods of reducing flood frequency. However, if Upper Basin depletions would reach the levels permitted in the Colorado River Compact, a reduction in maximum allowable storage by reserving exclusive flood control spacein Lake Powell would have a measurable impact on consumptive use. The reservoir system yield available for Upper Basin depletion would be reduced. This yield is defined as the sustainable annual quantity of water that could be depleted by the Upper Basin while making the required releasesto the Lower Basin during periods of Upper Basin drought. Using the critica125-year hydrologic period 1953-77and assuming full reservoir starting conditions, the current estimated annual Upper Basin yield is 6 maf. The impact of lower storage levels on yield can be estimated as follows: a 1-maf reduction in available storage would reduce the yield by 40,000acre-feetper year (1 maf divided by 25 years). This would be only 0.67 percent of the total Upper Basin yield. Reducing flood frequency by increasing the height of the spillways would have no effect on Upper Basin yield determination. The increased spillway height method was assumed for impact analyses. U.S. Department of the Interior (1989)provides a more thorough explanation of yield methodology . 185 Effects on the Upper Basin yield limit the ultimate amount of water that each State in the Upper Basin can deplete. This is particularly critical in New Mexico, where uses are approaching their compact allocation. Thus, even though the Upper Basin yield would be reduced by only 0.67percent, the water users who could receive a reduced or no allocation due to the overall reduction would be impacted substantially. High Fluctuating Flow Alternative Hourly streamflow patterns, daily fluctuations, and ramp rates would differ slightly from those under the No Action Alternative. The frequencies of minimum and maximum daily flows and daily fluctuations are summarized in figures IV-2,IV-3, and IV-4. Moderate Fluctuating Flow Alternative Hourly streamflow patterns, daily fluctuations, and ramp rates would differ from those under the No Action Alternative. The frequencies of minimum and maximum daily flows and daily fluctuations are summarized in figures IV-2, IV-3, and IV -4. The effects of habitat maintenance flows are not shown in these figures. However, such flows would increasethe maximums and minimums and reduce fluctuations in March or April when the reservoir is low (about half the years). During the habitat maintenance flow period, increasesin turbidity are likely, which would decreasethe depth that sunlight reachesin the water and thus affect water quality .Primary productivity may be temporarily reduced. However, resuspending sediment and organic material also may reintroduce nutrients and other constituents associatedwith the particles into the water. Thesenutrients may stimulate algal growth. The river stage would not be significantly reduced by shifting water from one month to another for habitat maintenance flows. Thus, instream temperatures and Cladophoraexposure would not change from no action. WATER [=:] 187 reservoir storage and the corresponding impacts on Lakes Powell and Mead would be negligible. 8,000-9,900 cfs 15,000-19,900 (:::::::::,: 10,000-14,900 cfs cfs >20,000 cfs 15.2% 1.6% 3.5% 0.2% 17.7% Fall (October) Monthly releasevolumes would be the same as under the restricted fluctuating flow alternatives, so impacts on water allocation deliveries under this alternative would be negligible. Also, the Upper Basin yield determination would be essentially the same as no action. Water quality impacts would not vary substantially from no action. Steady, lower flows may allow for a relatively small increasein river temperatures, particularly during the summer, but this increasehas not been quantified (see chapterIV , FISH). Temperatures in Lake Mead would not increasesignificantly. Seasonally Adjusted Steady Flow Alternative The annual releaseaveragesand medians would be the sameas under the No Action Alternative using the increasedspillway height method of reducing flood frequency and would differ negligibly using the lower storage method. Therefore, this alternative would have a negligible effect on annual releases. Winter (January) 0.1% 11.9% Spring (May) Summer (July) Figure IV-6.-Projected release patterns under the Existing Monthly Volume Steady Flow Alternative (50-year analysis, percent of months that specified releases are projected to occur). Sincemonthly releasevolumes under the Existing Monthly Volume Steady Flow Alternative would be the same as they are under the restricted fluctuating flow alternatives, monthly and annual Monthly releasevolumes are based on the steady schedulesfor the alternative as defined in chapter II. Streamflows would be steady, except during transitions from one month to the next. The median monthly values for 4 months are shown in table IV-4, along with their steady cfs equivalents. The fourth graph in figure IV -1 shows the monthly volume distribution for those 4 representative months. Also, figure IV-7 shows the frequencies of the steady flows in cis for the same4 months. The monthly distributions would differ in years when habitat maintenance or beach/habitat-building flows are scheduled. March or April volumes would about double, and other monthly volumes would decreasebetween 5 and 10 percent. The expected frequency of floodflows under the SeasonallyAdjusted Steady Flow Alternative would be reduced to less than 1 in 100years 188 Chapter IV Environmental Consequences floodflows. The annual releasepatterns under this alternative would differ negligibly from the No Action Alternative. Sincemonthly releasevolumes would be different under the SeasonallyAdjusted Steady Flow Alternative than under no action, monthly reservoir storage (within each year) also would be different for both Lakes Powell and Mead. Median elevation differences at Lake Mead would be 4 feet lower in February and 4 feet higher in June than under no action. Median elevation differences at Lake Powell would range from about 4 feet more than no action in February to 4 feet less than no action in June. Figure IV-8 Example Lake Mead S1orage DIfference. 1989 Flow Conditions 'i' 24 ! .S22 &20 . O 18 In 16 14 Figure IV-7.-Projected release patterns under the Seasonally Adjusted Steady Flow Alternative (50-year analysis, flood frequency reduced by raising spillway gates). Figure shows the percentage of months that the specified releases are projected to occur. becauseof flood frequency reduction measures. Annual water releasepatterns from Lake Powell are used as an indicator of spills other than m "512 -0 c 10 w 8' h O~ ".0 -~.«.,~..~-qq...~~~ ~v~~~ d"' ~ Qv ')~ « ""' ,... ""' 'S 'S " C3 ~ ~ U) m G ~ , .No Action Seasonally-Adjusted Steady Flow ---Year-Round Steady Flow Figure IV-8.-Comparison of monthly storage (1989.flow conditions) under the steady .flow alternatives and no action. WATER Table IV-4.-Seasonally Adjusted Steady Flow Alternative projected median streamflows 20-year analysis 50-year analysis 1 ,000 cfs acre-feet Fall (October) Winter (January) Spring (May) Summer (July) 492 798 ,156 768 8,000 13,000 18,800 12,500 shows storage and elevation for the steady flow alternatives compared to no action for example water year 1989. Detailed frequencies of monthly storagesare presented in appendix B. End-of-analysis storage values would be nearly the same as no action for the lower rule curve method of reducing flood frequencies,but the lakes would seea 100,000-to 400,000-acre-footincreasein average end-ofanalysis (50-year)storage using the increased capacity method. Lowest storage would be the same as under the No Action Alternative. The effects on annual storage would range from a negligible decreaseto a minor increaseover no action, depending on streamflow conditions. Sincemonthly releaseschedulescould be relaxed under high storage or inaccurate streamflow forecast conditions, water allocation deliveries under this alternative would be the same as under no action. Flood frequency reduction by increasing the height of the spillways would not affect water allocation deliveries. Upper Basin deliveries are projected to be the same as under the No Action Alternative. Lower Basin deliveries and deliveries to Mexico would differ negligibly from no action. Upper Basin yield determination would not be affected. Table IV-5.-Year-Round 1,000 acre-feet cfs 492 676 1,106 768 8,000 11,000 18,000 12,500 Water quality impacts would not vary significantly from no action under normal hydrologic conditions. Under low reservoir conditions, monthly reservoir levels would be approximately 2 to 8 feet lower than under no action from May through July. Additional reductions in reservoir levels due to seasonally adjusted steady flows may intensify impacts associatedwith low reservoir conditions (see discussion of water quality in chapter III and appendix C). As the reservoir refilled and reached normal levels, some of these impacts would be expected to diminish. Steady, lower flows may allow for increased river temperatures, particularly during the summer, but this increasehas not been quantified (see chapter IV , FISH). Greater minimum releases would increaseflow depth, which may enhance Cladophoragrowth. Habitat maintenance flows would result in a scenario similar to that described under the Moderate Fluctuating Flow Alternative. Year-Round Steady Flow Alternative The annual releaseaveragesand medians would be the same as under the No Action Alternative. Steady Flow Alternative projected median streamflows 20-year analysis 50-year analysis 1 ,000 1,000 acre-feet Fall (October) Winter (January) Spring (May) Summer (July) 189 699 835 820 699 cfs 11,400 13,600 13,300 11 ,400 acre-feet 699 703 699 699 cfs 11,400 11 ,400 11 ,400 11 ,400 Monthly releasevolumes are based on the steady schedulesfor the alternative as defined in chapter II. Streamflows would be steady under the Year-Round Steady Flow Alternative, except during transitions from one month to the next. The median monthly values for 4 months in acre-feetand cis are shown in table IV-5. The fifth graph in figure IV -1 shows the monthly volume distribution for those 4 representative months. Also, figure IV -9 shows the frequencies of flows in cis for the samerepresentative months. CJ End-of-analysis storage values would be nearly the same as under the No Action Alternative for the lower rule curve method of reducing flood frequencies. With higher spillway gates,the lakes would have a 100,000-to 400,000-acre-foot increasein average end-of-analysis storage. Lowest storage would be essentially the same as under the No Action Alternative. Effects on annual storage would range from a negligible decreaseto a minor increase,depending on streamflow conditions. Sincemonthly releaseschedulescould be relaxed under high storage or inaccurate streamflow 15,000-19,900 10,000-14,900cfs >20,000 cfs cfs 11.8% 3.7% The expected frequency of floodflows under the Year-Round Steady Flow Alternative would be reduced to less than 1 in 100years by the addition of flood frequency reduction measures. Spills other than floodflows would differ negligibly from no action. Sincemonthly releasevolumes would be different under the Year-Round Steady Flow Alternative than under the No Action Alternative, monthly reservoir storage also would be different within each year for both Lakes Powell and Mead. The monthly storage patterns within the year are found in appendix B. Median elevation differences at Lake Powell would range from about 3 feet less in June to no changefrom no action in September. Elevation differences at Lake Mead would be about the same except that the lake would be 3 feet higher than under no action in June. Figure IV -8 shows example storage and elevation differences for the steady flow alternatives compared to no action for water year 1989. 8,000-9,900 cfs 8.1% 1.0% Fall (October) Winter (January) 2.0% Spring {May) 8.3% Summer (July) Figure IV-9.-Projected release patterns under the Year-Round Steady Flow Alternative (50-year analysis, percent of months that the specified releases are projected to occur). forecast conditions, water allocation deliveries under this alternative would be the same as under no action. Flood frequency reduction measures would not affect water allocation deliveries. SEDIMENT Upper Basin deliveries are projected to be the same as under the No Action Alternative; Lower Basin and Mexico deliveries would differ negligibly. Upper Basin yield determination would not be affected. Impacts on water quality would be essentially the same as no action under normal hydrologic conditions. Under low reservoir conditions, monthly reservoir levels would be approximately 1 to 5 feet lower from May through July. Water quality changeswould be comparable to those discussedunder the SeasonallyAdjusted Steady Flow Alternative. SEDIMENT 191 by the magnitude, pattern, and duration of powerplant releasesfrom Glen Canyon Dam. Long-term impacts (20 to 50 years) would occur as sediment resourcesreached a state of dynamic equilibrium. Dynamic equilibrium means that the average sediment load transported by the Colorado River is in balance with the sediment loads being supplied by its tributaries. Sediment deposits (including sandbars) would increase and decreasein size and number as transport capacity and tributary supply varied, but monthly and annual changeswould balance out, resulting in no net change over the long term. Flood releasesmay result in immediate and potentially large changesthat diminish over a decade. Floods transport sand stored in the riverbed, erode low elevation sandbars, aggrade and erode high elevation sandbars, and widen the channel at debris fans and rapids. Floodflows greater than 45,000cis are assumed to occur over the long term. Analysis Methods This analysis of impacts to sediment resourcesis limited to the following areas: .Colorado River corridor between Glen Canyon Dam and Lake Mead .Deltas in Lake Powell and Lake Mead Direct impacts to sediment resourcesare those that vary with riverflow. Theseinclude changes in riverbed sand storage, aggradation and degradation of sandbars,and changesin capacity to move large boulders from rapids. Short-term impacts to sediment resourceswould occur within 20 years after an alternative is implemented. Flood releasesare assumednot to occur in the short term. In the absenceof floods, sediment resourceswould be affected primarily To the extent possible, a "system" approach, as discussedin the resource linkages section of this chapter, was used to evaluate impacts. Sediment resources,such as riverbed sand and sandbars, are linked-just as most other resourcesdiscussed in this EIS are linked to sediment. Impacts were analyzed on the basis of the following categories of information provided by the GCESprogram: .Records of river stage,streamflow, and sediment discharge at U.S. Geological Survey (USGS)gauging stations along the river and on the principal sediment-producing tributaries .Measurements and observations at selected sites during floods, various powerplant operations, specially designed researchflows, and interim flows .Scientific conclusions about depositional and erosional processesthat result in riverbed sand storage changes .Results from the CRSSand peak-shaving models (seeWATER in this chapter) 192 Chapter IV Environmental Consequences A comprehensive, mathematical flow and sediment-transport model of the river and associatededdies is under development in GCES (Wiele and Smith, 1991;Graf et al., 1993). The model should be useful in the Adaptive Management Program. Somepreliminary results from model development-wave transformation and reach-averagedhydraulic properties-were available for use in this impact analysis. Sand deposits (and sand-dependent resources)are affected by the amount of riverbed sand transported under a given alternative. A long-term net loss of riverbed sand would result in long-term loss in the number and size of sandbars,with corresponding changesin aquatic and riparian habitat. Future changesin riverbed sand depend primarily on tributary sand supply and the magnitude, frequencyI and duration of floods. Riverbed sand also would vary with the water volume and releasepattern of the alternative implemented. The exact amounts of future tributary sand supply and water releasevolumes are unknown but can be expressedusing probabilities, as demonstrated by Smillie, Jackson, and Tucker (1993). A mass-balancemodel was developed to estimate the impacts to riverbed sand (Randle et al., 1993). This model used 85 different hydrologic scenarios(50 years each) to evaluate changesin riverbed sand. These scenariosmatched projected releasesfrom Glen Canyon Dam (basedon historic flows in the Upper Basin from 1906to 1990)with Grand Canyon tributary flows from 1941to 1990. Details about this analysis and the assumptions used are described in Appendix D, Sediment. Information is not available to predict impacts to individual sandbars. On the basis of empirical studies at specific sandbars,however, predictions can be made for comparison of alternatives. Long-term lossesin the number and size of sandbars are assumedto result from a long-term loss of riverbed sand. That would occur if the sand-transport capacity of the river exceedsthe long-term supply from tributaries. Impacts to sandbars were determined using the principles of slope stability developed for Grand Canyon sandbarsby Budhu (1992). An illustration of theseprinciples is shown in figure IV -10. Sand and smaller-size sediment is deposited during high river stagesat slopes of about 26 degrees. As the river stage recedes,this slope may be unstable due to seepage,high velocities, or wave action. Under any of these conditions, erosion would likely occur until a stable slope of about 11 degreeswas achieved. Assuming sufficient quantities of riverbed sand, an eroded sandbar would likely rebuild during subsequent periods of high river stage. The active width of a sandbar is that part of the bar subjected to cycles of deposition and erosionthe hydrologically active zone. Estimates of average active widths are computed from average differences in river stage corresponding to changesin discharge. The modeling effort by Randle and Pemberton (1987)was extended to compute average daily and annual differences in river stageby reach for each alternative (see appendix D). The results compared well with independent computations by Smith and Wiele (written communication, 1992)for a somewhat different delineation of reaches. Summary of Imp(Jcts: Sediment The impacts of the alternatives on sediment resourcesare summarized in table IV -6. Numerical values, based on sourcesof information previously listed, were used as indicators of impacts for all sediment resources. Someuncertainty exists in the numerical values in table IV -6 and in the subsequent discussion of alternatives. Indicators of riverbed sand are mainly derived from modeling, and sandbar indicators are mainly the result of field surveys, modeling, and empirical data. Each has a different kind of uncertainty that cannot be stated quantitatively, due to insufficient information. In general, however, the uncertainty does not affect relative differences between alternatives. General impacts to riverbed sand, sandbars,high terraces,debris fans and rapids, and lake deltas are discussedbelow. Specific impacts to these resourcesare discussedunder each alternative. (1) .~ "'iii c: L2 ""ia >- "0 ~ c o joU.. a:>~"O ca ca Q).S >-(1) .= "ca CI -"0 E ~ W II.. ~ U) >~ ="Co laQ)~-u. o ~ >(/) --"C 1a"C1a Q)ctQ) cn CCI>-Q)O .-.c ~ "(;jC~>.-O ><~Oca W~>Q) E ".: 11. la la rL ><,.Q. la ~ ~ou EQ.<.> .-~ E'E>j~~ 0) c .r:~~ 0):]0 :I:uU. :] i:i: ~.2 (\I -~ ..(\I 41:]0 "0-oUI1. Q)O:J° .c --1-C ULL -:J fz iT w ~ CI ~ C O 01 :;: w :;:~Ia~ 0O ~ 0 U) ~-J-O ULL c: ~ ~ o LL (/) O m 41 ~ cU -.a. ~ E "tJ (1) "'iii a. :2 E cU O C:cU E E ::J l co ~ (1) ::0 cU f~ o .2 z... (.) d: 1Z w ~ a w ,!I ::§: :c co .c e c. c Q) ~ Q) c. ~ -~~ " vO r--o ~ <0 ~ ("I .-C\/ "' tY) .-(\I 0) ,n -t(') cot-. .-0 "' MIn "'..+ O>Co ...":I o~ LlI~ rnrn 0 COCO c~Q)Q) \Oc>->UI .~ o ... "C OJ C\J Lt) 41 -~ ... .c Q) Q) Q) .~0«« 41 c --~ I n mQ/,-C') C\lCO..t-.tOr-:. .-":I 0) .6 ~ ..j. 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Q) '- o(/)(/) "Ct:t: 0 Ernrn (/) U :] "C Q) :;:, c.> t: Q) :] C" Q) ~ "C 0 0 -.0 -aI O (/) -al ro :] t: t: aI -Q)"t="t= -:]:] Q) Q) 0 (/) o c.> '- (/) o -C»> aI .-Q) Q) E ~""Qj""Qj "~ ~ .-Q)Q) aI C\J x .-c.> c.> cx)Q)"Ealal '0 -a. alC.>"CQ)Q) c.> .£ .-c.> Q) N "' (/) '"C~"CQ)Q) $"Ct:rnrn ~Q)aI~~ :]"C(/)t:t: --c.> :] .c (/)-~t:t: Q)OQ)Q)Q) :]t:>'-'-.-Q) alQ)-~~ -al«oo > 'c.> 9 "<{ ~- 193 194 Chapter IV Environmental Consequences a. No Action Normal High Stage 31,500 cfs Fluctuating Zone Minimum 1,000 cfs L Active Width J b. ResbicledFluctuabi1gand SteadyFlows 131,500 ~~~ cfs Nonnal High Stage Auctuating 1,000 cfs Figure IV -10.-Cross section of sandbar affected by no action and by restricted .fluctuating and steady .flows. As the .fluctuating zone is reduced, so too is the zone of unstable sediment and sandbar heights. The effects of flood frequency reduction are included in the analysesof the restricted fluctuating and steady flow alternatives. Riverbed Sand A long-teml net loss of riverbed sand would result in long-temlloss in the number and size of sandbars. In the Glen Canyon reach (river mile (RM) -15.5-0),there is essentially no resupply of sand, and that reach would only continue to lose sand under any alternative. However, remaining sand deposits in this reach are fairly well protected; therefore, future erosion rates would be relatively low and not measurably different under any alternative. The reach between LeesFerry (RM 0) and the Little Colorado River (LCR) (RM 61) is much more vulnerable to net sand loss than the river downstream from the LCR becauseof the limited sourcesof supply-mainly the Paria River (supply from LCR not included). From the LCR to Lake Mead, differences in riverbed sand storage between alternatives would be negligible on the basis of available sand transport equations for gauging stations in that reach (Pemberton and Randle,1986). The probabilities of a net gain in riverbed sand at the end of 20 and 50 years for the reach between the USGSgauges at Lees Ferry and the LCR are listed in table IV -6. Tables listing the probabilities of a net gain in storage in a low, moderate, and high releaseyear (water years 1989,1987,and 1984)are included in appendix D. The probabilities were computed as described above under IIAnalysis Methods." The 20- and 50-year simulations include sequencesof the wide variety of hydrologic conditions-normaL wet SEDIMENT 195 dry-that occurred between 1906and 1990. The probabilities are computed as the ratio of the number of simulations ending with a net gain in riverbed sand to 85 (the number of simulations). For both the 20- and 50-year periods, the No Action, Maximum Powerplant Capacity, and High Fluctuating Flow Alternatives have relatively low probabilities of a net increasein riverbed sand; all other alternatives have relatively high probabilities. Sand transport capacity and probability of net gain in riverbed sand for each alterative are listed in table IV-7. The differences due to habitat maintenanceflows also are listed for the three alternatives that include them. During a minimum releaseyear, such flows generally would result in a net increasein sand transport capacity of about 30 percent and a decreasein the probability of net gain in sand storage of about 11 percent. The following conclusions from a mathematical sand transport model developed under GCESby Bennett (1993)support basic assumptions used in this EIS to evaluate the impacts of the alternatives on riverbed sand and sandbars. .For a given releasevolume, alternatives with greater flow fluctuations generally leave less total sand mass in the river channel but result in higher-elevation sandbars. Sandbarstend to aggrade during high flows and erode during low flows. .Sand transport capacity increased more rapidly than sand supply when the annual release volume increased from 8.23 to 10.5maf. This resulted in a net decreasein the amount of sand retained in the river channel but sandbar deposition at higher elevations within the eddy storage zones. .A beach/habitat-building flow following a high fluctuating flow would deposit higherelevation sandbars than when following a lower fluctuating or steady flow. Sandbarsthat start out higher will end up higher- .Results are inconclusive concerning the optimum duration of the beach/habitatbuilding flow. Sandbarsinitially may build and later erode if the duration is too long (perhaps more than 2 weeks). In all simulations, the amount of sand stored in the eddies is relatively small, seldom exceeding more than 30 percent of the total in the reach. Sandbars (BeachE's and Backwaters) If sufficient quantities of riverbed sand are available, the tradeoff with sandbars under the various alternatives is whether to have higher bars with steeper,less stable slopes or lower bars with flatter, more stable slopes. Less stable sandbars would experience greater and more frequent cycles of deposition and erosion than more stable sandbars. As discussed in chapter III, Table IV-7.-Sand transport capacity and probability of net gain in sand storage in the Colorado River between the Paria River (RM 0) and the Little Colorado River (RM 61 ), for a minimum release year (8.23 m~ Difference due to habitat maintenance flow Sand transport capacity Altemative No action Maximum powerplant capacity High fluctuating flow Moderate fluctuating flow Modified low fluctuating flow Interim low fluctuating flow Existing monthly volume steady flow Seasonally adjusted steady flow Year-round steady flow (1 ,000 tons) 517 530 463 434 424 307 259 390 196 Probability of net gain in sand storage (percent) 47 45 55 58 59 70 77 64 82 Sand transpor1 capacity (1 ,000 tons) Probabilityof net gain in sand storage (percent) +117 -12 -11 +124 .11 +116 196 Chapter IV Environmental Consequences SEDIMENT, sandbars that existed prior to Glen Canyon Dam were very unstable-building during floods and rapidly eroding following the return to lower flows. Habitat maintenance and beach/habitat-building flows are intended to partly restore this natural process. The long-term maintenance of sandbars requires deposition during high flows. Over the long term, the parts of sandbarshigher than the peak river stage of an alternative (including beach/habitatbuilding flow) would experiencenet erosion. Erosion by wind, local storm runoff, and human activity would be about the same under all alternatives. Eddy backwaters are dependent on the folmation of reattachment bars. Initially, the number and size of backwaters would depend on the level of discharge (seeFISH section of this chapter). However, retum-current channels that folm backwaters would tend to fill with sand, silt, and clay and re-form during the next beach/habitatbuilding flow or flood release. The addition of new silt and clay to the eddies would depend on maximum river stage and timing with tributary floods, which are most likely to occur during August-October . Annual range of sandbar active width and potential height for the widest and narrowest reachesare shown for a minimum releaseyear in table IV-6. Active widths are used as an indicator of areasgenerally not suitable for establishment of vegetation, although vegetation may grow in this zone if flow fluctuations are small. Complete tabulations of average sandbar active widths and heights for 11 reachesunder each alternative are included in appendix D. The potential sandbar heights listed on two lines of table IV -6 are differences between water surface elevations. These represent the range (between the widest and narrowest river reaches)in potential height of sand deposition if there is a sufficient supply. They also represent potential heights of silt and clay deposition, provided the high releasescoincide with high flows from one or more major tributaries. One line lists differences between elevations under normal minimum and maximum flows for the alternatives. The other line lists differences between elevations under normal minimum flow and 30,000cis for the three alternatives with habitat maintenance flows. The values in table IV-6 and the graphs in figure IV -11 show the general relationship between sandbar height and the probability of net gain in riverbed sand. Alternatives that include habitat maintenance flows have potential sandbar heights nearly the same as under no action, but with much higher probabilities of net gain in riverbed sand. Habitat maintenance flows would provide some dynamics of a natural system (deposition and erosion). Sand previously stored on the riverbed would be transported, and sandbar deposition would occur in low-velocity areasalong the channel. Other deposits exposed to high velocities would be reworked and may experiencenet erosion. Overall, net deposition would be expected at higher-than-normal elevations. These new deposits would erode at an unknown rate following the return to more normal flows. Beach/habitat-building flows might be as high as 45,000cfs; more information is needed about the effects of theseflows and the subsequent stability of the aggraded sandbars. Such information would be obtained from long-term monitoring and researchunder the Adaptive Management Program. Tables of potential sandbar heights for theseflows in each of the 11 reachesunder each alternative are included in appendix D. Habitat maintenance and beach/habitat-building flows that coincide with large, sediment-laden floods from one or more tributaries could deposit silt and clay at higher elevations. Conversely, there could be a net loss of silt/ clay if such high flows are not accompanied by tributary delivery of substantial amounts of silt and clay. Downstream from RM 236 in Lower Granite Gorge, sediment deposition and erosion along the channel margins are primarily driven by changes in the level of Lake Mead (seediscussion under "Lake Deltas"). SEDIMENT 197 100% - 10 c "'iU (!) G) z ::iiiiiiiiii 8 -:::0> ~ - :iiiiiiiiiii O ijil11ll ~ :5 la .0 O ~ ~:::i:i:i::: .2:' "u cu 0. cu () e::. "0 c la (/) 'E. cu c 'G) 3: o 0.. "0 G) .0 ~ G) > oc ~ .Q 10% ~ o z E ~ E "~ ~ 6 ~ o ii: 0) -0 0> 0 ::J :0c( :?::~ c o (/) cc 0> 00 I: ~ :J u :J ii: 0) ""tU '0) "0 0 ~ ~ o u: > "0 CG CD 00 "0 C ~ 0 (1: .:. CG CD >- 4 .c 01 "Qj :I: ... 111 .0 -0 c: 111 ~ "~ c 0> O 0. 2 0 0% Alternatives -E.~, ~~, Height with Habitat Maintenance Flows Figure IV-11.-Probability of a net gain in riverbed sand in reach RM 0-61 after 50 years and potential sandbar heights in wide reaches(without beachlhabitat-building flows) for each alternative. Theprobability of a net gain in riverbed sand and the potential sandbar heights dependon the magnitude and frequency of an alternative's normal peak discharge. The No Action Alternative could potentially deposit high sandbars but would have relatively little sand to deposit. In contrast, the Year-Round Steady Flow Alternative would have ample riverbed sand to deposit but relatively little potential to deposit it at high elevations. Beachlhabitat-building flows would infrequently increasethesepotential sandbars heights. High Terraces In the absenceof extremely large sediment-laden floods (greater than lOO,OOO cis), the fate of high terracesis gradual erosion, regardless of the alternative implemented (seechapter III, SEDIMENT). Beach/habitat-building flows and habitat maintenance flows may slow or somewhat reduce erosion of high terraces;however, the effects of such flows are not well known. Habitat maintenance flows under the Moderate and Modifled Low Fluctuating and SeasonallyAdjusted Somehigh terraces (mostly between the dam and RM 36) are subject to direct erosion from floodflows. This happens where there are no sandbars between the terrace and river (usually on the outside of a river bend) and, thus, no buffer against erosion. Therefore, an indicator of impacts to this type of terrace is the frequency of floods greater 198 Chapter IV Environmental Consequences than 45,000 cfs: 1 in 40 years for the No Action and Maximum Powerplant Capacity Alternatives and 1 in 100 years for the other alternatives. Flow Alternative would have relatively less capacity to remove material from aggraded debris fans than other alternatives. Debris Fans and Rapids Lake Deltas Changesin debris fans and rapids depend on tributary debris flows and discharge from the dam. While debris flows are independent of dam operations, the resulting debris fans historically have been reworked (boulders and smaller sediment moved downstream) by high flows, especially large floods (seechapter III, SEDIMENT) . The size of deltas depends on the amount of total sediment transported to the lake. Delta elevation depends on average lake elevation, which varies with the amount of inflow and monthly release patterns. Delta crest elevation therefore can be used as an indicator of the delta surface elevation to compare impacts among alternatives. Beach/ habitat-building flows and habitat maintenance flows would result in a 2- to 3-foot decreasein Lake Powell and a similar increasein Lake Mead over a 1- to 2-week period. Thesechangesin lake levels are not expected to result in measurable impacts to sediment deposits in either lake. Impacts to debris fans and rapids are considered here becauseof the concern that releaseswithin powerplant capacity may not be large enough to move large boulders that constrict the channel and thus affect white-water boating safety. The relative capacity of the normal peak discharge to move boulders is used as an indicator of impacts to debris fans and rapids (seetable IV-6). The percentageswere calculated by dividing the square of the normal peak discharge in a minimum releaseyear by the square of the 1983peak discharge (92,600cfs) and multiplying by 100. Beach/habitat-building flows were not considered becausethey would not occur every year, although such flows would remove larger material than could be removed by normal flows. The relative numbers in table IV -6 show that maximum flows under all alternatives have much smaller capacity to move boulders than the predam annual floods, which were about the same magnitude as the 1983flood. There probably is no measurable difference in capacity between alternatives with indicator values of 10 to 13 or between alternatives with values of 2 to 5. Further, the difference between these two groups probably is slight, but measurable. Even with beach/habitat-building flows or habitat maintenance flows, none of the alternatives is expected to result in significant impacts to debris fans and rapids over the short term. Over the long term, new debris flows are expected to aggrade debris fans and further constrict rapids. Steady flow alternatives and the Interim Low Fluctuating Lake Powell. The rate of growth of Lake Powell deltas is independent of dam operations. Delta crest elevations are represented by the 20- and 50-year averagesof projected monthly median lake elevations during April-August (3665and 3662feet above sealevel). Annual release volumes are the same under all alternatives, and monthly releasesvolumes are the same under all but two-Seasonally Adjusted and Year-Round Steady Flow Alternatives. Delta crest elevations under these alternatives would be either the same as no action or as much as 2 feet lower (see table IV-6). Elevations of the delta crestssurveyed in 1986, after a period of high inflow and full reservoir, were higher than either the 20- or So-year projected average lake elevations. Lake Powell deltas would continue to build downstream with new crestsforming at lower elevations. Although Lake Powell tributaries would likely cut a relatively narrow channel through these deltas, most sediment would remain in place and become vegetated. Lake Mead. Lake deltas consist of clay, silt, and sand. All sediment sizes must be considered when predicting impacts. The amount of clay and silt transported to the Lake Mead delta depends SEDIMENT 199 on upstream tributary supply and does not significantly vary among alternatives. However, the amount of sand transported to the delta over the short term does depend on the alternative. Short-term sediment delivery from the Colorado River to Lake Mead would be greater under fluctuating than under steady flow alternatives. The differences between short-term delivery rates of the various alternatives are indicated by the difference in riverbed sand storage. Over the long term, the river will adjust its sediment load to match the tributary supply, regardless of the alternative implemented. The long-term sediment delivery rate to Lake Mead is expected to equal 12 million tons per year, of which about 3 million tons would be sand--equivalent to the long-term averagesupplied by the Paria River and the LCR. The elevation of the delta crest in Lake Mead depends on lake elevation, which varies with the amount of inflow, as well as monthly release patterns at Hoover Dam. The indicator used to compare alternatives is the elevation of the delta crest, representedby the 20- and 50-year averages of projected monthly median lake elevations during July-October (1175and 1167feet above sea level). Annual releasevolumes are the same under all alternatives, and monthly releasevolumes are the same under all but two-seasonally Adjusted and Year-Round Steady Flow Alternatives. Under these two alternatives, elevations of the delta crests would be either the same as no action or as much as 1 foot higher (seetable IV-6). Sediment deposition and erosion along the channel margins downstream from RM 236 in Lower Granite Gorge depend on Lake Mead water level and do not vary measurably among alternatives. Under all alternatives, deposition when lake levels are high is expected to be followed by erosion (including bank caving) during subsequentperiods of lower lake leyels. Unrestricted Fluctuating Flows No Action Alternative Peak river stagesassociatedwith daily flow fluctuations under this alternative would have the potential to maintain high elevation sandbars (within normal peak river stage). However, the amount of riverbed sand would likely decline over time, and sandbars upstream of the LCR would experiencenet erosion. Riverbed Sand. Probabilities of a net gain in riverbed sand are not high during a low water year and decreasewith increasesin annual release volumes (seeappendix D). The probability of a net gain in sand storage (in the reach between the Paria River and LCR) is 50 percent at the end of 20 years and 41 percent at the end of 50 years. The sand balance downstream from the LCR would be expected to remain in a state of dynamic equilibrium. While some changesmay occur from year to year, they would be expected to balance out over the long term. Sandbars (Beaches and Backwaters). Sandbars would continue to be dynamic (cycles of deposition and erosion) under this alternative; they would change more rapidly as a result of floodflows. Somebars may be completely lost, and new bars may form. High elevation sandbars (separation bars above normal peak discharge) would be expected to erode during periods of normal operations. Low elevation sandbars (reattachment bars) downstream from Lees Ferry would be expected to aggrade in wide reachesof the canyon. During unanticipated floods, high elevation sandbars would be expected to aggrade in wide reaches. However, low elevation sandbars would be expected to erode. These predictions are based on analysesof historical data by Schmidt and Graf (1990)and Schmidt (1992). Sandbarswould continue to undergo cycles of deposition and erosion (seechapter III, sEDIMENT). Erosion would occur throughout the canyon due to the large daily changesin river stage and rapid decreasesin stageupstream from the LCR. Seepage-inducederosion would 200 Chapter IV Environmental Consequences increaseduring periods of lower minimum releasesand reduced fluctuations, such as weekends and holidays. tributary floods (typically during August-October) potentially could be deposited at elevations equivalent to the maximum flow. The large daily changesin river stagewould maintain existing active sandbar widths of unvegetated sand. Rapid increasesin river stage would have little or no effect on sandbars. Sandbars in the Glen Canyon reach tend to exist in naturally protected areasbut would likely erode at slow rates over the long term. Sandbarseroded from this reach would not be rebuilt. Erosion due to natural forces such as runoff from local rainfall, wind, and tributary flash floods would continue (not influenced by dam operations). However, sandbars eroded by sudden natural events may eventually be rebuilt by river-supplied sand. Debris flows would cover some sandbars with cobbles and boulders. Both the number and size of sandbarsbetween LeesFerry and the LCR would be expected to decline to some new equilibrium due to reduced riverbed sand. Generally, net erosion would decreasedownstream, with the addition of sand from tributaries and reduced daily fluctuations. Normal Operations.- The cycles of sandbar deposition and erosion would result in relatively large active widths of unvegetated sandbars. Daily discharge fluctuations from 1,000to 24,000cfs would result in river stage fluctuations ranging from about 7 feet in reach 5 to about 12 feet in reach 2. Active sandbar widths corresponding to these daily discharge fluctuations would range from 32 to 58 feet. Over the course of a minimum releaseyear, river stagefluctuations (potential sandbar heights above level of minimum flow) would range from about 10 feet in reach 5 to about 15 feet in reaches2 and 6. Active sandbar width would range from 44 feet (reach 5) to 74 feet (reach 2). Sand would not deposit above the 31,500-cfsriver stage during normal operations. Eddy backwaters (open return-current channels) are dependent on the fonnation of reattachment bars. In the short term, the number and size of stable backwaters would vary with discharge (see FISH section in this chapter). Over the long term, backwaters would tend to fill with sediment and later re-fonn during the next flood release(an average of once in 40 years for floods 45,000cis and greater). Additional silt and clay delivered by Unanticipated Floods.-Large unanticipated floods of sediment-free water generally have a much more dramatic and immediate impact on sandbars than releasesunder normal operations. The magnitude and extent of the effects depend upon the magnitude and duration of the flood and prior storage of riverbed sand, and the effects on individual sandbars would vary greatly. Floods of short duration (days or weeks) may result in net deposition, but floods of long duration (months) or occurring too frequently would result in net erosion. If flood releasescontinue for several years in a row, as happened during 1983-86, sandbars of all types would be expected to erode upstream from the LCR. High elevation sandbars deposited during flood releaseswould erode again under normal operations, with initially high rates of erosion becoming less with time. The greater the aggradation during floods, the greater the loss of sand during subsequent lower flows (Schmidt and Graf, 1990;Schmidt, 1992;Hazel et al., 1993; Kaplinski et al., 1994). Somesandbars may be irretrievably lost during floods. In the Glen Canyon reach, sandbars eroded during floods would not be rebuilt. Loss of sand from some bars between Lees Ferry and the LCR also might be permanent; the likelihood of irretrievable loss of sand downstream from the LCR is much less. High Terraces. High terraces in direct contact with the river would erode during floods greater than 45,000 cfs. On the basis of current information, 202 Chapter IV Environmental Consequences Maximum Powerplant Capacity Alternative Under this alternative, impacts on all sediment resourceswould be essentially the same as those under the No Action Alternative. Maximum releaseshigher than permitted under no action (31,500cIs) would be possible when Lake Powell elevation is at or above 3641feet, combined with a high demand for electrical power. Thesehigher maximum releaseswould result in a negligible decreasein the quantities of riverbed sand storage in either the short or long term compared to no action. Corresponding increasesin river stagebetween 31,500cfs and 33,200cfs would be about 0.5 foot. This would result in a negligible increasein active width and height of sandbars, compared to the No Action Alternative (seeappendix D). Impacts to high terraces, debris fans and rapids, and to lake deltas would be essentially the same as those under no action. Restricted Fluctuating Flows Impacts to sediment resourcesunder the High, Moderate, Modified Low, and Interim Low Fluctuating Flow Alternatives are described in this section. An overview of common impacts of these alternatives is presented first, followed by specific details about individual alternatives. Riverbed Sand More riverbed sand would be stored under the restricted fluctuating flow alternatives than under either the No Action or Maximum Powerplant Capacity Alternatives but less than under the steady flow alternatives. Storageof riverbed sand increasesas the allowable daily fluctuation range becomesmore restricted. Net accumulation would tend to be greater in wider reaches,where velocities are relatively low, than in narrower reaches. Becauseof flood frequency reduction measures,unanticipated floods would likely result in increased deposition relative to the floods under the No Action or Maximum Powerplant Capacity Alternatives. Sandbars (Beaches and Backwaters) Sandbarswould be dynamic (cyclesof erosion and deposition) but more stable than under the No Action or Maximum Powerplant Capacity Alternatives. Sandbar heights would be less,but the amount of riverbed sand available for deposition would increaseover time. Sandbar heights and active widths would be greater than under steady flow conditions, except the Seasonally Adjusted Steady Flow Alternative with habitat maintenance flows. On the basis of maximum flows during minimum releaseyears, the rate of filling of backwater return-current channels with sand and silt between floods or special high releaseswould be about the same as under no action. An exception is the Interim Fluctuating Flow Alternative, under which backwaters would be expected to fill at the greater rates expected under the steady flow alternatives. With higher maximum flows during the tributary flood season, restricted fluctuating flow alternatives are more likely than steady flow alternatives to result in deposition of new silt and clay in the eddies. Beach/habitat-building flows would have the potential to rebuild high elevation sandbars and re-form backwater return-current channels. Sand deposition may bury existing vegetation at some locations. Habitat maintenance flows under the Moderate and Modified Low Fluctuating Flow Alternatives also would rebuild sandbars and re-form return-current channels. Releasesresulting from emergency exception criteria are assumed typically to be of small magnitude and short duration or infrequent and of short duration, with negligible effects. High Terraces Erosion of high terracesin direct contact with the river would be less than under no action because the frequency of flood-caused erosion would average only 1 in 100years. SEDIMENT 203 Debris Fans and Rapids Impacts to debris fans and rapids under the fluctuating flow alternatives would be similar to those described under the No Action Alternative. In the absenceof large floods, there would be limited capacity to reshape debris fans because very high velocities are needed to widen the channel and decreasethe elevation drop at major rapids (Kieffer, 1987;1990). Channel width, vertical drop, and velocity at some rapids associatedwith new debris flows would be affected. The channel width would narrow, and the elevation drop would increaseto the point of adversely affecting river navigation. The capacity to move boulders is assumed to be proportional to the normal peak discharge squared relative to the 1983peak discharge (92,600cfs) squared. The capacity of the normal peak discharge to move boulders at debris fans during minimum release years would be about 12 to 5 percent of the capacity of the 1983peak discharge as shown below. discharge Capacity to move boulders relative to 1983 flood (cfs) (percent) 31,500 30,000 30,000 20,000 12 Normal Alternative High fluctuating flow Moderate fluctuating flow Modified low fluctuating flow Interim low fluctuating flow peak 10 10 5 Lake Deltas Lake delta crest elevations under the restricted fluctuating flow alternatives would be the same as elevations under the No Action Alternative becauseannual and monthly lake elevations would be the same. The Lake Mead delta would continue to increase in size and progress downstream toward Hoover Dam. Over the short term, the amount of sand and gravel reaching Lake Mead would be less under the restricted fluctuating flow alternatives than under the No Action or Maximum Powerplant Capacity Alternatives. Over the long term, the average rate of total sediment accumulation in Lake Mead would be equal to the average total sediment load supplied by Grand Canyon tributaries. High Fluctuating Ffow Alternative Impacts to sediment resourcesunder this alternative would be similar to those described under the No Action Alternative. However, there would be differences primarily due to the restrictions in the range of daily flow fluctuations. More riverbed sand would be stored, but sandbar heights and active widths would remain about the same as no action. The probability of a net gain in sand storage (in the reach between the Paria River and LCR) is 53 percent at the end of 20 years and 45 percent at the end of 50 years. The relatively high percentage of days with maximum hourly flows greater than 20,000cfs would likely result in little, if any, net gain in riverbed sand. Sandbars would continue to be dynamic with large active widths. Seepage-inducederosion would continue, especially during weekends and holidays when minimum flows would be lower. Daily discharge fluctuations from 3,000to 23,000cfs would result in river stage fluctuations from about 7 feet in reaches5 and 11 to about 11 feet in reaches2 and 6. Active sandbar widths corresponding to these daily fluctuations would range from 30 to 51 feet. Over the course of a minimum releaseyear, potential sandbar height above the level of minimum flow would range from about 7 feet in reach 5 to about 11 feet in reaches2,6, and 9, with active sandbar width ranging from 33 to 53 feet (seeappendix D). Sand would not deposit above the river stage corresponding to about 25,500cfs during normal operations. When Lake Powell storage is 19 maf or less, beach/habitat-building flows of 41,500cis would be expected to aggrade sandbars in all major eddies to elevations 3 to 4 feet higher than the normal peak river stage (seeappendix D). 204 Chapter IV Environmental Consequences Moderate Fluctuating Flow Alternative More riverbed sand would be stored under this alternative than under the No Action, Maximum Powerplant Capacity, or High Fluctuating Flow Alternatives. Peak river stageswould have less capacity to rebuild eroded sandbars,but seepage-inducederosion would be reduced. The probability of a net gain in sand storage (in the reach between the Paria River and LCR) is 61 percent at the end of 20 years and 70 percent at the end of 50 years. Effects of habitat maintenance flows are included; they increasethe annual sand transport capacity by about 117,000tons and reduce the probability of net increasein riverbed sand by about 12 percent in years when they occur. With habitat maintenance flows, sandbars would be dynamic, but less subject to long-term erosion than under the No Action, Maximum Powerplant Capacity, and High Fluctuating Flow Alternatives. Seepage-inducederosion would be lessbecauseof the reduced daily range in fluctuations, reduced down ramp rates, and becauseminimum flow criteria would be constant within each month (weekend minimum flows would not be less than allowable weekday minimum flows). Also, the shape and size of the recirculation zones would be more stable,but they would tend to gradually fill with sediment and become vegetated. Effects of wave-induced erosion would be distributed within a narrower range of fluctuating river stage than under the No Action or High Fluctuating Flow Alternatives. Daily discharge fluctuations from 5,000to 13,200cfs would result in river stagefluctuations ranging from about 3 feet in reaches5 and 11 to about 5 feet in reaches2,3, and 6. Active sandbar widths corresponding to these daily fluctuations would range from 10 to 21 feet. Over the course of a minimum releaseyear, normal river stage fluctuations would range from about 6 feet in reach 5 to about 10 feet in reach 6, with active sandbar width ranging from 28 to 47 feet. With habitat maintenance flows, potential sandbar heights would be about 2 to 4 feet higher, and active widths about 13 to 19 feet wider. Beach/habitat-building flows of 40,000cis would be expected to aggrade sandbars in all major eddies to elevations 3 to 5 feet higher than the river stage of habitat maintenance flows (appendix D). Modified Low Fluctuating Flow Alternative More riverbed sand would be stored under this alternative than under the No Action, Maximum Powerplant Capacity, and High or Moderate Fluctuating Flow Alternatives. With habitat maintenance flows, peak river stageswould have the capability to rebuild eroded sandbars. Seepage-inducederosion generally would be reduced; however, some would still occur during weekends and holidays due to lower minimum flows and reduced fluctuations. The probability of a net gain in sand storage (in the reach between the Paria River and LCR) is 64 percent at the end of 20 years and 73 percent at the end of 50 years. Effects of habitat maintenance flows are included. They increasethe annual sand transport capacity by about 118,000tons and reduce the probability of net gain in riverbed sand by about 11 percent in years when they occur . With habitat maintenance flows, sandbars would tend to be dynamic on an annual basis, but otherwise would be more stable and exist at lower elevations than under the other fluctuating flow alternatives. The shape and size of the recirculation zones would be similar to the other fluctuating flow alternatives. With maximum down ramp rates of 1,500cfs per hour, seepage-inducederosion would still occur but would be greatly reduced. Seepage-induced erosion would be most noticeable during periods of prolonged low releases,such as weekends and holidays. Maximum up ramps of 4,000cfs would have little or no effect on sandbars. Effects of wave-induced erosion would be distributed within a narrower range of fluctuating river stage than under other fluctuating flow alternatives. Daily discharge fluctuations from 5,000to 10,000cfs would result in river stage fluctuation: ranging from about 1 foot in reach 11 to about 206 Chapter IV Environmental Consequences from these alternatives is presented first, followed by specific details about individual alternatives. stage change)and would disappear from the hydrograph at some point between Lees Ferry and the LCR. Riverbed Sand When compared to other alternatives, steady flow alternatives would store the greatest amounts of riverbed sand. Larger accumulations of riverbed sand would mean greater potential for barbuilding during high flows. Annual peak river stageswould vary under the steady flow alternatives but would be less than those under the other alternatives, resulting in sandbars being rebuilt at relatively low elevations. However, seepageinduced erosion would no longer occur, and other erosion rates generally would be low. Between Lees Ferry and the LCR, the river would accumulate sand and gravel over time. Net accumulation would tend to be greater in wider reaches,where velocities are relatively low, than in narrower reaches. The sand balance in the reach between the LCR and Diamond Creek would be expected to remain in a state of dynamic equilibrium. Sandbars (Beaches and Backwaters) Sandbarswould tend to be more stable and at lower elevations under the Existing Monthly Volume and Year-Round Steady Flow Alternatives than under any of the fluctuating flow alternatives. Under the SeasonallyAdjusted Steady Flow Alternative, sandbars would be dynamic (due to habitat maintenance flows) but more stable than under the No Action Alternative. Sandbar heights would be about the same as under no action. Sandbarswould be subject to seasonalcycles of erosion and deposition due to seasonalvariations in releases. Sand would tend to deposit on bars at slopes approaching 26 degreesduring high river stage periods. The effects of allowable daily changes(plus or minus 1,000cfs) for power system load changeswould be negligible. Because of wave transformation and changesin channel width, the variation would be about plus or minus 500 cfs at Lees Ferry (plus or minus 0.2-foot river Annual peak dischargesunder steady flow alternatives would have relatively little capability to rebuild eroded sandbars. Erosion causedby riverflow would be minimal, and seepageinduced erosion would no longer occur. The rate at which backwaters in return-current channels would fill with sand and silt between floods or special high releaseswould be greater than under fluctuating flows. With lower maximum flows during the tributary flood season,the alternatives in this group are less likely than the fluctuating flow alternatives to result in deposition of new silt and clay in the eddies. Beach/habitat-building flows would have the potential to rebuild high elevation sandbars and would also re-fonn backwater return-current channels. Habitat maintenance flows under the SeasonallyAdjusted Steady Flow Alternative also would rebuild sandbars and re-fonn returncurrent channels. Unanticipated floods would have impacts similar to those under no action. However, becauseof flood frequency reduction measures,unanticipated floods would likely result in net deposition of sandbars. More sand would be available for transport and deposition during floods becauseof increased capacity to store sand during normal operations. High elevation sandbars would be expected to aggrade in wide reaches;low elevation bars would be expected to erode. Releasesresulting from emergency exception criteria are assumed typically to be of small magnitude and short duration or infrequent and of short duration, with negligible effects. High Terraces High terracesin direct contact with the river would erode less than under no action becausethe frequency of flood-caused erosion would average only 1 in 100years. SEDIMENT 207 Debris Fans and Rapids Lake Powell elevations (feet) Impacts to debris fans and rapids under the steady flow alternatives would be greater than those under the fluctuating flow alternatives. GenerallyI the constrictions at rapids would remain the same or becomenarrower and steeper when new debris flows occur. Annual peak dischargesunder the Existing Monthly Volume and Year-Round Steady Flow Alternatives have the least capacity to remove sediment from debris fans, and some rapids would become even more constricted. The capacity of the normal peak discharge to move boulders on debris fans during minimum release years would be about 3 percent of the capacity of the 1983peak discharge. With habitat maintenanceflows, the SeasonallyAdjusted Steady Flow Alternative would have a relatively higher capacity to move boulders. Normal peak dischargesand capacity to move boulders for the steady flow alternatives are listed below. Normal peak Steady flow alternative Existing monthly volume Seasonally adjusted Year-round discharge (cfs) 16,300 30,000 11 ,900 Capacity to move boulders relative to 1983 flood (percent) 3 10 2 Steady flow alternative Existing monthly volume Seasonally adjusted Year-round 20 years 50 years 3665 3664 3664 3662 3660 3660 Lake Mead. The average of the median monthly Lake Mead water surface elevations for July through October projected over the next 20 and 50 years are shown below. Lake Mead elevations (feet) Steady flow alternative 20 years 50 years Existing monthly volume 1175 1167 Seasonally adjusted Year-round 1176 1168 1176 1168 Over the short tenn, the amount of sand and gravel reaching Lake Mead would be less under the steady flow alternatives than under any of the fluctuating flow alternatives. Over the long tenn, the average rate of total sediment accumulation in Lake Mead would be equal to the average total sediment load supplied by Grand Canyon tributaries (approximately 12 million tons per year). Lake Deltas Impacts to lake deltas under the steady flow alternatives would be the same as or similar to those under no action becauseannual lake elevations would be the same. Monthly lake elevations under the Existing Monthly Volume Steady Flow Alternative would be the same as no action; monthly lake elevations under the other two steady flow alternatives would be different. Lake Powell. The average of the median monthly water surface elevations for Lake Powell for April through August over the next 20 and 50 years are shown below. Existing Monthly Volume Steady Flow Alternative The amount of riverbed sand transported under this alternative would be less than under the fluctuating flow alternatives and the Seasonally Adjusted Steady Flow Alternative. ConverselyI the amount of sand and gravel stored as riverbed material within the channel pools and eddies would be greater than under those alternatives. The probability of a net gain in sand storage (in the reach between the Paria River and LCR) is 71 percent at the end of 20 years and 82 percent at the end of 50 years. 208 Chapter IV Environmental Consequences Sandbars would tend to be more stable and exist at lower elevations under this alternative than under all but the Year-Round and Seasonally Adjusted Steady Flow Alternatives. The shape and size of the recirculation zones also would be more stable, but would tend to fill more rapidly with sediment and become vegetated. The channel would aggrade at a higher rate between the Paria River and the LCR than under all of the fluctuating flow alternatives. With greater amounts of stored sand, there is greater potential for aggradation of sandbars and less potential for net degradation of sandbars during spills. Over the course of a minimum releaseyear, monthly changesin river stagewould range from about 3 to 5 feet, with active sandbar width ranging from about 10 to 19 feet. Sandbar heights above the minimum river stagewould range from 3 to 5 feet. Sand would not deposit above the river stage corresponding to 16,300cfs during a minimum releaseyear (seeappendix D). Beach/habitat-building flows of 26,300cfs would be expected to aggrade sandbars in all major eddies to elevations 3 to 5 feet higher than the river stage of habitat maintenance flows if there is adequate sand in the river channel. Sand deposition may bury existing vegetation at some locations. During low and moderate releaseyears, flows would have less capacity to reshape debris fans than under all but the Year-Round Steady Flow Alternative. The constrictions at rapids would remain the same or become narrower and steeper when new debris flows occur. Lake Powell elevations would fluctuate seasonally (typically 15 to 30 feet) and tend to be lowest from February to April and highest from June to August. Lake Mead elevations would fluctuate less (typically 10 to 12 feet) and would tend to be lowest in summer and highest in winter. Seasonally Alternative Adjusted Steady Flow During normal operations, riverbed sand would be stored at lower elevations within the eddies than under the fluctuating flow alternatives becauseof the lower discharge and river stage. The probability of a net gain in sand storage in the reach between the Paria River and LCR is 71 percent at the end of 20 years and 82 percent at the end of 50 years. Effects of habitat maintenance flows are included. They increase the annual sand transport capacity by about 124,000tons and reduce the probability of net gain in riverbed sand by about 11 percent in years when they occur. Over the course of a minimum releaseyear, seasonalchangesin river stage would range from about 4 feet to about 7 feet, with active sandbar width ranging from 16 to 29 feet. With habitat maintenance flows, potential sandbar heights would be about 4 to 6 feet higher, and active widths about 21 to 31 feet wider (seeappendix D) Beach/habitat-building flows of 40,000cis under this alternative would be expected to aggrade sandbars in all major eddies to elevations 3 to 5 feet higher than the normal maximum river stage,if there is adequate sand supply in the river channel. Sand deposition may bury existing vegetation at some locations. During low and moderate releaseyears, normal flows under this alternative would have less capacity to reshape debris fans than those under all fluctuating flow alternatives. With habitat maintenance flows, this alternative would have a capacity to move boulders approximately equal to that under no action. Generally, the constrictions at rapids would remain the same or become narrower and steeper at some sites when new debris flows occur. Lake Powell elevations would fluctuate seasonally and tend to be 1 to 4 feet higher than under no action from December through May and 1 to 2 feet lower from June through August. Lake Mead elevations would typically be 1 to 2 feet lower from January through April and 1 to 2 feet higher from June through August than lake elevations under no action. FISH Year-Round Steady Flow Alternative Compared to all other alternatives, flows under this alternative would transport the least amount of riverbed sand but would store the greatest amount of sand and gravel within the main channel and eddies. Larger accumulations of sand in the river would mean greater potential for bar-building during high flows. During normal operations, sand would be stored at lower elevations within the eddies since this alternative has the lowest discharge and river stage. 209 elevations from April through July. Lake Mead elevations would typically be 1 to 2 feet higher during April, May, and June than lake elevations under no action. FISH The probability of a net gain in sand storage in the reach between the Paria River and LCR is 74 percent at the end of 20 years and 100 percent at the end of 50 years. Sandbars would tend to be more stable and exist at lower elevations under this alternative than under any other alternative. The shape and size of the recirculation zones would be more stable and would more rapidly fill with sediment and become vegetated than under the other alternatives. Steady flows under this alternative would exposethe greatest amount of sandbar area above normal high water. However, most reattachment bars would be submerged much of the time. Over the course of a minimum releaseyear, river stageswould fluctuate less than 1 foot, with virtually no active widths. Sandbar heights above the minimum river stagewould range from Oto 1 foot. Sand would not deposit above the river stagecorresponding to 11,900cfs during a minimum releaseyear. Beach/habitat-building flows of 21,900cis under this alternative would be expected to aggrade sandbars in all major eddies to elevations 4 to 6 feet higher than the normal peak river stage. Flows under this alternative have the least capacity to remove sediment from debris fans. Debris fans would aggrade, and rapids would become steeper and more constricted under this alternative compared to conditions under no action. Lake Powell elevations would fluctuate seasonally and tend to be 1 to 2 feet lower than no action The focus of this impact assessmentis on native fish, non-native warmwater and coolwater fish, interactions between native and non-native fish, and trout. The native fish considered in this section include the humpback chub, razorback sucker (both federally endangered species), £1annelmouthsucker (being considered for listing as a federally endangered species),bluehead sucker, and speckled dace. Each alternative analyzed in this section results in physical effects to the aquatic environment that alter fish habitats in Glen and Grand Canyons. Theseeffects are direct if they alter conditions necessaryfor the growth, survival, or health of a population. For example, mainstem water temperature has a direct effect on the ability of warmwater native fish to successfully reproduce or for young to survive. Effects are indirect if they influence one component of the aquatic community that then affects another. Reliable minimum flows of an alternative may directly influence Cladophoraand, in turn, indirectly affect fish becauseof their influence on the availability of food resources. 210 Chapter IV Environmental Consequences Likewise, effects may be short-term or long-term. Short-term effectsinfluence only lor 2 reproductive years. Long-term effects extend up to or beyond the generation time of an individual (from hatching through the reproductive life of that individual). Theseeffects may be retrievable or reversible. For example, loss of 1 year's reproduction for a long-lived fish may be made up in a subsequentyear when conditions are favorable. On the other hand, the same kinds of effectsmay be irretrievable or irreversible if they occur consistently. Analysis Methods Both biological productivity and physical characteristics of the environment (temperature, reliable flow, turbidity , etc.) determine the limits of fish development. Therefore, it is necessaryto assessthe biological productivity of the aquatic food base,as well as the environment's physical characteristics,when evaluating impacts to fish under each alternative. Aquatic Food Base The aquatic food basein Glen and Grand Canyons is the indicator for growth and condition of the system's fish. Cladophoraproduction in the Glen Canyon reach provides an important component of the food base for downstream reachesand responds to reliable inundation in a fashion similar to aquatic benthos in downstream reaches. Thus, the productive band of shoreline (wetted perimeter) that can be occupied by this important alga in the Glen Canyon reach reflects the condition of the aquatic food base as a whole. The reliable wetted perimeter, in turn, is determined by the minimum reliable river stage (flow) under each alternative. For purposes of the analysis, the river's productive capacity under each alternative can be estimated only tenuously. But, using no action conditions as a baseline, comparison of zones that would reliably experienceless than 12 hours of continuous exposure (asmeasured in vertical feet of stage and wetted perimeter at a site near Lees Ferry) is assumed to index the proportional differencesbetween no action and the other alternatives The minimum reliable stagenoted near LeesFerry under fluctuating flows may be relatively higher downstream, particularly below the LCR, because of a phenomenon known as wave transformation (chapter Ill, WATER). As waves produced by fluctuating releasesmove downstream, water volume tends to decreasein the peaks (lowering maximum river stage) and increasein the troughs (raising minimum river stage). Native Fish The analysis of effects on fish is based on their basic life requirements and addresses: .Direct .Potential sources of mortality to reproduce and recruit (survive to adulthood) .Potential for growth Alternatives are analyzed with regard to mainstem water temperature and tributary accessfor reproduction, food base and stable nearshore and backwater environments for recruitment and growth, flood frequency reduction measures,and beach/habitat-building flows. Reproduction of native fish requires warm water temperatures. Recruitment (the ability of these fish to survive to the next life stage) depends on warm tributaries and the processesthat develop and maintain backwaters and shallow nearshore areascapable of warming separately from the main channel. Fish growth is necessaryto achieve recruitment. The rate of growth is determined by water temperature and food base quality and availability .Necessary habitat conditions for each life stage must also be available (for example, young-of-year fish require low velocity areassuch as backwaters and nearshore habitats). Tributary confluences and the portion of the tributary immediately upstream have slower current or become ponded with increased river stage. Larval fish that rear in these areasmay be able to avoid or delay entering the harsher mainstem conditions. Therefore, river stagecan affect recruitment and growth. FISH Many humpback chub have been collected within an 8.5-mile reach approximately centered on the LCR (Valdez, Masslich, and Leibfried, 1992). Larvae or young-of-year humpback chub are transported out of that tributary (RM 61.4)into the mainstem (Angradi et al., 1992). Therefore, reach 4 (lower Marble Canyon beginning at RM 36) and reach 5 (Furnace Flats ending at RM 77) represent important humpback chub habitats and were selectedfor analysis. Non-Native Warm water and Coo/water Fish Table N-9 shows river stage and wetted perimeter associatedwith reliable minimum flows at three sites below Glen Canyon Dam: a point just below Glen Canyon Dam, a point in a shallow riffle area downstream of the dam, and a point at Lees Ferry . The difference between change in wetted perimeter and stage of pools and riffles illustrates the greater productive capacity of shallow, cobble riffles. Therefore, more surface area for colonization by benthic algae and invertebrates is available along wide cobble benchesthan along steep canyon walls. Native Fish Non-native warmwater and coolwater fish requirements are nearly identical to those of native fish. Evaluation criteria for non-native warmwater and coolwater fish include the aquatic food base,mainstem and tributary reproduction, and mainstem recruitment and growth. Interactions Between Native and Non-Native Fish Alternatives were qualitatively evaluated for potential interactions (competition and/ or predation) between native and non-native fish. This evaluation focused on each alternative's effects on nearshore and backwater habitats used by both native and non-native fish. Trout Alternatives were analyzed with regard to adult stranding mortality, redd successin the mainstem, and tributary accessfor spawning in Grand Canyon. Summary of Impacts: Fish The impacts of the alternatives on fish are summarized in table IV -8. Aquatic Food Base Figure IV -12 compares impacts to the aquatic food base,using reliable wetted perimeter as the indicator of effects. Wetted perimeter, hence the aquatic food base,tends to increaseas the minimum reliable discharge increases. None of the alternatives change the temperature of the water releasedfrom Glen Canyon Dam. This single fact constrains warmwater fish reproduction in the main channel and limits the likelihood that young native fish would grow to reproductive size. This condition emphasizesthe importance of warm tributaries, return-current channel backwaters, and shallow nearshore areas as recruitment sites under current conditions (Maddux et a1.,1987;Angradi et al., 1992;Valdez, Masslich, and Leibfried, 1992). Backwaters and nearshore areaswould warm somewhat during warm months under all alternatives, but would warm more under the steady flow alternatives. By introducing cold main channel water, daily fluctuations under some alternatives would destabilize and limit warming of backwater and nearshore areasused as nursery habitat by young fish. Becauseof limited warming of the main channel, backwaters, and nearshore areas,effects on mainstem reproduction for native fish are nearly identical under all alternatives, including no action. No alternative directly addresses modifying the temperature of the main channel (though further study of selective withdrawal is a common element). Thus, egg and larval survival in the main channel is unlikely. 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'" "' Q) c: -.-Q) ..'" 0 E " '" ., ~ > .c::2 -.c: ..0 ; " ., .,.-U m " 0 -Q) . m 0 .~ .S!.u .~ c. c: "'- C c. 0.5 .'u 8. ~ ...c: ..e? ., ~ ; 5-.c '"0 ., c .c: c -'" ~ " .S!.., .. Q) 0., .,~ CJ," ~ 7 CJ c ; 0 .2 c CI~ .-., ., '" .c " .c: " .= ..Q) Q) .c: U..0 -" .. Q) ::: E 0 c. c: - "(U 0 ~ ., ., ~ ..-U" .c: > -E CI ~ c: '" .-> U> mU -c '" ~. Q) ~ Q) '" c: ., -:0 ., = ~c. '" c.= U " 0 ., ..-Q) " -0 ..> iii= = C Q».G.c "'u Q) " ~ " 0 " Q) c: ~ Q) e., -~ 0C ., o~ ..~ ClC C8. °E E 0 '"" E U . ..0 C > Q) '" Z:.m C'" .c "',"Q),,= Q).C:> CJ.,~UC Q) =-O.c: -~ .u ~ Q).'"(U~~ §EE~~ .~ ~ 2. .c: "(U j C Q) U C " fQ;~ .C:~,"CJ~ -N U 214 Chapter IV Environmental Consequences Table in river stage IV-9.-Change minimum flows under --J each and wetted alternative Near ~n No action/maximum sites Canyon Dam ~Glen associated below A shallow, Glen with reliable Canyon Dam narrow Near Canyon Lees Ferry River Wetted River Wetted River Wetted stage perimeter stage perimeter stage perimeter powerplant capacity 1 ,000 cfs (winter) 3128.9 580.3 3,000 cfs (summer) 3130.9 588.5 High fluctuating 3,000 cfs perimeter at three 3123.9 3126.6 141.4 240.4 3110.9 3112.4 380.4 389.1 +2.7 +99 +1.5 +8.7 flow +2.0 Moderate fluctuating 5,000 cfs +8.2 flow +3.5 +14. +4.2 +153.4 +2.4 +14.1 5,000 cfs +3.5 +5.3 +14.1 +20.5 +4.2 +5.9 + 153.4 8,000 cfs +193.5 +2.4 +3.4 +20.2 +14.1 +20.5 +4.2 +5.9 + 153.4 + 193.5 +2.4 +3.4 +22.2 +6.5 +203.6 +3.7 +21.8 +20.5 +5.9 + 193.5 +3.4 +20.2 +25.9 +7.6 +287.2 +4.3 +25.4 Modified Interim low fluctuating low fluctuating flow flow 5,000 cfs +3.5 8,000 +5.3 cfs Existing monthly 9,000 cfs +14.1 volume steady flow +5.8 Seasonally 8,000 cfs adjusted steady flow +5.3 Year-round 11 ,400 cfs steady flow +6.9 +14.1 +20.2 loss would result in an irreversible, irretrievable loss of backwater rearing habitats, further confining recruitment of native fish to the tributaries. Floodflows also may inundate backwaters, which-depending on the timing of floods-could render them less useful to young native fish in the short term. non-native displacement are short term and reversible. Becauseof the large pool of potential immigrants to Glen and Grand Canyons from Lakes Mead and Powell, none of the alternatives would eliminate the possibility of non-native warmwater fish reestablishing themselves if suitable habitat conditions exist. At the same time, native fish of the Southwest are well adapted to flood events. Native fish have evolved with natural floods in the Colorado River (Minckley and Meffe, 1987);indeed, these floods define river channel fish habitat. Floods may displace non-native competitors and predators, potentially enhancing native fish populations (Minckley,1991). However, the effects of High flows also create and maintain returncurrent channel backwaters (figure III-16). Without some high flow disturbances, returncurrent channel backwaters eventually would fill with sediment and vegetation. Someclearing of thesebackwaters would take place under the alternatives that include habitat maintenance flows (short-duration, high flows within FISH powerplant capacity). However, only the highervolume beach/habitat-building flows-acting as planned floods-have the potential to restructure thesebackwater habitats. The magnitude, frequency, and duration of flows necessaryto sustain thesehabitats is still unknown. Several factors must be considered in scheduling habitat maintenance and beach/habitat-building flows: .Balance between the need to maintain the geomorphology of backwaters and their aquatic productivity .Presence of strong year classesof native fish .Rearing periods for native fish Reattachmentbar heights (seethe SEDIMENT section of this chapter) provide some insight into maintenance of backwaters under normal operations. fu the absenceof high flow events, the number and area of backwaters would likely decreasedue to filling and vegetation growth. Endangered fish researchflows (likely a seasonally steady releasepattern) would be implemented and evaluated through adaptive management. The extent to which steady flows would be permanently incorporated into the selectedalternative would depend on evaluation of the researchresults and a determination by the u.s. Fish and Wildlife Service (FWS). Because these researchflows might not occur every year and becauseresults will need to be evaluated, effects could not be integrated into the summary table of impacts. Endangered fish researchflows (when they occur) would have impacts on aquatic resourcessimilar to those described for the SeasonallyAdjusted Steady Flow Alternative. Non-Native Warm water and Coo/water Fish The same environmental variables that affect native fish also affect non-native warmwater and coolwater fish. For example, no alternative under consideration would increasemain stem water temperatures. Warming of backwaters and nearshore habitats would increaseas fluctuations are reduced, and some reproduction may occur in thesewarmer microhabitats under low fluctuations and steady flow conditions. However, 215 wannwater non-native fish would continue to rely on tributaries for reproduction under all alternatives. Mainstem recruitment and growth also would be affected by water temperatures. Warmer microhabitats such as backwaters and nearshore sites would continue to be important in providing requirements for young non-native warmwater and coolwater fish. In general, any change in daily dam operations or other management actions that result in improved habitat conditions for native fish also would improve conditions for non-native warmwater and coolwater fish (table IV-9). For example, habitat maintenance flows designed to prepare backwaters for subsequentuse by native fish would also benefit non-native fish. While beach/habitat-building flows may temporarily displace them, non-native warmwater and coolwater fish would quickly reestablish as suitable habitat conditions become available. Interactions Between Native and Non-Native Fish Conditions in the mainstem river present obstaclesfor various life stagesof both native and non-native fish. Mainstem water temperatures prevent reproduction, and fluctuating flows destabilize nearshore and backwater habitats important to young fish spawned in tributaries. No alternative directly addressesincreasing mainstem water temperatures, but nearshore and backwater microhabitats have the potential to warm into a temperature range more favorable to native and non-native warmwater and coolwater fish. Alternatives that would increasewater temperatures or result in more stable conditions in microhabitats would improve habitat conditions for both native and non-native fish. Nearshore and backwater habitats become more stable, and the potential for increased warming of thesemicrohabitats improves as flow fluctuations reduce in magnitude. Increased warming and stability of microhabitats would improve habitat conditions important for mainstem recruitment and growth for both native and non-native fish. 216 Chapter IV Environmental Consequences Conditions for mainstem recruitment and growth would improve over no action conditions under the Modified Low and Interim Low Fluctuating Flow Alternatives, and all three steady flow alternatives. If recruitment and growth increasein responseto improving conditions, interactions between native and non-native fish may increase. The potential for increased interaction is greatest under the steady flow alternatives (table IV-8). Resourcescientists are not in agreement about what improving habitat conditions means in terms of interactions between native and nonnative fish. One group believes that improving conditions would benefit both native and non-native fish. Another group is concerned that improving habitat conditions for both native and non-native fish may provide a competitive advantage to non-native fish that would ultimately result in adverse effects on native species. This uncertainty is reflected in table IV -8 under the steady flow alternatives and is an important issue for future monitoring and researchstudies. Trout While cold releaseslimit the ability of warmwater fish to reproduce and grow in the main channel, existing water temperatures are adequatefor coldwater fish, including rainbow and brown trout. Becausethe releasetemperature is the same among alternatives, no temperature limitation for trout spawning is assumedunder any alternative. Lack of seasonalwarming may limit trout growth rates and probably limits the diversity of aquatic invertebrates available as trout forage. Fluctuating flow alternatives would result in more adult stranding mortality than the steady flow alternatives. Higher fluctuations would result in more stranding than would lower fluctuations. Trout reproduction would be stocking dependent under the unrestricted fluctuating flow alternatives, and possibly self-sustaining under the steady flow alternatives. Under fluctuating flow alternatives, from 60 to 90 percent of redd sites would be affected by periodic dewatering. Under steady flow alternatives, redd sites would be unaffected. Direct effects of daily fluctuations on trout reproduction and survival are concentrated in the first 16 miles of river below Glen Canyon Dam. Impacts downstream of this reach are indirect and center on tributary accessand food availability .Access to spawning tributaries would not be limited under alternatives with minimum releasesof 5,000cis or more (Arizona Game and Fish Department, unpublished data). Periodic low flows (lessthan 5,000cfs) under unrestricted fluctuating flows may restrict access,though accessmay be gained during higher flow periods occurring in the same day. Unrestricted Fluctuating Flows No Action Alternative Aquatic Food Base. Under the No Action Alternative, prolonged exposure (greater than 12 hours) of shoreline would limit the potential of that shoreline zone to support Cladophora(Angradi et al., 1992;Blinn and Cole, 1991). Angradi found that 6 to 8 hours of exposure caused significant decreasesin Cladophorabiomass (Arizona Game and Fish Department, 1993). Therefore, extended low flow periods (weekends) would determine thE area occupied by Cladophoraand, in turn, the rest of the aquatic food base that directly or indirectly benefits from it-especially in shallow cobble bars Reliable minimum flows under no action would be 1,000cfs during winter months (Labor Day through Easter) and 3,000cfs during the remainder of the year. Winter minimums, especially those on weekends, would determine the reliable river stagethat would support Cladophora.Higher summer minimums would support limited recovery of Cladophorain the zone up to the river stagecorresponding to 3,000cis, but lower winter minimums would again expose it following the Labor Day weekend. River stage and wetted perimeter associatedwith reliable minimum flows under the No Action Alternative at three sites below Glen Canyon Dam are shown in table IV-9. The minimum flow between successivedaily waves releasedfrom the dam increaseswith distance traveled (seechapter III, WATER). As a FISH result, minimum stage is progressively higherand the associatedwetted perimeter larger-at sites downstream from the dam than it would be if the local minimum flow were the same as that at the dam. Native Fish. The absenceof successfulmainstem reproduction, impeded accessto spawning tributaries, disrupted mainstem nursery areas, disrupted gonadal maturation (temperaturerelated), and limited growth potential (temperature-related) would result in a stable to gradually declining abundance of native fish. Tributary Reproduction.-Owing to low water temperatures, successfulreproduction in the mainstem would not occur under no action flows (Valdez, 1991;Maddux et al., 1987). Access to tributaries for reproduction is therefore an important consideration in assessinghabitat suitability for native fish. Under no action, cold mainstem temperatures would restrict humpback chub spawning habitat to the LCR. Maintenance of LCR habitat and protection from catastrophic or adverse chronic events is not assured, so improving mainstem rearing habitat and identifying mainstem or additional tributary spawning opportunities are emphasized. According to Valdez (1991),daily fluctuations under no action may impede tributary access. Low flows of 1,000cfs (Labor Day until Easter) and potentially 3,000cfs (Easteruntil Labor Day) may limit accessto tributaries during some part of each day (except perhaps the LCR, which provides accessthrough its own perennial flows), especially if low river stage at tributary mouths occurred at night when adult spawners would likely be moving. Accessis considered unlimited at flows of 5,000cfs and higher (Arizona Game and Fish Department, unpublished data). Eggs and larval fish can be flushed from tributaries into the cold mainstem by periodic tributary flood events. Temperature shock to eggs and larval fish acclimated to warmer water may be fatal (Maddux et a1.,1987),thus reducing the potential successof tributary spawning. Loss or 217 reduction of a single year-classmay not be irretrievable; however, successivelossesof year-classesmay be irreversible. Short-lived fish, such as speckled dace, are most susceptible. The longer-lived native speciesalso are affected if the condition persists uninterrupted. Mainstem Recmitment and Growth.- The variable nature of native fish spawning and recruitment makes conclusions about their future difficult to assess.Humpback chub may live to 20 plus years (Minckley,1991). The upstream range of the humpback chub has contracted and may continue to contract due to death of old individuals in place before the dam, reduced recruitment resulting from unfavorable mainstem habitat conditions, or from unknown factors. The last date the specieswas reported above Lees Ferry (RM 0) was 1967;at Tiger Wash (RM 25), 1977-78;and at RM 30,1993 (Angradi et al., 1992; Valdez and Hugentobler, 1993). Reduced range may be directly related to loss of mainstem spawning and nursery areasresulting from fluctuating cold releases. The long life span of humpback chub provides the specieswith opportunities to capitalize on favorable conditions for spawning and rearing that may be encountered only rarely. Humpback chub do not appear to move great distanceswithin Grand Canyon, although records show that one individual moved 60 miles. The LCR currently provides habitat for all life stagesof humpback chub, including the spawning habitat that apparently supports the current population. Habitat for early life stagesin the mainstem is limited. Whether the LCR provides sufficient habitat to maintain viable aggregations of chub in the mainstem is unknown. Backwaters and shallow nearshore areasalong the mainstem are important nurseries for young native fish exiting tributaries. Native fish require the shallow, productive, wann refuges provided by these slackwater areasduring their first 2 years of life. Generally, wanning of backwaters and nearshore areasoccurs during warm months, but wanning would be limited by fluctuating flows under no action. Daily fluctuations would 218 Chapter IV Environmental Consequences continue to destabilize these areas (Valdez,1991) by both periodically drying and flooding them with cold water . Juvenile humpback chub, as well as other native species,might be displaced from eddies, nearshore areas,or large backwaters to seekmore suitable habitat during fluctuations (Valdez, Masslich, and Leibfried, 1992). Forcing thesefish into the main channel may result in direct mortality from several causesincluding temperature shock and exposure to non-native predators (Arizona Game and Fish Department, 1993). Also, additional energy expenditure would occur. Adults also might be forced to move due to changesin flow, but the energy cost has not been established. Suitable habitat for adults should be available under all flows. Return-current channel backwaters must be re-created periodically by high flow events. Otherwise, they would eventually fill and be eliminated as a habitat type. Beach/habitatbuilding flows are not included in the No Action Alternative; therefore, return-current channel backwaters would not be restructured under this alternative except during unanticipated floods. Riverine conditions that support recruitment of razorback suckers have not been found throughout the species'range, and the Colorado River in Grand Canyon is no exception. It is assumedthat conditions that affect other young native fish would affect razorback suckers even though their habitat requirement differs in some respects. Daily fluctuating flows would continue to erode sediment; flush backwaters; and dry out algae, zooplankton, and benthos that are unable to move. Non-Native Warmwaterand Coo/water Fish. The constraints on reproduction, recruibnent, and growth of warmwater non-native fish in the main channel are very similar to those limiting native fish. The single most important difference is the large pool of potential immigrants to Glen and Grand Canyons from Lakes Mead and Powell. The No Action Alternative would not eliminate the possibility of non-native fish reestablishing if suitable habitat conditions exist. Tributary Reproduction.- The effects of the No Action Alternative on warmwater non-native fish would be very similar to those on warmwater native fish. Cold releases,and possibly daily fluctuations and flood events, have considerably reduced the numbers of individuals and numbers of species(Minckley, 1991). Main channel habitat conditions for all warmwater non-natives are marginal. Channel catfish, common carp, and fathead minnow persist, but rely on tributary spawning (and backwater spawning in the caseof fathead minnow) to maintain their populations. Warmwater non-native fish species,such as carp, channel catfish, and fathead minnow present in Grand Canyon before the dam, may be adversely affected by cold temperatures and fluctuating releases(Carothers and Brown, 1991). For related reasons,some non-native fish species(green sunfish and black bullhead) abundant in other Colorado River reachesare found in very low numbers in Grand Canyon, greatly reducing the potential impact of those specieson humpback chub (Valdez, 1991). Conditions continue to favor persistenceof rainbow trout and brown trout in upper reaches and common carp and channel catfish in lower reachesof the river. As a result, rainbow trout are the most common non-native fish in Glen Canyon and upper Grand Canyon, while common carp and channel catfish are the most common nonnatives in lower Grand Canyon. Striped bassascendinto Grand Canyon from Lake Mead but do not appear to be establishing themselves. Their presenceis seasonaland limited in duration (Valdez, Masslich, and Leibfried, 1992). Mainstem Recruitment and Growth.Spawning and rearing habitat for warmwater non-natives is limited in the main channel due to perennially cold releases. Factors that limit the native fish likewise constrain the warmwater non-natives, and their growth is similarly limited Interactions Between Native and Non-Native Fish. Under no action conditions, the interactions between native and non-native fish described in chapter III, FISH, would continue into the future FISH Trout. Growth and condition of trout is related to Cladophorain Glen Canyon (Angradi et al., 1992). Extended low flow periods (weekends) would determine the aquatic food base available to trout and, in turn, the growth potential of the fish that directly or indirectly benefit from it. Effects on growth and growth potential would be indirect and potentially reversible. Under no action, the trout population would be limited to low natural reproduction in the Glen Canyon reach where it is dependent upon main channel spawning. Stranding of adult fish is expected at all 11 of the evaluated stranding sites under minimum flows. Downstream trout reproduction may be limited by accessto tributaries, but peak flows likely would provide adequate access,particularly in high water volume winter months. Adult Stranding Mortality.-Because stranded adults typically are spawning fish, the effects are twofold: 1. Relatively large individuals, the result of several years of accumulated growth in the river and of value to anglers, are removed from the population. 2. Potential reproductive contribution to the population is lost. Under the No Action Alternative, all11 stranding pools would continue to isolate fish and result in mortality .These effects would be direct and irretrievable. Davis (1991)suggestedthat careful strain selection for stocking could reduce the incidence of adult stranding. A recently domesticated strain of trout may spawn in late spring and early summer, taking advantage of higher water volume months. Glen Canyon Reproduction and Recrnitment.-Angradi et al. (1992)reported that more than 90 percent of the redd sites they mapped in the Glen Canyon reach were affected by minimum flows as low as 3,000cfs. Thesedata suggest that at least 90 percent of the utilized spawning habitat would be within the zone of potential daily fluctuation under no action and, if used by trout, the spawn would likely fail. Actual minimums during peak trout spawning seasons 219 could be as low as 1,000cfs. Natural reproduction would be directly affected and minimized under this alternative, and population size would be maintained through stocking and regulation. Downstream Reproduction and Recruitment.- Trout accessto tributaries is a result of both river and tributary flow. High peak flows in the river during winter months would provide accessto tributaries that have sufficient flow for trout use. As with native fish, low minimums may limit trout accessto tributaries. The population of rainbow and brown trout in downstream reachesreflects natural reproduction in tributaries Maximum Powerplant Capacity Alternative Impacts of this alternative would differ from no action only becausethis alternative could increase the duration of low flows, which could intensify concernsabout accessto tributaries. Under this alternative, the potential range in river fluctuations is 1,000to 33,200cfs, an increase over no action conditions. Minimum 1,000-cfsflows would be the same as under no action; thus, tributary accessfor humpback chub, razorback sucker, flannelmouth sucker, and other native and non-native fish would continue to be restricted during certain periods. The Maximum Powerplant Capacity Alternative could, in some ways, affect non-native warmwater and coolwater fish more than native fish. Native fish are adapted to systems prone to severe flood events. It has been hypothesized (Minckley, 1991;Valdez, 1991)that wider fluctuations or flood events could temporarily destabilize and displace non-native fish in canyon-bound Southwestern streams. The effects of fluctuation would be direct but, becauseof the large pool of potential immigrants to Glen and Grand Canyons from Lakes Mead and Powell, the effect would be short term and reversible. Interactions between native and non-native fish and impacts on trout would be the same as under no action. 220 Chapter IV Environmental Restricted Fluctuating Consequences Flows Someeffects on fish under the restricted fluctuating flow alternatives share similarities and are discussedin this section. Effects that differ from this general responseare described separately under the individual discussions that follow. Successfulspawning of native fish in the mainstem apparently would be prevented by the unchanged temperature of releasesfrom Glen Canyon Dam. Larval and young-of-year nurseries (backwater areasand tributary mouths) would be affected by these alternatives in much the same ways as under no action, particularly during the high volume months of July, August, and Septemberwhen young fish require warm, sheltered areas. Daily fluctuations and ramp rates under these alternatives could force movements of both adult and juvenile native fish from preferred sites, directly causing individuals to expend energy and potentially limiting their growth, survival, and reproduction, as under no action (Valdez, 1991; Valdez and Hugentobler, 1993). Frequent fluctuations would limit solar warming of backwaters, would flush out organisms and nutrients important as food resources,and could force the early life stagesof native fish-such as humpback chub-out of quiet, protected waters into unfavorable main stem conditions. The High Fluctuating Flow Alternative would also affect special status fish speciesdirectly by restricting accessto tributaries during low flow periods. While the aquatic food base might increase somewhat due to higher minimum flows, that effect could be offset. Reduced fluctuations may reduce the amount of algae and invertebrates in drift. Leibfried and Blinn (1987)explained that rising discharges could increasedrift; Arizona Game and Fish Department (1993)reported a positive correlation between coarseparticulate organic matter and flow under fluctuating conditions. Valdez and Hugentobler (1993) observed increasesin invertebrate drift during declining daily fluctuating discharges. The suggestion is that daily changesin flow may increasethe density of invertebrates in drift and, in turn, availability of the aquatic food base to drift-feeding fish. "It is unknown at this time if the drifting food resourcesare a limiting factor for Colorado River fishes" (Valdez and Hugentobler, 1993). Turbidity may be increasedby fluctuations, with several implications for native fish. Valdez and Hugentobler (1993)observed that turbidity is a primary influence on activity patterns of humpback chub in Grand Canyon. They observed increasedpresenceand activity of adult humpback chub near the surface during daytime hours under turbid conditions, and it has been inferred that near-surfacepresencemay reflect foraging opportunities. Turbidity also may provide cover and a degree of protection from predation. Yard et al. (1993)indicated that the major factors influencing light attenuation were associatedwith suspended sediment and identified those factors as: .Sediment .Releases .Sediment .Channel discharge from tributaries from Glen Canyon Dam differences below major tributaries geometry Turbidity in nearshore areasresulting from flow fluctuation could provide foraging opportunities for adult chub or some protection from predation for young chub. It has been argued that daily fluctuation may destabilize nearshore habitats and backwaters for young non-native warmwater fish in the same ways as those described for native fish. Daily fluctuation and temperature limitations would continue to suppress reproduction and recruitment of non-native warmwater fishes in the mainstem. Beach/habitat-building flows are included in these alternatives, and habitat maintenance flows would occur under the Moderate and Modified Low Fluctuating Flow Alternatives. These flows could reverse the long-term trend toward filling of return-current channel backwaters. It is assumed that these scheduled flows would maintain backwaters as a habitat type. 222 Chapter IV Environmental Consequences spawning tributaries for downstream populations, and a minor increase in growth potential for trout. daily fluctuations. Populations are expected to range from stable to gradually declining. Moderate Fluctuating Flow Alternative Without some type of disturbance-such as periodic high flows-return-current channels that support backwaters would eventually fill with sediment, become colonized with vegetation, and lose their habitat value for native fish. Periodic high flows are assumed to re-form retum-current channels and thus maintain conditions favorable for native fish at these sites. The aquatic food base would increaseover no action and high fluctuating flows under the Moderate Fluctuating Flow Alternative. Reliable minimum flows under this alternative would be 5,000cfs throughout the year. Becausethe daily range of fluctuations would be set for the entire month based on the monthly volume, minimum flows in higher volume months would be higher than the described minimum of 5,000cfs. (Projectedminimum flows for December,January, and July are above 7,000cis.) Ultimately, low flows would return to the minimum reliable 5,000cfs after a 2- to 3-month increase. Increasesin river stage and wetted perimeter associatedwith the increased reliable minimum flow of the Moderate Fluctuating Flow Alternative at three sites below Glen Canyon Dam are shown in table IV-9. Wave transformation effects would increase minimum discharges (thus minimum stage and wetted perimeter) in downstream reaches. The effects of moderate fluctuating flow on native fish would be very similar to those of no action, with the exception of increasesto the aquatic food base. Minimum releasesof 5,000cfs would not limit fish accessto tributaries. Monthly volumes during the high flow months of July and August during an 8.23-maf water year would result in a mean flow of 16,700cfs, with daily fluctuations not to exceed12,000cfs. For reachesnear the LCR, the average daily range would be 5 feet. Very few backwaters would be available due to the high mean flow. The cold water of the main channel would continue to.strongly influence the remaining backwaters. Stability of nearshorehabitats would be increased due to the reduced range of daily flow and ramp rates, although maximum fluctuations would occur when larval and youngof-year fish leave the tributaries and enter the mainstem. Tributary confluenceswould benefit from the high mean flow but would be subject to The Moderate Fluctuating Flow Alternative includes habitat maintenance flows designed to re-form beachesand backwaters. Habitat maintenance flows would provide high (30,000cis), steady flows for up to 2 weeks each spring when Lake Powell is not predicted to fill. The scheduling of flows in March is not intended to mimic the pattern of high spring flows that historically occurred later in the season. fustead, maintenance flows in March would prepare backwaters for use by larval and young-of-year native fish when they move into the mainstem from tributaries later in the year. Under this alternative, daily fluctuations would inundate backwaters and associatedsandbars, thus reducing the assumedbenefits derived from providing habitat for early life stagesof native fish. As discussedpreviously, some caution must be exercisedwhen scheduling habitat maintenance flows since the frequency and duration needed to maintain backwaters is unknown. Without some type of disturbance, backwater habitat would become progressively more stable and thus more suitable for non-native warmwater and coolwater fish. Fathead minnow and common carp, in particular, could dominate in very stable backwaters (Maddux et al., 1987). Lower fluctuations and protection from floodflows under this alternative would be beneficial to non-native fish over no action conditions. However, habitat maintenance flows would offset these assumedbenefits and cause some displacement of individual non-native fish. Interactions between native and non-native fish under this alternative would be the same as those that occur under no action conditions. FISH Under the Moderate Fluctuating Flow Alternative, the daily range of fluctuation would be decreased, and the minimum flow would be increased. Both of thesefactors could prove beneficial to trout. Higher reliable minimum flows would reduce the degree of stranding from that experienced under no action. Monthly minimums of 5,000cfs would have isolated only 80 percent of the trout stranding pools evaluated by Angradi et al. (1992). Additionally, becausethe daily range would be limited by the mean daily releasefrom Glen Canyon Dam, the absolute minimum would increaseduring high volume months. (Projected minimum flows for December,January, and July are above 7,000cfs.) As a result, potentially fewer trout stranding pools would become isolated, especially during high volume months. Higher minimum flows under this alternative would reduce the effects of trout redd exposure over short periods. A minimum flow of 5,000cfs would have exposed approximately 83 percent of the trout redd sites evaluated by Angradi et al. (1992). Becausethe daily range would be constrained under this alternative, the actual minimum flow might be greater than the required minimum. The daily range may also limit the realized maximum flow and force trout to select redd sites lower on gravel bars. Thesesites might be proportionately less susceptible to exposure. Days with flows below 3,000cfs would be eliminated, and the daily range of fluctuation would be constrained to less than 12,000cfs per day. Trout would have adequate accessto tributaries for spawning. Accesswould be possible at higher flows, and it is unknown if the increased minimum flows would enhancetheir access.The aquatic food basefor trout would increasewith the increasedreliable minimum flow, as would trout growth potential. Overall effects of the Moderate Fluctuating Flow Alternative on trout would include a reduction in stranding effects, a potential increasein recruitment from mainstem spawning, unconstrained accessto spawning tributaries for downstream populations, and moderate increasein growth potential. Modified Low Fluctuating 223 Flow Alternative Dam releasepatterns under the Modified Low Fluctuating Flow Alternative would be similar to those under the Interim Low Fluctuating Flow Alternative except for the inclusion of habitat maintenance flows and an increased ramp rate of 4,000cfs per hour. The habitat maintenance flows would re-form backwaters and help maintain these important sites for young fish. Under this alternative, reliable minimum flows would be 5,000cis throughout the year, with flows no less than 8,000cis from 7 a.m. to 7 p.m. As a result, the shoreline zone between the reliable river stagesassociatedwith 5,000-and 8,000-cfs releaseswould support an aquatic food base. The quality of this portion of the aquatic food base would not be expected to be comparable to the zone below 5,000cfs becauseof its periodic, daily exposure. Areas just above the 5,000-cfsstage would be better maintained than areasjust below the 8,000-cfsstagebecausethe latter would be exposed for greater periods. In high volume months, minimum flows would be greater than the reliable minimums. Weekend flows would still be relatively low, however, so little development of the aquatic food basewould take place above the 8,OOO-cfs river stage. Increasesin river stage and wetted perimeter associatedwith the increased reliable minimum flow of this alternative at three sites below Glen Canyon Dam are shown in table IV-9. As with other fluctuating flow releasepatterns, wave transformation effects would increaseminimum discharges (thus minimum stage and wetted perimeter) in downstream reaches. Drift of food items from upper reacheswould be likely, as with other fluctuating flow alternatives Effects on native fish would be similar to those under other fluctuating flow alternatives in that fluctuating flows disrupt backwater and nearshore areas. However, this alternative includes the narrowest range of flow fluctuations and habitat maintenance flows. Therefore, some increasesin the aquatic food base and stability of backwater and nearshore nursery areaswould be 224 Chapter IV Environmental Consequences expected over no action. Additionally, the reduced fluctuating flows might allow for limited spawning in the mainstem near warm spring inflows as documented during the 1993summer seasonof interim operations (Arizona Game and Fish Department, 1994). There currently is no indication that such spawning would result in recruitment. The increased stability of nursery habitats could be offset by the higher daily low flows releasedduring July and August, which could inundate backwaters and reduce their numbers. Increasesin the aquatic food base and decreasesin fluctuation would result in the potential for minor population increases. Under this alternative, the potential range in river fluctuations is 5,000to 25,000cis, a reduction from no action conditions. Tributary accesswould not be limited with 5,000-cfsminimum releases. 5,000cfs would have isolated only 80 percent of the pools evaluated by Angradi et al. (1992). The requirement to increaseminimum flows to 8,000cfsbetween 7 a.m. and 7 p.m. could also limit the period of isolation for some stranding pools. Stranding pools recaptured by the river during this 12-hour period could not causethe same rate of mortality .Angradi et al. (1992) showed that stranded trout died in 4 to 64 hours after stranding. Higher minimum flows under this alternative would reduce effects on trout redd and fry habitat similarly to the Moderate Fluctuating Flow Alternative. In addition, the aquatic food base for trout would increasewith the increased reliable minimum flow, as would trout growth potential. Interim Low Fluctuating Flow Alternative The habitat maintenance flows would be designed to re-fonn and maintain backwaters in a productive state for native fish. Without such flows, it is assumed that backwaters would fill with sediment, become colonized by vegetation, and progressively lose their habitat value for young native fish. Dam releasepatterns under this alternative would be similar to those of the Modified Low Fluctuating Flow Alternative except for the exclusion of habitat maintenance flows. These effects,which focus on the aquatic food base and trout, are discussedunder the Modified Low Fluctuating Flow Alternative. Without disturbance, nearshore habitats become progressively more stabilized. This increasing stability is assumedto improve habitat conditions for non-native warmwater and coolwater fish. Hence, in addition to re-forming and interrupting trends toward backwater stabilization, maintenance flows may also temporarily displace individual non-native fish. Increasesin river stage and wetted perimeter associatedwith the increased reliable minimum flow of the Interim Low Fluctuating Flow Alternative at three sites below Glen Canyon Dam are shown in table IV-9. Some stabilization in nearshore habitats under this alternative would result in a potential minor increase in interactions between native and non-native fish. Impacts on trout would include reduced stranding, potential increasein recruitment from mainstem spawning, and potential moderate increasein growth potential. Minimum flows under this alternative would reduce the degree of stranding experienced in the Glen Canyon reach. Monthly minimums of Wave transfonnation effects would increase minimum discharges (thus minimum stage and wetted perimeter) in downstream reaches. The effects of low fluctuating flows on native fish would be similar to those under no action in that fluctuating flows disrupt backwater and nearshore areas. However, a relative increase in stability of backwater and nearshore nursery areas would occur due to the decreasedrange of flow fluctuations with a higher minimum reliable flow. There would be a moderate increasein the aquatic food base. Additionally, the reduced fluctuating flows under interim operations allowed for limited spawning in the mainstem near warm spring inflows during 1993(Arizona Game and FISH 225 Fish Department, 1994). However, there currently is no indication of recruitment of thesemainstem spawned fish. The increased stability of nursery habitats could be offset by the higher minimum flows releasedduring July and August, which could inundate backwaters and reduce their numbers. Increasesin the aquatic food base and decreasesin fluctuation would result in the potential for minor population increases. Daily fluctuations in river stagewould be expected to average approximately 3 feet in reachesRM 36 to RM 77 during July and August, when flows would range from 12,000to 20,000cfs. Young humpback chub and other native fish may experiencesome increased growth owing to more stable nearshore habitats. Drift of food items from upper reacheswould be likely, as under other fluctuating flow alternatives. Preliminary information from studies conducted during interim operations (flows similar to this alternative) showed that juvenile humpback chub could hold their position in reachesadjacent to the LCR and not be moved downstream (Valdez, Wasowicz, and Leibfried, 1992). Juvenile humpback chub that remain in this area might benefit from the higher food production in the upper mainstem and from the reduced numbers of fish predators compared to the lower reaches. Tributary confluenceswould be somewhat ponded but still subject to daily fluctuations. Humpback chub may move from some habitats, which would subject the speciesto some unknown energy cost; however, the cost may not be significant (Valdez, 1991). Ramp rates of 2,500cfs up and 1,500cfs down, with an allowable daily change in flow between 5,000,6,000and 8,000cfs, would improve habitat conditions for humpback chub. Minimum 5,00o-cfsflows are 4,000cfs greater than under no action; thus, tributary accessfor humpback chub, razorback sucker, and flannelmouth sucker would be unrestricted. The effects of the Low Fluctuating Flow Alternative on non-native warmwater and coolwater fish would differ from those under no action and the other fluctuating flow alternatives in one respect: the advantage of progressively more stable backwaters. As backwater stability increases,they would become progressively more suitable for some non-native fish. Fathead minnow, in particular, could dominate very stable backwaters (Maddux et al., 1987)and might reflect a minor increasein the abundance of non-native warmwater fish. Factors that limit non-native warmwater fish would be very similar to those that constrain native warmwater fish, and their responsescould be similar. Daily fluctuations would continue; therefore, the optimal stable conditions for warmwater non-native fish would not occur. Becausethe daily range of fluctuation would be reduced, this alternative would less likely displace individual non-native fish. Under the Interim Low Fluctuating Flow Alternative, nearshore habitats would be more stable than under no action, creating the potential for a minor increasein interactions between native and non-native fish. Impacts on trout would include reduced stranding, potential increasein recruitment from mainstem spawning, and potential moderate increasein growth potential as discussedunder the Modified Low Fluctuating Flow Alternative. Steady Flows Many of the impacts of the steady flow alternatives on fish are similar, and these are discussedin this section. Effects that differ from this general responseare described separately under the individual alternatives that follow. Reliable minimum flows under the steady flow alternatives all would equal or exceed8,000cfs. As a result, shoreline zones up to at least the reliable river stage associatedwith 8,000-cfs releaseswould support an aquatic food base. Shoreline zones inundated seasonally or monthly could be recolonized by Cladophora,but that portion of the aquatic food base would not be as stable as in zones below the reliable minimum river stage. Under steady flows, successivedaily release waves would not be generated. As a result, flows 226 Chapter IV Environmental Consequences released from Glen Canyon Dam would not progressively increase in stage downstream except for contributions from tributary flow. The absenceof water velocity changestypical of fluctuating flows could reduce the amount of Cladophoraand invertebrate drift, which could reduce the availability of fish forage and slow its transport downstream. Leibfried and Blinn (1987) showed a positive connection between increasing range of dischargesand the drift of Gammarus during transition from steady flows to fluctuating flows. Cladophoraand chironomid larvae did not show similar responses. Angradi et al. (1992) showed increasesin concentration of coarse particulate organic matter (largely Cladophora debris) associatedwith increasing daily flow. Blinn et a1.(1992)observed that steady flow conditions decreasedCladophoraand invertebrates in the LeesFerry reach. The significance of reduced drift is unknown. Successfulspawning in the main channel would be limited by cold releasesfrom Glen Canyon Dam under all steady flow alternatives. Stable flows would likely result in limited spawning habitat for native fish speciesnear warmwater springs in the mainstem or near warmwater inflow at tributary confluences. This reasoning is supported by recent evidence indicating that limited humpback chub spawning occurred under the reduced daily fluctuations of interim operations (Arizona Game and Fish Department, 1994). While moderately stable backwaters could warm somewhat, there is no evidence that they provide spawning habitat for native fish, other than speckled dace. With the allowable daily changein flow not exceeding2,000cis (:f:l,OOO cfs) per 24 hours, inundation and exposure of habitats along the channel margins would be limited. This would allow for increased warming of connected backwaters, which would benefit young-of-year and other subadult humpback chub in the mainstem. Young fish using nearshore habitats might not be forced to expend energy seeking suitable habitats when flow conditions change. Food production (zooplankton and invertebrates) in backwaters might be increased by stable water levels and higher water temperatures. A vailability of food as drift from upstream reaches might be decreaseddue to reduced flows or ramp rates (Leibfried and Blinn, 1987). Steady flows might adversely affect maintenance of backwaters. Backwaters become isolated and change to terrestrial habitats as they fill with sediment. Releaseshigher than normal operations might be necessaryto maintain backwaters. Beach/habitat-building flows would be designed and planned to redistribute sediment from pools to channel margins. Theseflows also would assist in controlling non-native fish speciesthat might increaseas conditions becamemore favorable for warmwater fish in general. Tributary confluences that serve as rearing habitats for young fish would benefit becausethey would not be subject to daily stage changes. Improved habitat conditions for native fish species(including endangered fish) might also benefit non-native fish speciesthat are competitors or predators of endangered fish. The impacts of a possible increasein non-native specieson endangered fish are unknown. Native fish speciespersist over non-natives in the tributaries, and operational changeswould not be expected to change this relationship. Monitoring the fish community would be an essential element of any alternative. Continued collection of data on speciesinteractions, habitat requirements, and food resourcesas they relate to operations and the dynamics of a riverine system would be necessary. As under the fluctuating flow alternatives and no action, increasedbackwater stability favors some non-native warmwater fish as well as native fish. Fathead minnow and common carp, in particular, could benefit from stable backwaters {Maddux et al., 1987). Growth of warmwater non-natives and natives would be limited by temperature. Stable backwater areascould enable non-native fish to out-compete native fish for resourcesthat enhance growth. Steady flow alternatives have the greatest potential for enhancing conditions for non-native warmwater fish. FISH 227 Nearshore and backwater microhabitats would be stabilized under steady flow alternatives. futeractions between native and non-native fish would experiencea potentially moderate increaseover no action conditions. The outcome from increasedinteraction between native and non-native fish under steady flow alternatives is uncertain. shoreline zones up to at least the reliable river stage associatedwith 9,OOO-cfs releaseswould support an aquatic food base. Shoreline zones inundated monthly by higher steady flows could be recolonized by Cladophora,but that portion of the aquatic food base would not be as stable as in zonesbelow the reliable minimum river stage. Steady monthly flows under these alternatives would reduce trout stranding compared to no action. Additionally, conditions likely to strand fish in the Glen Canyon reach would be limited to monthly or seasonaladjustments. Even then, only downward adjustments would strand fish. As a result, significantly fewer pools would become isolated. Once a pool becameisolated, it would be highly unlikely for the river to recapture the pool and releasestranded fish. Those stranded during seasonalflow adjustments would likely perish. Increasesin river stage and wetted perimeter associatedwith the increased reliable minimum flow under the Existing Monthly Volume Steady Flow Alternative at three sites below Glen Canyon Dam are listed in table 1V-9. Higher steady flows under these alternatives would reduce the effects of redd exposure during at least 30-day periods. Redd exposure is not likely without daily fluctuations. Downward adjustments in flow between months could expose redds. Becauseflows would be steady and dependable over 3O-day,seasonal,or annual periods, successfulemergenceof larval fish from redds would be likely. Larval, fry , and subadult trout would not be forced to move among rearing habitats, resulting in higher likelihood of survival. Enhanced redd successand increased recruitment would be direct effects of monthly steady flows. All three of the flow-related factors that Persons et al. (1985)noted as negatively associatedwith year-classstrength for trout would be addressed by these alternatives. The relatively high reliable minimum flows of thesealternatives would maintain accessto tributaries and increasetrout growth potential Existing Monthly Volume Steady Flow Alternative Reliable minimum flows under this alternative typically would exceed9,000cfs, even though the absolute minimum is 8,000cis. As a result, Many of the impacts on native fish that occur under no action also would occur under this alternative, though the mechanisms by which the effects occur would differ. For example, daily fluctuations would be replaced by discharge changesbetween months. While the frequency of discharge changeswould be drastically reduced under this alternative, some of the effects could stilloccur. Low flows in March through May would be counter to historic hydrologic patterns of high spring flows, which may provide "cues" to stimulate spawning in native fish such as humpback chub (Valdez, 1991). Under this alternative, high flows in the summer (Junethrough August) would not support backwater or nursery areasin the mainstem but would contribute to tributary access.Food resourcesin backwaters and other nearshore habitats might not have sufficient time (1 month) to develop before flows change. The daily flushing of backwaters would be elirninated under this alternative, but high steady flows during high volume summer months could inundate return-current channel backwaters when they would be most valuable to native fish as rearing habitats. Adjustments between months could force movement of juvenile fish, requiring energy expenditures and potentially exposing young fish to predation for relatively short periods. Somenursery backwaters might not be formed (i.e., they would remain eddies} by the higher June,July, and August flows of this alternative. Those that did form would be stable during each 228 Chapter IV Environmental Consequences month and would warm, providing rearing habitat for juvenile native fish. Rearing habitats would be destabilized only temporarily by the monthly adjustments in steady flows, though the frequency of theseevents would be much less than under the No Action Alternative. An increasedaquatic food base, along with stable backwaters (but perhaps fewer in number) would createpotential for stable to increasing numbers of native fish. Spawning and rearing habitat for non-native wannwater and coolwater fish would be limited in the main channel due to perennially cold releases. While the number of available backwaters may be reduced due to high summer flows, the stability of the remaining backwaters could directly increasethe recruitment of some non-natives (particularly fathead minnow and carp). The absenceof daily fluctuations would eliminate displacement of individual non-native fish. Beach/habitat-building flows could, however, destabilize populations of non-native fish. Under the Existing Monthly Volume Steady Flow Alternative, interactions between native and non-native fish would experiencea potentially moderate increaseover no action. Monthly steady flows (all monthly flows would likely be greater than 9,000cis) would have isolated only 45 percent of the trout pools evaluated by Angradi et al. (1992). Stranding would occur only during downward adjustments between months. Overall, the Existing Monthly Volume Steady Flow Alternative would greatly reduce trout stranding, greatly increase recruitment from mainstem spawning, maintain accessto spawning tributaries for downstream populations, and possibly increasegrowth potential. Seasonally Alternative Adjusted Steady Flow Reliable minimum flows under this alternative typically would equal or exceed8,000cis. As a result, shoreline zones up to at least the 8,000-cfs stagewould support an aquatic food base. Shoreline zones inundated seasonallyby higher steady flows could be recolonized by Cladophora, but that portion of the aquatic food basewould not be as stable as in zones below the reliable minimum river stage. Increasesin river stage and wetted perimeter associatedwith the increased reliable minimum flow under the SeasonallyAdjusted Steady Flow Alternative at three sites below Glen Canyon Dam are listed in table IV-9. The effects of this alternative on native fish would differ markedly from those of no action in many ways. While the alternative would establish some conditions that would enhancenative fish, those same conditions could also enhance conditions for non-native warmwater fish that compete with or prey on the natives. The two effects could offset one another. There is concern among resource specialists about potential increased interaction (competition and predation) if mainstem temperatures increasesignificantly. The swift water habitats of Marble and Grand Canyons may favor the native species. This alternative provides for an annual spring peak of 18,000cis to facilitate humpback chub spawning. Accessto tributaries would be enhanced in the spring. Releasesof 9,000cfs in August and Septemberwould support backwater habitat development. Habitats for early life stages of humpback chub would stabilize and warm somewhat during the steady, lower flow period (July through September),resulting in increased growth and survival of young-of-year humpback chub. Lessmovement and, consequently, reduced energy expenditure would be anticipated for the juvenile humpback chub during steady flows. Shallow, protected juvenile habitats associated with tributary inflows, cobble shorelines, and cobble riffles would likely be enhanced (Valdez, 1991). Food resourcessuch as algae, zooplankton, and invertebrates might develop in seasonally inundated zones. The responseto this quarterly change is unknown but might be more beneficial than monthly changesin river stage. Accessto tributaries for spawning fish would be enhanced,and ponding of tributary confluenceswhich benefits larval fish-would be constant throughout the year. This ponding might benefit humpback chub, but might benefit non-native speciesas well. The number of backwater habitats would decreasedue to the high mean flows, but nearshore and backwater habitats would be stable throughout the year. A net sediment balance for the reach important to humpback chub would be predicted to occur every year (50-yearsediment s~pply), supplying the most sediment for that reach of any alternative. Beach/habitat-building flows may be necessaryto create backwaters or other habitats. Somelarval and young-of-year nurseries (backwater areasand tributary mouths) and juvenile habitats would likely be enhancedunder this alternative. However, many return-current channel backwaters would be inundated by the high steady discharges typical of this alternative. Backwater stability during July, August, and Septemberwould provide dependable rearing areasthat warm daily, resulting in improved growth for young-of-year fish. Too much stability , however, could decreasethe acceptability of backwater areasas rearing sites. Long-term stability could result in establishment of marsh vegetation and eventually riparian vegetation, ultimately eliminating these stable backwater areasas native fish rearing areas. High, flushing releases--such as the beach/habitatbuilding flows discussedearlier-would be necessaryto maintain thesehabitats; however, there is disagreement concerning the desired frequency of such events. The absenceof fluctuations and between month adjustments virtually would eliminate destabilization of non-native warmwater and coolwater fish by flow-related factors. Very stable flow conditions and reliable accessto tributaries for spawning would result in population increases. Backwater habitats could be limited under this alternative becausethey tend to form at lower flows, but those that formed would provide very stable rearing habitats for warmwater non-natives, which could directly increaserecruitment (particularly of fathead minnow and common carp). A potential moderate increasein interactions between native and non-native fish would occur under this alternative. Year-round steady flows would reduce the degree of trout stranding experienced under no action. Monthly steady flows of 11,400cfs or greater would have isolated none of the pools evaluated by Angradi et al. (1992). Stranding would occur only during adjustments to accommodate forecast change. Therefore, the Year-Round Steady Flow Alternative would result in greatly reduced stranding, greatly increased recruitment from mainstem spawning, accessto spawning tributaries for downstream populations, and increased growth potential. VEGETATION Shallow, protected juvenile habitats associated with tributary inflows, cobble shorelines, and cobble riffles might not be enhanced under this alternative (Valdez, 1991). Thesesites typically would be limited at moderate to high flows. Improved accessto spawning tributaries, relatively stable nursery areasin the short tenn, limited habitat for juvenile fish, and potentially enhanced aquatic food basewould result in stable to potentially increasednumbers of native fish. Glen Canyon Dam operations affect downstream vegetation through several different mechanisms, especially daily releasepatterns repeated over time and major uncontrolled flood releases. Effects from thesemechanisms are reflected as changesin both plant abundance and species VEGETATION composition. Such changesare directly linked to changesin sediment deposits that support riparian vegetation and to water releasepatterns that provide water for plant growth. Thus, the abundance and composition of the riparian plant community are influenced through effects on sediment and water from daily releasepatterns and major flood events. Effects resulting from each alternative are represented by changesin the vegetation indicators identified in chapter III. Becausemodels used for this analysis are still under development, the results presented here are subject to change as more information becomesavailable and the models are refined. Analysis Methods The short-tenn period of analysis is defined as 5 to 20 years following implementation of an alternative. During this time span, it is assumed that changesin vegetation would closely follow changesto exposed sediment deposits resulting from daily releasepatterns. Detailed analysis of vegetation generally is limited to the river corridor between the dam and Separation Canyon (although data are available only to Diamond Creek). Below Separation Canyon, riparian vegetation along the river corridor is linked to water levels in Lake Mead. Although no major flood events are included in short-term analyses,different water yearsranging from low through moderate to high-are anticipated. Infrequent releasesabove the maximum flow identified for each alternative, habitat maintenance flows, and beach/habitat-building flows of unknown stage may occur in the short term. It is impossible to predict the types or the sequenceof water years that would occur in the future. The basic analysis assumesa sequenceof minimum releaseyears with modifications where appropriate. Minimum releaseyears would maximize differences in riparian vegetation responsesto flows identified for each alternative. The reader should note that higher water volumes would result in stageconditions similar to 231 alternatives with higher maximum flows. Thus when medium and high water years are interspersedwith minimum releaseyears in the future, the differences in plant responsespresented in the following analysis will be diminished, and alternatives would become more similar in terms of their effects on riparian vegetation. The long-term period of analysesis defined as the period from 20 to 50 years following implementation of an alternative. Changesin vegetation during this period become more difficult to predict but are assumed to closely follow changes to exposed sediment deposits. Sediment deposits are expected to reach a state of dynamic equilibrium (seechapter IV, SEDIMENT). Area coverage and speciescomposition of vegetation during this period would stabilize within the constraints of sediment and discharge characteristics of each alternative. Woody Plants Analyses of change in area coverage of woody plants rely on previous analyses of active width of unstable sandbars (seechapter IV, SEDIMENT). It is assumed that the average active width of unstable sandbars computed for each of the 11 river reachesunder analysis can be subtracted from no action conditions to yield an estimate of sandbar stability for each action alternative. These stabilized sandbar widths are assumed available for plant growth and provide the estimates for change in area of woody plants (figure IV-13). While the width of stabilized sandbars can be computed, such widths may not actually occur at all beachesbecausesome parts of the canyon are too narrow. The data are useful, however, in a comparative sense. The data are presented as a range in feet and percentagesfrom smallest river reach change to largest reach change. Somealternatives would include an annual habitat maintenance flow designed to move and deposit sediment at higher elevations than would be possible under the alternatives' maximum flows. Theseflows would affect existing vegetation and those plants that would develop in areasof stabilized sandbars up to an elevation equivalent to the maintenance flow stage. 232 Chapter IV Environmental Consequences a. Postdamand FutureConditionsUnderNo Action Figure IV-13.-Reduced maximum .flows would affect riparian vegetation in the new high water zone (NHWZ) by reducing the width of unstable sandbars and, thus, increasing the area of stable deposits available for plant development. In general, mesquite occupies the upper, dryer elevations with other plants occupying sites closer to the high flow stage (a). Tamarisk, willow, horsetail, and cattails also would develop on suitable sites exposed by reduced high .flows (b). Some mortality of woody plants may occur at upper elevations of the NHWZ under alternatives with reduced maximum .flows. However, changes in species composition (and area) depend on site-specific characteristics and cannot be estimated. However, it is assumedthat becauseof limited duration and magnitude, such flows would not scour or drown plants. Someburial of plants would occur. Partial burial may not affect plants, while complete burial may provide an advantage for plants able to grow through the covering sediment. Burial-tolerant woody plants include tamarisk, willow, and arrow weed. The effects of habitat maintenance flows on riparian plants are speculative at this time and would be monitored closely. However, the following pattern appears reasonablebased on plant responsesafter the 1983-86high flows. New plant growth below the 30,OOO-cfs stagemay be buried during the first few maintenance flows. Plants that survive burial would grow up through new deposits and contribute to an increasein area of riparian vegetation. In time, some level of stability would develop so that plants would no longer be affected by burial. VEGETATION An estimate of the maximum effect of maintenanceflows, based on active width of unstable sandbars,is presented. However, becauseof their limited magnitude and short duration, it is assumedthat maintenance flows would not affect the area of vegetation to the degreeindicated by active width analyses. Thus, for alternatives with maintenance flows, the future area of woody riparian plants is assumedto reach some level between estimatesof stabilized sandbar widths before and following such flows. Beach/habitat-building flows would be an important element of all alternatives except the Maximum Powerplant Capacity and the No Action Alternatives. For vegetation, the magnitude and duration of these flows are important considerations. In order to deliver water to the entire new high water zone (NHWZ), flows would have to be at least 40,500cfs. Discharges delivering water to stage elevations equivalent to 40,500cfs or greater would affect vegetation in at least three ways. First, such flows periodically would provide water to riparian plants in the NHWZ. Second,depending upon stage and duration, beach/habitat-building flows may eliminate some plants, such as mesquite and acacia,that establish in the upper elevations of the NHWZ but cannot tolerate extended inundation. Finally, some burial and scouring of plants would occur with effects that would largely depend on the speciesand flow magnitude and duration (see chapter III, VEGETAnON). Under the restricted fluctuating and steady flow alternatives, periodic beach/habitat-building flows would disrupt the level of stability that would develop between sediment, plants, and habitat maintenance flows. Sediment deposits would be reworked and some plants lost. A new level of stability would become established following a beach/habitat-building flow and continue until the next high flow. The NHWZ vegetation that developed in the short term would occupy the same area and have basically the same speciescomposition in the long term (figure IV-14). In the long term, it is assumed that stagereduction would affect woody riparian 233 plants in the upper elevations of the NHWZ through a replacement of tamarisk, willow, and other plants by mesquite and other plants requiring less moisture. Willow, which is less drought-resistant, would disappear first (in the short term) with tamarisk persisting for some time. The abundance of mesquite and other plants would be influenced by beach/habitatbuilding flows. All alternatives except the No Action and Maximum Powerplant Capacity Alternatives include flood frequency reduction measures. Effects on the old high water zone (OHWZ) associatedwith reduced flood frequency are assumed to be identical for all alternatives and are discussedhere rather than under each alternative. Recruitment (addition of young plants to the population) in the OHWZ is assumed to require conditions historically created by periodic high flooding. Without flooding, young riparian plants would not be added to the OHWZ and, thus, would n<;>t be available to replace mature plants as they die. More drought-tolerant desert plants may gradually invade the OHWZ. Future major flood events are expected to be so far apart that any differences in flood frequencies between alternatives would not be detected during the long-term period of analyses. Thus, for the purposes of analysis, all alternatives are assumed to contribute equally to the decline of riparian vegetation in the OHWZ. Becausemany plant speciesin the OHWZ are long-lived, changeswould be difficult to detect during both the short- and long-term periods of analyses. A more noticeable change would be the continuing establishment of honey mesquite and other speciesfrom the OHWZ into the upper (dryer) elevations of the NHWZ. These species would be important components of the riparian zone that develops under any alternative. It is assumedthat at some future time, one or more major uncontrolled floods would occur. In this analysis, a major flood is assumed to occur after 50 years for alternatives with flood frequency reduction measures. For the No Action and Maximum Powerplant Capacity Alternatives, at 234 Chapter IV Environmental Consequences a. Postdamand FlItlIm ConditionsUnderNo Action - b. Long-TennEffectsof RestrictedFluctuatingand SteadyRows Figure IV-14.- Area coverage of woody plants would increase under alternatives with reduced maximum flows, and species composition would stabilize into similar patterns in the long term. Some mortality of woody plants may occur at upper elevations of the NHWZ under.alternatives with reduced maximum flows. However, changes in species composition (and area) depend on site-specific characteristics and cannot be estimated. least one major flood event is assumed to occur between 20 and 50 years following implementation. A flood occurring early in the long-term period of analysis would give vegetation up to 30 years to recover, while a flood later in the period would permit less time for recovery. Although the timing of a flood event cannot be predicted, it is assumed that enough time would be available between a major flood and the end of the long-term period of analysesfor vegetation to recover to a level similar to baseline conditions under these two alternatives. chargesabove 45,000cis), uncontrolled (lasting longer than 1 month) floods return riparian zones to earlier successionalstages. In general, vegetation initially would be lost (up to 50 percent at some sites in 1983)through scouring, drowning, or burial beneath sediment. After floodwaters recede,sediment redistributed by floodflows would be available for plant expansion. Since vegetation returned to 75 percent of 1982levels in less than 10 years (Stevensand Ayers, 1993),it is assumedthat riparian vegetation would return to preflood conditions within 10 to 15 years. Although the magnitude and duration of a major flood event cannot be predicted, the effects on downstream vegetation are expected to be similar to those described in chapter III. Major (dis- Effects of uncontrolled flood releasesare independent of daily dam operations and would be sirnilar to effects described in chapter ill, regardless of future darn operations. Becauseof the assumed VEGETATION similarity in effects between historic and future floods, uncontrolled floods are not addressed under each alternative. This lack of treatment, however, should not be interpreted as a statement on the lack of importance of uncontrolled floods in the dynamics of riparian plant communities. Major high flow events affect processesand "reset" ecosystemcomponent levels, and-at least for riparian vegetation-can be defined as the single most important system event affecting this resource. However, once reset, riparian vegetation is again defined by daily operations. It is assumedthat water leyels in Lakes Powell and Mead would rise during the short-term period of analysesand approach or reach full reservoir capacities. Lake levels are assumed to depend on regional water supply, which is dictated by climatic conditions. Rising lake levels would affect riparian vegetation that has developed during several years of low lake levels following the high flow years of 1983-86.This is especially true for Lake Mead. As Lake Mead fills, riparian vegetation would be inundated and its nutrients recycled into the aquatic system. With another dry cycle, lake levels would recede and riparian vegetation would again increase. 235 reservoir water level. Deposits at full reservoir levels would becomepermanently vegetated after floodwaters recede. The time required for delta aggradation to reach full reservoir level is unknown but is assumed to be longer than 50 years. Therefore, riparian plants supported by Lake Mead would tend to increase area coverageunder all alternatives. However, it should be noted that during this long-tenn trend of increasing vegetation, riparian plants would disappear periodically during the processesof delta fonnation. One of the proposed flood frequency reduction measureswould raise the spillway gates at Glen Canyon Dam an additiona14.5 feet, increasing Lake Powell's potential surface acresby 2 percent. If implemented and ultimately used, this measure could result in infrequent and temporary flooding of riparian vegetation currently above Lake Powell's full pool elevation of 3700feet. If such temporary flooding occurred, it would causeno adverse effects to plants; short-term inundation may even benefit these riparian plant communities. Emergent Marsh Plants The effects of changing lake levels on riparian vegetation are assumed to be similar under different dam operations and are discussedhere and not under each alternative. Plants develop on delta deposits that are exposed during prolonged periods of low reservoir levels (seediscussion of deltas under SEDIMENT in chapters III and IV). Cycles of low reservoir levels followed by full reservoir levels would continue into the long term. Vegetation would flourish during low reservoir periods. As Lake Mead fills, vegetation would be inundated and disappear, and nutrients would be recycled into each lake's aquatic system. Short-term responsesof emergent marsh vegetation to certain common elements of the proposed alternatives are difficult to predict. Under baseline (no action) conditions, 95 percent of wet marsh vegetation would exist in a fluctuating flow zone between stagesequivalent to 10,000and 20,000cis. Elements such as flood frequency reduction measures,reduced maximum flows, habitat maintenance flows, and beach/ habitat-building flows would create quite different conditions under some alternatives. As lake levels inundate vegetation, the presenceof plants causesadditional sediment to aggrade deltas. Major flood events would enhance aggradation by permitting higher flows to build higher deposits. At some point in delta formation, high floodflows would aggrade sediment deposits behind the delta crest to an elevation equal to full Reduced flood frequency and reduced maximum daily and/ or seasonalflows would create dryer conditions for some patches of emergent marsh plants that historically have been supported by regular patterns of inundation. However, plants such as cattails can persist without inundation for extended periods-perhaps years. Thesepatches of emergent marsh plants would be replaced by woody plants while others would develop at suitable sites made available by reduced flows. The exact total area or number of patches of emergent marsh vegetation that would develop or be supported under each alternative cannot be predicted becausethe area suitable for marsh plants (sites providing both water and appropriate soil/nutrient composition) is unknown. Future suitable sites are either under water or have not yet formed. However, the responseof vegetation to the interim flows implemented in 1991indicates that marsh plants will rapidly develop in suitable sites exposed at lower elevations. No data exists at this time to indicate that either fluctuating or steady flow patterns would support more or fewer areasof marsh plants than no action conditions. However, it is assumedthat fluctuating flow alternatives would more closely mimic the No Action Alternative than would steady flow alternatives. It is further assumed that, becausesteady flows would wet a smaller area than fluctuating flows, steady flows would support fewer patches and smaller areasof emergent marsh plants. To help readers evaluate changesamong baseline patches of marsh plants and the alternatives, a qualitative evaluation of changesto aggregatearea of wet marsh plants relative to no action is provided. For example, when compared to no action conditions, the aggregatearea of wet marsh plants under the action alternatives would either be the same as, same to less than, or less than no action conditions. Two alternatives-seasonally adjusted and year-round steady flows-would affect water levels in Lakes Powell and Mead seasonally in any water year. Elevation changesfor both lakes would be within historic average annual fluctuations, with generally lower high elevations and higher low elevations for Lake Powell and higher water levels during the growing seasonfor Lake Mead. Any differences in annual responses between these alternatives and others would be overridden by the cyclic effects of regional weather patterns as described above. Summary of Impacts: Vegetation Alternative operations of Glen Canyon Dam would affect riparian vegetation within the river corridor in several different ways during the short-term (5 to 20 years) period of analyses. First, reduced frequency of major uncontrolled flood releaseswould result in an unknown, but assumedequal, decline in area coverage of riparian vegetation in the OHWZ under all alternatives. Some speciesfound in the OHWZ would expand into the NHWZ to become an important part of this plant community .As vegetation shifts from riparian to desert shrub, the OHWZ may disappear as a distinct zone of vegetation sometime in the distant future beyond 50 years. Second,becauseof higher maximum flows than no action, the Maximum Powerplant Capacity Alternative would result in reduced area of riparian vegetation in the NHWZ. Third, under no action, woody plants within the NHWZ would be maintained within stage boundaries equivalent to flows between about 22,000and 40,500cfs. Speciescomposition would continue to develop toward an undefined equilibrium. Periodic inundation, in patterns similar to existing conditions, would permit continued maintenance of emergent wet marsh vegetation at sites currently occupied (stage elevations equivalent to la,aaa to 20,000-cfsflows). The restricted fluctuating and steady flow alternatives all would pennit riparian vegetation to expand into sites created by reduced maximum flows (table IV-I0). Area coverage of woody plants in the NHWZ would increase (fi~re IV-13). Somenew establishment of emergent marsh plants would occur at the mouths of return-current channels and other suitable sites. Patchesof emergent marsh plants that lose their water supply would be dominated by woody plants and disappear. The Moderate and Modified Low Fluctuating Flow Alternatives and the SeasonallyAdjusted Steady Flow Alternative include habitat maintenance flows. Maintenance flows are assumedto affect the area available for vegetation, but the magnitude of effect is unknown. 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Q) c -!!!. c ,v3: E Q) Q» ~~ -c ~~~ c- .c:2 ffi2"0 cO»- -5(1j(1j Q) 00== "OE.C -(1j 'v- (1j (/) (/) (/) 0 Q)(/).c E .c Q) ~ -(1j oE ~c~ 0) .t: "0 C (1j ffi (1jC.(/) .CE (J 0 C "0 C (1j ~ ~o (1j (/) C Q) « c"' (1j(J$ ~ Q) ~ (1j.~~-0~~ -.u~.c2!.~(J E~c.~(J"iO Q)~:E-(1jC. o.P.~~~3: Q. ":5 .Q Q)(1j(/)-0 :J ~ 237 240 Chapter IV Environmental Consequences No beach/habitat-building flows would occur under this alternative. As with woody vegetation, it is assumedthat a major flood would greatly reduce existing patches of marsh plants before they are replaced by woody plants. However, timing of the assumedflood would permit recovery of emergent marsh vegetation, by the end of 50 years, to levels comparable to no action conditions. Restricted Fluctuating Flows Daily flow fluctuations would affect vegetation through two processes: .Deposition substrate .Changes Becauseof flood control measures,plant species composition in the NHWZ would be somewhat different than under no action. Tamarisk would be concentrated near the maximum discharge stage,with honey mesquite and other native speciesoccupying higher NHWZ elevations. Coyote willow and arrowweed would occupy sandy sites. Emergent marsh plants would continue to occupy current sites or expand in the short term. and erosion of sediments serving as in river stage The effects of alternative operations discussed below are presented in tenns of the flow patterns anticipated during a minimum releaseyear (8.23mat). Basedon historic data, minimum releaseyears would occur about 40 to 50 percent of the time. During moderate or high water years, total area coverage of riparian vegetation may be reduced. Under a fluctuating releasepattern, riparian vegetation under the High, Moderate, Modified Low, and Interim Low Fluctuating Flow Alternatives would be affected by higher water volumes becauseof increasesin maximum stages. Higher flows would tend to shift conditions, including the active width of unstable sandbars, toward those under the No Action Alternative. The amount of reduction in riparian vegetation would depend on the magnitude and frequency of dischargesand subsequentdeviation from the patterns described below. High Fluctuating Flow Alternative The area available for expansion of woody plants (as representedby the difference between unstable bar width for no action and this alternative) would increasean average of 10 to 15 feet (15 to 35 percent) over no action throughout the 11 river reachesin the study area. Beach/habitat-building flows would maintain the above pattern. Depending on the timing of these flows, either tamarisk, native plants, or both would germinate on suitable wetted sites. With a return to normal flow patterns, native plants would dominate. New sites suitable for emergent marsh plants would be maintained or created in the short term. Moderate Fluctuating Flow Alternative Habitat maintenance flows under this alternative would affect woody plants to an unknown degree. The area available for plant expansion would approach, but be less than, the area available for expansion under identical flow patterns that do not have annual maintenance flows. Three considerations are involved in this prediction. First, without modifications from maintenance flows, the potential maximum area available for expansion by woody plants on stabilized sandbars in each river reach would increasean average of 15 to 26 feet (23 to 40 percent) over no action. Second,sediment transported by maintenance flows initially would bury some vegetation to an unknown extent. However, the maximum estimate is that all areasup to an elevation equivalent to the 30,000-cfsstage could be affected. Those areasunaffected by maintenance flows would average (by river reach) a 0- to 5-foot increase (0 to 12 percent) over no action conditions. Becauseof the limited magnitude and duration of these flows, it is assumed that not cill vegetation would be buried. VEGETATION Finally, speciesthat tolerate burial would eventually grow through new deposits and join those plants that are not buried to expand the areasof woody plants. The relationships between discharge, sediment, and woody plants would probably require several years to stabilize to the point where plants are no longer buried by maintenance flows. Vegetation within the NHWZ would be affected by reductions both in active width of sandbars and maximum stageunder this alternative. A zone between 22,300and 31,500cfs would no longer be regularly inundated during minimum releaseyears, except during maintenance flows. Coupled with flood control, this would result in dryer conditions dictating plant speciescomposition in the NHWZ. Young tamarisk would be concentrated near the 22,300-cfsstage. Coyote willow, arrow weed, and other specieswould expand from higher elevations in the NHWZ to suitable sites at lower elevations. Willow and arrow weed would continue to expand on high sand deposits. Emergent marsh plants initially would occupy historic sites and expand into suitable sites created by lower maximum flows. Patchesabove the stageequivalent to 22,300cfs would no longer be subject to frequent inundation. Thesedry sites eventually would fill with sediment transported by habitat maintenance flows and be lost. A 29-percent reduction in maximum stage would create or make available additional marsh plant sites. Aggregated sites may equal or be less than the area of emergent marsh plants under no action conditions. Habitat maintenance flows would support this plant pattern until some other flow regime occurs. The higher dischargesof periodic beach/habitatbuilding flows would likely disrupt any stability that would develop among sediment, plants, and maintenance flows. After a beach/habitat building flow, a new level of stability would become established and continue until the next high flow event. It is assumed that beach/habitat-building 241 flows would also restructure return-current channels important for marsh plants below the 20,000-dsstage. Modified Low Fluctuating ,Flow Alternative Habitat maintenance flows under this alternative would result in effects on woody plants similar to those discussedunder the Moderate Fluctuating Flow Alternative. The area available for woody plant expansion would be between the potential maximum area of stabilized sandbars-211o 31 feet (30 to 47 percent) over no action-and the area of sandbarsunaffected by maintenance flowS-O to 5 feet (0 to 12 percent) over no action. The increasein woody plants would likely approach, but be less than, the potential maximum area of stabilized sandbars under this alternative. A zone between 20,000and 31,500cfs would no longer be inundated during minimum release years, except during habitat maintenance flows. This change, along with flood control, would result in dryer conditions that would dictate plant speciescomposition in the NHWZ. Thesechanges in speciescomposition would be similar to those discussedunder the Moderate Fluctuating Flow Alternative. Emergent marsh plants would respond to changesin discharge similarly to the Moderate Fluctuating Flow Alternative. Patchesabove the stage equivalent to 20,000cis would no longer be subject to frequent inundation and would disappear. A 37-percentreduction in maximum stage would create or make available additional marsh plant sit~s. Aggregated sites may equal or be less than the area of emergent marsh plants under no action conditions. Habitat maintenance flows would support this plant pattern until disrupted by a beach/habitatbuilding flow as discussedunder the Moderate Fluctuating Flow Alternative. After a beach/habitat-building flow, a new level of stability would develop among sediment, riparian vegetation, and maintenance flows. 242 Chapter IV Environmental Interim Low Fluctuating Consequences Flow Alternative The assumed area available for expansion by woody plants in the short term representsan increaseof 21 to 31 feet (30 to 47 percent) over no action. Also, a zone between 20,000and 31,500cfs would no longer be inundated by fluctuating flows during minimum releaseyears. Young tamarisk would be concentrated near the 20,000-dsstage. Coyote willow, arrow weed, and other specieswould expand from higher elevations in the NHWZ to suitable sites at lower elevations. Willow and arrow weed would continue to expand on high sand deposits. Emergent marsh plants would continue to occupy historic sites and expand into suitable sites created by lower maximum flows. Patchesabove the stageequivalent to 20,000cfs would no longer be subject to frequent inundation and would disappear. A 37-percentreduction in maximum stagewould create or make available additional sites suitable for marsh plants. This prediction is consistent with plant responsesto interim flows conditions. Aggregate area of wet marsh plants would be the same as or less than no action. Beach/habitat-building flows would maintain this plant pattern in the short term. While such flows could be timed to coincide with seedreleaseof several different plants, it is assumed that tamarisk would be the dominant colonizer on suitable sites made available by reduced flows. However, based on observations since the 1983-86 floodflows, native plants would quickly become established and even have an advantage at newly deposited sand beaches. Beach/habitat-building flows would also maintain return-current channelsimportant for marsh plants below the 20,000-cfsstage. Steady Flows The effects of steady releaseson the indicators of vegetation resourceswould depend on stage and duration of flows. Stageslower than historic conditions would encourage expansion of woody plants into suitable sites at lower elevations (figure IV-15). Future responsesof emergent marsh plants to steady flows are unknown. Lower maximum stageswould dry out patches of wet emergent marsh plants, while higher steady flows for extended periods may result in scouring or drowning of some plants. However, the following analysesare based on the same assumptions applied to all alternatives with reduced maximum stages. Theseassumptions, plus beach/habitatbuilding flows (and habitat maintenance flows under the SeasonallyAdjusted Steady Flow Alternative), indicate aggregatearea coverage of marsh plants would be less than under the No Action Alternative. During moderate and high water years, the release patterns identified for steady flow alternatives could not be maintained. The Seasonally Adjusted and Year-Round Steady Flow Alternatives would resemble the Existing Monthly Volume Steady Flow Alternative as releases increased. In high releaseyears, all three steady flow alternatives would have high steady flows for extended periods, with a reduction in riparian vegetation from scouring and drowning. In the long term, alternatives with reduced maximum flows would exhibit shifts in location of riparian plants in the NHWZ, including both replacement by plants requiring less moisture in higher elevations and expansion into suitable sites at lower elevations. Thesechangeshave been described for fluctuating flows and are assumed to be equally applicable to steady flow alternatives. Existing Monthly Volume Steady Flow Alternative Vegetation in the NHWZ would be affected by both a reduction in active width of sandbars and a reduction in maximum stageunder conditions of this alternative. The area available for expansion by woody plants represents an average increase of 26 to 41 feet (45 to 65 percent) over no action conditions. A zone between about 16,300and 31,500cfs would no longer be periodically inundated by fluctuating flows. Tamarisk would be 40,500 Actual 1989 Daily Range ~ - Steady Flow Alternative 32,000 28,000 ~I z ~I 24,000 ,, 20.000 i -16,000 ~ --.3 o LL ~I ~ ~1 12,000 ~ I 8,000 4,000 OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP Water Year 1989 (8.2 mafannual release) Figure IV-15.-Because of reduced maximum flows under some alternatives, area coverage of woody plants in the new high water zone would increase. The potential for increase is greatest under the Year-Round Steady Flow Alternative. concentratednear the 16,300-cfsstage. Honey mesquite and other specieswould expand from higher elevations into the NHWZ, and coyote willow and arrow weed would occupy sandy sites. Under this alternative, emergent marsh plants would be subjectedto steady flows that varied monthly. Marsh plants above the 16,300-cfsstage would lose their water supply and be lost. Reduced stage would create or make available additional sites suitable for marsh plant development. Aggregated sites supporting wet marsh plants would equal a smaller area than under no action conditions. Seasonally Adjusted Steady Flow Alternative Habitat maintenance flows under this alternative would result in effects on woody plants similar to those discussedunder the Moderate Fluctuating Flow Alternative. In the 11 river reaches,the area available for this expansion would be between the maximum area of stabilized sandbar&-26 to 36 feet (38 to 58 percent) over no action, and the area of sandbarsunaffected by maintenance flows-o to 5 feet (0 to 12 percent) over no action. The increasein woody plants would likely approach, but be less than, the potential maximum area of stabilized sandbars under this alternative. ~ 244 Chapter IV Environmental Consequences An areabetween 18,000and 31,500cfs would no longer be regularly inundated, except during annual habitat maintenance flows. This reduction in maximum stage,together with flood control, would result in dryer conditions dictating plant speciescomposition in the NHWZ. Tamarisk would be concentratednear the 18,00Q-cfsstage. Honey mesquite and other specieswould expand from higher elevations into the NHWZ. Coyote willow and arrow weed would occupy sandy sites. Under this alternative, emergent marsh plants would either completely lose their water supply for 5 months (8,000-cisflows), be partially inundated for 5 months, or completely inundated for 2 months (along with a 1- to 2-week period of inundation to 30,000cis during maintenance flows). The responsesof patches of marsh plants to this variable water regime are difficult to predict. For example, some patches would experienceinundation in May and June (a critical growth period), while drying would occur in August through December. Reducedstagewould create or make available additional sites suitable for marsh plant development. However, all sites would aggregateto an area less than the area of emergent marsh plants under no action. It is assumedthat stagereduction would affect woody riparian plants as described above for the long-term period of analyses. The abundance of mesquite and other plants would be influenced by beach/habitat-building flows. The NHWZ would maintain the increasein overall area coverage described for the short term. Year-Round Steady Flow Alternative The area available for expansion by woody plants representsan average increaseof 36 to 57 feet (63 to 94 percent) over no action. During a minimum releaseyear, a zone between 11,400and 31,500cis would no longer be inundated by fluctuating discharges. Such changesare quite different from the No Action Alternative. Changesin woody plant speciescomposition are assumedto be similar or identical to those predicted under the SeasonallyAdjusted and Existing Monthly Volume Steady Flow Alternatives. A reduction in maximum discharge would affect area coverageof emergent marsh plants. Any marsh plants below the 11,400-cfsstage would be permanently inundated and presumed lost. Reduced stage(64 percent) would create or make available additional sites suitable for marsh plant development. However, becauseof the limited area wetted by a year-round steady flow, the aggregatearea of emergent marsh vegetation under this alternative would be less than that supported by no action conditions. WILDLIFE AND HABITAT l~~I~; li~.t;~; This section addressesthe effects of alternatives on terrestrial wildlife other than special status species. Very little wildlife population data exists for either the predam or postdam habitats found along the river corridor. However, it is assumed that almost all wildlife concernscan be addressed by considering the effects on wildlife habitat as representedby riparian vegetation. Many speciesuse woody plants directly as nest sites or cover or, in the caseof beaver and others, use some plants as food. Other species,such as waterfowl, nest in emergent marsh plants and other suitable sites. Riparian vegetation also provides cover for insects important as food for mammals, birds, and amphibians and reptiles (herpetofauna). Therefore, no specific analysesof impacts on individual wildlife specieswere conducted for each alternative. mstead, it is assumedthat changesin area coverage of riparian vegetation are directly linked to changesin riparian wildlife habitat. WILDLIFE AND HABITAT 245 One notable wildlife resource does not fit the above pattern. Waterfowl are attracted in winter to the Colorado River below Glen Canyon Dam by open water and the food it provides. While various speciesfeed on different foods, it is assumed that Cladophoracan be used as an index of food availability for wintering waterfowl. Cladophora and associateddiatoms serve as food as well as cover for macroinvertebrates such as Gammarus, chironomid and simuliid larva, and others. Like the analysespresented in the FISH section, Cladophorais used here as an indicator of the aquatic food baseavailable to wintering waterfowl. Powerplant Capacity Alternatives. Flood events would affect vegetation and, in turn, habitat in ways previously described (seechapter III, VEGETAnON). Habitat and its value to wildlife would be reduced until replaced through natural successionof vegetation. Most wildlife populations are resilient and able to adapt to cycles of habitat abundance. However, a few specieswith small populations could experience adverse impacts from flood-related reductions in habitat. Thesespecieshave special status and are treated in another section (seeENDANGERED AND OTHER SPECIAL STA TUS SPECIESin this This analysis of riparian habitat, as based on riparian vegetation, generally is limited to the river corridor between the dam and Separation Canyon (although only data to Diamond Creek are available). It is assumedthat dam operations affect vegetation and, in turn, habitat through two processes-the dynamics of beach aggradation and degradation and prolonged change in river stage (seeWATER, SEDIMENT, andVEGETATION in this chapter). Together, theseprocesses are reflected as changesin area coverage of woody plants and, to a lesser degree,changesin species composition. Thesechangesaffect habitat suitability for area wildlife. Woody and Emergent Marsh Plants Analysis Methods During the short-term period of analysis, it is assumed that changesin wildlife habitat would closely follow changesin riparian vegetation, which would follow changesin exposed sediment deposits resulting from daily water release patterns. mfrequent releasesabove the maximum flow identified for each alternative, habitat maintenanceflows, and beach/habitat-building flows of unknown stagemay occur in the short term. Additional impacts resulting from these sources are identified where appropriate. Daily dam operations also would affect food for wintering waterfowl during the short-term period of analysis. Major uncontrolled flood events are expected under only two alternatives during the long-tenn period of analyses: the No Action and Maximum chapter). Changesin area of emergent marsh plants resulting from implementation of any of the alternatives would depend largely on changesin river stage and duration of flows. Most patches of marsh plants occur in the NHWZ and are maintained by a water releasepattern that alternately floods and then exposesthem. Changesin this pattern would result in changesin area coverageof marsh plants and the habitat value of these sites. It is assumedthat Lakes Powell and Mead would cycle through periods of low and high water levels during both the short- and long-term periods of analyses. As described under VEGETAnON, riparian vegetation that develops during low lake level periods would be lost and develop again (recycle) as lake levels increaseand then decrease.Vegetation supported by low lake levels is important habitat for many species, especially breeding birds. Increasesand decreases in habitat area would depend on regional water conditions and are, therefore, independent of all alternatives. Aquatic Food Base Most wintering waterfowl use occurs in the upper reachesof the river, while Cladophoraabundance generally is highest between the dam and Lees Ferry. Over 90 percent of the 2,780waterfowl surveyed in January 1991were observed between the dam and the LCR (Kline, written communica- 246 Chapter IV Environmental Consequences tion,1992). Evaluation of effects on the aquatic food baseis limited to wetted perimeter data from two sites: one near the dam and one near Lees Ferry (seeFISH in this chapter). Comparisons made from these data are useful in evaluating relative differences between no action and action alternatives. The specific effects of a major flood event on Cladophoraand the associatedaquatic food base are unknown. It is reasonableto assume, however, that effects would not be irreversible, since the Cladophorapopulation survived the high flows of 1983-86. Summary of Impacts: Habitat Wildlife and In general, individual animals would not be directly affected by daily operations of Glen Canyon Dam. For example, mammals, birds, herpetofauna, and invertebrates occupying or using riparian habitat generally are mobile and would move as required by daily fluctuations. Birds using the riparian zone as a travel lane through Grand Canyon would not be directly affected by any of the alternatives. However, those speciesthat nest in riparian vegetation would be indirectly affected by changesin area coverage of plants. In the short term, woody plant coverage,and therefore riparian habitat, would increaseunder most alternatives. Emergent marsh plants would either remain similar in coverage to no action or decrease. A summary of impacts on wildlife and habitat, based on impacts to either riparian vegetation or the aquatic food base, is presented in table IV -11. Alternative Glen Canyon Dam operations would affect riparian vegetation, and therefore habitat, in several different ways during the short-term (5 to 20 years) period of analysis. Briefly, all alternatives would contribute to the gradual decline of the OHWZ. No action would maintain the existing riparian vegetation area,while the Maximum Powerplant Capacity Alternative would create conditions leading to a decline in habitat area. The remaining alternatives would permit woody riparian vegetation to expand, in differing amounts, into sites created by reduced maximum flows. Although no data are available on habitat patch size along the river corridor, it is assumed that as area of woody riparian vegetation increasesso too will habitat and patch size. The ecological value of habitat to wildlife is, in part, also related to the patch size of a vegetated area. In order for a patch of habitat to be valuable to mammals, breeding birds, herpetofauna, or invertebrates, it must be large enough to provide adequate food resources and shelter. For example, larger patch sizes are likely to have a greater number of bird species present. Wilson and Carothers (1979)tested this hypothesis in Grand Canyon and determined that as habitat patch size decreased,bird species diversity and density were similarly reduced. As patch size increased,additional specieswere found to occur within the habitat. An annual habitat maintenance flow is included in the Moderate and Modified Low Fluctuating Flow Alternatives and the SeasonallyAdjusted Steady Flow Alternative in order to move and deposit sediment higher than would be possible under daily flow patterns. As discussed under VEGETAnON (earlier in this chapter), some vegetation would be buried by initial maintenance flows, and thus its value as habitat reduced. Vegetation that is not buried or that grows up through new deposits would be unusable to area wildlife during the period of inundation. In the long-term period of analyses(20 to 50 years), differences among alternatives would continue to develop. At least one major flood is assumedto occur under the No Action and Maximum Powerplant Capacity Alternatives. Successionof riparian vegetation would be set back to an earlier stage due to loss of plant coverage. 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C).J:: -.J:: C .~ ~ ~ EI:;:C)E aJaJ« Ez ..~ .; c .Q a. E :J "' "' "' "' c o . .!Q "E. ~E -:J "' "' c "' "' "' O .!Q c "' 0.2:""", a.C .., "' c.> Z "' O~ t= "' < f-.,Q W:I: ~(/) W>u. ~~ Q; Q; a.a. "' "' .c.c c.> c.> Q) Q) Q) Q) (/)(/) 247 248 Chapter IV Environmental Consequences term. All alternatives with flood control would support increasesin woody plant coverageat the end of the long-term period of analysis. Dryer conditions in the upper elevations of the NHWZ would favor a shift from tamarisk and willow to mesquite and other plants. Willowwhich is less drought resistant-would disappear first, with tamarisk persisting for some time and perhaps arrow weed moving into suitable sites. Tamarisk, willow, and other plants would be favored downslope at wetter sites. Increasesin area and diversity of plant specieswould mean increasedhabitat. Beach/habitat-building flows would continue to support existing and expanded coverage of riparian vegetation and changesin species composition initiated in the short term. However, such flows may temporarily reduce the aggregate area of riparian vegetation and, therefore, wildlife habitat (seeVEGETAnON in this chapter). Wintering waterfowl would be affected by changesin minimum discharge. The No Action and Maximum Powerplant Capacity Alternatives have a minimum discharge of 1,000cis. The remaining alternatives increaseminimums from 3,000to 11,400cfs. Increasedminimum discharges,as well as brief high releaseperiods during habitat maintenance and beach/habitatbuilding flows, are assumed to benefit the aquatic food baseand ultimately wintering waterfowl. Unrestricted Fluctuating Flows No Action Alternative The area of woody and emergent marsh plants, and thus riparian wildlife habitat, would remain similar to baseline conditions as described in chapter III. Cladophora,representing the aquatic food base, is limited by minimum reliable flows. Under no action conditions, these flows would be 1,000cfs, with a wetted perimeter of 580.3feet near the sampling site at the dam and 380.4feet at the site near Lees Ferry (seechapter IV , FISH). Maximum Powerplant Cclpacify Alternative Stagechange and associatedeffects on woody and emergent marsh plants depend on local channel widths within the fluctuating zone, and thus differ among sites and reachesfor the same riverflows. For each reach, an area of beach Oto 5 feet wide (or Oto 9 percent of the width of unstable sandbars under no action) would become active and unstable under this alternative. It is assumed that some vegetation, and thus habitat, at affected sites would be lost through erosion. The Maximum Powerplant Capacity Alternative would have the sameminimum flow as the No Action Alternative. Therefore, it is assumed that effects on the aquatic food base for wintering waterfowl would be identical to no action conditions. Restricted Fluctuating Flows Daily changesin discharge have both positive and negative affects on wildlife habitat. Alternatives with lower maximum discharges would make sites available for expansion of woody plants. Many patches of emergent marsh plants would no longer be inundated on a regular basis. Patchesof emergent marsh plants above the maximum discharge stagewould receive water only during periods of habitat maintenance and beach/ habitat-building flows. Thesepatches of vegetation would temporarily supply structural diversity to the vegetative community but would function as upland vegetation rather than as aquatic plants. Thesesites would be replaced with woody vegetation. Sudden deviations from either fluctuating or steady flow patterns, as would occur during habitat maintenance and beach/habitat-building flows, could have temporary adverse effects on ground-dwelling, ground-nesting, and burrowing forms of wildlife including insects, reptiles, and small mammals. The effects on all resources would be considered when scheduling such flows. WILDLIFE AND High Fluctuating Flow Alternative Impacts on riparian habitat, including woody and emergent marsh plants, would be identical to those described for vegetation. The area of beach available for expansion of woody riparian plants would increasean average of 10 to 15 feet (15 to 35 percent) overno action conditions throughout the study area (seechapter IV, VEGETA naN). Emergent marsh plants would continue to occupy historic sites or expand slightly in the short term. The wildlife speciesthat use theseplants would respond accordingly. Increasedminimum flows would mean benefits for the aquatic food base and, therefore, for wintering waterfowl. Increasedminimum flows represent an additiona12,OOO cis of permanent inundation-a 1.5- (LeesFerry) to 2.0-foot (near the dam) increasein stage and up to an 8.7-foot increasein wetted perimeter over no action. Moderate Fluctuating Flow Alternative Woody plants would expand into suitable sites made available by lower maximum flows. The exact extent of expansion is unknown becausethe relationships between sediment, riparian plants, and habitat maintenance flows are not defined at this time. As was discussedunder the analysis of VEGETAnON, it is assumed that the area available for woody plant expansion would approach, but be less than, the area available for expansion under identical flow patterns without annual maintenance flows. For this alternative, the upper range of beach widths available for expansion is 15 to 26 feet for the 11 river reaches(a 23- to 40-percentincreaseover no action conditions). The lower range, or those areasunaffected by maintenance flows, would average a 0- to 5-foot increase(0 to 12 percent) over no action conditions. Emergent marsh plants would initially occupy historic sites and expand into suitable sites created by lower maximum flows. Patchesof marsh plants above the 22,300-cfsstage would no longer be frequently inundated. Thesesites would be dry, would eventually fill with sediment, and emergent marsh plants would be replaced by woody vegetation. A 29-percentreduction in HABITAT 249 maximum stage would make additional marsh plants sites available. In aggregate,the area occupied by emergent marsh plants under this alternative would be equal to or less than no action. Habitat maintenance flows would occur before most wildlife nesting activity. While high flows may temporarily displace some individual animals, maintenance flows would redistribute the sediment critical for riparian plant growth and thus benefit habitat. Increasedminimum flows to (5,000cis yearround) would translate into some benefits for the aquatic food base and, therefore, wintering waterfowl. Increasedminimum flows represent about a 2.4- (LeesFerry) to 3.5-foot (near the dam) increasein stageand up to a 14.1-foot increasein wetted perimeter. Modified Low Fluctuating Flow Alternative Effects on wildlife habitat and wintering waterfowl would be similar to those discussed under the Moderate Fluctuating Flow Alternative. First, the upper range of beach widths available for expansion of woody plants is 21 to 31 feet for the 11 river reaches(a 30- to 47-percent increase over no action conditions). The lower range, or those areasunaffected by maintenance flows, would average a 0- to 5-foot increase (0 to 12 percent) over no action conditions. Second,patches of emergent marsh plants above the stage equivalent to 20,000cfs would lose their source of abundant water, become dry , and eventually fill with sediment. A 37-percent reduction in maximum stage would create or make available additional sites suitable for marsh plants. The aggregatearea occupied by emergent marsh plants would be equal to or less than the area supported under no action. Although the daytime minimum low flow is 8,000cfs under this alternative, it is assumed that the aquatic food base would be limited by the nighttime (and weekend) minimum of 5,000cfs. This low representsa 4,000-cfsincrease over no action conditions and is assumed to represent improved conditions for wintering waterfowl. This increaseequatesto a 2.4-foot (LeesFerry) to 3.5-foot (near dam) increasein stage and up to a 14.1-foot increasein wetted perimeter. It is assumed that the 1- to 2-week habitat maintenance flow included in this alternative would not affect the aquatic food base or disturb wintering waterfowl. Interim Low Fluctuating Flow Alternative Habitat for some specieswould increaseunder this alternative as woody plants in the NHWZ colonize suitable beach sites down to the 20,000-cfsstage. The area of beach available for expansion of riparian habitat would average21 to 31 feet, or a 30- to 47-percent increaseover no action conditions. A zone between 20,000and 31,500cfs would no longer be inundated by fluctuating flows during minimum releaseyears. Combined with flood control, this would result in dryer conditions for NHWZ vegetation, and plants would expand into the fluctuating zone. Young tamarisk would be concentrated near the 20,000-cfsstage, while mesquite and other native specieswould continue to become established in upper elevations of the NHWZ. Emergent marsh plants would continue to occupy postdam sites plus expand into suitable sites created by lower maximum flows. Patchesabove the 20,OOO-cfs stagewould no longer be subject to frequent inundation. Although these sites would be dry, their plant structure would be maintained by periodic beach/habitat-building flows. A 37-percent reduction in maximum stagewould create or make available additional sites suitable for marsh plants. This alternative includes a daytime minimum of 8,000cfs and a nighttime minimum of 5,000cfs. For purposes of analyses,the 5,000-cfsminimum is believed to limit Cladophoraand the aquatic food base available to wintering waterfowl. Increasedlow flows represent an additional 4,000cfs of permanent inundation over no action conditions. This increaserepresents a 2.4- (Lees Ferry) to 3.5-foot (near the dam) increasein stage and up to a 14.1-foot increasein wetted perimeter. Steady Flows The effects of steady flows on riparian vegetation and wildlife habitat would depend on stage and duration. Stageslower than no action conditions would permit expansion of woody riparian vegetation into suitable sites previously inundated in the fluctuating zone. Lower stageswould remove water from emergent marsh plants, while higher steady flows could drown some plants. Existing Monthly Volume Steady Flow Alternative Area of riparian habitat for some specieswould increaseunder this alternative as woody plants in the NHWZ colonize suitable sites down to the 15,000-cfsstage. The area of beach available for expansion of woody riparian plants would range from 26 to 41 feet, or a 45- to 65-percent increaseover no action conditions. A zone between about 16,300and 31,500cfs would no longer be inundated by fluctuating flows during minimum releaseyears. Combined with flood control, this would result in dryer conditions for vegetation in the NHWZ. Young tamarisk would be concentrated near the 16,300-cfsstage,while mesquite and other native specieswould dominate the NHWZ. Emergent marsh plants would continue to occupy postdam sites plus expand into suitable sites created by lower maximum flows. Patchesabove the stagesequivalent to 16,300cfs would no longer be subject to frequent inundation. These sites would be dry, and the marsh plants eventually would be replaced by woody plants (see VEGETAnON in this chapter). A reduction in maximum stage would create or make available additional sites suitable for marsh plants. However, the aggregatearea of marsh plants supported under this alternative would be less than under no action. Minimum flows of 8,000cfs year-round would benefit the aquatic food base and, therefore, wintering waterfowl. This increase represents about a 3.4- (LeesFerry) to 5.3-foot (near the dam) increasein stage and up to a 20.5-foot increasein wetted perimeter. ENDANGEREDAND OTHERSPECIALSTATUSSPECIES Seasonally Adjusted Steady Flow Alternative Habitat maintenance flows under this alternative would have effects on riparian habitat similar to those discussedunder the Moderate Fluctuating Flow Alternative. The area available for expansion of woody plants would be between the maximum area of stabilized sandbars without maintenance flows-26 to 36 feet (38 to 58 percent) over no action-and the area unaffected by maintenanceflows-O to 5 feet (0 to 12 percent) over no action (seeVEGETATION in this chapter). The increasein woody plants, and therefore wildlife habitat, would approach the potential maximum area of stabilized sandbars under this alternative. Under this alternative, some patches of emergent marsh plants and the wildlife that use these sites as habitat would: (1) completely lose their water supply for 5 months, (2) be partially inundated for 5 months, or (3) be completely inundated for 2 months (plus a 1- to 2-week period during maintenance flows). The reduced maximum stage would create or make available additional sites suitable for marsh plant development. Overall, however, fewer marsh plants would be supported under this alternative than under no action (see VEGETAnON in this chapter). 251 with flood control, this would result in dryer conditions for NHWZ vegetation. Young tamarisk would be concentrated near the 11,400-cfsstage,while mesquite and other native specieswould dominate the NHWZ. Emergent marsh plants would occupy suitable sites createdby lower maximum flows. Patches above the 11,400-cfsstage no longer subject to frequent inundation would be replaced by woody plants. The aggregatearea of emergent marsh plants supported by this alternative would be less than that under no action. illcreased minimum flows year-round would benefit the aquatic food base and, therefore, wintering waterfowl. illcreased minimum flows represent an additional 10,400cfs of permanent inundation over no action conditions. This increaserepresentsa stage increase of about 4.3 (LeesFerry) to 6.9 feet (near the dam) and up to a 25.9-foot increasein wetted perimeter. ENDANGERED AND STATUS SPECIES OTHER SPECIAL Increasedminimum flows would benefit the aquatic food base and, therefore, wintering waterfowl. This increaserepresentsa stage increaseof 3.4- (LeesFerry) to 5.3-feet (near the dam) and up to a 20.5-foot increasein wetted perimeter. Year-Round Steady flow Alternative Area of riparian habitat, represented by woody plants in the NHW2, would expand down to the 11,400-cfsstage during minimum releaseperiods under this alternative. The area of beach available for expansion of woody riparian plants would average36 to 57 feet, or a 63- to 94-percent increaseover no action conditions. A zone between about 11,400and 31,500cfs would no longer be inundated by fluctuating flows during minimum releaseyears. Combined Both aquatic and terrestrial special status species occupy or use the river corridor through Glen and Grand Canyons. Becausethe river is regulated by Glen Canyon Dam, special status native fish could be directly affected by changesin dam operations. 252 Chapter IV Environmental Consequences For example, minimum flows below some stage may limit accessto tributaries. In contrast, the effects on terrestrial specieswould be more indirect and occur through dam-induced changes in habitat. For example, an uncontrolled flood event could eliminate nesting habitat for the southwestern willow flycatcher and thus reduce the numbers of young flycatchers produced in Grand Canyon. In an attempt to reduce repetition of information, impacts on special status native fish are not presented in this section. Readers interested in a detailed assessment of impacts on humpback chub and razorback and £1annelmouth suckers should refer to the FISH section of this chapter . Analyses of the indicators for terrestrial special status speciesare limited to the river corridor between Glen Canyon Dam and Separation Canyon (although data only to Diamond Creek are available). The analysesrely heavily on work presented in other sections. For example, the analysis presented in the FISH section of this chapter provides information for impact assessmentrelevant to the bald eagle and belted kingfisher. Evaluation of habitat for the southwestern willow flycatcher is based on analysespresented in chapter IV , VEGETA naN. Three special status speciesdiscussedin chapter III would not be affected by changesin dam operations. These species---southwestern river otter, peregrine falcon, and osprey-are discussedbelow and are not treated under the individual alternatives. A fourth species,the Kanab ambersnail, would be affected by maximum flows above 20,000cfs. Effects would be similar among alternatives and are discussedin the "Summary of Impacts" and not under the individual alternatives. The southwestern river otter is a subspecies considered extinct and will not be treated further. Any river otter in Arizona is regarded as an escapedindividual from a reintroduced population of unknown subspecies. Numbers of peregrine falcons are increasing nationwide following the prohibition on use of certain pesticides in the 1970's. It is assumed that increasesin peregrine numbers have occurred in Grand Canyon as well (Brown et al., 1992). Although the reasonsfor these apparent increases are undoubtedly complex, changesin primary productivity within the river following construction of Glen Canyon Dam and subsequent increasesin the peregrine falcon's prey base (swallows, swifts, and bats) are assumed to have played a major role (Carothers and Brown, 1991). Primary productivity within the river is controlled by many factors, but the alternatives would affect only light transmittance through changesin water clarity .Sediment mixing from fluctuating releases and sediment supply from tributaries both affect river water clarity .The alternatives may affect sediment mixing through changesin daily fluctuation patterns. If such effects occur, they would be difficult to quantify but would be assumed to improve water clarity somewhat over no action conditions (except for the Maximum Powerplant Capacity Alternative). Improved water clarity would result in improved food conditions for peregrine falcons via food-chain linkages described in chapter III. No data exist to indicate that peregrine falcons within Grand Canyon are limited by lack of food. In fact, recent surveys indicate that available nesting habitat may be approaching full occupancy (Brown et al., 1992). The availability of suitable nesting territories would then limit future populations. In summary , the alternatives would not affect nest sites within nesting territories and may improve food baseconditions. Therefore, it is concluded that none of the alternatives would affect peregrine falcons in Grand Canyon. Ospreys seenalong the river in Grand Canyon are assumed to be transients using the river as a travel lane to other habitat. None of the alternatives would affect the river's suitability as a travel lane and, therefore, ospreys are not treated further in this report. ENDANGEREDAND OTHERSPECIALSTATUSSPECIES 253 FWS issued a final biological opinion on the preferred alternative containing a finding of no jeopardy for the bald eagle,Kanab ambersnail, and peregrine falcon and a jeopardy finding for the humpback chub and razorback sucker. In accordancewith the regulations governing proposed speciesand proposed critical habitat, Reclamation is currently conferendng with FWS on the status of the southwestern willow flycatcher (seechapter V). Components of the final reasonableand prudent alternative (attachment 4), which could in the future remove the likelihood of jeopardizing the continued existenceof the humpback chub and razorback sucker, have been incorporated into the preferred alternative. Analysis Methods Special status speciesoccupy diverse niches in the Grand Canyon ecosystem. Unlike the topic of "wildlife," no single resource can be used as an indicator of impacts to special status species. Studies of rare speciesmight describe parameters characteristic of remaining habitats that reflect marginal rather than optimal conditions. Management recommendations based on limited data for special status speciesrisk perpetuating marginal conditions. The analysesapproach taken here relies on the concept of linkages among resources. it is assumed that a trout fishery would be maintained in the future, and trout would continue to attempt tributary spawning if conditions permit. Although there is no evidence that the southwestern willow flycatcher is habitat-limited in Grand Canyon, uncontrolled flood events would reduce area coverageof riparian vegetation and would probably affect habitat patch size. The relationships among habitat requirements, patch size, and willow flycatchers in Grand Canyon are not understood. However, a reduction in area of riparian vegetation below some threshold likely would affect habitat suitability for this species. Becausethe level of this threshold is unknown, reductions in riparian vegetation should be avoided. Such avoidance is best accomplished through flood control. Effects on the belted kingfisher would follow effects on fish-basically the relationship between daily operations, tributary access,and the aquatic food base. Flood frequency reduction measures and beach/habitat-building flows should benefit native fish in the long term over no action conditions. Belted kingfishers would benefit from any improvement in habitat conditions for fish. Summary of Impacts: Endangered and Other Special Status Species Daily dam operations would affect some special status speciesdirectly and others indirectly during the short term. Becausepopulation data are limited for most special status species,the indicators presented at the beginning of this section will be used to evaluate effects of the alternatives on the speciesof concern. Table IV -12 summarizes impacts on endangered and other special status species. The endangered and special status fish speciesare influenced by factors and processessimilar to those described for native fish speciesand are discussed in this chapter under FISH. Becausebald eaglesuse trout as food when available, it is assumedthat impacts discussed under the short-term period of analysis (i.e., daily operations) would be identical to long-term impacts. This assumption is supported by the observation that uncontrolled flood releases historically have occurred in the spring or early summer after the period of eagle use. In addition, Many of the action alternatives would affect minimum flows and therefore affect tributary accessand the aquatic food base used as indicators in impact assessmentfor both bald eaglesand belted kingfishers. The No Action and Maximum Powerplant Capacity Alternatives have a minimum discharge of 1,000cfs. 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"'-u",uuQ) CIUO"0 -c. C) .- .!c.,E "OE~., .-IU .,--C ., O o C) u~.,1UO .-~ .,.'~c "0-"0 .->-Q) ~ IU .-Q) .,CU~ ctct5IU -N ~ (I) ENDANGEREDAND OTHERSPECIALSTATUSSPECIES 255 Alternative. mcreased minimum flows are assumedto benefit tributary accessand the aquatic food base. affected: 5 square yards at 25,000cfs, 50 square yards at 33,000cfs, and 103square yards at 45,000cfs. Although not treated in detail in this section, it should be noted that native fish reproduction in the mainstem is restricted by cold temperature (seeFISH in this chapter). Native fish are a food source for other special status species. Limited spawning in the mainstem near warm springs and tributary confluences may occur when fluctuations are reduced. Somemainstem spawning of humpback chub occurred in 1993,but no recruitment was recorded (Arizona Game and Fish Department, 1994). The significance of such mainstem spawning to special status speciesis unknown. All alternatives would potentially affect Kanab ambersnail habitat or individuals becauseall alternatives either have maximum flows above 20,000cfs or contain provisions for beach/habitatbuilding and habitat maintenance flows that would be above 20,000cis. Since this population survived the 1983-86floodflows (90,000cis), it is assumed that infrequent flows of about 45,000cis would not jeopardize the continued existenceof the Kanab ambersnail population in Grand The Grand Canyon population of Kanab ambersnails generally occurs above the elevation equivalent to a river stage of 40,000cfs, although the population size appears to vary widely between seasons. Prior to interim flows, Kanab ambersnails were found above the no action maximum flow level of 31,500cis. Sinceinterim flows were implemented, individual ambersnails have been found near the river's edge at 20,000cfs. A survey and habitat evaluation conducted in September1994indicated that a large number of Kanab ambersnails were present between the 20,000-and 45,00o-cfsflow levels. When compared to no action conditions (prior to interim flows), none of the alternatives would affect ambersnails. However, these survey results make an analysis using this baseline invalid. Therefore, current data were incorporated into the analysis. Reclamation's GCESand FWS are closely monitoring the Grand Canyon Kanab ambersnail population. Although studies are underway, the area of habitat occupied by Kanab ambersnails is unknown, and any evaluation of the importance of maximum flows on habitat area is difficult to determine. FWS estimatesthat approximately 2 square yards of habitat are affected at flows of 20,000cfs. As flows increase,more area is Canyon. Someincidental take of Kanab ambersnails would likely occur under all alternatives. Incidental take is unavoidable mortality resulting from authorized activities such as dam operations. Somemortality would likely occur upon implementation of the selectedalternative and again during either habitat maintenance or beach/habitat-building flows. Consultation under the Endangered SpeciesAct would be necessaryto determine reasonableand prudent measuresnecessaryor appropriate to minimize such impacts. Consultation between Reclamation and FWS is ongoing. The area of woody riparian vegetation is used as an indicator of potential habitat for the southwestern willow flycatcher, although changes in potential habitat may not translate into changes in bird numbers, The Maximum Powerplant Capacity Alternative would result in less riparian vegetation, the No Action Alternative would show no change, and the remaining alternatives would all support varying degreesof increasein woody plants. Periodic beach/habitat-building flows would maintain these conditions (see VEGETAnON in this chapter). Somealternatives include habitat maintenance flows designed to re-form beachesand backwaters. Habitat maintenance flows would provide high (up to 33,200cfs), steady flows for 1 to 2 weeks each spring when Lake Powell is near or below 19 maf. 256 Chapter IV Environmental Consequences For terrestrial special status species,maintenance flows would: Support a general increasein woody plants Have no effect (becauseof short duration) on the aquatic food base Unrestricted Fluctuating Flows No Action Alternative Analyses of effects on special status speciesunder no action conditions in the short term basically project existing trends. It should be noted that habitat use by two of the three special status birds (bald eaglesand willow flycatchers) has developed postdam under conditions similar to no action. Humpback Chub and Razorback and flannelmouth Suckers. The analysis of impacts on special status native fish is presented in the FISH section of this chapter. In general, populations of native fish are considered stable to declining under no action conditions. Bald Eagle. Bald eagle use of Grand Canyon primarily is linked to the presenceof trout in the Colorado River-specifically, the abundance of trout attempting to spawn in Nankoweap Creek. It is possible that numbers of eagleswill continue to increase-if trout remain abundant-and eventually disperse to other locations within the study area. However, the focus of this analysis is tributary accessfor spawning trout. It is assumed that low flows of 1,000cis under no action conditions would limit trout accessto tributary spawning sites during some periods. The aquatic food base is certainly important to many resourcesincluding special status native fish (seeFISH in this chapter). However, changes in wetted perimeter are used here to estimate effects on trout, which are prey for bald eagles. Baselineconditions for wetted perimeter under l,OOO-cfs minimum flows are 580.3feet near the dam and 380.4feet near Lees Ferry . Belted Kingfisher. Belted kingfishers use the river and its tributaries for feeding and nest in suitable banks wherever they are found. Nesting banks would not be affected under any alternative, but low minimum flows would periodically restrict tributary accessfor fish and limit the aquatic food basepotential. Food production and availability would be both benefited and disadvantaged by fluctuating flows. Fluctuations may displace Cladophoraand associateddiatoms and invertebrates and provide them as drift downstream of Glen and Marble Canyons. Excessivedisturbance would reduce productivity of food resources,extended periods of extreme low flows would desiccatealgae, and high flows would inundate some algae beyond the depth of usable light for photosynthesis (Angradi et al., 1992). SouthwesternWillowFlycatcher. Data are not available that can be used to interpret specific relationships between breeding willow flycatchers and woody plants used as nesting habitat in Grand Canyon. However, the analysis presented here assumesthat conditions that would change the area of woody plants would result in changes in area of potential habitat for willow flycatchers. No data were discovered that indicate that numbers of willow flycatchers using Grand Canyon are habitat-limited. The composition of woody plants within the riparian corridor (exclusive of the OHWZ) would follow trends described in chapter III, with coyote willow, arrow weed, honey mesquite, and other speciesincreasing in abundance. Southwestern willow flycatchers in Grand Canyon nest in large patches of riparian vegetation. Conditions that favor increasesin woody plants are assumed to favor potential habitat for this species. Maximum Powerplant Capacity Alternative Analysis of impacts on humpback chub and razorback and flannelmouth suckers are presented in the FISH section of this chapter. Populations of native fish under this alternative are considered the same as under no action conditions ENDANGEREDAND OTHERSPECIALSTA TUSSPECIES 257 Tributary accessfor trout used as prey by bald eagleswould not change from no action conditions. Becauseminimum flows would not differ from no action under this alternative, no change would occur in the area of wetted perimeter. Therefore, conditions for the aquatic food base-important in supporting trout and other fish used as prey by bald eaglesand belted kingfishers-would not change. An increasein maximum stageunder this alternative would affect woody plants and, therefore, may affect potential habitat of the southwestern willow flycatcher. Under this alternative, unstable sandbar width would increaseby 0 to 9 percent (0 to 5 feet) over no action. Vegetation occupying unstable sites would be lost through erosion. In summary, tributary accessand wetted perimeter would not change. Thus, conditions for bald eaglesand belted kingfishers would not change under this alternative. However, woody plants that may be potential habitat for southwestern willow flycatchers would be reduced. Therefore, conditions for the willow flycatcher under this alternative would be less favorable than those under no action. Restricted Fluctuating Flows Factors such as minimum discharge, which would affect numbers or availability of trout in Nankoweap Creek and to a lesserdegree in the river corridor, would likely affect bald eagles. None of the alternatives would affect parameters of Nankoweap Creek-such as discharge, water temperature, or icing-that are important in determining the creek's suitability as a trout spawning site. Trout stranded in isolated pools would be available as food for bald eagles. Location of foraging efforts are affected by fluctuating flows; however, thesepatterns do not appear to affect foraging success.This impact analysis is based solelyon trout accessto tributaries (Nankoweap Creek) and effects on the aquatic food base. All restricted fluctuating flow alternatives have minimum flows higher than no action conditions, but only the Moderate, Modified Low, and Interim Low Fluctuating Flow Alternatives have minimum flow restrictions of 5,000cis or greater that would permit unlimited tributary access. Minimum discharge is an important parameter in defining the aquatic food base and, thus, food for fish and belted kingfishers. The effects of alternative operations on habitat for the southwestern willow flycatcher are presented in terms of anticipated flows during a minimum releaseyear. In moderate or high water years, riparian vegetation under the High, Moderate, Modified Low, and Interim Low Fluctuating Flow Alternatives would be affected by higher water volumes through increasesin maximum stages. During moderate or high water years, total area coverage of riparian vegetation may be reduced. High Fluctuating Flow Alternative Analysis of impacts on humpback chub and razorback and flannelmouth sucker is found in this chapter under FISH. Populations of native fish under this alternative are considered the same as no action (stable to declining). Increasedminimum flows to 3,000cfs year-round would mean some increasein tributary accessand some benefits to Cladophoraand the aquatic food base. Theseare assumed to benefit bald eagles and belted kingfishers through their linkages to trout and the aquatic food base. Increasedlow flows represent an additiona12,000 cfs of permanent inundation-a 1.5- (at LeesFerry) to 2.0-foot (near the dam) increasein stage and up to an 8.7-foot increasein wetted perimeter over no action. Under this alternative, riparian vegetation would increase 10 to 15 feet (15 to 35 percent) over no action conditions (seeVEGETAnON in this chapter). Thus, some change in potential habitat for the southwestern willow flycatcher would occur. However, it should be noted that increases in potential habitat may not translate into increasesin the numbers of flycatchers surveyed during any future monitoring program. 258 Chapter IV Environmental Consequences Moderate Fluctuating Flow Alternative Modified Analysis of impacts on humpback chub and razorback and £1annelmouth sucker is found in this chapter under FISH. Populations of native fish under this alternative are considered the same as no action (stable to declining). The FWSbiological opinion on this preferred alternative stated that the Modified Low Fluctuating Flow Alternative would likely not jeopardize the continued existenceof the bald eagle,peregrine falcon, and Kanab ambersnail but would likely jeopardize the humpback chub and razorback sucker. Therefore, the preferred alternative was designed to be consistent with the "reasonable and prudent alternative" (see attachment 4) contained in the biological opinion. The reasonableand prudent alternative was provided as a plan that could remove the likelihood of jeopardizing the continued existence of the humpback chub and razorback sucker in Grand Canyon (seeFISH in this chapter). Increasedminimum flows of 5,000cfs year-round would mean some increasein tributary accessand some benefits to Cladophoraand the aquatic food base. Theseconditions also would be assumed to benefit bald eagles and belted kingfishers through their linkages to trout and the aquatic food base. Increased low flows represent an additional 4,000cfs of permanent inundation-a 2.4- (at LeesFerry) to 3.5-foot (near the dam) increasein stage and up to a 14.1-foot increasein wetted perimeter over no action. Riparian vegetation would increaseover no action conditions. The area of beach available for expansion of woody plants would averageOto 6 feet, or an increaseof Oto 40 percent over no action (see VEGETAnON in this chapter). This change is assumedto indicate an increasein potential habitat for the southwestern willow flycatcher. For terrestrial special status species,maintenance flows would provide unlimited accessto tributaries important to spawning trout (and therefore bald eagles),support a general increase in woody plants that may be used as habitat (southwestern willow flycatcher), and have no effect on the aquatic food base (an important consideration for eaglesand belted kingfishers). In summary, both tributary access-important for trout reproduction-and the aquatic food baseimportant to bald eaglesand belted kingfisherswould increaseunder this alternative. Thus, food conditions for bald eaglesand belted kingfishers would be enhanced,and woody plants that may be potential habitat for southwestern willow flycatchers would increase. Low Fluctuating Flow Alternative Analysis of impacts on humpback chub and razorback and £1annelmouth suckers can be found in this chapter under FISH. Under this alternative, populations of native fish are expected to have the potential for minor increases. The aquatic food base is important in supporting trout and other fish used as prey by bald eagles and belted kingfishers. Wetted perimeter would increaseover no action 14.1feet near the dam and 14.1feet near LeesFerry under this alternative. It is assumed that becauseboth reliable minimum flows and wetted perimeter increase,conditions for the aquatic food base would also improve. A decreasein maximum stagewould affect woody plants and, therefore, may affect potential habitat of the southwestern willow flycatcher. Becausethis alternative includes habitat maintenanceflows, the exact change in area of woody plants is difficult to predict. However, the area available for woody plant expansion would be between the potential maximum area of stabilized sandbars--21 to 31 feet (30- to 47-percent increase over no action) and the area unaffected by maintenanceflows--0 to 5 feet (0- to 12-percent increase). It is assumed that an increasein woody plants would indicate an increasein potential habitat for the willow flycatcher . 259 As described under the Moderate Fluctuating Flow Alternative, habitat maintenance flows are expected to re-form and prepare backwaters for later use by larval and young-of-year fish. Terrestrial specieswould experiencethe same effects (or lack of effects) discussedunder the Moderate Fluctuating Flow Alternative. In summary, both tributary accessand the aquatic food basewould increaseunder this alternative. Thus, conditions for bald eaglesand belted kingfishers would be enhanced. Woody plants that may be potential habitat for southwestern willow flycatchers would increase. Therefore, for all special status species,habitat conditions would increaseover no action. Interim Low Fluctuating Flow Alternative Analysis of impacts on humpback chub and razorback and £1annelmouth suckers is presented in this chapter under FISH. Under this alternative, populations of native fish are expected to have the potential for minor increases. Wetted perimeter would increaseover no action 14.1feet near the dam and 14.1feet near Lees Ferry under this alternative. It is assumed that becauseboth reliable minimum flows and wetted perimeter increase,conditions for the aquatic food basewould improve. The aquatic food baseis important in supporting trout and other fish used as prey by bald eaglesand belted kingfishers. A decreasein maximum stageunder this alternative would affect woody plants and, therefore, may affect potential habitat for the southwestern willow flycatcher. The area available for woody plant expansion would average21 to 31 feet (30- to 47-percentincreaseover no action). It is assumed that an increasein woody plants indicates an increasein potential habitat for the willow flycatcher. In summary, under the Interim Low Fluctuating Flow Alternative: Aquatic food base,important to bald eaglesand belted kingfishers, would increase. .Woody plants that may be potential habitat for willow flycatchers would increase. Therefore, habitat conditions would increasefor all special status speciesover no action. Steady Flows General effects of steady flow patterns on tributary accessand the aquatic food base were described under FISH, and effects on woody plants were described under VEGETATION . Existing Monthly Volume Steady Flow Alternative Analysis of impacts on humpback chub and razorback and £1annelmouth suckers can be found in this chapter under FISH. Under this alternative, populations of native fish have the potential to experiencea major increase. Increasedminimum flows of 8,000cfs year-round would mean increased tributary accessand large benefits to Cladophoraand the aquatic food base. Thesewould be assumedbenefits to bald eagles and belted kingfishers through linkages to trout and the aquatic food base. Increasedminimum flows represent an additiona17,000cfs of permanent inundation-a 3.4- (at LeesFerry) to 5.3-foot (near the dam) increasein stage and up to a 20.5-foot increasein wetted perimeter over no action. Riparian vegetation would increaseover no action conditions under this alternative. The area of beach available for expansion of woody plants would average26 to 41 feet, or an increaseof 45 to 65 percent over no action. This change is assumed to indicate an increasein potential habitat for the southwestern willow flycatcher. Seasonally Alternative Adjusted Steady Flow Analysis of impacts on humpback chub and razorback and £1annelmouth suckers can be found in this chapter under FISH. Under this alternative, populations of native fish have the potential to experiencea major increase. 260 Chapter IV Environmental Consequences Minimum flows of up to 8,000cfs year-round would mean increased tributary accessand large benefits to Cladophoraand the aquatic food base. Thesewould be assumedbenefits to bald eagles and belted kingfishers through linkages to trout and the aquatic food base. Increasedlow flows represent an additional 7,000cfs of permanent inundation-a 3.4- (at LeesFerry) to 5.3-foot (near the dam) increasein stage and up to a 20.5-foot increasein wetted perimeter over no action. Riparian vegetation would increaseover no action conditions under this alternative. The area of beach available for expansion of woody plants would range from Oto 36 feet, or an increaseof Oto 58 percent over no action (seeVEGETAnaN in this chapter). This change is assumedto indicate an increasein potential habitat for the southwestern willow flycatcher. fu summary , under the Seasonally the dam) increase in stage and up to a 25.9-foot increase in wetted perimeter over no action. Riparian vegetation would increaseover no action conditions under this alternative. The area of beach available for expansion of woody plants would average 36 to 57 feet, or an increaseof 63 to 94 percent over no action. This change would indicate an increasein potential habitat for the southwestern willow flycatcher. CULTURAL RESOURCES Adjusted Steady Flow Alternative: Aquatic food base,important to bald eaglesand belted kingfishers, would increase. Woody plants that may be potential habitat for willow flycatchers would increase. Therefore, habitat conditions would increasefor special status speciesover no action. Becausethis alternative would provide flow conditions closer to predam conditions than any other alternative, it is believed to be the most beneficial alternative for native fish. Year-Round Steady Flow Alternative Analysis of impacts on humpback chub and razorback and flannelmouth suckers can be found in this chapter under FISH. Under this alternative, populations of native fish have the potential to experience a major increase. Minimum flows of 11,400cfs year-round would mean increasedtributary accessand large benefits to Cladophoraand the aquatic food base. These also would be assumedbenefits to bald eagles and belted kingfishers. Increasedlow flows represent an additional 10,400cfs of permanent inundation-a 4.3- (at Lees Ferry) to 6.9-foot (near Cultural resourcesin the Colorado River corridor are numerous, with 475 archeological sites and 489 isolated occurrencesdocumented between Glen Canyon Dam and Separation Canyon. Isolated occurrencesare findings of artifacts or other remains located apart from an archeological site. Becauseit can be inaccurate to determine the National Registerof Historic Places(National Register) eligibility of a single artifact, isolated occurrenceswere not used in the impact analysis. In addition to those resourcesidentified as archeological sites, numerous additional resources significant to Native Americans occur within the river corridor. Theseresources,which are culturally important becausethey represent areas of spiritual significance and/ or traditional use, are called traditional cultural properties and resources in this document. Though there is some overlap between categories,traditional cultural properties CULTURALRESOURCES 261 and traditional cultural resourcesare discussed separately from properties identified as archeological sites. Of the archeological sites located during the survey, 336 either have been affected by the existenceand operation of Glen Canyon Dam or have the potential to be affected by floodflows that could be releasedfrom the dam. The remaining 139 sites are unaffected by the dam and have been excluded from further discussion. The specific sites identified as potentially impacted are all locations which contain physical manifestations and are recorded as archeological sites. Somearcheological sites are also important as traditional cultural properties. Impacts to archeological sites, including those with traditional cultural significance, are discussed for each alternative. Determination of eligibility for the National Register was concurred by the Arizona State Historic Preservation Officer for the 336 sites potentially impacted by dam operations (attachment 5). Of theseidentified sites, 319 have been determined eligible for inclusion on the register, 16 are ineligible, and 1 will require testing. Criteria for National Register eligibility include those used for evaluating the significance of archeological properties under 36 CFR 60.4and the guidelines for evaluating traditional cultural properties (Parker and King, no date). Specific details on individual site impacts are found in a technical archeological survey report (Fairley et al., 1994). Numerous locations within the project area contain no archeological remains but are nonethelesstangible sites and places with cultural significance becauseof their use in Native American practices and beliefs. Virtually all prehistoric sites are affiliated with contemporary Indian Tribes, often more than one group due to multiple traditions or multiple uses of many sites found along the Colorado River. Thesetraditional cultural properties are considered eligible for the National Register if they are rooted in the living community's history and important in m~intaining the community's cultural identity. Traditional cultural properties can include specific plant gathering areas,landforms, springs, prayer offering locations (shrines), archeological sites, ancestralburials, mineral deposits, and other resourcecollection sites. In addition, many resourcesare extremely important, or even vital, for continuing traditional cultural practices, but may be obtained in many locations. Thesetraditional resources,because they are not place-specific or becausethey encompasslarge areasas cultural landscapes,are not eligible for the National Register. Their importance to Native Americans, however, is not lessenedbecauseof the way current cultural preservation law is defined. In addition, many of them are governed by the National Park Service (NPS) management policies that require all cultural landscapesto be treated as cultural resources,regardless of the type or level of significance. Summary of Impacts: Resources Cultural Impact analysesof cultural resourcesunder alternative darn operations are based on the present understanding of changesin these resourcesknown to have occurred as a result of Glen Canyon Dam. Some impacts are direct, while others are indirect. Predicted influences of alternatives on traditional cultural properties and resourcesare based on information provided by ethnographic researchand knowledge shared by Indian Tribes known to have contemporary and ancestral involvement with Grand Canyon. Evaluation of isolated occurrencesalong the river corridor is ongoing by individual tribes and, if they are determined to be traditional cultural properties, their potential for impacts will be assessed.Anticipated impacts to certain other cultural resourcesare linked to impacts on riparian vegetation. A summary of impacts on cultural resourcesresulting from all alternatives is shown in table IV-13. Impacts on cultural resourcesare irretrievable and generally regional or national in scope. 262 .0 C/) w () a: :> 0 C/) w a: -l! t11 "C ~ c o ~OIL a:>'-."C IV IV aI aI>In ii: uU. ia CI .5 E ..o ~~.~ Dl C ~ e- 11. '0 O ~ iii ~ 1 E E >- u: ~ ~"0~ lUalC-U. O~>UI .-"0 IU"OIU aIC--.-.c -U)c~>.-0)(~om w~>GI E .~ GlO~o --l-c -~ .§ :I:UU. .I:~~ DI~O :> 0) ~ "0 c GI .:> ;~1U~ () .-0 ~ c: "O..J-- uU. O o ~ ~ cn iL u tU a. Dl .§ aI C -0"0 tU-'> aI:lO 1U -0-a. OCJU. :§ ~~ IL c tU O ~ tU E E :J l C') ... I ~ <~c.~(') 1O~10~~ ~0(.) C .-~ OI .$. C\I ~ C? ;:::01 LO -T~ c: 01 la U.c: 0~I/I 1/1 R ~ Q)L!) -~ ~ c: Q) (\I "C.c 0~I/) I/) j:::' Q)Ln !I) ~~ Q) 10 "O.c 0~!I) .,91, t:::' Ll) Q)~ m c ...ttI Q).c "CO (I) ~(I) ~. r:::11) ~- Q).'<0 c ..as Q).c "00 U) ~U) r::Q)1l) (/I ~~ Q) (\I "O.c 0~(/I ~. O o 0-CtJ ~ -"1 -E~ CtJ :;:O>co C: E 0> -o ~~ o u C..0> .2. g .c UI ~ .in la U .61 o -o~ u .~ ~ c O u Q) ~ ~ (/) c (\I O Q)U E (\I (\I 0 (/) c ()o c: -0- uc: 0) 0 (/)~ <0 () 0) 0) to c -a, -0 Q) C/); "' Q) 00 c -a, "C 0> UI~ tU 0> "0 Q) (/):;:: cIS Q) 0) 10 Qj -0 O :5 0) '§ 0) -0 O ~ Q) ~ Q) -0 O ~ 0> to Qj -0 O ~ o .9. -(1! roE ;0) ~ E -o o o a. 0) n O "ro 5 ""iU I.. .a "S (.I -Ul (0 C 0 .-~ ;!:0 "OUI (0 I.. 1- GI I.. GI (.I I.. (/) c U) c co o (1! O Q)'§ Q)"i:;: E co E (1! co o (1! o (/) .- cn c O "iO' :5; la ... .a 3 () -1/1 Q) cca 0ot -Q) ~a. "Ce Ea. !- ui Q) (I) Q) .c c ~ ro a. .~ Q) Ca "0 Q) u ro a. .§ .?:~ c Q) O a. (I) 2 .ih O Q) .Q E ~ Z Qj O Z u 2 "Qj Q) ~ Q) > "0 =m O u 2 "Qj Q) ~ Q) > o "0 m =c O c .Q -co c .E O:i "Qj "0 (,i c .Q '§ Q) a. o ~ c ~ (.) P. Q) :c m '5 ~ -co "' u m a. .§ Co c Q) a.>a.m~ >-= =0 "00 ma) Q)t a:m ..a. 2?;a: ~u. Q)U -gCO ~C') . C £ .~ iIj c o ~ Qj c. o 9 -g 10 ~ (/) U Q) ::= Q) U ~ Ec. '5>. c.-Q) ~~ 0= -0 ()o Q)a) .= "t: "C CO ea: -u. Uu CO - Q)::= ~ Q) "C co () Q) Q) > Q) Q) (/) (/) ~ >-~ ="C .~ co c =~ Q) 0 0= CO C 0 C.u ..~ 5"G) .m Q) E ~ Q) Q) E~ 0 CO () 0 Q) C .a= go m ; C; Q) -C 0.- C.E Qj -a; "C O o CX) t= ca a. a: u. ~ (') >.c "0 Q) .s "Q) "0 ~ U) . cC:-Q) o ; > ~ 0 Q) l) c.~ ca o -0 l) l) Bi6 "0"0 Q) Q) i6-a; ~"Q. U) E .!C) C .- C -C Q) .-> l)Q) 0 ~ > .-C "0.- 0- .-0 ~ ca -C) l) .Q) .--= .= E "0>E- . ca .g~ U).c i3 .--= ca ~ c.= Ei3 .-Q) Q)::: U) Q) Qj Q) > ~ Q) Q)"0 ~ -g~ >Q) 0 C/) C .0 ;.-; 0 ca .-C ca .- ~E Qj -a; "0 CULTURALRESOURCES 263 With the closure of Glen Canyon Dam in 1963,the pattern of deposition, erosion, and flooding on the Colorado River through Glen and Grand Canyons was changed forever. As a result, general loss of river-deposited terraceshas occurred. Archeological sites and traditional cultural properties once protected by sandbars and terraceshave become increasingly exposed to erosion by the river and rainfall-induced terrace erosion (seefigure 111-22). The postdam river cannot rebuild high terraces, resulting in more site erosion than occurred during the predam environment (seediscussion of high terracesin chapter III, SEDIMENT) .The 1983-86floodflows were known to causedirect erosion of terraces. Extreme rainfall conditions during 1978-85led to acceleratederosion of archeological sites and traditional cultural properties. Becausethe dam traps sediment and reduces floods, little or no sediment is deposited at the mouths of small ephemeral tributary streams,which makes the situation worse. Only low elevation sediment deposits can be replenished in the postdam environment. Large sediment-laden floods may rebuild the basesof high terracesat most locations but erode terraces at other locations. The initial impacts to archeological sites and traditional cultural properties began with the construction of Glen Canyon Dam and the resulting changein the amount and distribution of sediment. Thesesites depend on the terracesthat have formed along the river corridor. Without a mechanism for sediment augmentation and redeposition to predam terrace levels, all alternative operations would impact cultural resources. None of the action alternatives considered in this EIS could alter the basic change in postdam sediment input to the system; thus, it is expected that dam-related impacts to archeological sites would continue regardless of alternative flow patterns. Theseimpacts are permanent; the damage irretrievable. However, the rate at which impacts would occur could be affected by alternative operations, principally through flood frequency reduction measures. Many of the traditional cultural resources (especially riparian plant and animal species)also depend on sandbars and terracesalong the river. The alternatives that allow for maximum growth and protection of the riparian habitat also would favor protection of these traditional resources. Postdam changesin the riparian ecosystem within Grand Canyon have favored growth of NHWZ vegetation, while OHWZ vegetation is thought to be declining (chapter Ill, VEGETAnON). The net effect of these changesin riparian vegetation is still in a dynamic state; however, some of the traditional resources(willows, giant reeds,yellow warblers, yellow-throats, and other plants and riparian birds) have clearly increased since construction of the dam. Although none of the action alternatives would influence OHWZ vegetation, the extent of the NHWZ-and thus the abundance of some traditional resources-would be affected by alternative discharge patterns. It is important to note that the alternatives that restrict maximum flows to less than powerplant capacity (33,200cfs) would allow an increasein NHWZ vegetation during low water years. During moderate and high water years, water releasescould increaseto a maximum of 33,200cfs, thus limiting the area of sediment deposits available for vegetation growth. One well-known traditional cultural property located within the river corridor, the salt mines and associatedsediment deposits, would be better protected by alternatives that allow sediment accumulation on the sandbar at the base of the mines. Generally, alternatives that have the capability to maintain the sediment balance and allow for sediment distribution along the river corridor would enhancelong-term preservation of cultural resources. Although sediment transport is variable and depends on flow regimen, alternatives that would most likely produce a net positive sand balance in the system-while maintaining a high baselevel of sediment deposition-would be most favorable. The alternatives listed below would allow for a net positive sediment balance in the system and the possibility of sediment redeposition in areasthat would protect cultural resources: 264 Chapter IV Environmental Consequences .Moderate, Modified Low, and mterim Low Fluctuating Flow Alternatives .All steady flow alternatives Sediment deposition is a critical factor in preserving terracesand related deposits that contain cultural resources. This is particularly true in the areasbetween Glen Canyon Dam and the LCR, where predam terraces are often in direct contact with the river. Although impacts to some sites would still occur due to the existenceof the dam, it is likely that the rate of impact would be less than under no action. Of the elements common to all restricted fluctuating flow and steady flow alternatives, the most important for cultural resource protection is flood frequency reduction. The flood releasesduring 1983-86caused direct erosion of approximately 33 archeological sites and scoured or buried a large portion of the riparian vegetation in the NHWZ. Another uncontrolled flood of that magnitude and duration (4 plus years) could severely damage or destroy certain archeological sitesprincipally in Glen and Marble Canyons- and temporarily destroy riparian vegetation. Adopting flood frequency reduction measureswould reduce the risk of uncontrolled flooding, thereby helping to preserve the river's physical cultural history . The concept of adaptive management has implications for cultural resources. National Historic Preservation Act requirements recommend a longterm monitoring program (through a programmatic agreement and historic preservation plan) to assesschanging conditions of cultural resources. Long-term monitoring is now required under the Grand Canyon Protection Act of 1992. These assessmentsof site integrity and stability offer mechanismsfor remedial actions which include site-specific mitigation along with management alternatives which could affect the entire system. The actions described in the programmatic agreement and accompanying monitoring plans are common to all alternatives (attachment 5). Unrestricted The habitat maintenance and beach/habitatbuilding flows described in chapter II might benefit some of the cultural resourcesin the system. Adding sediment at the mouths of tributaries and creating sandbars at slightly higher elevations is a systemwide approach to rebuilding and slowing the erosion of the high terracesupon which the sites depend. Although more researchis needed on the successof these flows, creation of stable sandbars-even at lower levels-could result in a more stable situation for predam terraces. Flows No Action Alternative Archeological Sites. Under no action conditions, continued degradation and eventual loss of significant prehistoric and historic archeological sites would occur. It should be noted that all archeological resourcesare nonrenewable, and damage to them is both irretrievable and irreversible. Impacts to these sites are categorized as follows: .Direct .Indirect Reduced flood frequency is included in all of the alternatives except no action and maximum powerplant capacity.It is assumedthat with flood control, flows greater than 45,000cfs would not occur more often than once in lOOyears on average,except for beach/habitat-building flows. Fluctuating .Potential impacts = 33 sites impacts = 124 sites impacts = 179 sites The potential for degradation of al1336 archeological sites would continue due to the loss of sediment in the system, arroyo-cutting through predam river-deposited terraces,and the risk of uncontrolled flooding. Sediment erosion and arroyo-cutting are linked to archeological site erosion. Impacts from the dam and its operations have occurred since 1963,with direct and indirect damage documented for 157sites. Continuation of dam operations under the No Action Alternative could lead to the eventual loss of all 336 sites identified within the river corridor . Postdam operations have had deteriorating effects on a National Register property-the Charles H. Spencerpaddle wheel steamboat-due to exposure. The fluctuating flows causeconstant CULTURALRESOURCES 265 wetting and drying of the steamboat that has led to its deterioration. Low flows have allowed additional damage to the steamboatby visitors who use parts of the steamboat (the boiler) for recreational purposes (fishing). The 1983-86clear-water floods were detrimental to some archeological sites. The risk of flooding remains unchanged under this alternative, and all 336 sites have the potential to be damaged or destroyed. Site-specificmitigation is possible for some sites within the river corridor. Specificsof mitigation are discussedin the documentation found in attachment 5. Native American TraditionalCultural Propel1ies. The river corridor has been used traditionally over hundreds or thousands of years by the native peoples of the region. The Colorado River, its tributaries, the canyons through which it flows, the canyon rims, and the mountains and plateaus that surround them form a sacred landscape that is culturally significant to the Indian Tribes with ties to Grand Canyon. Within this landscape are specific places, ranging from archeological sites to mineral collection areas,considered important for a variety of reasonsby each tribe. The locations of these traditional cultural properties are sometimes closely held secrets,and it is often with reluctance that tribes reveal specific sites. In addition to archeological sites, a number of traditional cultural properties have been identified for this EIS..However, there are additional areas whose locations have not been revealed becauseof their sensitive nature. In addition to the specific sacredsites or locations, other natural resourcesof significance are found in the Colorado River corridor. Although these resourcesmay be linked to specific locations, some are place-independent or encompassnumerous locations. They also may have spiritual meanings. Most natural resources are considered sacredby Indian Tribes, and some resourcesare vital for the continuation of traditional cultural practices. In general, no action conditions have fostered the growth (over predam conditions) of many culturally important riparian plants and animals as well as many speciesof birds of prey. This growth is primarily due to the lack of annual scouring floods and the increasein the NHWZ vegetative community .Under no action, however, the 1983-86floods resulted in removal of approximately 40 percent of NHWZ vegetation that had established since closure of the dam (see VEGETATION in this chapter). Havasupai.-Many traditional cultural properties are associatedwith the Havasupai Tribe. Locations that contain archeological remains have been discussed above. In addition to theseplaces,traditional cultural properties and resourcesalso have been identified. Under the No Action Alternative, degradation would continue to the archeological sites identified as ancestral for the Havasupai. In addition, degradation of the entire ecosystemwould be allowed to continue, seriously impacting Havasupai uses of the area. Hopi.- The entire Grand Canyon and its immediate surroundings are of universal importance to the Hopi people. Specific places and conceptslinked to Grand Canyon are referenced in daily prayers and playa profound role in Hopi ceremonial activities. The very presenceof Glen Canyon Dam and its effect on the environment have a detrimental influence on Hopi lifeways. It is Hopi belief that if the natural and cultural elements of the canyon are being damaged by dam operations, daily prayers also are damaged and less effective. Hopis believe that natural erosion is an integral processin the Grand Canyon environment, but this is distinguished from the erosion causedby dam operations. Hopis believe that Glen Canyon Dam should be operated to minimize humanmade erosion. Within the canyon, both natural and cultural features are considered important. All springs are considered sacred to the Hopi people. Also sacred are the Hopi Salt Mines and the sand at its base. All biological resourcesare considered important, especially birds with yellow feathers, endangered and candidate species,aquatic organisms, and vegetation found in marsh and riparian habitatsespecially reeds, willows, and cattails. 266 Chapter IV Environmental Consequences Under the No Action Alternative, continued degradation of the canyon's resourcesof Hopi concern would occur. Although considered a rare event, the situation that resulted in the floods of 1983-86would be allowed to continue. Damage to archeological sites would continue, as previously discussed. Riparian habitat for the yellow birds would decline in quality and quantity. Ecological stability would not occur. Marsh habitat for reeds and cattails would continue to degrade. Although during nonnal operations the immediate area around the Hopi Salt Mines would not be affected, the sand at the baseeventually would be lost. Someendangered speciesmay be impacted by no action. For example, opportunities for humpback chub to recover from jeopardy would not occur, and existing chub populations may decline further; wintering bald eaglesat Nankoweap Creek may decline due to lack of food resources (inability for trout to accesstributaries); willow flycatcher populations may continue to decline due to lack of habitat. The Hopi people believe that during their migration their ancestorsleft behind archeological sites, potsherds, rock art, and other archeological materials to serve as markers that the Hopi people had fulfilled their pact with Ma'saw. Thus, the archeological record servesto validate the cultural claim of the Hopi people to the landscape. The erosion of archeological sites in Grand Canyon would diminish the cultural ability of the Hopi people to interpret their past as evidenced by thesemarkers. Under the No Action Alternative, the erosion that would damage archeological sites and sacred ancestral graves remains a threat. The No Action Alternative would be more damaging to resourcesof Hopi concern than any other alternative except the Maximum Powerplant Capacity Alternative. Hualapai.-Many traditional cultural properties are associatedwith the Hualapai Tribe. Those locations that contain archeological remains have been discussedpreviously. Traditional cultural properties not associatedwith archeological remains also have been identified and are discussedbelow. Resourcesfound in the natural environment are considered traditional cultural properties by the Hualapai people. The deserts,plateaus, mountains, and valleys are considered important, as well as the botanical resourcesand wildlife. Plants have usesboth for horticultural and medicinal purposes. Specific locations within the canyon have significance as places for religious or ceremonial activities. Specific plants important to the Hualapai people include cattails, willows, arrow weed, mesquite, catclaw, agave, and yucca. Bighorn sheep,deer, elk, and a variety of other mammals are resources traditionally used by the Hualapai. Numerous side canyon locations, along with mineral collection areasand springs, are sacredplaces to the Hualapai. Springs, such as Honga, and collection areasfor minerals, such as hematite, also are sacred places. Under the No Action Alternative, degradation of the river corridor would continue and result in the continued loss of archeological places identified as ancestralto the Hualapai, along with the continued loss of resourcesconsidered traditional cultural properties. All resources- natural, cultural, and spiritual-would be impacted by this alternative. Navajo.-Navajo residents of Grand Canyon area have identified many separatelocalities that represent traditional cultural properties. In addition to archeological sites and the larger landscape of which they are a part, more specific places of traditional significance also have been identified. Twelve such places are within the area of potet:1tialimpact, and many more have been identified immediately outside the impact area. Theseplaces include various kinds of trails or routes into the canyon, the salt mines, prayer offering locations, river crossings,places associatedwith stories of holy beings or historically significant figures, plants used for medicinal and subsistencepurposes, minerals used for secular or sacredpurposes, winter camps, cornfields, livestock grazing areas,places where people hid from enemies,areaswhere people CULTURALRESOURCES 267 lived during drought years, and places in side canyons where water may be collected. Specific plants and animals in and around Grand Canyon also are important to the Navajo people. Plant life of importance includes beargrass,agave, monnon tea, mullen, cholla and prickly pear cactus,snakeweed, datura, filaree, four 0' clocks, dogweed, narrow leaf, and banana yucca. Important wildlife (and habitat) include bighorn sheep,deer, turkey, coyote, beaver, fox, and mountain lion. Birds such as red-tailed hawks, owls, eagles,and falcons also are considered important to the Navajo people. The existenceof cultural resources,including plants and wildlife in the Colorado River corridor, depends on the beachesand terracesthat support them. Theseresourcesare components of a dynamic ecosystemthat erodes and rebuilds as part of a natural process. Cultural resourcesare exposed,buried, and even eroded away as part of this process. Their natural erosion and disappearanceare not considered negative impacts by the Navajo Nation. Human-induced changesthat result in the loss of resourcesare not viewed as part of this natural process,however. The Navajo Nation believes that the negative impacts of human interference with natural processesmust be controlled. While the No Action Alternative has only a minimal direct impact on cultural resourcesimportant to the Navajo Nation, the lack of flood control makes this alternative potentially more damaging than those alternatives with flood protection. Southern Paiute.-Hundreds of archeological sites, several traditional cultural properties, and numerous other areasof cultural significance to the Southern Paiute are located within the Colorado River corridor. Sometraditional sites have already been lost due to erosion. Other sites are near the water, and under alternatives that allow unrestricted fluctuating flows these sites would be destroyed. Southern Paiute people believe that their ancestorsleft things in the river corridor for a purpose. They believe that those things will return to the earth naturally, but impacts on them resulting from dam operations should be stopped. Southern Paiutes differentiate between impacts that are due to natural causes and those that are the result of human activities. Sixty-eight speciesof plants found within the canyon were used traditionally and are currently used for food, medicine, ceremony, construction, and other purposes. Younger generations continue to be instructed about their traditional uses. The Southern Paiutes support alternatives that will minimize flooding, erosion, and removal of vegetation. Southern Paiute people believe that under the unrestricted fluctuating flow alternatives many plants would continue to be negatively affected. Southern Paiutes also are concerned with the effects of water releasepolicies on tourist behavior in the Colorado River corridor. As the water from Glen Canyon Dam erodes more and more beaches,tourists are forced to camp at fewer and fewer places. When tourists camp, they walk around and pick up Native American artifacts and trample, clear, and pick vegetation. Under the No Action Alternative, the beachesavailable to tourists would continue to disappear, and impacts to cultural resourcesat the remaining beaches would grow worse. The Southern Paiutes support alternatives that reduce erosion to beachesand tourist camping spots and recommend that problems causedby tourists be addressed. Zuni.-The Zuni Tribe has many ties to the canyon, and many ancestral archeological sitesas well as other locations and resourcesof traditional and cultural importance-are known to be located along the Colorado River and the LCR. Under the No Action Alternative, serious degradation of ancestral archeological sites, traditional cultural properties, and other culturally important resourceswould occur. The Zuni Tribe is in the processof identifying cultural resources of importance to the tribe within the study area. When thesestudies are completed, the Zuni Tribe will be able to more fully assessimpacts to the resourcesand traditional and cultural values. 268 Chapter IV Environmental Consequences Maximum Powerplant Capacity Alternative Under this alternative, degradation of archeological sites and traditional cultural properties and resourceswould be the same or worse than under no action. Loss of sediment and channel margin deposits would continue. More frequent high flows of up to 33,200cfs would acceleratethe loss of sediment from the system, hastening the loss of cultural resources. Arroyo-cutting through high terraces,which is linked to archeological site erosion, would continue. Impacts to all 336 archeological sites identified within the river corridor would be likely to occur. Impacts to traditional cultural properties of all tribes also would continue under this alternative (table IV-13). For example, impacts to the Hopi Salt Mines would continue due to the lack of flood frequency reduction measures. With increased high flows and wider fluctuations, it is possible that the sand at the base of the mines would be eroded away-a serious impact to the Hopi people. Similar impacts would occur to other resourcesidentified as traditional cultural properties for all the tribes. Impacts on traditional cultural resourcesfollow the patterns discussedin those sectionsof this document (seeFISH, VEGETAnON, WILDLIFE AND HABITAT, and ENDANGERED AND OTHER SPECIAL STATUS SPECIESin this chapter). With the increased range of flows under this alternative and no reduction in flood frequencyI there would be a high probability of net loss of sediment in the system. This loss would likely result in damage to traditional cultural properties and resourcesand would createconditions similar or more adverse than those under the No Action Alternative. Restricted Fluctuating Flows Degradation of archeological sites and traditional cultural properties and resources would decrease from no action primarily due to flood frequency reduction measures. The probability of net loss of sediment would be less than under the No Action or Maximum Powerplant Capacity Alternatives. Arroyo-cutting of high terraces,which is linked to archeological site erosion, would continue. Flood control measuresincluded in all restricted fluctuating and steady flow alternatives would provide increased protection of these resources. Physical cultural resourceswithin the river corridor are linked to sediment. Flows that cause a net decreasein stored sediment also will hasten deterioration of the cultural resourcesdependent on it. SinceGlen Canyon Dam blocks the downstream passageof sediment, typical maximum flows less than 20,000to 22,000cfs appear to provide the best opportunity for a net positive balance of sediment in the system. Minimum flows of 8,000cfs or more would provide the best protection for the Charles H. Spencersteamboat located upstream from Lees Ferry . Site-specific mitigation would sites considered to be directly, potentially impacted by these Specifics of mitigation actions section 106 compliance, found be required for all indirectly, or alternatives. are included in the in attachment 5. Existing impacts to traditional cultural properties would be reduced under the restricted fluctuating flow alternatives becauseof the flood frequency reduction measuresadded to these alternatives. Theseare measureswhich would lengthen the time between scouring floods (from an average 1 in 40 years to 1 in 100years), resulting in increased growth and stability of NHWZ riparian habitat. High Fluctuating Flow Alternative Under this alternative, degradation of archeological sites would be less than under no action becauseof the flood frequency reduction measuresdiscussedabove. However, high fluctuating flows could continue to causenet loss of sediment, similar to the No Action and Maximum Powerplant Capacity Alternatives. Maximum hourly flows would be greater than 21,000cfs 62 percent of the time and greater than 25,000cfs 47 percent of the time. The relatively high frequency of these flows may not allow 270 Chapter IV Environmental Consequences greater than 21,000cfs 4 percent of the time and greater than 25,000cfs 2 percent of the time. This would likely allow sediment to accumulate in the river during most years. Beach/habitat-btillding flows between 30,000and 45,000cfs would help maintain sandbars,which protect high terraces and archeological sites. Impacts on those sites directly impacted by postdam operations would continue; however, the likelihood of additional impacts to those directly and indirectly impacted sites would lessen. Effects on potentially impacted sites that lie within predam river deposits would continue. Traditional cultural properties within the river corridor would continue to be impacted under this alternative, although impacts would be less than under no action. However, with lower maximum releases,fewer impacts would occur to resourcesvalued by the various Indian Tribes. Those biological (riparian habitat, wildlife) and mineral resourcesthat have been identified as important traditional cultural resources would be protected or enhanced to a greater extent under the controlled flows of this alternative than under no action. Steady Flows Impacts on cultural resourceswould vary under the steady flow alternatives. Degradation of archeological sites and traditional cultural properties would decreasefrom no action primarily due to flood frequency reduction measures. The probability of net loss of sediment would be less than under the No Action or Maximum Powerplant Capacity Alternatives. Arroyo-cutting of high terraces,which is linked to archeological site erosion, would continue. Flood control measureswould provide a potential measure of increased protection to these resources. Physical cultural resourceswithin the river corridor are linked to the sediment resource. Flows that acceleratesediment erosion also would hasten the deterioration of cultural resources. Flows less than 20,000to 22,000cfs appear to provide the highest probabilities for a positive net sand balance in the system. Minimum flows greater than 8,000 cfs w ould provide the best protection for the Char! es H. Spencersteamboat, along with providing a relatively stable sediment base level. Those biological (riparian habitat, wildlife) and mineral traditional cultural resources that have been identified as important to Indian Tribes would be protected to a greater extent under the steady flow alternatives than under no action. Site-specific mitigation would be required for all sites considered directly, indirectly, or potentially impacted by these alternatives. Specifics of mitigation actions are included in section 106 compliance, found in attachment 5. Existing Monthly Volume Steady Flow Alternative Degradation of archeological sites would continue under this alternative but would be less than under no action due to the higher probabilities of a positive sand balance in the system. Flows would be expected to exceed20,000cfs 7 to 17 percent of the time. This would likely allow sediment to accumulate in the river during most years. Beach/habitat-building flows between 26,300and 45,000cfs would help maintain sandbars, which protect high terracesand archeological sites. Effects on those sites that have been directly impacted by postdam operations would continue; however, the likelihood of additional impacts on those sites and indirectly impacted sites would lessen. Effects on potentially impacted sites that lie within predam river deposits would continue. Impacts on traditional cultural properties under this alternative generally would be less than under no action becausesediment loss would be slowed. Similarly, traditional cultural resources would tend to be enhancedby the greater security of the riparian zone due to reduced flood frequency, positive sediment balance, and potentially greater area of riparian habitat. AIR QUALl1Y Seasonally Alternative Adjusted Steady Flow Under this alternative, degradation of archeological sites would continue but would be less than under no action due to the higher probabilities of a positive sand balance in the system. Effects on those sites which have been directly impacted by postdam operations would continue; however, the likelihood of additional impacts on those sites and indirectly impacted sites would lessen. Effects on potentially impacted sites that lie within predam river deposits would continue. Flows would be expected to exceed20,000cis 5 to 27 percent of the time. This would likely allow sediment to accumulate in the river during most years. Habitat maintenance and beach/habitat-building flows would help maintain sandbars,which protect high terracesand archeological sites. Impacts on traditional cultural properties and resources would be the same as those described for the Existing Monthly Volume Steady Flow Alternative. Year-Round Steady Flow Alternative Degradation of archeological sites would continue under year-round steady flows but would be less than under no action due to the higher probabilities of net positive sand balance in the system. Effects on those sites directly impacted by postdam operations would continue; however, the likelihood of additional impacts on those sites and indirectly impacted sites would lessen. Effects on potentially impacted sites that lie within predam river deposits would continue. Flows would be expected to exceed20,000cfs 8 to 12 percent of the time, allowing sediment to accumulate in the river during most years. Beach/habitat-building flows between 21,400and 45,000cfs would help maintain sandbars,which protect high terracesand archeological sites. The probability of a net positive sand balance would be very high. Although sediment deposition would not be substantial enough to increasethe stability of the sediment deposits, erosion of terracesin direct contact with the river would be reduced. 271 Impacts on traditional cultural properties and resources would be the same as those described for the Existing Monthly Volume Steady Flow Alternative. AIR QUALITY Impacts on air quality in the immediate Grand Canyon vicinity and acrossthe region served with Salt Lake City Area Integrated Projectspower were evaluated for each alternative. Although hydroelectric power production at Glen Canyon Dam has no direct influence on air quality , a change in its operations would affect the electrical power system of which it is a part. Glen Canyon Dam historically has been used to produce peaking power. If it were used as a baseload or base-assistfacility instead, another source of peaking power would be required to generate the amount of peaking power that could not be compensatedfor through conservation or renewable energy technologies. If the alternative source of power used fossil fuel, there would be a net change in system emissions, either in the region or somewhere in the Salt Lake City Area Integrated Projects marketing area. Fossil fuels contain hydrocarbons, whose combustion can result in emissions of such atmospheric pollutants as sulfur dioxide and nitrogen oxides. Natural gas combustion turbines are a common type of facility used to produce peaking power . Like hydroelectric generators, gas combustion turbines can be used to follow load during peak periods of demand. Natural gas is a hydrocarbon 272 Chapter IV Environmental Consequences fuel, but is relatively clean compared to coal. Although it might be necessaryto use gas turbines to replace peaking power if dam operations are changed, it is also likely that Glen Canyon Powerplant would be used to replace power production at baseload or base-assistfacilities, many of which bum coal. It is also possible that a change in operations could influence the schedule for adding new baseload facilities to the power system (seeHYDROPOWER in this chapter). Emissions from coal combustion usually have components of 5O2 and NOx in greater amounts than emissions from natural gas. Analysis Methods This EI5 considered 502 and NOx emissions and factors such as the Clean Air Act provisions mandating a national ceiling on such emissions. Information on other substances-such as carbon monoxide and particulates-was not available for this EI5. However, numbers for 502 and NOx can be considered representative of changesin carbon monoxide and particulate concentrations. Impacts to regional air quality were evaluated as part of the power systems analysis for the draft EIS. This analysis showed less than a I-percent change in emissions under any alternative. However, it was later found that the analysis did not correctly account for the reduction in emissions at other locations within the region. The analysis procedure was corrected, and the preferred alternative was reanalyzed for this final EIS. The analysis does not specify the location and concentration of atmospheric pollutants. Emissions could have an influence on the air quality in Grand Canyon and the other national parks on the Colorado Plateau, all of which are classI areas (chapter III, AIR QUALITY). However, the source of emissions would not necessarilybe in the immediate vicinity; it could be elsewhere in the load control area. If there were not enough peaking power capacity within the region and it becamenecessaryto construct a new facility , it would be necessaryto conduct a new source review. However, in this analysis it is not as important to know the source as it is to understand the relative tradeoffs of different alternatives and their influence, in terms of emissions and their relative influence on air quality . The first 5 years of operation under each alternative and how that operation would influence air quality are defined as short-tenn impacts. Since modeling results did not provide emissions estimatesfor a 5-year period, this analysis looks at what short-tenn system expansion might be needed and how that expansion would influence, in qualified tenns, system emissions. For the long-term period of analysis, emissions representing a SO-yearperiod and acrossthe regional power grid area are evaluated. This emissions analysis includes assumptions for power system expansion plans. Emissions would vary by alternative becauseeach would require a different power system expansion plan. The impacts are speculative in that changesover the SO-yearperiod are possible in power generation technology, demand for power, public attitudes, and political and economic climates. Summary of Impacts: Air Quality The geographic area of potential impacts would be the same as for hydropower-the Salt Lake City Area Integrated Projects service area, which includes all or part of Wyoming, Utah, Colorado, Arizona, Nevada, and New Mexico. Glen Canyon Dam is in the samepower system as the Navajo Generation Station, which was identified as a source of Grand Canyon air quality problems and is scheduled to be modified to reduce emissions, beginning in 1995. Navajo Generating Station is independent of Glen Canyon Dam operations, and its modifications will be made regardless of which EIS alternative is implemented. Grand Canyon air quality would likely improve due to the modifications at Navajo Generating Station no matter which alternative is selected. Table IV-14 presents impacts on air quality that would likely result from each alternative. The Q) .~ 1U El Q) = cu ~I cn .~ ~ c: cu O "C O .t: Q) 0. ... cu Q) >61 Ln Q) £ C) c: .t: :J "C ~ :J « => O a: ;( c: O cn ~ 0. .E "C Q) 1U 0. .u "+:: c: cu O ~ cu E E :J I ..;f .~ Q) :c ~ "0 ~ c o j011. a:> ."0 ..IV Q) IV Q)... > '/I ~,,~ - > " ~ o (/) 11. 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Unrestricted Fluctuating Flows No Action Alternative Glen Canyon Powerplant is used as a peaking power facility , but it is part of a regional power system that is made up of both hydropower and fossil fuel plants. Power production at the dam varies annually based on the volume of water available to pass through the turbines. It is anticipated that demand for power from the system will increase,but most short-term increasesin demand can be absorbedby greater energy efficiency. It is also anticipated that, by as early as 1995,gas combustion turbines will be added to the power system to replace older and inefficient facilities. Sincenatural gas is a cleaner fuel than coal, these additions probably will reduce system emissions over the short term. In the long term, the need for additional baseload coal-fired capacity is anticipated. The emissions of the power system for the entire period would be approximately 2 million tons of 502 and 2 million tons of NOx. would be needed sooner than under no action. New powerplants would produce less emissions than existing plants becauseof today's more restrictive emissions standards and becausesome of these new powerplants would bum natural gas. Although total emissions from all new and existing powerplants may increase during the day, there would be an even greater reduction of emissions at night becauseGlen Canyon Powerplant and additional new, more efficient powerplants would be producing more power at night. Therefore, the net effect on regional air quality under all restricted fluctuating and steady flow alternatives would be a slight reduction in emissions. Additional power modeling studies completed since the draft EIS for the preferred alternative support this conclusion. The analysis predicted that total emissions of SO2would be reduced by 100,000tons, and emissions of NOx would be reduced by nearly 80,000tons over a 20-year period relative to the No Action Alternative. RECREATION Maximum Powerplant Capacity Alternative Power production under the Maximum Powerplant Capacity Alternative would be essentially the same as that under the No Action Alternative. Restricted Fluctuating Flow Alternatives and Steady The restricted fluctuating and steady flow alternatives would reduce the amount of electrical energy produced during the day and correspondingly increasethe amount of energy produced at night. This would mean that as demand for electrical energy increases,additional powerplants Discharge from Glen Canyon Dam affects recreation through its influence on flow-sensitive attributes or through changesin the recreation environment. Impacts on recreation would range from regional to international in scope. RECREATION 275 Analysis Methods Fishing Recreation would be impacted immediately by changing discharge, and impacts would occur over both the short and long term. Water years 1989,1987,and 1984are used for analyzing impacts under low, medium, and high annual water releaseconditions. For fluctuating flow alternatives, the magnitude of impacts associated with daily fluctuations for low, moderate, and high releaseyears are compared using certain representative days in those years (figure 11-7). Typical conditions, rather than exceptional ones, are evaluated under each alternative. Impacts may be similar for most alternatives during high water years, while quite different during low and moderate water years. Fishing trip quality for most anglers in the Glen Canyon reach is highest during moderate, steady dischargesbecausethey believe such discharges improve several attributes of fishing trips. Impacts on the recreation environment, the resource upon which the activity is focused or dependent, are long term (20 to 50 years). Analyses of impacts on resourcesupon which recreation depends are discussed elsewhere in this chapter (primarily SEDIMENT, FISH, and VEGETATION) and will be only referencedin this section. Summary of Impacts: Recreation The impacts of the alternatives on recreation activities are summarized in table IV -15. Numerical values are listed where possible; otherwise, qualitative assessmentsare made. Impact assessments for many activities are based on rankings of alternative operational scenariosin a study of visitor preferencesby Bishop et al. (1987). Each alternative was ranked as more or less favorable for recreation overall and for each indicator activity. As discussedin chapter III, indicator activities are fishing, day rafting, white-water boating, and lake facilities and activities. Effects of habitat maintenance flows are discussed under the three alternatives that include them. Basedon preferencesdetennined by the Bishop et al., study, net economic values also were estimated for each alternative. Net economic benefits are discussedunder "Economics of RecreationalUse" at the end of this section. Anglers using the Glen Canyon trout fishery place a high value on catching large fish (chapter III, RECREAnON). It is believed that under the fluctuating flow alternatives with a wide range of daily fluctuations, trout would be less likely to reproduce and survive until they reach trophy size. Under the Moderate, Modified Low, and Interim Low Fluctuating Flow Alternatives, the potential for catching large fish would increase, and, therefore, fishing trip quality also would have the potential to increase. The steady flow alternatives are believed to have the greatest potential for benefiting aquatic productivity, which could result in trophy-size fish. Rapid stage change puts wading anglers in Glen Canyon at risk of inundation. If their waders are filled with water, it becomesdifficult for them to wade or swim toward shore. In the alternatives without ramp rate restrictions, stage can increase within 20 minutes by 0.62foot at Lees Ferry and by 0.88 foot at the dam (the latter is more representative of the reach). This risk would be reduced under the alternatives with ramp rate restrictions and would be eliminated in the steady flow alternatives, as shown in table IV-16. During high water volume years, fluctuations would be at a minimum under all alternatives. High water velocity may present hazards to wading anglers, but they also would be able to assessrisk before putting themselvesin a hazardous position. There are 18 camping beach sites potentially available in Glen Canyon; only 6 of these are formally designated campsites. Six others are available only at discharges of less than 15,000cfs. 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Altemative 277 -Stage change in the Glen Canyon reach by alternative Stage change per day at Lees Ferry Maximum 20-minute Maximum 20-minute stage change at Lees Ferry stage change at Glen Canyon Dam (feet) (feet) (feet) 0.88 0.88 0.88 0.50 0.30 0.30 0 No action Maximum powerplant capacity 4.5 0.62 4.5 0.62 High fluctuating flow Moderate fluctuating flow Modified low fluctuating flow Interim low fluctuating flow 4 0.62 2.5 0.24 1.5 0.10 1.5 0.10 Existing monthly volume steady flow 0 ° Seasonally adjusted steady flow Year-round steady flow 0 ° 0 ° primarily becausemost fishing activities take place from boats or shore. Historically I trout spawning successhas been adequate to maintain the downstream trout fisheries without depending on stocking or restrictive management of fishing activities. Trout population successwould likely continue under all alternatives. This issue is discussedin this chapter under FISH and will not be tracked further in this section. 0 0 However, there is no significant preference by users as to the origin of their trip (Bishop et al., 1987),so impacts would be negligible. All alternatives are thought to have similar influences on day rafting, and habitat maintenance flows are unlikely to have any impact on the quality of day rafting below Glen Canyon Dam. Since this is not a significant issue, it will not be tracked further . White- Water Boating Day Rafting Boatersin the Glen Canyon reach, most of whom are anglers, have difficulty navigating 3-Mile Bar when discharge is 3,000cfs or less (U.S.Department of the Interior, 1990). Most boaters are unable to move up or downstream, and some of those attempting to navigate the channel hit rocks and sustain boat and motor damage. Difficulties typically occur during morning hours, a popular fishing time. Boaterswould have navigation problems under the No Action, Maximum Powerplant Capacity, and High Fluctuating Flow Alternatives. The other fluctuating flow alternatives, which have minimum flows of 5,000cfs, would eliminate navigation and safety impacts for most day rafters and other boaters. Steady flow alternatives should make 3-Mile Bar passableto all boaters. Day rafters in Glen Canyon benefit slightly by launching at the dam rather than at LeesFerry White-water boaters prefer moderate fluctuations and steady flows becauseof their influence on important trip attributes, including itinerary , character of rapids, wilderness values, and boat management at camp. White-water boaters were asked to rank several operational scenariosin the Bishop et al. (1987)study. Of the EIS alternatives, the steady flow alternatives would be most similar to the preferred scenarios. Fluctuating flow alternatives with daily range and ramp restrictions and S,OOO-cfs minimum flows would be more tolerable than those without. Wilderness values are influenced by daily fluctuating flows. When the river undergoes wide daily fluctuations, most river-runners are aware of these fluctuations and feel they make the trip seem less like a natural setting (Bishop et al., 1987). Thesefluctuations are unlike the predam fluctuations that resulted from tributary and side canyon flooding. Fewer river-runners would be aware of the daily fluctuations under alternatives 278 Chapter IV Environmental Consequences with more restricted daily ranges. Noticeable fluctuations would decreasewith distance below the dam becauseof wave transformation (see chapter III, WATER). Under the steady flow alternatives, more river-runners would feel that the river provided a more natural setting than fluctuating flows, thus improving wilderness values. mile in noncritical (wide) reaches. Steady flow alternatives would have 0.9 site per mile in critical reachesand 1.1sites per mile in noncritical reaches. The number of sites is not fixed through time but is affected by sediment erosion and deposition and vegetation encroachment. These factors vary among alternatives (seeSEDIMENT and VEGETATION in this chapter). An index of white-water accident risk, developed by Brown and Hahn (1987),was used to compare safety of alternatives. Specific assessmentswere made for private and commercial groups. The No Action and Maximum Powerplant Capacity Alternatives have the highest overall risk index becausethey would have more time at low flows, when accident potential is great for commercial motor and small oar-powered craft. The probability of people going overboard is highest at dischargesthat exceedpowerplant capacity (Brown and Hahn, 1987).Risk would be reduced most under the steady flow alternatives, while the restricted fluctuating flow alternatives would reduce risk half as much. Over the long term, under all alternatives including no action, debris flows would continue to be a factor in boater safety.All alternatives improve safety relative to no action becauseof higher minimum flows. The size of a particular camping beach would be highly variable depending on flow, as determined by the maximum daily discharge. In most years, campable area would average 7,720square feet or less under the No Action, Maximum Powerplant Capacity, and High Fluctuating Flow Alternatives; more than 7,720square feet under the restricted fluctuating flow alternatives; and up to 9,200square feet under the steady flow alternatives. Site size is not fixed through time but is affected by sediment erosion and deposition and vegetation encroachment (seeSEDIMENT and VEGETAnaN in this chapter). Handicapped accessibility was raised as an issue in scoping and is a concern for NP5, which issues preferential permits for trips with handicapped individuals. Low flows (lessthan 5,000cis) increasethe potential for having to walk handicapped individuals around a rapid, while extremely high flows increasethe potential for a passengerand rescuer going overboard. Effects on accessibility under each alternative follow the samepattern as accident risk above. The number, size, and character of camping beachesin Grand Canyon have a direct effect on the total recreational capacity of the river corridor and the experiencefor white-water recreationists. The absolute limits on numbers of people are determined by the reachesin which campable beachesare critically limited. Under the fluctuating flow alternatives, distribution of sites within powerplant capacity would be 0.7 site per mile in critical (narrow) reachesand 1.1 sites per Fluctuating flows would influence mooring quality, causing boat management problems and stranding. Under the fluctuating flow alternatives, mooring would be fair to good at 64 percent of camping beachescompared to 92 percent fair to good under the steady flow alternatives. The reach below Diamond Creek (RM 225 to RM 260) is extremely critical; 11 beachescurrently are available-a site distribution ratio of only 0.3 beach per mile. Studies relating campsite availability to various discharges are not being performed on this part of the river. Becausea negligible amount of the campable areaswould be available below the high water line and fluctuations would attenuate downstream, it can be assumed that any difference in campsite availability due to discharge levels would be minor to negligible. fu general, however, the availability and carrying capacity of camping beachesbelow Diamond Creek would be assumed to follow the same responsetrends under fluctuating and steady flow alternatives as beachesin other Grand Canyon reaches,and they will not be treated further in this analysis. 279 RECREATION Camping area lossesdue to erosion and/ or vegetation overgrowth have been recorded (Ross, written communication, 1992). To what degree this is attributable to dam operations is being studied by the Hualapai Tribe. A comparison of campable area under the various alternatives is shown in table IV-17. Vegetation encroachment likely would occur at camping beaches. However, visitor use would limit permanent expansion at popular sites under all alternatives. On less popular beaches,vegetation encroachmenteventually would make the site difficult to use. If dam operations could be used to limit vegetation encroachment, consistent with ecosystemobjectives,habitat maintenance and beach/habitat-building flows likely would be scheduled to do so. However, ecosystemneeds are a more important consideration than camping beaches,especially since clearing vegetation is an option, and much of the encroaching vegetation is non-native. Vegetation patterns would vary by alternative and are discussedunder VEGETAnaN, earlier in this chapter. It would be difficult to project the number of camping beachesthat would exist under each alternative over the long term. However, sediment storage and active sandbar height were used to indicate the relative potential for maintaining and rebuilding camping beachesover the long term. After the high flows of 1983,more beacheswere present than had been in 1975 (figure 111-38).Most of the increaseprobably is evidence of beach-building, meaning many sites are resilient and can be maintained through either habitat maintenance or beach/habitat-building flows. However, some beacheswould be lost under all alternatives due to site characteristics and the presenceof the dam. Vegetation clearing may be an option for maintaining some camping beacheswhere encroachment is a factor . Lake Activities and Facilities Lake Powell level depends on annual inflow and water deliveries. The costs to adjust facilities such as marinas, docks, and launch ramps to the lake level are approximately $1,275per 1-foot change, $33,460per 25-foot change, and $2 million per single adjustment of 50 or more feet (Combrink and Collins, 1992). Capacities for boating and camping depend on space,which increaseswith reservoir elevation. Annual fluctuations are much greater than the seasonalfluctuations that occur throughout the year (approximately 18.5feet under no action in the 50-year analysis); thus, costs of making annual adjustments would be much greater than those for seasonaladjustments. The variability among years would be much greater than the seasonalvariability among the Floodflows would be more frequent under the No Action and Maximum Powerplant Capacity Alternatives, which could reduce the number of beaches,especially in critical reaches. Under the other alternatives, floods would be reduced owing to the addition of flood frequency reduction measures. Under alternatives that maintain a sediment balance,beacheswould be restored to varying degrees (seechapter IV, SEDIMENT). Table IV-17.-Comparison of campable area by alternative Number Campable area Alternative (square feet) No action 7,720 7,720 7,720 7,720 >7,720 >7,720 9,200 7,720 to 8,200 9, 199 Maximum powerplant capacity High fluctuating flow Moderate fluctuating flow Modified low fluctuating flow Interim low fluctuating flow Existing monthly volume steady flow Seasonally adjusted steady flow Year-round steady flow Noncritical reaches of sites per mile Critical reaches 1.1 0. 7 1.1 0. 7 1.1 0. 7 1.1 0. 7 1.1 0. 7 1.1 0. 7 +.15 Same to +.15 +.15 + ,2 Same to +.2 +. ,2 280 Chapter IV Environmental Consequences alternatives (approximately 6-foot difference among the alternatives). Under all alternatives, the cost of seasonaladjustments most likely would be incremental and generally would not exceed $33,460.Between-yearvariability for all alternatives could result in adjustments that cost as much as $2 million. Raising the height of the spillway gates to reduce flood frequency would infrequently increasethe level of Lake Powell up to elevation 3704.5. This increasewould affect facilities and facility operation at Glen Canyon National Recreation Area, although such impacts have not been fully studied. Navigability of the Colorado River where it interfaces with upper Lake Mead is influenced by several factors including reservoir level, riverflow, and the recent releasepattern and its influence on sedimentation processes. Becausereleasepatterns would vary among all alternatives, effects would vary also and are discussedunder each alternative. Habitat maintenance flows are expected to have little or no effect on access through the Colorado River delta under any alternative. Unrestricted Fluctuating Flows No Action Alternative Fishing. Most anglers prefer moderate, steady flows (chapter III, RECREAnON). However, during low water releaseyears, the historical water releasepattern under no action has been widely fluctuating flows (chapter III, WATER). This pattern is preferred over some scenarios, such as very high (greater than 40,000cfs) or very low (lessthan 3,000cfs) steady flows. During moderate water releaseyears, the reduced range of fluctuations would be seenas an improvement, but not a significant one. During high water years, the range of fluctuations would be reduced becauseof the high volume of water released. However, such high steady discharge would not be preferred becauseof its negative impact on fishing success. The effects of no action on the fishery itself parallel the effects on trout described in the FISH section of this chapter. Anglers prefer wild fish over stocked fish, but continued trout stocking would be necessarybecauseof stranding and spawning bed exposure resulting from fluctuating flows. Dam operations limit the aquatic food base,thus limiting the trout population that can be supported by the system. Fishery managers have therefore had to limit the trout population and, in turn, restrict harvest either by reducing the creel limit or limiting angler accessto the fishery .This policy may be detrimental for anglers who prefer larger bag limits but would likely continue under no action. Fishing is an activity of regional importance. In the Glen Canyon reach, 18 camping sites potentially are available, but only 12 normally are available. The other six are low water sites that are available only when flows are at or below 15,000cfs. Maximum daily flow would be less than 15,000cfs 12 percent of the time. At LeesFerry, where most angler wading occurs, there can be more than a 4-foot stage change during the day in low water years and even more at the dam. The representative stage change over 20 minutes typically is around 0.62 foot at Lees Ferry and 0.88 foot near the dam (more representative of most of the reach). A rapid change of this magnitude would place wading anglers at risk of inundation. Day Rafting. During periods of 3,000-cfsflows or less,few (unquantified) boaters can successfully navigate 3-Mile Bar (U.S. Department of the Interior, 1990). Becausefew anglers would be able to move upstream during hours they prefer, impacts are of major concern. Some of those attempting to navigate the channel hit rocks and sustain boat and motor damage. Under no action, the low end of the daily range commonly reaches 3,000cfs between Easter and Labor Day and 1,000cfs between Labor Day and Easter. During low water years, 1,000-cfsflows occur often. In moderate water years, 1,OOO-cfs flows are less frequent; however, 3,OOO-cfs flows may continue to occur, especially during the spring RECREATION months. Typical summer releaseswould be around 5,000cIs, higher than in low water years, with the proportion of successfulboat passages increasing to 75 percent during periods of minimum discharge. During high water years, the potential would diminish for both a wide range of fluctuations and extremely low flows. Boats with 10 horsepower or smaller motors would have problems getting upstream during high water years. White-Water Boating. The impacts on white-water recreation, discussed below, typically are short term and of national and international importance. River Trip Attributes.-Many white-water boating guides and trip leaders have expressed highest preference for either a narrow range of daily fluctuations or steady flows and lowest preference for operations similar to no action. The No Action, Maximum Powerplant Capacity, and High Fluctuating Flow Alternatives rank lowest among alternatives. Under no action, there are numerous impacts on white-water boating trip attributes. A majority of river-runners feel that flow fluctuations during low water releaseyears make the river seemless natural. During low flow periods, problems with stranding, navigation, and passengerenjoyment may occur (chapter III, RECREAnON). During high flow periods, travel time improves as does navigability at some rapids. During high water years, steady flows would be closer to the preferencesof most boaters, although optimum conditions occur under flows of 22,000to around 31,000cfs. During high water years, there is more possibility that passengerson oar-powered trips would have to walk around one of the major rapids. Campsites would become smaller, and the likelihood of camping with or near another group would be increased. Wilderness Values.-Under no action, the range of fluctuations occurring under all but the highest water volume months (and years) would be noticed by up to 87 percent of all river-runners, Of these,75 percent of private and 50 percent of commercial passengersfeel fluctuating flows 281 make a river trip setting seemlessnatural. The magnitude of the impact would likely be greatest during low water years when the range of fluctuations is greatest. It is likely that the river seemsmost natural during high water years, due to the lack of daily fluctuations. White-Water Safety (Accident Occurrence).The No Action Alternative has the highest potential of all the alternatives except the Maximum Powerplant Capacity Alternative for accident occurrence. This is due to the length of extremely low and extremely high discharge periods and would be especially true during low water years. During periods of low flow (lessthan 5,000cis), the relative risk index of having an accident would be greatestfor commercial motor and small oar-powered craft (Brown and Hahn, 1987;Jalbert, 1992). During the high flow periods of the day, risk would decreasefor all boat types. During high water volume years, floodflows may occur. The probability of having an accident while running a rapid during floodflows is highest for all trips, but especially for small, oar-powered craft. No action would have the greatest overall relative level of risk. Over the long term, debris flows would continue to become a greater factor in boater safety. Handicapped Accessibility.-Under no action, passengerspotentially would have to walk around rapids during low water periods, a situation that could impact physically challenged persons. Having to walk around rapids occurs most with motor rigs and smaller oar-powered craft. During high flow periods, this problem decreasesfor all boat types; however, the risk of people going overboard is increased. Floodflows increasethe potential of handicapped individuals having to walk around some rapids. The overall risk of capsizing a boat is also greatest. Theserisk patterns are similar to those experienced by the general population, but the effects are potentially greater. Camping Beaches.-Even though size of a particular camping beach may be highly variable owing to fluctuating flows, the amount of 282 Chapter IV Environmental Consequences campable area under no action can be determined largely by the maximum discharge within the daily period. In other words, a new beach exposed during the low flow period does not provide additional camping area becauseit could still be inundated during the high flow period. On typical days in low and moderate water releaseyears, the maximum daily releasewould be in the range of 25,000to 30,000cfs. The average campsite area above this discharge would be less than 7,720square feet (the averagefor 25,000cis), with large, medium, and small sites averaging less than 11,720;4,950;and 2,390square feet, respectively. During high water releaseyears, usable campsite area would be further reduced; campable area during flows above powerplant capacity has not been quantified. The absolute limits on the Grand Canyon's recreational carrying capacity are determined by camping beach distribution in critical (narrow) reaches. Somesites are usable at all discharges within powerplant capacity-approximately 0.7 site per mile in critical reachesand 1.1 sites per mile in noncritical reaches. Additional low water sites-approximately 0.2 per mile in critical reachesand 0.15per mile in noncritical reaches-are not usable under no action due to range of fluctuations. In the long tenn, it is expected that the number of beacheswould decline to a new equilibrium value, especially in critical reaches,due to the low probability of storing sand in the system (tablelV -9). This decline in camping beach numbers would reduce the canyon's carrying capacity so that the numbers of parties that could be accommodated would progressively decrease. Under no action, there would not be enough sand stored in the system to rebuild sandbars and camping beaches. During low and moderate water years, mooring quality is poor at 36 percent of the camping beachesdue to fluctuating flows and the resulting influence on boat management and stranding. Lake Activities and Facilities. Changes in dam operations could affect lake levels-and therefore facilities and recreation activities-at both Lakes Powell and Mead. Lake Powell Facilities.-lake elevation may rise or decline with water deliveries, requiring adjustment of lake facilities such as marinas, docks, and launch ramps. Under no action, the median amount of seasonalchange in lake elevation (50-yearanalysis) is approximately 18.5feet, with minimum elevation occurring during March and maximum elevation occurring during July. Between-yearvariability in lake elevation is greater than seasonalvariability . During successiveyears of high water inflow from the Upper Basin, lake Powell can be maintained at a high level. During theseperiods, annual adjustment costs are low, but operators of lake facilities incur approximately $1,275of seasonal expensefor every foot of adjustment necessary. During periods of moderate water inflow, Lake Powell elevation may drop. The approximate cost of seasonaladjustments remains the same,but the one-time cost of making an annual adjustment for lake fluctuations exceeding 25 feet is approximately $33,460. When the lake level declines more than 25 to 30 feet, capital costs increase. For every 50-foot drop in lake elevation, the capital investment is estimated to be $2 million; these between-year costs are more likely to occur during successivelow water years. Lake Powell Boating.-As the density of boats on the lake increases,so does the potential for collisions and other recreational accidents. Safeboating capacity increasesas surface area increasesand declines with lake elevation. At 3700-foot elevation, which would result under successivehigh water years, the lake has a safe boating density of approximately 17,932boats. In moderate water years, if lake elevation dropped to around 3680feet, safe boating density would decreaseto 16,387boats. If the reservoir level reaches3660feet, as it might following several low water years, safe boating density could decreaseto 14,920boats. RECREA TION Lake Powell Camping.- The number of campsites the shoreline can accommodate decreasesas lake elevation declines. (Boaters generally camp at the lakeshore,near their boats.) Recreationaluse levels ultimately would be limited by suitable campsites. Potential campsite capacity for Lake Powell at full pool would be approximately 7,360campsites. At a 3680-foot elevation, potential campsite capacity may decreaseto approximately 7,134sites. Shoreline campsite capacity would decreaseto approximately 7,105sites at 3660-foot elevation and 6,586sites at 3620-foot elevation. Navigability of Upper Lake Mead/Colorado River.-High lake elevations and sediment deposition during 1983-86causedLake Mead to submerge all rapids through Lower Granite Gorge downstream from RM 235 (seechapter III, SEDIMENT) .In 1987,Lake Mead began to recede, and a shallow river channel formed. The Colorado River delta now restricts passageinto or out of the Lower Gorge within Grand Canyon. The channel also is choked by new sediment being dropped along the low-velocity river that runs through the area. Marsh habitat has spread on the delta along the channel banks. The extent and magnitude of thesenavigation problems have not been thoroughly investigated; however, it is known from observations that the number of takeouts at South Cove (further downlake) increasesduring successivelow water years becausenavigation is difficult in Piercebasin. During low and moderate water years, when fluctuating flows are prevalent, navigation is most difficult becausethe configuration of the river channel can change daily. During the low water portion of the day, navigation can be difficult where the river interfaces with flat lake water becausethe river channel can be shallow and sandbars sometimes are exposed. Conditions for navigation are best during high water years, when lake levels are high. Impacts are unquantified. Maximum Powerplant Capacity Alternative The influences of this alternative on recreational resourceswould be essentially the same as those 283 that occur under no action. Recreation variables influenced under no action would likely be influenced to an even greater extent under this alternative. However, the relative difference is not supported by research;therefore, impacts of this alternative will be characterized as the same as no action. Restricted FluctucJting Flows Impacts to recreation under the High, Moderate, Modified Low, and Interim Low Fluctuating Flow Alternatives are described in this section. An overview of common impacts from these alternatives is presented first; specific details follow under the individual alternatives. Under the restricted fluctuating flow alternatives, impacts on fishing would vary , but all would potentially reduce dependenceon stocking. Becauseof the reduced range of fluctuations, all restricted fluctuating flow alternatives would reduce angler safety problems compared to no action, but the amounts would vary by alternative In the Glen Canyon reach, the samenumber of campsites probably would exist in July and August under all restricted fluctuating flow alternatives as under no action. During low volume months, six additional sites would be usable, except under the High Fluctuating Flow Alternative. Up to 75 percent of all day rafting boats should be able to navigate the 3-Mile Bar under all restricted fluctuating flow alternatives except the High Fluctuating Flow Alternative, which would be similar to no action. The Moderate, Modified Low, and Interim Low Fluctuating Flow Alternatives would have improved impacts on white-water boating trip attributes and would be closer to preference than no action. The High Fluctuating Flow Alternative would have impacts on river trip attributes comparable to no action. River-runners would be aware of fluctuations under all alternatives. There likely would be a difference in the magnitude of such impacts compared to no action, but this difference has not been quantified. The relative risk of accident occurrencewould vary among the four restricted fluctuating flow alternatives from 4 to 10 percent less than under no action. The High Fluctuating Flow Alternative would be similar to no action, while the others would reduce the amount of time at low flow risk. There would be no differences among alternatives during floodflows. All alternatives improve safety relative to no action becauseof higher minimum flows. Effects on handicapped accessibility would vary among the restricted fluctuating flow alternatives. Low flow risk would be greatest during low water releaseyears under the High Fluctuating Flow Alternative. Under all restricted fluctuating flow alternatives except high fluctuating flows, there would be numerous months when maximum discharge would not exceed15,000cis and when beach availability and distribution in Grand Canyon would increase-up to 0.9 site per mile in critical reachesand 1.28sites per mile in noncritical reaches. However, boaters using these sites would be at risk of being inundated in the event of emergency exception criteria (chapter II, "Common Elements"). The availability and distribution of beachesin Grand Canyon over the short term would be comparable to no action. Under restricted fluctuating flows, camping beacheswould be dynamic but more stable than under the No Action and Maximum Powerplant Capacity Alternatives. Beachheight would be lower, but the amount of riverbed sand available for deposition would increaseover time (table IV-6). Sandbar heights and active widths would be greater than under steady flow alternatives, and the bar heights under Moderate and Modified Low Fluctuating Flow Alternatives would be maintained due to the habitat maintenance flows. The potential for rebuilding and maintaining camping beachesis greater than under no action, although site loss would continue in some places due to erosion and vegetation growth (table IV-I0). Enough sediment would be available under all restricted fluctuating flow alternatives to contribute toward maintaining and rebuilding camping beacheswith beach/habitat-building flows. Reduced flood frequency would likely maintain beachesin critical reachesbecausethere would be fewer floods of a magnitude to top debris fans. Managed beach/ habitat-building flows would help maintain beach distribution under all alternatives; longevity of benefits would vary by alternative. Vegetation encroachment would likely be greater than under no action, causing loss of sites over time. However, vegetation clearing remains a management option. Mooring quality would be essentially the same as under no action-poor at 40 percent of the camping beaches-although the severity of boat stranding and mooring difficulties would decrease as the range of fluctuations decreased. Stage change would be much reduced in the summer months under the Modified Low and Interim Low Fluctuating Flow Alternatives. Concerning lake activities and facilities, Lake Powell's annual water storage and surface area would be the same as under no action. As a result, the costs of making facility adjustments under most alternatives would be the same as those incurred under no action. Safeboating capacity and recreation use levels, as determined by the number of suitable campsites, also would be the same as no action under all fluctuating flow alternatives. Navigability of upper Lake Mead under all restricted fluctuating flow alternatives would be improved compared to no action. High Fluctuating Flow Alternative Regarding fishing trip attributes, the High Fluctuating Flow Alternative would have impacts similar to no action, although the reduced ranges in daily flows would result in improvements. Management of the fishery in Glen Canyon and in Grand Canyon would be similar to no action. The overall (relative) risk of having a white-water boating accident would be 4 percent less than under no action. The risk for commercial users RECREATION would be approximately the same as under no action, while the risk for private users would be 12 percent less. Moderate Fluctuating Flow Alternative Increasedreliable minimum flows (5,000cfs) during the trout spawning seasonwould improve fishing by reducing trout stranding, increasing recruitment and aquatic productivity, and reducing reliance on trout stocking. Habitat maintenance flows included in this alternative are likely to have short-term effects on angling quality in Glen Canyon. During the early stagesof the habitat flow, there would be increased drift of macroinvertebrates and detritus. This would likely stimulate increased trout feeding and thereby improve fishing quality . During the latter days of the habitat maintenance flow period, drift would decline, and continuing high releasesmight make fishing more difficult than at lower flows. The net effect on angling quality is unknown but likely to be minor due to the short duration of theseevents. The daily stage change affecting wading anglers at LeesFerry would be approximately 2 feet less than under no action. Representative20-minute stagechangeswould be approximately 0.24foot (61 percent less than no action) at Lees Ferry and 0.5 foot (43 percent less than no action) at the dam. Habitat maintenance and beach/habitat-building flows also would have some effect on the safety of wading anglers. This effect generally would be limited to the transition period when flow is being increased from normal operations to the higher habitat maintenance flows. During this transition, increasing flows might catch unwary anglers in midstream. However, since Lees Ferry is the sole accesspoint for this reach, this potential safety problem could be easily mitigated by notifying anglers in advance of this impending flow change. Once target flows are reached, the risk of angler inundation due to fluctuations would be elirninated. Higher velocity flows would present some increasein risk to wading anglers, but most 285 individuals can recognize this risk and avoid placing themselves in a dangerous situation. Approximately 75 percent of all day rafting parties would be able to negotiate 3-Mile Bar at minimum discharge (5,000cis), compared to only a few at 3,000cis (U .5. Department of the Interior, 1990). Someboat and motor damage would likely occur. High, steady habitat maintenance flows would make boating accessover 3-Mile Bar easierbut might make upstream passagemore difficult for boats with smaller engines. Additional caution on the part of boaters might be required to avoid being stranded at mooring sites as the water level recedes. Discharge levels would improve white-water boating trip attributes in tenns of guide andirip leader preferences. Fewer white-water boaters (69 percent, or 18 percent less than under no action) would be aware of fluctuating flows becauseof increased restrictions. Effects of habitat maintenance flows on whitewater boating would be negligible becausethey would be scheduled before the peak rafting season. Individuals taking trips during the period when habitat maintenance flows begin undoubtedly would notice the transitions between normal operations and maintenance flows. The changes in river stagewould be similar to naturally occurring tributary flood events except that they would not include large sediment inflows. Some individuals might perceive high flows without sediment as artificial, which could impact their wilderness experience. Conversely, habitat maintenance flows would contribute to maintenance of the natural environment, including sandbars and beaches. This might improve the wilderness character of trips for the majority of individuals. The overall risk of having a white-water accident would be 10 percent less than under the No Action Alternative. The risk index for commercial users would be 7 percent less than under no 286 Chapter IV Environmental Consequences action; for private users, risk would be 16 percent less. The potential for having to walk around a rapid would be diminished for all trip types. The risk of people going overboard in a rapid would remain during high flow periods. During habitat maintenance flows, the probability that some passengersmay opt or be required to walk around major rapids would be somewhat increased. This could be a problem for handicapped individuals boating during this period. High flows also could increasethe risk of white-water boating accidents. However, these flows would be scheduled for only 1 to 2 weeks during low-use periods. For these reasons,the influence of habitat maintenance flows on handicapped accessand on white-water boating accidentslikely would be negligible. Average campable area would be greater than the average of 7,720square feet available under no action. During habitat maintenance flows included in this alternative, changesin stage would require carefully locating camps and mooring sites. Concerning lake activities and facilities, there would likely be improved navigability in the river and at the interface with Lake Mead, but difficulties would remain due to fluctuations in river stage. Sandbarswould continue to be exposed during low flow periods, but conditions might be lessvariable becauseriver velocity would be less variable. In a year when habitat maintenance flows are scheduled, the level of Lake Powell would be about 1.5 feet above normal from October through March. During the 1 to 2 weeks of habitat maintenanceflows in March/ April, the level of Lake Powell would fall about 3 feet, resulting in facility adjustment charges of approximately $4,000. Following habitat maintenance flows, the lake would be approximately 1.5 feet below normal. Compared to a year without habitat maintenance flows, lake elevation would gradually increase from March through September. Modified Low Fluctuating jr;low J~lternative This alternative would have the greatest potential (along with interim low fluctuating flows) among the restricted fluctuating flow alternatives to enhance fishing by reducing trout stocking in the Glen Canyon reach. Habitat maintenance flows included in this alternative would likely have short-tenn effects on angling quality in Glen Canyon. During the early stagesof the habitat flow, there would be increased drift of macroinvertebrates and detritus. This would likely stimulate increased trout feeding and thereby improve fishing quality . During the latter days of the habitat maintenance flow period, drift would decline and continuing high releasesmight make fishing more difficult than at lower flows. The net effect on angling quality is unknown but likely to be minor due to the short duration of these events. The stagechange at LeesFerry would be approximately 1.5 feet, or 3 feet less than under no action. Representative20-minute stage changestypically would be in the range of 0.1 foot (83 percent less than no action) at LeesFerry and 0.3 foot (66 percent less than no action) at the dam. As such, the risk of major impacts to anglers would be reduced. Habitat maintenance and beach/habitat-building flows also would have some effect on the safety of wading anglers during the transition period when flow is being increased from normal operations to the higher flows. Theseeffects would be the same as described under the Moderate Fluctuating Flow Alternative. Campable area would have a slight, unquantified improvement over the Moderate Fluctuating Flow Alternative. During most months, the number of available camping areaswould be the same as under no action. During days with maximum flows less than 15,000cis, the number of available beachesin Glen Canyon would increaseby six. High, steady habitat maintenance flows would make boating accessover 3-Mile Bar easierbut might make upstream passagemore difficult for boats with smaller engines. RECREATION White-water boating trips would benefit because the minimum flow and range restriction would reduce effects on mooring/boat management and navigation of rapids. The range of fluctuations would be among those most preferred for both guides/trip leaders and passengers. Effects of habitat maintenance flows on white-water boating would be the same as those described under the Moderate Fluctuating Flow Alternative. The overall risk of white-water rafters having an accident would be 10 percent less than under no action. The risk index for commercial users would be 7 percent less than under no action, while the index for private users would be 15 percent less. The effects of habitat maintenance flows on handicapped accessand on white-water boating accidentslikely would be negligible. Campable area would be slightly improved over the Moderate Fluctuating Flow Alternative. During most months, the number of available camping areaswould be the same as under no action. However, during those days when the maximum flow would be less than 15,000cis, the number of available beachesin Grand Canyon wol,lld increaseby 0.2 site per mile in critical reachesand 0.15site per mile in noncritical reaches. During habitat maintenance flows, changesin stage would require carefully locating camps and mooring sites. Concerning lake activities and facilities, navigability of upper Lake Mead would improve over most other fluctuating flow alternatives, but difficulties would remain since stagewould continue to change with the variable flow. Sandbars would continue to be exposed during low flow periods, but conditions would be among the least variable of any fluctuating flow alternative. In a year when habitat maintenance flows are scheduled, the level of Lake Powell would be about 1.5 feet above normal from October through March. During the 1 to 2 weeks of habitat maintenance flows in March/ April, the level of Lake Powell would fall by approximately 3 feet (resulting in facility adjustment chargesof approximately $4,000). Following habitat 287 maintenance flows, the lake would be approximately 1.5 feet below normal. Compared to a year without habitat maintenance flows, lake elevation would gradually increasefrom March through September. Interim Low Fluctuating Flow Alternative Except for the influence of habitat maintenance flows, impacts on recreation under the Interim Low Fluctuating Flow Alternative would be the same as under modified low fluctuating flow compared to no action. Steady Flows Impacts to recreation under the steady flow alternatives are described in this section. An overview of common impacts is presented first, followed by specific details about individual alternatives. Releasesduring low and moderate water years would be comparable to anglers' most preferred fishing scenarios. The fishing environment and associatedboating activities would be improved the most under these alternatives. As a result, these three alternatives have the highest preference ranking for fishing among alternatives, with the Year-Round Steady Flow Alternative being the most preferred, followed by the Existing Monthly Volume and SeasonallyAdjusted Steady Flow Alternatives (seeFISH in this chapter). Under all steady flow alternatives, risk of inundation would be removed for wading anglers. Although some day rafting navigation problems might occur during low discharge months (data suggest that elimination of navigation problems would require lO,OOO cis), the frequency of navigation problems would be extremely low. All three steady flow alternatives would lessen impacts on white-water boating trip attributes. Since there would be virtually no daily fluctuations, the risk of stranding moored boats would be eliminated. On the average,rapids would provide a bigger "roller coaster ride" and would thus be more exciting. There would be a low likelihood of passengershaving to walk around 288 Chapter IV Environmental Consequences rapids. Flows during all months of most years would not impede navigation; as a result, rafting parties would not frequently encounter each other. Except during extreme low flow months, the predictable nature of the flow should result in improvement over no action, reducing effects on itinerary. As a result of thesebenefits to white-water recreation, steady flow alternatives have three of the highest four preference rankings among alternatives, with seasonally adjusted steady flows being the most preferred. Since flows would be steady, the river would seemmore like a natural setting under all steady flow alternatives as compared to no action. Approximately 38 percent of white-water boaters would be aware of minor stagechanges,such as those between months and for power system emergencies. Becausethese events are rare, impacts would be considered negligible. Risk of white-water boating accidentswould range from 14 to 21 percent less than under no action, with the Year-Round Steady Flow Alternative being lowest. All alternatives would improve safety relative to no action becauseof higher minimum flows. None of the alternatives would move large material out of debris flows. Flows under the steady flow alternatives would be relatively moderate (except in high water volume years) compared to no action. Due to the lack of daily lows and peaks, both the need for handicapped passengersto walk around rapids and the risk of their going overboard would be reduced. Another benefit of these alternatives would be that handicapped individuals would not need to prepare for both low and high flows within one trip. Steady flow alternatives would improve usable camping area, distribution, and mooring characteristics compared to no action and fluctuating flow alternatives. Benefits would vary by alternative. Sandbarsgenerally would be less dynamic and more stable, with greater potential for vegetation encroachment. Sandbar heights and active widths would be less under the Existing Monthly Volume and Year-Round Steady Flow Alternatives than under any other alternatives. Bar heights under the SeasonallyAdjusted Steady Flow Alternative would be maintained due to habitat maintenance flows (table IV-6). The potential for rebuilding and maintaining camping beacheswould be greater than under no action and would be similar to those under moderate and modified low fluctuating flows. The loss of sites would continue in some places due to erosion and vegetation development (table IV-I0). Vegetation encroachment,and thus potential dependenceon vegetation clearing, would be greatestin the long term under the Year-Round and Existing Monthly Volume Steady Flow Alternatives. Under the Existing Monthly Volume Steady Flow Alternative, the monthly delivery pattern-and therefore the impacts on lake activities and facilities-would be the same as under no action. The water releasepattern would change under the SeasonallyAdjusted and Year-Round Steady Flow Alternatives, but the consequential influences on lake facilities, boating capacity, and shoreline campsite capacity essentially would be the same. The steady flow alternatives would affect navigability similarly to no action during successivelow water years. Daily flows at the river flake interface would improve navigation becausesteady flows would not alter the river channel as fluctuating flows would. Conditions would continue to be variable, depending on riverflow and velocity, lake level, and prevailing sediment conditions. Existing Monthly Volume Steady Flow Alternative This alternative would benefit fishing activities and success.Sincetrout stranding would be eliminated and potential for recruitment and aquatic productivity would be improved, trout stocking would be reduced. In the Glen Canyon reach, there would be as many as 18 beachesavailable for camping and RECREATION day use in low water years-an increaseof 6 (50 percent) more than under no action. However, during peak discharge months, impacts would be the same as under no action. Steady flows would result in the near elimination of navigation and accessproblems for day rafting parties at 3-Mile Bar. White-water boating trip attributes would improve to match preferences. Since daily flows would be steady, the river would seemmore like a natural setting to river-runners. The overall risk for white-water boaters under this alternative would be approximately 14 percent less than under no action. The risk for commercial users would be 13 percent less than under no action, while the risk for private users would be 15 percent less. In most years, additional camping area would be available in Grand Canyon compared to no action and the fluctuating flow alternatives. The averagearea for campsites would be greater than 9,200square feet, an increaseof more than 25 percent. Campable area for large, medium, and small sites would average,respectively, more than 13,980;4,940;and 2,660square feet larger than under no action (for 25,OOO-ds discharge). During low discharge months, the area would increasefor all beachesto 11,740square feet, or an increaseof more than 52 percent compared to no action. Large, medium, and small campsites would increasein average area to 17,660;6,490;and 3,560square feet, respectively. On most days of the year, low water campsites would be usable, increasing distribution of camping beachesto 0.9 site per mile in critical reachesand 1.28sites per mile in noncritical reaches,an increase of 0.2 (25 percent), and 0.15 (16 percent) site per mile, respectively, compared to no action. During months well above 15,000cfs, the low water sites would be unusable. Mooring quality would be good at 92 percent of camping beaches,compared to 64 percent under no action. 289 Concerning lake activities and facilities, navigability of upper Lake Mead would be the same as under no action during successivelow water years. The steady nature of daily flows during all years would improve navigation at the river's interface with the lake. Seasonally Alternative Adjusted Steady Flo w This alternative would improve fishing compared to the No Action Alternative, but has the lowest preference ranking for anglers among the steady flow alternatives. Habitat maintenance flows included in this alternative are likely to have short-term effects on angling quality and the safety of wading anglers in Glen Canyon. Theseeffects would be the same as those described under the Moderate Fluctuating Flow Alternative. Habitat maintenance flows would make boating accessover 3-Mile Bar easierbut might make upstream passagemore difficult for boats with smaller engines. Additional caution on the part of boaters might be required to avoid being stranded at mooring sites as the water level recedes. The overall risk index for white-water boating would be 16 percent less than under no action. The index for commercial users would be 16 percent less than under no action, while the index for private users would be 17 percent less. Effects of habitat maintenance flows on whitewater boating would be negligible becausethey would be scheduled before the peak rafting season. Such effects are identical to those described under the Moderate Fluctuating Flow Alternative. The influence of habitat maintenancE flows on handicapped accessand on white-water boating accidents likely would be negligible. All steady flow alternatives would increaseusable camping area compared to no action and the fluctuating flow alternatives. During habitat maintenance flows included in this alternative, changesin stage would require carefully locating camps and mooring sites. 290 Chapter IV Environmental Consequences Concerning lake activities and facilities, the seasonalpattern of Lake Powell elevation would be influenced by the change in water releases(a median seasonaldifference of 12.7feet, which is approximately 6 feet less than under no action). However, the resulting effects on lake facilities, safeboating capacity, and shoreline campsite capacity essentially would be the same as under no action. In a year when habitat maintenance flows are scheduled, the level of Lake Powell would be about 1.5feet above normal from October through March. During the 1 to 2 weeks of habitat maintenanceflows in March/ April, the level of Lake Powell would fall by approximately 3 feet (resulting in facility adjustment chargesof approximately $4,000). Following habitat maintenanceflows, the lake would be approximately 1.5 feet below normal. Compared to a year without habitat maintenance flows, lake elevation would gradually increasefrom March through September. primarily becauseof the low volume of water that would be releasedduring summer, the peak white-water season. The overall risk index for white-water boaters under this alternative would be 21 percent less than under no action. The index for commercial users would be 20 percent less than under no action, while the index for private users would be 23 percent less. Concerning lake activities and facilities, the pattern of discharge would result in lake elevations that would differ seasonally (median elevations in some months would be as much as 4 feet different than under no action). The median within-year range for Lake Powell's elevation would be approximately 18 feet for both the Year-Round Steady Flow and the No Action Alternatives. Slightly higher deltas would impair navigability in upper Lake Mead. Compared to other steady flow alternatives, navigation in upper Lake Mead might progressively diminish in quality during the course of the year becauseof a lack of variability and the possibility of some river sedimentation. Year-Round Economics Steady Flow Alternative Fishing attributes would improve becausemore reliable minimum flows (11,400cis) during the trout spawning seasonand steady flows throughout the year would result in near elimination of conditions that contribute to stranding and recruitment failure. The trout fishery would be less dependent on stocking than under any other alternative. Year-round steady flows would have the greatest potential for improved spawning, meaning a larger trout population. As a result, this alternative would have the highest preference ranking for anglers. Since discharge during low water years is likely to be above 12,000cis, this alternative would nearly eliminate navigation and accessproblems for day rafting at 3-Mile Bar. This alternative is the least preferred of the steady flow alternatives for white-water rafters, of Recreational Use Analysis Methods Statistical models for angling and commercial and private white-water boating were developed by Bishop et al. (1987)and are reported in Boyle et al. (1988). Thesestatistical models describe the relationship among the economic benefits of each recreation activity, the average flow during the month, and the occurrence of fluctuations exceeding 10,000cfs during the month. For each type of recreation activity, the model calculates net economic benefits per trip and then aggregates benefits over the actual distribution of recreation trips recorded in 1991. The statistical models predict the same economic benefits for several of the alternatives because some alternatives have identical inputs to the statistical models. For example, both the Interim Low Fluctuating Flow and Existing Monthly RECREATION Volume Steady Flow Alternatives have the same averagemonthly flows. There would be no fluctuations under the Existing Monthly Volume Steady Flow Alternative and no fluctuations over 10,000cfs under the Interim Low Fluctuating Flow Alternative. Consequently, the statistical models cannot distinguish between these two alternatives. Likewise, the No Action, Maximum Powerplant Capacity, and High Fluctuating Flow Alternatives all allow daily fluctuations exceeding 10,000cis and would have identical average releases. Consequently, the statistical models cannot distinguish among these alternatives. The 50-year analysis is based on hydrology trace number 60, the same20-year hydrology trace used in the hydropower impact analysis. The use of this 20-year sequencefor analyzing recreation benefits required several steps. First, mean monthly flows were calculated using the monthly releasevolumes for each alternative. Second,it was determined whether or not fluctuations exceeding 10,000cfs occurred during the month. The result of these two steps was a 20-year series of data for each alternative. Like the power system analysis, the 20th year was repeated for an additional 30 years to obtain a 50-year data series. The resulting SO-yeardata seriesfor each alternative was then used in the previously described models. This procedure yielded a SO-yearseriesof net economic values for each alternative. Using the samemethodology as the power economics study, the equivalent annual value of this SO-year serieswas calculated.2 Next, the equivalent annual value for each alternative was subtracted from the No Action Alternative's equivalent annual value to obtain the change under each alternative. The discussion for each alternative focuses primarilyon water years 1989(a low water year), 1987(a moderate water year), and 1984(a high water year). Monthly average flows in water year 1984were extremely high-ranging from about 291 24,000cfs to nearly 43,000cfs. Under the SeasonallyAdjusted and Year-Round Steady Flow Alternatives, monthly average flows would range from about 20,000cfs to over 55,000cfs. While analysis of the alternatives must include these extremes,water years 1985and 1986may represent more typical high flow years. Therefore, analysis of these additional water years has been provided for comparison. Summary of Impa(;ts on Recreoltion Economics Recreation Use. The 1991level of recreation use is shown in figure I11-40in chapter III. Current NPS regulations restrict the number of trips that can be taken, preventing any increasein whitewater boating in Grand Canyon. Thus, it seems unlikely that the number of white-water boating trips will changein responseto any of the alternatives. The long waiting list for private permits and the number of commercial passengers who cannot be accommodated due to these restrictions appear to ensure that visitation is unlikely to fall below present levels. For these reasons,white-water boating use is held constant at 1991levels for this study. Angling trips may vary with general economic conditions, fishing regulations, and the quality of the fishery .Studies have documented a relationship between angling quality and the number of trips taken. In these studies, angling quality has been measured by the species,number, and size of fish caught as well as by the presenceof native fish in the catch. Some alternatives may result in changesin average catch, average fish size, and composition of the fish stock. Presumably, any change in fishery quality would result in a change in the number of trips taken. Biological models which could predict angling quality are unavailable, and economic models that could predict the number of trips based on angling quality have not been developed. As a result, the magnitude and direction of the biological responseto each alternative cannot be 2 The levelized or equivalent annual value of this series is the amount of money which, if received each year, would yield an amount equal to the present worth of the varying SO-yearseriesof payments. The details of this calculation may be found in Shaner (1979). RECREATION 293 Becauseno other Native American-owned or operated river-based businesseshave been identified, no measurable economic impact would be expected under any of the proposed alternatives. the proposed alternatives result in long-teml impacts on the recreation environment, the estimates in table IV -18 may overstate or understate the true effects on net economic value. Regional Economic Ac"vity. Since the number of white-water boating trips is not expected to change and the number of angling trips taken is held constant for this analysis, there is no change in regional economic activity for any of the alternatives. Estimates of local economic activity for the No Action Alternative are reported in chapter III, table III-15. Theseestimates depend on the number of trips taken by nonresidents and their pattern of expenditures. Unrestricted Fluctuating Flows Under the unrestricted fluctuating flow alternatives, releasesin low water years are characterized by low minimum flows with relatively high peak flows of short duration. As a result, flows fluctuate considerably within the constraints imposed by available storage. Flows generally would be below the optimal recreation level, and fluctuations would affect recreation benefits. Recreation, Economics, and Indian Tribes.A number of commercial and private white-water boating trips launch from Diamond Creek on the Hualapai Reservation. Estimatesof the net economic value of white-water boating below Diamond Creek are described in tables IV-19 through IV-25 for representative water years and in table IV -18 for the 50-year analysis. Minimum flows in a moderate releaseyear generally would be higher than in low water years, although flow fluctuations would remain large. In a high water releaseyear, minimum flows are higher than under low and moderate releaseconditions. In addition, becauseof the need to releasea large volume of water, flow fluctuations are reduced. White-water boating use below Diamond Creek, as measured by the number of trips taken, is expected to increaseover time until use reaches capacity limits. The nature and timing of this increaseis unknown; however, any change in the number of trips is expected to be unrelated to dam operations. Therefore, white-water boating use is held constant at 1991use levels, and local economic activity would be identical acrossall alternatives. No Action Alternative. Net economic benefits to white-water boaters and anglers under the No Action Alternative are presented in table IV-19. Maximum Powerplant Capacity Alternative. Under this alternative, the net economic benefits of white-water boating and angling are the same as under no action (see table IV-19). Table IV-19.-Net economic benefits of recreation for representative years under the No Action, Maximum Powerplant Capacity, and High Fluctuating Flow Alternatives Annual benefits (1991 nominal Low (1989) Moderate (1987) High 1 (1984) High 2 (1985) High 3 (1986) 5.4 1.1 6.4 1.2 12.4 2.0 11.0 1.7 10.4 1.6 $ millions) .104 .122 .230 .204 .186 7.904 8.922 15.730 14.004 13.286 294 Chapter IV Environmental Consequences Table IV-20.-Net economic benefits of recreation for representative years under the Moderate Fluctuating Flow Altemative Annual benefits (1991 nominal $ millions) Type of release year Commercial white-water Private white-water boating boating Anglers Low (1989) Moderate (1987) High 1 (1984) High 2 (1985) High 3 (1986) Restricted Fluctuating 5.2 0.9 6.4 1.2 12.4 2.0 11.0 1.7 10.4 1.6 White-water boating below Diamond Creek .098 .122 .230 .204 .186 Total 7.698 8.922 15.730 14.004 13.286 Moderate Fluctuating Flow Alternative. In a typical low water releaseyear, habitat maintenance flows would take place for approximately 10 days in March, resulting in a small decreasebetween the benefits under the Moderate Fluctuating Flow Alternative and benefits under no action. In moderate and high water releaseyears, habitat maintenance flows would not be scheduled, and benefits would be the same as under no action. The results for commercial white-water boating, private white-water boating, and angling are shown in table IV-20. Flows The effects of restricted fluctuating flow alternatives on net recreation benefits would vary depending on the type of water year and the actual water volume and pattern of releases during that year. Daily fluctuations over 10,000cfs would be greatly reduced as the alternatives becomeprogressively more restrictive. For example, under the High Fluctuating Flow Alternative, daily fluctuations over 10,000cfs would be relatively common, while under the Interim Low Fluctuating Flow Alternative, daily fluctuations exceeding 10,000cfs would never occur. Modified Low Fluctuating Flow Alternative. Habitat maintenance flows are a component of the Modified Low Fluctuating Flow Alternative. Including these flows during March changesthe volume of water releasedduring the remaining 11 months of the year. In a low water releaseyear, High Fluctuating Flow Alternative. There would be no difference between the economic benefits generated under this alternative and those generated under no action in any water year (see table IV-19). Table IV-21.-Net economic benefits of recreation for representative years under the Modified Low Fluctuating Flow Alternative Annual benefits (1991 nominal $ millions) Low (1989) Moderate (1987) High 1 (1984) High 2 (1985) High 3 (1986) 6.3 1.0 9.1 1.6 13.3 2.1 13.6 2.1 12.9 2.0 .117 .174 .247 .259 .236 9.217 12.974 16.947 17.759 16.536 296 Chapter IV Environmental Consequences Table IV-24.-Net economic benefits of recreation for representative years under the Seasonally Adjusted Steady Flow Alternative Annual benefits (1991 nominal $ millions) Low (1989) Moderate (1987) High 1 (1984) High 2 (1985) High 3 (1986) 6.7 1.0 9.9 1.8 11.6 2.0 13.1 2.2 13.8 2.2 benefits would be approximately 8 percent more than under no action. Net economic benefits, by activity, are presented in table IV-22. Steady Flows The effect of each steady flow alternative on net recreation benefits would vary depending on the type of water year and actual water volume and pattern of releasesduring that year.The steady flow alternatives would eliminate daily flow fluctuations exceeding 10,000cfs. In general, reducing these fluctuations would increasenet recreation benefits over no action. However, the Existing Monthly Volume and Seasonally Adjusted Steady Flow Alternatives would decreasemean monthly flows during the season when white-water boating use is high. Depending .128 .189 .233 .252 .260 9.528 13.489 15.033 16.952 17.760 on the water year, this decreasecould offset the benefits gained by eliminating flow fluctuations, ExistingMonthly Volume Steady Flow Alternative. In a low water year, this alternative would generateapproximately 22 percent more recreation benefits than no action. In a moderate water releaseyear, the Existing Monthly Volume Steady Flow Alt~tnative would produce a 45-percent increasein recreation benefits compared to no action. In a high water releaseyear such as 1984, recreation benefits would be 8 percent more than no action. The results for angling, commercial white-water boating, and private white-water boating are presented in table IV-23. Seasona/1y Adjusted Steady Flow Alternative. In a typical low water year, habitat maintenance flows would be scheduled for approximately 10 days Table IV-25.-Net economic benefits of recreation for representative years under the Year-Round Steady Flow Altemative Annual benefits (1991 nominal $ millions) Low (1989) Moderate (1987) High 1 (1984) High 2 (1985) High 3 (1986) 5.8 1.0 9.9 1.8 11.7 2.0 13.1 2.2 13.8 2.3 .110 .189 .233 .251 .260 8.81 13.489 15.133 16.951 17.860 HYDROPOWER 297 during March; otherwise, there would be little flow fluctuation within the season. In a low water year like 1989,net recreation benefits would increaseby 20 percent over no action. On the whole, reduced flow fluctuations in a moderate release year would result in increased benefits to white-water boaters and anglers. Compared to no action, this alternative would result in a 51-percent increase in total net benefits. In high water volume years, the Seasonally Adjusted Steady Flow Alternative would be characterized by relatively high flows during the summer. The flows for 1984(a representative high flow year) would be higher than the optimal flows for white-water boating and angling, which would decreasenet economic benefits by 4 percent from no action. For comparison, two other high water years-1985 and 1986-were analyzed. The releasesin these years may be more typical of high water years. Basedon the 1985flows, seasonally adjusted steady flows would result in a 21-percentincrease in total recreation benefits compared to no action. Basedon the 1986flows, seasonally adjusted steady flows would increase34 percent over no action. Net economic benefits are presented in table IV-24. Year-RoundSteady Flow Alternative. Minimum flows in low and moderate water years would be higher than under no action, and flow fluctuations would be nearly eliminated. Net economic benefits would be increasedby 11 percent over no action in a typical low water year. In a moderate water releaseyear, net economic benefits would increaseby 51 percent. In high water years, the Year-Round Steady Flow Alternative would be characterized by relatively high constant flows. In some months, the flows for the 1984high water releaseyear would be in excessof the optimal flows for white-water boating and angling. Under these conditions, recreation benefits would decreaseby 4 percent. Net economic benefits for all activities under this alternative are shown in table IV-25. Two other high water years-1985 and 1986-also were analyzed. The releasesin these years may be more typical of high water years. Under the 1985water year, net recreation benefits under year-round steady flows would increase21 percent over no action. Basedon the 1986water year, net recreation benefits would increase34 percent over no action. HYDROPOWER Impacts on power operations relate to changesin how Western Area Power Administration (Western) interacts with and provides electrical servicesto its Salt Lake City Area Integrated Projects (sLCA/IP) firm power customers and other utilities in the region. Power marketing impacts are based on effects on long-term firm power marketing to about 180preference customers (Western Area Power Administration, 1992). Thesepreference customers consist of municipal and county utilities, rural electric cooperatives, water districts, irrigation districts, U.S. Government installations, and other nonprofit organizations. In total, approximately 1.7 million end-use customers in Arizona, Colorado, Nevada, New Mexico, Utah, and Wyoming purchase electricity from one of these preferencewholesale customers. Analysis Methods This impact analysis was based on studies prepared by the GCESPower Resources Committee (power ResourcesCommittee, 1993) and interviews with operations personnel at 298 Chapter IV Environmental Consequences Western's Montrose District Office. Standard electric utility integrated resource planning techniques and the latest available data were used to quantify the impacts of operational changesat Glen Canyon Dam. Computer models used were: CRSS(to simulate future hydrological conditions), the Electric Power Researchmstitute's Electric Generation Expansion Analysis System and Environmental DefenseFund's Electric Utility Financial and Production Cost Model (to simulate operations of the regional interconnected power system), and Western's Power Repayment Study (to calculate the SLCA/IP firm power rates). The economic analysis assumed two marketing arrangements: hydrology and contract rate of delivery (CROD). The hydrology approach assumed that (1) Western would sell only the capacity and energy generatedby SLCA/IP resourcesresulting from the available hydrology each year, and (2) customers would have to purchase firm capacity and energy elsewhere on an annual basis to meet any additional needs. The analysis of the magnitude of power impacts depends on the forecasted demand for electricity , the hydrologic sequenceused, the baseyear used, and the relative resource prices in 1991(the base year). If actual conditions vary from those assumedin the study, impacts will vary accordingly. The sensitivity of the results presented in this EIS to changesin study assumptions is described in PowerSystemImpactsof Potential Changesin Glen CanyonOperations(Phase,II and III) (Power ResourcesCommittee, 1993and 1994). The CROD analysis assumed capacity and energy would be marketed according to the post-1989 criteria. That is, Western would contract to provide its customers with long-term firm capacity and energy based on the projected generating capability of SLCA/IP resourceswith some acceptablelevel of risk. Under this arrangement, Western would purchase capacity and energy to meet customer contracts in years when SLCA/IP generation wasn't sufficient due to poor hydrology. Long-term firm power marketing impacts were based on the following factors: In both the hydrology and CROD marketing approaches,it was the customer's responsibility to replace capacity and energy lost as a result of constrained Glen Canyon Dam operations. Another marketing approach that was considered but not studied by the Power ResourcesCommittee was studied by Argonne National Laboratory in preparing the post-1989power marketing EIS. Under that marketing approach, Western would maintain a high marketing commitment and replace lost capacity on behalf of its SLCA/IP customers. Power system studies performed to support the power marketing EIS confirmed that economic and financial impacts could be reduced considerably by having Western use its expansive transmission system to replace lost capacity . .SLCA/IP marketable resource-<:apacity and energy available for marketing on a long-term basis with an acceptablelevel of hydrologic risk assumedby Western .Economic costs-associated with replacing lost capacity at Glen Canyon Dam from a societal or national perspective .Financial costs-<::ostsand/ or benefits associatedwith replacing lost capacity at Glen Canyon Dam from the perspective of an individual utility or groups of utilities .Wholesale rates-SLCA/IP combined firm power rate for long-term capacity and energy .Retail rates-charged by SLCA/IP firm power customers to their residential, commercial, and industrial end users The tenns "economic" and "financial" often are used interchangeably, but here they represent two different concepts. The economic analysis takes a societal or national perspective. It focuseson economic gains or losseswithin the electrical power industry as a whole. The financial analysis looks at individual utilities or groups of utilities. The financial analysis based on the CROD marketing arrangement examined impacts on utilities, including their costs to build new facilities or buy power elsewhere (utility economic impacts) and costs of transfer payments to buy power elsewhere (interutility transfers). Transfer payments were excluded from the economic analysis HYDROPOWER 299 becausethey were considered a redistribution of wealth that would not affect national economic development. However, interutility transfer payments are a real cost to power customers and so were included in the financial analysis. Estimatesof financial impact differ from estimates of economic impact in several respects. First, estimates of financial impact include the fixed and variable costs of generation for both existing and new facilities. Second,financial impact estimates include the costs of insurance, taxes,private capital, and depreciation that are not included in an assessmentof economic impact. Third, the estimatesof financial impact presented here include both the costs of generation incurred by the producer (if modeled) and the payments made by purchasers. Both costs are aggregated for each transaction between the original producer and the end user. Thus, the estimates of financial impact do not represent an estimate of net financial impact within the modeled region. Additional analysis of the financial impact is available in the Power ResourcesCommittee PhaseIII report (Power ResourcesCommittee, 1994). Part of the financial analysis used the SLCA/IP firm power rate, replacement resource costs,and administrative costs to estimate resulting retail rates. Revenuerequirements (how much a utility must make to stay in business) are affected by: .Increases rate .Reductions in the SLCA/IP combined wholesale in Federal firm power allocation .Increased costs of purchasing replacement power (including transfer payments) The Power ResourcesCommittee did not specifically study short-term impacts on hydropower. However, impacts would occur immediately following the Record of Decision (ROD), particularly if the ROD does not allow financial exception criteria for 5 to 7 years while long-term replacement resourcesare being secured. Until contracts between Western and its customers are renegotiated, Western might have to purchase replacement capacity to fulfill its contract obligations. Thesereplacement purchaseswould increasethe cost of service to firm power customers by increasing purchased power costs and/ or increasing the SLCA/IP firm power rate. Long-term impacts (up to 50 years) would include both reduced operational flexibility and less available firm capacity and on-peak firm energy for the region's electrical power market. Long-term impacts to capacity would likely accelerate construction of new gas-fired thermal generation facilities to replace capacity lost at Glen Canyon Dam-construction that otherwise would have been deferred for 5 to 10 years. Direct impacts would be those that affect day-today operations and change the character of the power resource available to Western's customers. Direct impacts also would include those that affect future planning for hydroelectric service, wholesale customers, other interconnected utilities, and power rates. mdirect impacts would affect end-use customers and the goods and services they provide. Summary of Impacts: Hydropower The principal values of Glen Canyon Powerplant are its ability to generate electricity without air pollution or using nonrenewable fuel resources and its flexibility to quickly and effectively respond to changesin an interconnected generation and transmission network. Removing the components that make hydropower so flexible and responsive-namely, control of how and when water is released-diminishes those values. Impacts on power operations and marketing are summarized in table IV-26. Since effects on operations are difficult to quantify in economic and financial terms, they are discussed qualitatively in terms of operational flexibility. The power marketing analysis identifies impacts on long-term firm power marketing due to changes in the amount of marketable resource, economic and financial costs,and wholesale and retail rates. Initially, endangered fish researchflows (likely a seasonallysteady pattern) would occur during minimum releaseyears through the Adaptive Management Program. The extent to which steady flows would be permanently incorporated 300 HYDROPOWER would depend on evaluation of the research results. Becausethese researchflows might not occur every year and becauseresults will need to be evaluated, effects of these flows could not be integrated into the summary table of impacts. Endangered fish researchflows would have the potential to increaseimpacts of the selectedalternative on power economics up to the level of impacts described under the SeasonallyAdjusted Steady Flow Alternative. If such researchflows occur only during the initial years of implementation, additional impacts would be minor. However, if steady flows were permanently incorporated in the operating criteria, impacts would be closer to those under the Seasonally Adjusted Steady Flow Alternative. Power Operations Impacts on power operations range from minor under the Maximum Powerplant Capacity Alternative to major under the SeasonallyAdjusted and Year-Round Steady Flow Alternatives. Many factors go into determining the ultimate impact of an alternative on power operations, and changing one factor may affect all the others. Operational restrictions imposed by all but the No Action and Maximum Powerplant Capacity Alternatives would reduce Western's ability to meet its obligations with maximum efficiency and economy and would reduce Glen Canyon's value as a load following and peaking facility . Although restrictions on dam operations result in reduced flexibility for power operations, it is important to point out that, given the number of variables involved, impacts can vary from minor to major even within an alternative, depending on the frequency and duration of particular events. An example of how these variable electrical system events can result in different effects is provided in Appendix E, Hydropower. Power Marketing All alternatives, except the No Action and Maximum Powerplant Capacity Alternatives, would restrict Glen Canyon Powerplant's flexibility to operate in a way that maximizes the value of electrical generation. Operational 301 restrictions would reduce how much long-term firm power could be marketed. In general, the relative magnitude of impacts to long-term firm power marketing would be: .Minor to no impact: No Action, Maximum Powerplant Capacity , and High Fluctuating Flow Alternatives .Moderate to potentially major impacts: Moderate Fluctuating, Modified Low Fluctuating, and mterim Low Fluctuating Flow Alternatives .Major impacts: Existing Monthly Volume, Seasonally Adjusted, and Year-Round Steady Flow Alternatives SLCAlIPMarketable Resources. Limiting maximum allowable releaseswould result in less available capacity; restrictions on ramp rates and allowable daily change in flow would further reduce available capacity. Increasing the minimum flows would reduce the value of energy by forcing increa~edoff-peak releasesand limiting the ability to make economy energy salesand purchases. Capacity.-In going from no action to restricted fluctuating and steady flows, operational flexibility would be increasingly limited. The maximum allowable water releases would go down, and the minimum allowable water releaseswould go up. This pattern would result in a narrower range of flows that would be further restricted by limits on the allowable daily change in flow. Reduced capacity would mean customers would need to generate or purchase additional capacity from other suppliers independently or through Western. Costs of these transactions have been analyzed and are described under individual alternatives. Also, the limits on allowable up and down ramp rates would determine how fast water releases could get from an existing flow to a desired flow, Figure IV-16 illustrates the drop in seasonal marketable capacity, primarily due to the decreasedmaximum allowable releasesfrom fluctuating flows to steady flows. Figures in appendix E show impacts of the alternatives on the cumulative distribution of capacity HYDROPOWER 303 Build additional generation resources Ask Western to securereplacement resources using their transmission system Smaller utilities, without significant generating resources,could: Purchasecapacity and energy from auxiliary suppliers Build their own peaking resources Ask Western to securereplacement resources using their transmission system Becauseof the large amounts of low cost surplus capacity in the regional power market for a considerable portion of the study period, the economic costs of Glen Canyon alternatives were significantly reduced (by over 50 percent) due to cost discounting procedures. Becausethis discount rate was 8.5 percent, any low values early in the study period significantly weight the results to the low side of the range (e.g., at an 8.5-percent discount rate, $1 promised 10 years in the future has the present worth of only 44 cents). Conversely, large values later in the study period have little impact in weighing the impacts one way or another. Table IV-26 summarizes the economic costs of each alternative. Figure IV-17 shows the range of costs associatedwith replacing lost capacity from Glen Canyon Dam. Financial Costs. The total cost of new generating resourcesand power purchasesfor all utilities combined is shown by alternative in table IV -26. The range of financial impacts on utilities is shown in table IV -27. Someutilities would incur higher financial impacts than others, depending on the extent to which they rely on SLCA/IP power. ';;j' c ~ E P! IU =s C Alternatives -Hydrology Contract Rate of Delivery Figure IV-17.-Net annual economic costs would decrease slightly under the Maximum Powerplant Capacity Alternative and increase under all other alternatives compared to no action. ~ 304 Chapter IV Environmental Consequences Table IV-27.-Financial impacts on large and small utilities by alternative Large systems Small 0 0 o 0 0 0 0 0.01 0.03 1.57 0.05 1.81 0.03 1.55 1.13 4.58 2.61 8.91 50 33 3. 75 3. 30 11. 14 29. 15 5.19 15. 0.98 , Does not include impacts of habitat maintenance Wholesale and Retail Rates. Western primarily markets power at wholesale rates to customers who, in turn, sell at retail rates to their customers. Wholesale Power Rates.- The SLCA/ IP combined wholesale long-term firm power rate is set at a level consistent with repayment of allocated project costs over a project's useful life or 50 years, whichever is less. Changesin Glen Canyon Dam operations-with possible resulting changesin the marketable resource and in nonfirm salesand purchases-would affect allocated costs,project revenues,and wholesale rates. The effects of reduced hydropower production at Glen Canyon Powerplant on long-term firm power rates-used to repay Federal investment in the Colorado River StorageProject (CRSP)and participating projects-are shown in figure IV-18. Theserates assumethat, other than purchased power costs,the current SLCA/IP repayment obligation remains unchanged. Firm power rates are used in calculating the impacts on retail power rates. Retail Power Rates.- Of the 5.6 million end-use customers (residential, commercial, and industrial) in the six-Stateimpact region, approximately 3.9 million (70 percent) do not receive power from the dam. Theseend users would either experienceno increasein power rates or their rates could decline slightly if their utility is able to make additional salesas a result of changesin Glen Canyon Dam operations. The o o o o o o o o o 0. 3. and beach/habitat-building systems 77 0 0 0. 04 0. 45 0. 50 0. 45 0.'65 0. 88 0 0 0.74 8.71 9.59 8.65 12.56 17.00 0; 78 14.76 flows retail rates of the other 1.7 million (30 percent) end users in the region would be affected to varying degrees. Tables IV-26 and IV-281ist the weighted mean retail rate impact for a subset of 0.4 million (7 percent) of these affected end-use customers. Due to a lack of data, time, and resources,the retail rate impact for the remaining 1.3 million (23 percent) large system end-use customers is not now known. Becausethese large systems are less reliant on Federal hydropower and have greater accessto alternative sourcesof supply, the rate ... ~ o .c tU ~ 0 10 ~ ii: l:' 00 as 0. as () ::;2 ... . -0 III 01 ~ o .Q 11. ii: 01 C .-~ 00 .. ~ E ::::::" -- 'i ~ ~- e ~:~:~:~: ,:,:,::: :~:~:~:~ ~ :::::~:: ~ L'.'" E ~