Potential Impacts of the
Sonoran Desert Conservation Plan
on Water Quality and Quantity
in Pima County
A Report for the Pima County Sonoran Desert Conservation Plan 2002

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

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POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

The Issues
Water Supply for Humans

For more than 100 years Pima County
residents have been almost entirely
dependent on groundwater for all uses.
This has led to an significant decline in
the water table in much of Eastern Pima
County, which is turn presents a serious
threat of land subsidence. Ever since the
start of the twentieth century Tucsonans
have had to go farther and farther away
to find adequate water for their use.
Once people could collect water from
springs in what is now downtown. Water
was brought from the river first near
22nd Street and later from as far south
as Valencia. Road Once surface water
was depleted, wells were used to supplement the supply and the search for new
places to pump water went as far as the

Avra Valley, where Tucson gets a large
portion of its water today.
Recently, water from the Colorado
River, via the Central Arizona Project
(CAP), has begun to supplement groundwater for customers of Tucson Water
and some other users. This new supply
will help to prolong the supply of water
for people, agriculture, and industry, but
will not in the long run prevent further
mining of groundwater under current
population projections. Depending on the
assumptions, the demand for human use
will begin to exceed renewable supplies
in twenty to thirty years. Projections of
the impacts of climate change are liable
to change those assumptions if the local
climate becomes warmer and periods of
drought more extensive. The drought of

Figure 1. Projected water
use in the Tucson AMA.
Agricultural use is projected
to decline, so that increased
municipal use will not substantially change the total use
for a while. Amounts are in
acre-feet. Groundwater mining will continue. Note that
water for riparian protection
is not calculated except for
a small constant amount for
evapotranspiration along the
Santa Cruz River. Source
of information: Tucson AMA
Third Management Plan.

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

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Figure 2. Cycles of drought
and plenty in the Colorado
River basin based on studies
of tree rings. Note the extended drought in the late 1500s
and the extended period of
plenty in the early twentieth
century. Source: Meko, D et
al. The Tree-Ring Record
of Severe Sustained Drought.
Water Resources Bulletin.
October 1995. Page 798.

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the early 21st century is an indication
of the tenuousness of our surface water
supply. Droughts of several hundred
years ago were far more long lasting
and if they recurred in this century serious supply problems could result. Pima
County residents are shielded from many
of the short-term impacts of drought
by using a combination of groundwater
and surface water from the Colorado
River. The surface water supplies are
dependent on annual renewal of supplies
by precipitation while groundwater is
affected in the long term by lessened
natural recharge.
Residents of western Pima County
are entirely dependent on a very limited
supply of groundwater and very low
annual precipitation. There is almost no
chance that CAP water will ever reach
this area so water supplies are a clear
limiting factor for growth. Residents of
the middle San Pedro area have both
groundwater and a small amount of
surface water in the San Pedro River
and tributaries. Neither of these areas is
in the Tucson Active Management Area

(TAMA) discussed below. Arivaca, on
the other hand, is a relatively isolated
basin within the AMA but hydrologically separate from the aquifers beneath
the Tucson area. Replenishment in
the metropolitan area would not benefit
Arivaca where just a small increase in
pumping could severely impact the cienega and streams.
Two techniques used for prolonging
the supply are reuse and recharge. Only
about ten percent of the effluent produced in Pima is directly reused, primarily for turf irrigation. The remainder is
allowed to flow in the Santa Cruz River
where most of it eventually recharges
the water table, although some of that
recharge occurs in Pinal County. Projects
to recharge CAP water and effluent in
the Avra Valley, at Pima Mine Road and
along the Santa Cruz River save water
for a time when it will be needed.

Water for Riparian Use

In Pima County as in most other parts
of Arizona, adequate water for human
use has long taken priority while water

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

for riparian and habitat needs has been
secondary. When water budgets are calculated on the basis of human demands
for water for agriculture, industry, and
urban use are included, but water to
preserve streamflow for riparian needs
is not. Water for riparian uses can be
assured by protecting the existing supply
in shallow groundwater areas and along
perennial and intermittent streams or by
bringing in alternate sources of water.
Protecting existing supplies can be
accomplished by restricting groundwater
pumping and by management of the
watershed to optimize water supplies
for the stream. The areas of shallow
groundwater in Pima County as well as
the perennial and intermittent streams
and springs have been identified. Priority
shallow groundwater areas most in need
of protection are in the vicinity of Arivaca,
Tanque Verde Creek, Cienega Creek and
Davidson Canyon because there is potential for increased groundwater pumping
in the area that would negatively impact
the streams.

Water Management
Authority to Influence Water Use
More than 130 different water companies, irrigation districts, municipalities,
and water cooperatives provide water in
Pima County. More than 20,000 people
and businesses have their own wells,
as do many commercial users (most
notably the mining companies) and agricultural entities. Within TAMA, The
Department of Water Resources (ADWR)
sets rules under the Groundwater
Management Act, but there is no central
water management agency.
ADWR
has no authority under state law to
manage groundwater and surface water
conjunctively to protect riparian areas as
discussed below.
Pima County has little authority to
regulate water use even in the unincorporated areas. What ability there is to
regulate water use lies primarily in the
Arizona Department of Water Resources
and the many water providers in the
area, the largest of which is Tucson

Water. Pima County does have the
authority to implement land use policies
that promote conservation, including golf
course approval and floodplain regulation. Pima County processes most of the
wastewater produced in the county, but
because of an intergovernmental agreement with the City of Tucson, does not
own most of the effluent or have the
right to determine its use.
Central
Arizona Project Water in Pima County
is primarily managed by the City of
Tucson.
The Tohono O’odham Nation has a

Figure 3. The Tucson Active
Management Area. Note that
it does not include the headwaters of Cienega Creek, the
Pima County portion of the
San Pedro River or anything
west of Avra-Altar Valley.
Source: Arizona Department
of Water Resources.

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

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Figure 4. Shallow groundwater and springs in Eastern
Pima County. Source: Pima
County Technical Services
Department.

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POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

significant CAP allocation, which the
tribe uses in the San Xavier District and
the Shuk Toak District and has control
over use there. Most of the water is used
for agriculture, but a portion in the
San Xavier District is being used for
riparian restoration projects. The tribe
also has rights to a portion of the treated
wastewater from Pima County facilities.
Outside TAMA ADWR has jurisdiction but the laws for those non-AMA
areas are less stringent than they are in
the AMAs.

Water Law

Arizona water law makes a big distinction between groundwater and surface
water. Surface water is legally considered a different entity from groundwater. Surface water is managed under
the Prior Appropriation doctrine that
requires people to apply for rights to
use the water. People with seniority in
terms of time of permit application have
the right to use all of the water to which
they are entitled even if junior users do
not get water - “first in time, first in
right.” The only significant way a right
can be lost is by failure to use the water
beneficially over a period of time - “use
it or lose it.”
Within surface water law, there is
a provision for granting instream flow
permits, leaving water in the stream for
the benefit of wildlife, riparian vegetation
or recreation. Within Pima County a
very small number of such permits have
been granted. An instream flow permit
does not guarantee a continued supply
of water since senior rights holders have
priority over these later permits, and
because of the legal problems involved in
protecting surface water rights holders
from pumping of groundwater.
Groundwater, on the contrary is
managed under the Groundwater
Management Act, which has special provisions within Active Management Areas
(AMA). Most of Pima County east of
the Tohono O’odham Nation except for
the San Pedro River watershed and a
portion of the Cienega Creek watershed
is in the Tucson Active Management

Area. The goal of the Tucson AMA
is to attempt to reach Safe Yield by 2020,
reach a balance between supply and
demand. Large new wells may be drilled
only if they meet certain conditions and
the owner can demonstrate a legally
defined 100-year supply exists, but small
domestic wells are allowed with few
or no restrictions. Within the AMA
there are rules requiring conservation
measures for industry, agriculture and
water providers. Outside of the AMA
there are very few legal restrictions on
groundwater pumping.
Both inside and outside the AMA
groundwater and surface water rights
are separate. People may pump water
even if it affects streamflow and the
senior rights of surface water users.
Arizona Supreme Court decisions, allow
restrictions on pumping within the “subflow” area of a stream, but this remains
to be fully defined. This failure to
manage the waters conjunctively, even
though they may be physically connected
makes it difficult to use water law to
protect streams in shallow groundwater
areas in Pima County. Streams most
in jeopardy from increased groundwater
pumping in Pima County are Arivaca
Cienega and Creek, Tanque Verde Creek,
Rincon Creek, Davidson Canyon, Cienega
Creek, Middle San Pedro River, and
Agua Verde. Watersheds that would
benefit most from improved management to improve water flow are those
that are extensively grazed or used for
recreational purposes such as off-road
driving, especially where grazing or vehicle use occurs in a riparian area.

Water Quality

Having adequate water supplies
depends not only on water quantity,
but also on having water of a quality
adequate for the desired use whether it
be for humans or wildlife. For the most
part, the water in Pima County is of high
quality for both purposes. There are,
however, a number of locations in the
urban area where the groundwater has
been contaminated to the point that
drinking water standards are exceeded.

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

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Figure 5. Generalized table of
water supplies for the various
subareas of Pima County.

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Surface water in Pima County generally
meets standards for its designated uses.
According to the Environmental
Protection Agency (EPA) the major sources of water pollution nationally are industrial releases, urban storm runoff, agriculture and grazing, landfills, septic
tanks, spills in transportation corridors,
and leaking underground storage tanks.
Sedimentation from cleared land, burned
lands, and eroded watersheds is also a
concern.
Because there is so little surface water
in the areas of Pima County that are not
within National Forest, National Park
or State Park boundaries, there have
been few surface water contamination
problems. The Cienega Creek Preserve is
traversed by railroad tracks and Interstate

10, spills from which could contaminate
the water. Some surface water contamination has been caused by improper grazing techniques even on protected lands.
More study is needed of the impacts
of septic systems, especially in shallow
groundwater areas. While the use of septic
systems can benefit water supply through
direct recharge, it can negatively affect
groundwater quality through recharge of
inadequately treated water either because
the area was not suitable for septic systems or because of poor maintenance.
More study is also needed of the
water quality impacts of recreations uses,
especially trail use by horses and by
off-road vehicles. Erosion leading to
sedimentation is a major concern but the
impacts are not well documented.

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

Brief Summaries of SDCP Reports
The reports discussed below have provided a strong body of background material for water-related proposals and for
evaluating impacts of those proposals
on water supply and water quality for
humans and wildlife.

Water Resources and the Sonoran
Desert Conservation Plan (1999)
This report provided the first general
overview of SDCP-related water issues in
Pima County. It examined the peculiarity of Arizona water law that treats
groundwater and surface water as separate entities making conjunctive management extremely difficult. It generally
looked at how mining of groundwater
has affected the area, its riparian systems, and its wildlife. This report also
looked at five strategies for dealing with
these problems, including adopting a
regional water policy, adopting strategies
to reach Safe Yield, develop a recovery
plan for riparian systems, adopt a multispecies conservation plan and an integrated regional effluent, recharge and
reclamation plan that maximized use of
renewable resources. In the conclusion,
the author stated that in the “next
century, beneficial use will have to recognize hydrologic principles and environmental realities in addition to consumptive uses.”

Water Resources in the Arivaca
Area (2000)
This report, written by the Arivaca Water
Education Task Force, looked at how

additional groundwater pumping would
affect surface water in the area. It
concludes that even with no new zonings
or new groundwater pumping rights, the
cienega would be negatively affected.

GIS Coverages of Perennial and
Intermittent Streams and Areas of
Shallow Groundwater (2000)
This study mapped perennial streams,
intermittent streams, and areas of shallow groundwater. The areas mapped
then became available as GIS data layers to use in developing protection and
recovery strategies. The report identified 55 perennial stream reaches and 82
intermittent stream reaches on a total of
74 different streams. A high proportion
of the identified streams are on land
already at least partially protected by
some level of government, especially the
U.S.D.A. Forest Service. In conclusion,
the authors recommended that further
study be made of some specific areas.
Continued monitoring was considered
important in maintaining an up-to-date
information base. The authors also
expressed the hope that a similar inventory could be done of streams on the
Tohono O’odham Nation.

Water Uses Along Selected Streams
in Pima County (2000)
This study mapped out wells within
one mile of identified perennial and
intermittent streams and areas of shallow groundwater, including exempt wells
in those areas. It also identified water

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

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Water Conservation in Pima
County (2001)
This report looked at the development
of water conservation measures in Pima
County, including actions by the Arizona
Department of Water Resources, Tucson
Water and private water providers.
Options for additional measures that
Pima County could adopt were offered.
These measures were adopted as part of
the Pima County Comprehensive Plan
in December 2001.

Lower Cienega Basin Source Water
Study (2001)

Figure 6. Arivaca Cienega
is in a shallow groundwater
area that is highly threatened
by increased groundwater
pumping. Photo:

users and amount of water being used,
with emphasis on pumping, although
some surface water diversions were also
examined. The authors concluded that
more information is needed to determine
a variety of factors that influence water
available for riparian needs.

Springs in Pima County (2000)
This study provided mapping of springs
in Pima County, many of which were
well-documented for the first time in this
report. The information was provided
as a GIS layer to be used in a variety
of purposes. A high proportion of the
springs are on already at least partially
protected lands, especially the U.S.D.A.
Forest Service.
Some very significant
springs, however, occur on lands that do
not have protected status. The report
also identified species of plants, fish and
other wildlife associated with springs. The
authors recommended that more information be gathered, that biological inventories be conducted, that certain springs
be evaluated in terms of the protection
potentially available to protect them, and
the necessary legal measures be taken.

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This study investigated the source of
water for the lower-most perennial reach
of Cienega Creek. It was determined,
using water chemistry data, stable isotope data, and hydrologic data, that the
source of flows was upstream reaches of
Cienega Creek, rather than Agua Verde
Creek, which is a significant tributary,
or the surrounding bedrock aquifer. The
study also noted that Cienega Creek and
the bedrock aquifer seemed to be in
hydraulic connection.

Water Resources in Pima County
(2001)
This report looked at availability of water
supplies in Pima County from four perspectives:
1. Would
the
Tucson
Active
Management Area meet and continue to
meet the goal of Safe Yield as required
under state law?
2. Would Pima County as a whole
have adequate water for human use?
3. Would specific regions within Pima
County have water supply problems even
if the region as a whole did achieve a
balance?
4. Would there be adequate water to
meet the goals of riparian protection and
restoration under SDCP?
The report concluded that if all assumptions were valid regarding CAP water
availability, effluent use, recharge, and
changes in state water law, there would
be adequate supplies for human use for

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

at least the next quarter of a century
or so, although subsidence could be a
consideration. It concluded, however,
that water for riparian uses is not generally calculated in the regional water
budget and as human uses increase,
water supplies for riparian protection
and restoration could be in short supply,
especially in some specific areas where
alternate supplies are not available.

Groundwater Level Changes in the
Tanque Verde Valley Update, (2002).
In this report and two preceding studies
of the same area, the authors looked
at how groundwater pumping along a
portion of Tanque Verde Creek affects
riparian vegetation along the creek. The
major pumping in the area is by Tucson
Water, but quite a few private wells also
pump water from the area. The report
noted that since arrival of CAP water
in the urban area, Tucson Water has
attempted to reduce its pumping in the
area to maintain a high water table.

Water Quality Issues (2001)
This study identified improving or maintaining groundwater quality, dealing with
contamination from leaking underground
storage tanks, landfills, industrial operations and other land uses, and septic tanks
as the issues most in need of attention.
With regard to surface water, the issues
were spills, runoff from urban areas leading
to sedimentation, erosion, and discharge of
household chemical such as pesticides. The
report recommended additional monitoring, attention to the needs of aquatic species, and proper watershed management
plans.
The authors recommended a
number of policies with emphasis on making land use decisions in light of possible
impacts of new development on cumulative
impacts on streams and aquatic species.
Policies for improvement of wastewater
quality and emphasizing regional treatment in a few large well-managed treatment plants, rather than a proliferation of
smaller facilities. It also recommended the
use of effluent for riparian restoration.

Water Quality of Priority Streams
in Pima County (2002)
This report looked at the quality of
21 priority streams in the county. The
conclusion that overall the quality is very
good. Seven streams were recommended
for more investigations and monitoring.
Most of the priority streams are at least
partly within protected lands and unlikely
to experience significant deterioration. The
authors recommend that land use planning identify which future land uses are
appropriate near the streams, that impacts
of those land uses be minimized, and that
the quality be regularly monitored.

Water Quality in Pima County
(2002)
This report summarizes water quality for
groundwater and surface water in Pima
County. The report discusses more
than ten groundwater contamination
sites in the urban area, stormwater quality, monitoring of surface water, effluent
quality and quality of CAP water. The
conclusions are that except for some contaminated groundwater sites, groundwater is of good quality, stormwater runoff
meets EPA standards as does treated
wastewater and that in the few streams
with surface water, the quality is adequate for the intended use.

Water Quality Requirements of
Native Aquatic Species in Pima
County (2002)
The report looked at the water quality
requirements of priority vulnerable aquatic species, including two frog species and
six fish species. The findings were that
native aquatic species have a relatively
high tolerance for wide ranges in temperature, pH levels and salinity. The
study also looked at sites with multiple
species. The report concluded that water
quality was generally within the required
range for supporting native species. It
concludes with the statement that the
greatest threats to aquatic species are loss
of habitat and water supply and introduction of non-native invasive species.

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

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SDCP Proposed Actions
Water Conservation

New water conservation ordinances and
policies including encouraging water harvesting and the use of domestic gray
water will help to reduce water use.
These measures include retrofit of indoor
conservation devices in older homes
when ownership changes, new commercial landscape requirements, and stricter
conditions for water use in newly constructed golf courses.

Floodplains

Proposals to further limit construction on
floodplains and acquire floodprone lands
will promote recharge of the aquifer by
allowing water to percolate along the
floodplains. Land acquisition will mean
that the county can build fewer new flood
control structures to protect buildings and
infrastructure in and close to flood and
erosion areas. This approach has proved
successful in the case of Cienega Creek
where the county acquired a perennial
stretch of stream using flood control funds,
arguing that preserving the natural functions of the stream would lower future
flood control and damage repair costs,
while promoting recharge. Proposals to
purchase additional floodprone land in
selected areas will have multiple benefits.

Water for Riparian Protection and
Restoration

Pima County and the City of Tucson
have signed an intergovernmental agreement to reserve 10,000 acre-feet of treated wastewater to use for habitat enhancement and restoration purposes. Projects
to make optimal use of this water source

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will benefit aquatic and riparian habitat.
Pima County will also look to alternate
sources of water to protect streamflow.
One option is to provide incentives to
persuade landowners in shallow groundwater areas to stop pumping in those
areas and connect to an alternate supply.
Pima County is seeking ways to acquire
water rights in Cienega Creek through
trading for an alternate water source.
Making arrangements with Tucson
Water or other entities for the use of CAP
water for riparian purposes is another
option under consideration.

Land and Water Rights Acquisition

Acquisition of land and water rights
to minimize groundwater pumping in
the vicinity of certain perennial and
intermittent streams and springs will
help preserve priority areas. Finding
ways to help people with wells in shallow
groundwater areas find alternate water
sources, such as CAP water or purchase
from a utility such as Tucson water can
also help protect flows in specific areas.

Changes in Arizona Water Law

Pima County has worked with the
Governor’s
Water
Management
Commission in an attempt to make significant changes in Arizona water law.
The Commission made significant riparian protection recommendations, but
Arizona Legislature did not deal with
those recommendations in the 2002 session. Pima County will continue to work
for needed changes in the water law in
order to have more tools for protection
of riparian areas.

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

Potential Impacts under Alternatives
None of the alternatives involve construction of any potentially polluting
facilities or introduction of hazardous
wastes, thus no negative water quality
impacts are anticipated. None of the
alternatives involve increasing human
water use in the area as a whole or in any
specific location, thus no negative water
supply impacts are anticipated. Some of
the alternatives involve increasing water
use for riparian use and protection or
reintroduction of priority species. Since
this water will also be desired for human
use in some situations, conflicts may
arise, especially in the later years if
the population continues to increase as
projected. Building infrastructure to
transport water to where it will be used
could possibly have negative environmental impacts.
Since none of the proposed alternatives involve reducing total population
levels, but instead accept PAG projections, none of the alternatives will substantially alter the total human water
budget for the region.
Some of the
alternatives, however, will alter the local
water availability projections for specific
areas, especially with regard to water
for wildlife and riparian protection and
restoration.
None of the alternatives will significantly impact water quality. The main
threats to groundwater quality would be
possible migration of existing contaminant plumes and the main threats to the
water quality of priority streams would
be sedimentation from non-point sources
and degraded range conditions in the
watersheds. No serious human health

Figure 7. Preservation of natural watercourses where appropriate rather than radically altering them is a goal of SDCP. Photo: Barbara Tellman

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

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effects are anticipated to occur from these
sources under any alternative. Decrease
of water quality for wildlife may occur
in a few situations, but the greatest
concern for wildlife and riparian areas
is reduction of water supply rather than
impairment of water quality.

Continuation of present growth patterns
(No Action)

This alternative has the greatest potential for negatively impacting water supplies in specific areas. For example, if
growth and water use increase in the
Arivaca area, the water supply for the
Arivaca Cienega and creek are liable to be
severely impacted. Increases in pumping in shallow groundwater areas such
as Tanque Verde Creek will negatively
impact riparian vegetation. Subdivision
development in the vicinity of the Cienega
Creek Preserve could affect water levels
if local water sources are used. If
Pima County succeeds in transferring
the downstream water right in the area,
the perennial reach of the creek would
lengthen, but development near the creek
in that area could still impact the riparian area. In all cases, further construction in watersheds could lead to deterioration of water quality, especially an
increase in sedimentation.
Allowing
additional septic tanks in certain areas
could negatively impact water quality,
although further studies are needed to
demonstrate impacts in specific areas.

Expansion of County Parks

While in all the options discussed below,
park expansion could have some positive
impact on water quality and supply, the
impacts could be affected by how the area
is managed. In particular, recreational
use of the area would have to be managed to minimize negative impacts from
use of trails and off-trail travel by horses,
off-road vehicles, and hikers.
Illegal
dumping is often a problem in undeveloped areas and less so in preserves.
Expansion of Tucson Mountain Park
would have little direct impact on water
supply or water quality since there are
no perennial or intermittent streams

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or shallow groundwater areas on the
periphery of the park. Expansion of the
park, however, might mean fewer new
homes are built in the area, which,
in turn, would mean that fewer septic
tanks would be constructed there, and
less sedimentation would occur, both of
which could impact downstream water
quality.
Expansion of Colossal Cave or the
Cienega Creek Preserve could have a
major beneficial impact on water supply
and quality on this far east side of
the metropolitan area.
The major
stream near Colossal Cave is Agua Verde
Creek. Other perennial streams are
within Saguaro National Monument for
the most part, although Rincon Creek
extends outside the park boundary. Agua
Verde Creek would receive additional
protection from impacts of septic tanks,
wells, and urban runoff if it were included in the park expansion. Removal of
cattle from the area would benefit the
stream, which is perennial and has native
fish. Expansion of parks in this area
would probably also serve to protect the
water supplies for numerous significant
limestone caves in the general area.
Expansion of Tortolita Mountain Park
would not have a significant impact on
perennial or intermittent streams, as the
only such streams are at the edge of the
park boundary and within incorporated
Oro Valley. Limiting of new subdivisions
on the Tortolita Fan, however, could
have a positive impact in that less urban
runoff and sedimentation would occur in
this very active floodplain region.

Emphasis on riparian area
protection

This alternative offers the greatest potential for preservation and protection of
water supply for riparian areas and wildlife. The majority of perennial and intermittent streams and shallow groundwater areas are in areas already at least partially protected. The perennial and intermittent streams and shallow groundwater areas that would benefit most
from additional protection are Davidson
Canyon, Cienega Creek, Agua Caliente,

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

Arivaca Cienega and Creek, and the
middle San Pedro River. In all of these
cases, construction of additional homes,
businesses, and roads has the potential
to impact both water supply and water
quality. The overall impacts can be
found in the Riparian Area Issue Paper.
In this paper, only the water quality and
quantity impacts are discussed.
Additional pumping in shallow groundwater areas is liable to impact water supplies for the riparian area and thus any
measures to assure that new pumping
does not occur would benefit the area.
Purchase of land in these areas will have
a major direct positive impact on water
supplies by reducing the potential for
new pumping. In addition, acquisition of
a surface water right at the downstream
end of Cienega Creek would help to
protect and extend the perennial reach.
Adoption of new riparian protection
legislation at the state level would greatly
assist Pima County in protecting certain
riparian areas.
Availability of treated wastewater and
CAP water for use in riparian projects
will benefit habitat by creating or expanding existing riparian/wetland habitat in
selected areas.
Reintroduction of rare or extirpated
aquatic species of flora and fauna will
be dependent on using alternate water
supplies and protecting existing water
supplies for perennial and intermittent
areas. Using alternate water supplies to
reconstruct or simulate relatively natural
streamflow functions in areas where
those have been impaired would be crucial to most successful reintroduction.

Emphasis on limiting development in the
unincorporated areas on the Northwest
side of the metropolitan area
This alternative will have little impact
on either water supply or water quality
for riparian areas or wildlife. The
only perennial/intermittent stretches of
streams in this area are either in protected areas (Tortolita Mountain Park,
Catalina State Park or the Coronado
National Forest) or in incorporated
areas (Oro Valley and Marana).

Limiting further growth in this area
would, however, help preserve a limited
supply of groundwater in this area.
Water for most of the area is, or can be,
made available by several water providers in the area.

Emphasis on ranch conservation

This alternative offers high potential for
protection of both water supply and water
quality in specific locations, depending
on how the areas are managed.
If
ranchlands were used for either wildcat
or subdivision development strains on
the local water supplies would increase
wherever the development occurs since
there are few alternate supplies in the
more remote areas.
Ranch conservation in the Altar Valley
could be highly beneficial to preserving
surface water supplies by limiting new
groundwater pumping which would happen if more people moved into the area.
Studies by the Arivaca Water Education
Taskforce show that just a small increase
in the amount of pumping in the area
would reduce water supplies for the
cienega and creek. Since there are no
options within current Arizona water
law for preventing additional pumping
by legal means, land acquisition is the
most feasible method for limiting new
groundwater use.
The water quality in the Altar Valley
is quite high except for a manmade
lake upstream of the town of Arivaca.
According to the Arizona Department of
Environmental Quality this lake is contaminated by leakage from abandoned
mines in the area and no workable
measures have yet been found to clean
up the contamination. Land acquisition
or cooperative agreements with ranchers
would have no impact on this problem.
Water quality in the area may to some
extent be affected by grazing, although
little information is available. Water
quality in the streams appears to be
generally of high quality. Control of
grazing along riparian areas is liable
to have a beneficial impact on water
quality.
Ranch conservation in the Avra Valley

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY

15

would have less of an impact on water
supply and water quality since there are
no priority streams in the area.
Ranch conservation along the San
Pedro River could be beneficial to water
supply. Reduction or elimination of
irrigated agriculture through land acquisition or cooperative agreements would
benefit the river by increasing water supply. The Arizona Nature Conservancy
has begun to acquire land with water
rights along the river especially downstream of the Pima County portion of
the river and thereby reduce agricultural
water use along the river. The possibility
of ranches being acquired for subdivision
development in this area is much lower
than in the Altar or Avra Valleys because
of remoteness of the area and lack of
a paved road. Acquisition of land to
prevent subdivision development in the
area would probably be less beneficial
than acquisition elsewhere.

Summary

SDCP has the potential to improve
and enhance water supplies for riparian
purposes and protection and reintroduction of aquatic species. There are no
anticipated impacts on water supplies
for humans.

16

There are no anticipated negative
water quality impacts from SDCP proposals. There may be some water quality
benefits from the various alternatives.
The riparian area and ranchland protection alternatives offer the greatest positive impacts to both water supplies for
riparian purposes and water quality. The
No action and emphasis on the northwest
side have the least positive impact.

References

The SDCP reports discussed above contain extensive references and are the
basis for much of the information in this
summary report. The most significant
of the references are:
Arizona Department of Water Quality.
web site www.deq.az.us
Gelt, J. et al. 1999. Water in the Tucson
Area: Seeking Sustainability. Water
Resources Research Center. University
of Arizona. Tucson. and WRRC web
site www.ag.arizona.edu/azwater/
Tucson Active Management Area. 1997.
Third Management Plan and web site
www.water.az.gov

POTENTIAL IMPACTS OF THE SONORAN DESERT CONSERVATION PLAN ON WATER QUALITY AND QUANTITY IN PIMA COUNTY