FACT SHEET
Ambient Groundwater Quality of the Aravaipa Canyon Basin:
A 2003 Baseline Study – May 2013
INTRODUCTION
A baseline groundwater quality study of the Aravaipa
Canyon basin was conducted in 2003 by the Arizona
Department of Environmental Quality (ADEQ) Ambient
Groundwater Monitoring Program. ADEQ carried out this
task pursuant to Arizona Revised Statutes §49-225 that
mandates ongoing monitoring of waters of the state
including its aquifers. This fact sheet is a synopsis of the
ADEQ Open File Report 13-01.1
The Aravaipa Canyon groundwater basin covers
approximately 517 square miles in southeastern Arizona
within Graham and Pinal counties (Map 1). Largely undeveloped, the remote basin has an estimated 135 residents
and includes the community of Klondyke.2 Low-intensity
livestock grazing is the predominant land use although
there are some irrigated fields and orchards along
Aravaipa Creek. Historic mining activity resulted in the
creation of the Klondyke Tailings Water Quality Assurance
Revolving Fund (WQARF) site in 1998.3 Groundwater is
used for all domestic purposes within the basin as well as
most irrigation and stock water supplies. Irrigation uses
the most groundwater in the basin.2
The basin is bounded on the north by the Turnbull
Mountains, on the northeast by the Santa Theresa and
Pinaleno mountains, and on the southwest by the Galiuro
Mountains. To the southeast, a subtle ridge forms the
boundary between the Aravaipa Canyon and Willcox
groundwater basins. Elevations range from 7,540 feet
above mean sea level (amsl) at Kennedy Peak in the
Galiuro Mountains to 2,400 feet amsl where Aravaipa
Creek flows into the Lower San Pedro groundwater basin.
The basin consists of federal land managed by the U.S.
Forest Service (26 percent) and Bureau of Land
Management (BLM) (21 percent), State Trust lands (38
percent), private land (14 percent) and Native American
land (1 percent) of the San Carlos Apache Tribe.2
SURFACE WATER HYDROLOGY
The basin is drained by Aravaipa Creek, a tributary to
the San Pedro River. The creek flows from the southeast
to the northwest. The creek is intermittent in its upper
reach but has perennial flow where bedrock brings
groundwater to the surface at Araviapa Spring. Perennial
flow typically lasts for 17 miles until surface water infil-

Figure 1 - A perennial reach of Aravaipa Creek created by
groundwater being brought to the surface by bedrock in
Aravaipa Canyon. This stream segment was named one of
Arizona’s Heritage Waters in 2007 based on its cultural, historical,
political, scientific and social significance. 4

trates into streambed alluvium about five miles above its
confluence with the San Pedro River. 2
The perennial segment of Aravaipa Creek was named
an Arizona Heritage Water based on its cultural, historical,
political, scientific, and social significance.4 This stretch is
partially located within the 19,700-acre Aravaipa Canyon
Wilderness Area, administered by the BLM, and the
9,000-acre Aravaipa Canyon Preserve managed by the
Nature Conservancy. Both entities have instream-flow
rights that are used to maintain base flows for conservation purposes.4

METHODS OF INVESTIGATION
To characterize the basin’s regional
groundwater quality, samples were collected from 15 sites (13 wells and two
springs). None of the samples appeared
to be water from the confined, basin-fill
aquifer. Field data indicated none of the
wells were flowing and drill logs were
not available for most wells.
Inorganic constituents, radon, and
isotopes (oxygen and deuterium) were
collected from each site. Sampling
protocol followed the ADEQ Quality
Assurance
Project
Plan
(see
www.azdeq.gov/function/programs/lab/).
The effects of sampling equipment and
procedures were found to be not significant based on quality assurance/quality
control evaluations.
WATER QUALITY SAMPLING RESULTS
Groundwater sample results were
compared with the Safe Drinking Water
Act (SDWA) water quality standards.
Public drinking water systems must meet
these enforceable, health-based, water
quality standards, called Primary
Maximum Contaminant Levels (MCLs),
when supplying water to their customers.
Primary MCLs are based on a daily lifetime
(70 years) consumption of two liters
Map 1 – Sample sites in the Aravaipa Canyon basin are color-coded according to
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of
water.
Primary MCLs were not
their water quality status: No Water Quality Exceedences and Secondary MCLs
exceeded at any of the 15 sites.
Exceedences.
Groundwater sample results were also
GROUND WATER HYDROLOGY
compared with SDWA water quality guidelines. Public
drinking water systems are encouraged by the SDWA to
Groundwater occurs primarily in two aquifers: stream
meet these unenforceable, aesthetics-based water quality
alluvium and basin-fill alluvium. The main aquifer is
guidelines, called Secondary MCLs, when supplying
stream alluvium which varies in width from 0.5 to 1 mile
water to their customers. Water exceeding Secondary
following Araviapa Creek and some of its major tributaries.
MCLs may be unpleasant to drink and/or create unwanted
Streambed alluvium is very productive, yielding up to
cosmetic or laundry effects but is not considered a health
1,500 gallons per minute. Fine-grained lake bed sediconcern.5 Of the 15 sites sampled, four (27 percent) had
ments separate the stream alluvium from the basin-fill
constituent concentrations that exceeded Secondary
alluvium, causing confined conditions in the latter
MCLs. Constituents above Secondary MCLs include
aquifer. Well yields in the basin-fill aquifer are variable
fluoride (three sites) and manganese (one site).
but tend to be much less than the streambed alluvium
Radon is a naturally occurring, intermediate breakaquifer. Minor amounts of groundwater are found in the
down product from the radioactive decay of uraniumsurrounding bedrock, especially along faults, fracture
238 to lead-206. Of the 15 sites sampled for radon, none
zones, and/or localized perched aquifers.2
exceeded the proposed 4,000 picocuries per liter (pCi/L)
Groundwater flow direction is from the surrounding
standard that would apply if Arizona establishes a multimountains to the valley floor and then northwest towards
media program to address the health risks from radon in
Aravaipa Canyon. Total recharge in the basin is estimated
indoor air. Seven sites (47 percent) exceeded the proto range from 7,000 to 16,700 acre feet per year.
posed 300 pCi/L standard that would apply if Arizona
Streambed infiltration of runoff is the primary source of
does not develop a multimedia program.5
recharge for the streambed aquifer and mountain-front
recharge replenishes the basin-fill aquifer.2
2

Constituents such as temperature, specific conductivity
(SC), TDS, bicarbonate, oxygen-18, and deuterium had
significantly greater concentrations in recent summer
precipitation than in recent winter precipitation.
Constituents such as SC, TDS, calcium, bicarbonate,
chloride, and oxygen-18 had significantly greater concentrations in sites located in consolidated rock than in
unconsolidated sediment (Kruskal-Wallis test, p <
_ 0.05).
DISCUSSION
Groundwater in the basin is suitable for drinking water
use based on the results of this ADEQ ambient study. This
conclusion is supported by a number of other factors
including limited development in the basin, the results of
other ADEQ ambient groundwater studies in the region,
and limited data from prior studies in the basin conducted
by the U.S. Geological Survey in 1975 and ADEQ’s
WQARF program in 2001. In the latter study, 15 wells
sampled in the vicinity of the Klondyke WQARF site by
ADEQ had “very good groundwater quality.” 3
Secondary MCL exceedances for fluoride may be the
result of hydroxyl ion exchange or sorption-desorption
reactions. These have been cited as providing controls on
lower (< 5 mg/L) levels of fluoride. As pH values increase
downgradient, greater levels of hydroxyl ions may affect
an exchange of hydroxyl for fluoride ions thereby increasing
the levels of fluoride in solution.8 The pH level of only
one of the three exceedances however, appears to follow
this pattern so there may be yet other influences causing
the elevated fluoride concentrations.
The only other Secondary MCL exceedance was an
elevated concentration of manganese. Groundwater in
the Aravaipa Canyon basin would normally be expected
to be oxidizing and have very low manganese concentrations. The one sample site however, appears to be have a
reducing environment, or one in which there is a decrease
in the groundwater oxidation state, as evidenced by not
only the elevated manganese concentrations but also the
basin’s only detections of iron and ammonia.8 Thus, the
Secondary MCL for manganese appears to be site specific
and not reflective of regional groundwater conditions.
Some aspects of groundwater quality in the Aravaipa
Canyon basin remain uncharacterized. Radionuclide
samples were not collected at any of the sample sites and
these constituents are often elevated by mining activity
such as the Klondyke tailings piles. ADEQ’s WQARF
program also did not collect radionuclide samples at any
wells.3 Radionuclide constituents such as gross alpha and
uranium often exceed drinking water standards in
Arizona. Also uncharacterized by the study is the
confined, basin-fill aquifer. During sample collection, no
samples were collected from wells known to be producing
water from this aquifer. In nearby basins, samples from
confined aquifers often had water quality exceedances
for fluoride, arsenic, and TDS.

Figure 2 – A domestic well drilled in the floodplain downgradient of the Aravaipa Canyon Wilderness Area.

GROUNDWATER COMPOSITION
Groundwater chemistry in the basin is most commonly
calcium-bicarbonate. Levels of pH measured in the field
were alkaline (above seven standard units) at all 15 sites
and three sites exceeded eight standard units. Total dissolved solids (TDS) concentrations were considered fresh
(below 999 mg/L) at all 15 sites. Hardness concentrations
were soft (below 75 mg/L) at one site, moderately hard
(75 - 150 mg/L) at six sites, and hard (150 - 300 mg/L) at
eight sites. Nitrate (as nitrogen) concentrations do not
appear to have been influenced by human activities,
being divided into natural background (three sites at <0.2
mg/L) and may or may not indicate human influence (12
sites at 0.2 – 3.0 mg/L).6 Most trace elements such as aluminum, antimony, arsenic, barium, beryllium, boron,
cadmium, chromium, iron, lead, manganese, mercury,
nickel, selenium, silver, thallium, and zinc were rarely
detected. Only fluoride was detected at more than one
third of the sites.
Oxygen and deuterium isotope values at most sites
appeared to consist of recently recharged winter precipitation. Two sites with more enriched isotope values
appeared to consist of recently recharged summer
precipitation.7
GROUNDWATER PATTERNS
Some groundwater constituent concentrations appear
to be influenced by recharge source and geology.

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Figure 3 – Isotope samples are plotted according to their oxygen-18
and deuterium values and fall into two groups: recent summer and
recent winter precipitation. A surface water sample from Aravaipa
Creek consisted of recent winter precipitation.

Figure 5 – Sample sites located in consolidated rock have significantly higher hardness concentrations than sample sites located in
unconsolidated sediment (Kruskal-Wallis, p <
_ 0.05). Other groundwater basins in Arizona have also had more mineralized groundwater
in hardrock areas than the valley alluvium.

References Cited
1 Towne, D.C., 2013, Ambient groundwater quality of the Aravaipa
Canyon basin: A 2003 baseline study: Arizona Department of
Environmental Quality Open File Report 13-01, 47 p.
2 Arizona Department of Water Resources Web site,
www.azwater.gov/azdwr/default.aspx, accessed 02/4/13.
3 Arizona Department of Environmental Quality, 2009, Klondyke
Tailings Water Quality Assurance Revolving Fund (WQARF) Site.
ADEQ WQARF program, ADEQ Factsheet 09-16, 2 p.
4 Arizona Heritage Waters website, 2013, http://www.azheritagewaters.nau.edu/loc_aravaipa_creek.html, accessed 01/9/13.
5 U.S. Environmental Protection Agency website,
www.epa.gov/waterscience/criteria/humanhealth/,
accessed 11/20/12.
6 Madison, R.J., and Brunett, J.O., 1984, Overview of the occurrence of nitrate in ground water of the United States, in
National Water Summary 1984-Water Quality Issues: U.S.
Geological Survey Water Supply Paper 2275, pp. 93-105.
7 Earman, Sam, et al, 2003, An investigation of the properties of
the San Bernardino groundwater basin, Arizona and Sonora,
Mexico: Hydrology program, New Mexico Institute of Mining
and Technology, 283 p.
8 Robertson, F.N., 1991, Geochemistry of ground water in alluvial
basins of Arizona and adjacent parts of Nevada, New Mexico,
and California: U.S. Geological Survey Professional Paper 1406C, 90 p.

Figure 4 – Sample sites with summer recharge have significantly
higher bicarbonate concentrations than sample sites derived from
winter recharge (Kruskal-Wallis, p <
_ 0.05). Elevated bicarbonate
concentrations are often associated with recharge areas.

ADEQ CONTACTS
Douglas C. Towne
ADEQ Hydrologist, Monitoring Unit
1110 W. Washington St. #5330D, Phoenix, AZ 85007
E-mail: dct@azdeq.gov
(602) 771-4412 or toll free (800) 234-5677 Ext. 771-4412
Hearing impaired persons call TDD line: (602) 771-4829
Web site:
azdeq.gov/environ/water/assessment/ambient.html#studies
Maps by Jean Ann Rodine

Publication Number: FS 13-04

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