II
III
Ambient Groundwater Quality of the
Dripping Springs Wash Basin:
A 2004-2005 Baseline Study
By Douglas C. Towne
Maps by Jean Ann Rodine
Arizona Department of Environmental Quality
Open File Report 2010-02
ADEQ Water Quality Division
Surface Water Section
Monitoring Unit
1110 West Washington St.
Phoenix, Arizona 85007-2935
Thanks:
Field Assistance: Karla Burnley and Shaunel Wytcherley.
Special recognition is extended to the many well owners who were kind enough
to give permission to collect groundwater data on their property.
Photo Credits: Douglas Towne
Report Cover: Stone Cabin Spring, located in the Dripping Springs Mountains, supplies water
for livestock use. The sample from the spring (DSW-8), as with all twelve
samples collected from the Dripping Springs Wash basin, met all health-based
and aesthetics-based water quality standards.
IV
Other Publications of the ADEQ Ambient Groundwater Monitoring Program
ADEQ Ambient Groundwater Quality Open-File Reports (OFR):
McMullen Valley Basin OFR 11-02, June 2010, 99 p.
Gila Valley Sub-basin OFR 09-12, November 2009, 99 p.
Agua Fria Basin OFR 08-02, July 2008, 60 p.
Pinal Active Management Area OFR 08-01, June 2007, 97 p.
Hualapai Valley Basin OFR 07-05, March 2007, 53 p.
Big Sandy Basin OFR 06-09, October 2006, 66 p.
Lake Mohave Basin OFR 05-08, October 2005, 66 p.
Meadview Basin OFR 05-01, January 2005, 29 p.
San Simon Sub-Basin OFR 04-02, October 2004, 78 p.
Detrital Valley Basin OFR 03-03, November 2003, 65 p.
San Rafael Basin OFR 03-01, February 2003, 42 p.
Lower San Pedro Basin OFR 02-01, July 2002, 74 p.
Willcox Basin OFR 01-09, November 2001, 55 p.
Sacramento Valley Basin OFR 01-04, June 2001, 77 p.
Upper Santa Cruz Basin OFR 00-06, Sept. 2000, 55 p. (With the U.S. Geological Survey)
Prescott Active Management Area OFR 00-01, May 2000, 77 p.
Upper San Pedro Basin OFR 99-12, July 1999, 50 p. (With the U.S. Geological Survey)
Douglas Basin OFR 99-11, June 1999, 155 p.
Virgin River Basin OFR 99-04, March 1999, 98 p.
Yuma Basin OFR 98-07, September, 1997, 121 p.
ADEQ Ambient Groundwater Quality Fact sheets (FS):
Dripping Springs Wash Basin FS 11-02, July 2010, 4 p.
McMullen Valley Basin FS 11-03, June 2010, 6 p.
Gila Valley Sub-basin FS 09-28, November 2009, 8 p.
Agua Fria Basin FS 08-15, July 2008, 4 p.
Pinal Active Management Area FS 07-27, June 2007, 7 p.
Hualapai Valley Basin FS 07-10, March 2007, 4 p.
Big Sandy Basin FS 06-24, October, 2006, 4 p.
Lake Mohave Basin FS 05-21, October 2005, 4 p.
Meadview Basin FS 05-01, January 2005, 4 p.
San Simon Sub-basin FS 04-06, October 2004, 4 p.
Detrital Valley Basin FS 03-07, November 2003, 4 p.
San Rafael Basin FS 03-03, February 2003, 4 p.
Lower San Pedro Basin FS 02-09, August 2002, 4 p.
Willcox Basin FS 01-13, October 2001, 4 p.
Sacramento Valley Basin FS 01-10, June 2001, 4 p.
Yuma Basin FS 01-03, April 2001, 4 p.
Virgin River Basin FS 01-02, March 2001 4 p.
Prescott Active Management Area FS 00-13, December 2000, 4 p.
Douglas Basin FS 00-08, September 2000, 4 p.
Upper San Pedro Basin FS 97-08, August 1997, 2 p. (With the U.S. Geological Survey)
These publications are available on-line at:
www.azdeq.gov/environ/water/assessment/ambient.html
V
VI
Table of Contents
Abstract ................................................................................................................................................................... 1
Introduction ............................................................................................................................................................ 2
Purpose and Scope ..................................................................................................................................... 2
Physical and Cultural Characteristics.......................................................................................................... 2
Hydrology................................................................................................................................................................ 2
Investigation Methods ............................................................................................................................................ 7
Sampling Collection................................................................................................................................... 7
Laboratory Methods ................................................................................................................................... 9
Data Evaluation ...................................................................................................................................................... 9
Quality Assurance ...................................................................................................................................... 9
Data Validation ........................................................................................................................................ 10
Groundwater Sampling Results ........................................................................................................................... 15
Water Quality Standards / Guidelines ....................................................................................................... 15
Suitability for Irrigation............................................................................................................................ 15
Analytical Results .................................................................................................................................... 15
Groundwater Composition .................................................................................................................................. 19
General Summary..................................................................................................................................... 19
Isotope Comparison.................................................................................................................................. 24
Groundwater Quality Variation................................................................................................................. 25
Summary and Conclusions .................................................................................................................................. 28
References ............................................................................................................................................................. 29
Appendices
Appendix A – Data on Sample Sites, Dripping Springs Wash basin, 2004-2005 ..................................... 30
Appendix B – Groundwater Quality Data, Dripping Springs Wash basin, 2004-2005 ............................. 31
VII
Maps
ADEQ Ambient Monitoring Program Studies......................................................................................................... IV
Map 1. Dripping Springs Wash basin ..................................................................................................................... 3
Map 2. Sample Sites ............................................................................................................................................... 8
Map 3. Water Quality Status................................................................................................................................. 16
Map 4. Water Chemistry....................................................................................................................................... 20
Map 5. TDS........................................................................................................................................................... 22
Map 6. Hardness ................................................................................................................................................... 23
Tables
Table 1. ADHS/Test America laboratory water methods and minimum reporting levels used in the study......... 11
Table 2. Summary results of Dripping Springs Wash basin duplicate samples from the ADHS laboratory ....... 13
Table 3. Summary results of Dripping Springs Wash basin split samples from the ADHS / Test America labs . 14
Table 4. Summary statistics for Dripping Springs Wash basin groundwater quality data .................................... 17
Table 5. Variation in groundwater quality constituent concentrations using Kruskal-Wallis test ........................ 26
Table 6. Summary statistics for groundwater quality constituent with significant differences among aquifers ... 27
Figures
Figure 1. Dripping Springs Wash basin................................................................................................................. 4
Figure 2. Pinal Peak.............................................................................................................................................. 4
Figure 3. Dripping Springs Wash .......................................................................................................................... 4
Figure 4. Walnut Spring........................................................................................................................................ 5
Figure 5. Squaw Spring ........................................................................................................................................ 5
Figure 6. Dripping Springs Wash .......................................................................................................................... 5
Figure 7. Domestic well........................................................................................................................................ 5
Figure 8. The Tablelands ...................................................................................................................................... 6
Figure 9. Challenger Windmill .............................................................................................................................. 6
Diagrams
Diagram 1. Piper tri-linear water chemistry diagram ............................................................................................ 19
Diagram 2. Hardness classification pie chart......................................................................................................... 21
Diagram 3. Isotope graph ..................................................................................................................................... 24
Diagram 4. Sodium boxplot.................................................................................................................................. 25
Diagram 5. Nitrate boxplot................................................................................................................................... 25
VIII
Abbreviations
amsl above mean sea level
ac-ft acre-feet
AGF/yr acre-feet per year
ADEQ Arizona Department of Environmental Quality
ADHS Arizona Department of Health Services
ADWR Arizona Department of Water Resources
ARRA Arizona Radiation Regulatory Agency
AZGS Arizona Geological Survey
As arsenic
bls below land surface
BLM U.S. Department of the Interior Bureau of Land Management
oC degrees Celsius
CI0.95 95 percent Confidence Interval
Cl chloride
DSW Dripping Springs Wash basin
EPA U.S. Environmental Protection Agency
F fluoride
Fe iron
gpm gallons per minute
hard-cal hardness concentration calculated from calcium and magnesium concentrations
HUC Hydrologic Unit Code
LLD Lower Limit of Detection
Mn manganese
MCL Maximum Contaminant Level
ml milliliter
msl mean sea level
ug/L micrograms per liter
um micron
uS/cm microsiemens per centimeter at 25° Celsius
mg/L milligrams per liter
MRL Minimum Reporting Level
MTBE Methyl Tertiary-Butyl Ether
ns not significant
ntu nephelometric turbidity unit
pCi/L picocuries per liter
QA Quality Assurance
QAPP Quality Assurance Project Plan
QC Quality Control
SAR Sodium Adsorption Ratio
SDW Safe Drinking Water
SC Specific Conductivity
su standard pH units
SO4 sulfate
TDS Total Dissolved Solids
TKN Total Kjeldahl Nitrogen
USGS U.S. Geological Survey
VOC Volatile Organic Compound
* significant at p ≤ 0.05 or 95% confidence level
** significant at p ≤ 0.01 or 99% confidence level
*** for information only, statistical test for this constituent invalid because detections fewer than 50
percent
IX
X
Ambient Groundwater Quality of the Dripping Springs Wash Basin:
A 2004-2005 Baseline Study
Abstract - In 2004-2005, the Arizona Department of Environmental Quality (ADEQ) conducted the first ever
baseline groundwater quality study of the Dripping Springs Wash basin located in central Arizona. The Dripping
Springs Wash basin covers about 445 square miles; its western and southern portions are in Pinal County, its
northern portion is in Gila County and its eastern portion is in Graham County. Most of the eastern half the
groundwater basin is located within lands of the San Carlos Apache tribe. 4
The basin is located in a mountainous area that contains small sediment-filled valleys which store only minor
amounts of groundwater. The largest of the valleys is drained by the Dripping Springs Wash which is a tributary to
the Gila River. The Gila River enters the basin from the east, just down gradient of Coolidge Dam, and splits the
basin roughly in half flowing from the northeast to southwest. Groundwater development in the basin is mostly
limited to domestic and stock wells located along the alluvium of the Dripping Springs Wash. 5
Since much of the Dripping Springs Wash basin is located within lands of the San Carlos Apache tribe, the report
essentially covers the western portion of the basin including the groundwater quality along the Dripping Springs
Wash and its drainages. The main source of groundwater in the basin is the alluvium of the Dripping Springs Wash;
the hard rock constituting the surrounding mountains contain only minor amounts of groundwater from which
springs emanate flowing at less than two gallons per minute. 5
To characterize regional groundwater quality, samples were collected from 12 sites, consisting of domestic and
stock wells and springs, located on non-tribal lands north of the Gila River. Collecting more samples than this
proved to be difficult because of the lack of well development in the basin and the extreme remoteness of many of
the springs in the basin. Inorganic constituents and oxygen and deuterium isotopes were collected at all twelve sites.
Radon and radiochemistry samples were also collected at seven sites. At two surface water sites, samples were also
collected for oxygen and deuterium isotopes.
Health-based, primary maximum contaminant levels (MCLs) are enforceable standards that define the maximum
concentrations of constituents allowed in water supplied for drinking water purposes by a public water system.
These water quality standards are based on a lifetime daily consumption of two liters. 23 Health-based primary MCLs
were not exceeded at any of the 12 sites. Aesthetics-based Secondary MCLs are unenforceable guidelines that define
the maximum constituent concentration that can be present in drinking water without an unpleasant taste, color, or
odor.23 Aesthetics-based Secondary MCLs were not exceeded at any of the 12 sites. Radon is a naturally occurring,
intermediate breakdown product from the radioactive decay of uranium-238 to lead-206.23 Of the 7 sites sampled for
radon, none exceeded the proposed 4,000 picocuries per liter (pCi/L) standard that would apply if Arizona
establishes an enhanced multimedia program to address the health risks from radon in indoor air. Six sites exceeded
the proposed 300 pCi/L standard that would apply if Arizona doesn’t develop a multimedia program. 23
Interpretation of the analytical results of the groundwater quality samples indicates that groundwater in the Dripping
Springs Wash basin meets drinking water quality standards and guidelines and is suitable for domestic, municipal,
stock and irrigation purposes. The groundwater can be characterized as generally fresh, slightly-alkaline, hard to
very hard based on total dissolved solids, pH and hardness concentrations.12, 15 The majority of sites were of
calcium-bicarbonate or mixed-bicarbonate chemistry. Nutrient concentrations were low. Fluoride and zinc were the
only trace elements detected at more than twenty percent of the sites.
Six sample sites consisted of generally shallow wells located in the alluvium of Dripping Springs Wash. The
remaining six samples consisted of five springs and one windmill located up-gradient in the hard rock of
surrounding mountains. Comparing these two groups, the sample sites in the alluvium exhibited significantly higher
temperature and concentrations of, sodium, and nitrate then sample sites in the up-gradient, hard rock areas; the
opposite pattern occurred with potassium (Kruskal-Wallis test, p ≤ 0.05). The potential reasons for these
groundwater quality patterns vary according to constituent. For sodium, in down-gradient areas, the dominant cation
often evolves from calcium to sodium which would explain the significantly higher concentrations found along
Dripping Springs Wash.21 There is more development in down-gradient alluvial areas along Dripping Springs Wash;
impacts from domestic septic systems and livestock likely affect the significantly higher nitrate concentrations found
in those locations. 18
2
INTRODUCTION
Purpose and Scope
The Dripping Springs Wash groundwater basin
encompasses approximately 445 square miles in
central Arizona.5 The western and southern portions
of the basin is located in Pinal County, the northern
portion is in Gila County and the eastern portion is in
Graham County (Map 1). Approximately the eastern
half the groundwater basin is located within lands of
the San Carlos Apache tribe while the western half
consists of Bureau of Land Management, State trust,
private and Forest Service lands. 6
Located in a remote mountainous region, there are no
towns located within the boundaries of this lightly
populated basin. The settlement of Christmas is
shown on some maps but this is now a ghost town
located on private property ever since the nearby
Christmas Mine closed in 1980. Arizona Highway 77
runs through the basin providing access to scattered
ranches and domestic residences along Dripping
Springs Wash. Groundwater is the primary source
for agricultural, stock and domestic water supply
within the basin.6 This ADEQ study is the first
comprehensive examination of the groundwater
quality of the Dripping Springs Wash basin.
Sampling by the Arizona Department of
Environmental Quality (ADEQ) Ambient
Groundwater Monitoring program is authorized by
legislative mandate in the Arizona Revised Statutes
§49-225, specifically: “...ongoing monitoring of
waters of the state, including...aquifers to detect the
presence of new and existing pollutants, determine
compliance with applicable water quality standards,
determine the effectiveness of best management
practices, evaluate the effects of pollutants on public
health or the environment, and determine water
quality trends.” 2
Benefits of ADEQ Study – This study, which
utilizes accepted sampling techniques and
quantitative analyses, is designed to provide the
following benefits:
A general characterization of regional
groundwater quality conditions in the
Dripping Springs Wash basin including
identifying areas with impaired conditions.
��� A process for evaluating potential
groundwater quality impacts arising from a
variety of sources including mineralization,
mining, agriculture, livestock, septic tanks,
and poor well construction.
A guide for identifying future locations of
public supply wells.
A guide for determining areas where further
groundwater quality research is needed.
Physical Characteristics
Geography – The Dripping Springs Wash basin
overlaps the Basin and Range and Central Highlands
physiographic provinces and consists of mountainous
areas with small, sediment-filled valleys. 5 The basin
is bounded by the Mescal and Pinal Mountains to the
northeast and the Dripping Springs Mountains to the
southwest. Elevation ranges from over 7,800 feet
above mean sea level to around 1,900 feet where the
Gila River exits the basin to the west.
The Gila River dissects the basin cutting across the
northwest-southeast trending mountains. This
perennial portion of the Gila River is controlled by
releases from Coolidge Dam to meet downstream
legal obligations.6
The basin is characterized by a mid-elevation
mountain range and Arizona uplands Sonoran desert
scrub, interior chaparral, semi-desert grassland and
madrean evergreen woodland vegetation. Riparian
vegetation includes mesquite along the Gila River. 6
Climate – The arid climate of the Dripping Springs
Wash basin is characterized by hot summers and mild
winters. Precipitation occurs predominantly as rain
in either late summer, localized monsoon
thunderstorms or widespread, low intensity winter
rain that sometimes includes snow at higher
elevations. Annual precipitation averages almost 16
inches at Coolidge Dam. 6
HYDROLOGY
Previous research indicates that three hydrologic
units are found along Dripping Springs Wash. These
include the younger alluvium, the Gila Conglomerate
(or older alluvium) and the consolidated rocks,
predominately of sedimentary origin along with
volcanic rocks south of the Gila River and outcrops
of granitic rock north of the Gila River. 5, 19
3
Figure 1 -
4
Figure 1 – The basin looking down-gradient toward
the alluvium of Dripping Springs Wash. The image
illustrates the remoteness and pristine nature of the
region.
Figure 2 – Pinal Peak, located on land managed by
the U.S. Forest Service, denotes the northern extent of
the Dripping Springs Wash basin.
Figure 3 – Dripping Springs Wash, labeled with a
highway sign where it crosses Dripping Springs Road, is
an ephemeral waterway that is the main drainage in
the northwestern half of the basin.
5
Figure 4 – In the northern portion of the Dripping
Springs Wash basin, springs such as Walnut Spring
(DSW-6/7) pictured above, are often the only
means of collecting groundwater quality data.
Figure 5 – Squaw Spring (DSW-10/11), located near
the summit of Pinal Peak, is sampled by former
ADEQ hydrologist Karla Burnley. The sample from
the spring had a TDS concentration of 110 mg/L, the
lowest of any site in the basin.
Figure 6 – Most samples collected in down-gradient
areas of the basin were low production,
domestic and stock wells drawing water from the
alluvium of the Dripping Springs Wash shown here
at Dripping Springs Road.
Figure 7 – This 89-foot-deep well (DSW-14/15)
providing water for domestic uses is located along
Dripping Springs Wash. Like all samples collected in
the basin, samples from the well met all health and
aesthetics based water quality standards.
6
Figure 8 – The Tablelands, an easily recognizable sedimentary geologic feature, are located
south of the Gila River within the Dripping Springs Wash basin. This area of the basin is mostly
lies within lands of the San Carlos Apace tribe.
Figure 9 – A 392-foot-deep Challenger windmill (DSW-9) provides water for domestic
and stock uses in an upgradient area of the basin. The sample from the well contained hard
water but met all health and aesthetics based water quality standards.
7
The major water producing unit is the younger
alluvium that consists of sand, silt and a small
amount of gravel located along the course of
Dripping Springs Wash. Probably not more than 150
feet thick, the younger alluvium is used for domestic
and stock purposes. The older alluvium consists of
stream deposits containing gravel and silty sand as
well as lake deposits consisting of clay, silt, tuff and
gypsum.5 The consolidated rocks which make up the
surrounding mountains contain only minor amounts
of groundwater and issue less than two gallons per
minute to springs in the basin. 6
Limited water development has occurred in the
Dripping Springs Wash basin with most wells having
been drilled along Dripping Springs Wash. In 1985,
an estimated 620 acre-feet of groundwater was
pumped. 5 Groundwater levels range from about 10 to
300 feet below land surface.
Groundwater moves from both the north and south
toward the Gila River in the center of the basin;
outflow from the basin occurs via the Gila River near
the community of Christmas. Recharge occurring
from both mountain-front and streambed sources in
the basin is estimated at 3,000 acre-feet per year.
Groundwater storage in the basin, to a depth of 1,200
feet below land surface, is estimated at 0.15 million
acre feet. 6
INVESTIGATION METHODS
ADEQ collected samples from 12 groundwater sites
to characterize regional groundwater quality in the
Dripping Springs Wash basin (Map 2). Specifically,
the following types of samples were collected:
oxygen and deuterium isotopes at 12 sites
inorganic suites at 12 sites
radionuclide at 7 sites
radon at 7 sites
Two (2) additional surface water sites were also
sampled for oxygen and deuterium isotopes. No
bacteria sampling was conducted because
microbiological contamination problems in
groundwater are often transient and subject to a
variety of changing environmental conditions
including soil moisture content and temperature. 14
Wells pumping groundwater for domestic and stock
purposes were sampled for this study provided each
well met ADEQ requirements. A well was
considered suitable for sampling if the owner gave
permission to sample, if a sampling point existed near
the wellhead, and if the well casing and surface seal
appeared to be intact and undamaged.1, 7 Other factors
such as construction information were preferred but
not essential. Some requests to sample wells were
denied because of fears of how the data would be
used; other wells were not sampled because they
lacked proper sampling ports.
For this study, ADEQ personnel sampled 7 wells all
served by submersible pumps except for 1 windmill.
Five springs were also sampled for the study.
Additional information on groundwater sample sites
is compiled from the ADWR well registry in
Appendix A. 6
Sample Collection
The sample collection methods for this study
conformed to the Quality Assurance Project Plan
(QAPP) 1 and the Field Manual For Water Quality
Sampling. 7 While these sources should be consulted
as references to specific sampling questions, a brief
synopsis of the procedures involved in collecting a
groundwater sample is provided.
After obtaining permission from the owner to sample
the well, the volume of water needed to purge the
well three bore-hole volumes was calculated from
well log and on-site information. Physical
parameters—temperature, pH, and specific
conductivity—were monitored at least every five
minutes using an YSI multi-parameter instrument.
To assure obtaining fresh water from the aquifer,
after three bore volumes had been pumped and
physical parameter measurements had stabilized
within 10 percent, a sample representative of the
aquifer was collected from a point as close to the
wellhead as possible. In certain instances, it was not
possible to purge three bore volumes. In these cases,
at least one bore volume was evacuated and the
physical parameters had stabilized within 10 percent.
Sample bottles were filled in the following order:
1. Radon
2. Inorganic
3. Radionuclide
4. Isotope
Radon, a naturally occurring, intermediate
breakdown from the radioactive decay of uranium-
238 to lead-206, was collected in two unpreserved,
40-ml clear glass vials. Radon samples were filled to
minimize volatilization and subsequently sealed so
that no headspace remained.13
8
9
The inorganic constituents were collected in three, 1-
liter polyethylene bottles: samples to be analyzed for
dissolved metals were delivered to the laboratory
unfiltered and unpreserved where they were
subsequently filtered into bottles using a positive
pressure filtering apparatus with a 0.45 micron (μm)
pore size groundwater capsule filter and preserved
with 5 ml nitric acid (70 percent). Samples to be
analyzed for nutrients were preserved with 2 ml
sulfuric acid (95.5 percent). Samples to be analyzed
for other parameters were unpreserved. 20
Radionuclide samples were collected in two
collapsible 4-liter plastic containers and preserved
with 5 ml nitric acid to reduce the pH below 2.5 su. 3
Isotope samples were collected in a 500 ml
polyethylene bottle with no preservative.
All samples were kept at 4oC with ice in an insulated
cooler, with the exception of the isotope and
radiochemistry samples. Chain of custody procedures
were followed in sample handling. Samples for this
study were collected during three field trips between
December 2004 and May 2005.
Laboratory Methods
The inorganic analyses for this study were conducted
by the Arizona Department of Health Services
(ADHS) Laboratory in Phoenix, Arizona. Inorganic
sample splits analyses were conducted by Test
America Laboratory in Phoenix, Arizona. A
complete listing of inorganic parameters, including
laboratory method, EPA water method and Minimum
Reporting Level (MRL) for each laboratory is
provided in Table 1.
Radon samples were analyzed by Radiation Safety
Engineering, Inc. Laboratory in Chandler, Arizona.
Radionuclide samples were analyzed by the Arizona
Radiation Agency Laboratory in Phoenix. The
following EPA SDW protocols were used: Gross
alpha was analyzed, and if levels exceeded 5
picocuries per liter (pCi/L), then radium-226 was
measured. If radium-226 exceeded 3 pCi/L, radium-
228 was measured. If gross alpha levels exceeded 15
pCi/L initially, then radium-226/228 and total
uranium were measured. 3
Isotope samples were analyzed by the Department of
Geosciences, Laboratory of Isotope Geochemistry
located at the University of Arizona in Tucson,
Arizona.
DATA EVALUATION
Quality Assurance
Quality-assurance (QA) procedures were followed
and quality-control (QC) samples were collected to
quantify data bias and variability for the Dripping
Springs Wash basin study. The design of the QA/QC
plan was based on recommendations included in the
Quality Assurance Project Plan (QAPP) and the
Field Manual For Water Quality Sampling. 1, 7
Types and numbers of QC samples collected for this
study are as follows:
Inorganic: (2 duplicates, 3 splits, and 2
blanks).
Radionuclide: (no QA/QC samples)
Radon: (no QA/QC samples)
Isotope: (no QA/QC samples)
Based on the QA/QC results, sampling procedures
and laboratory equipment did not significantly affect
the groundwater quality samples.
Blanks – Three equipment blanks for inorganic
analyses were collected to ensure adequate
decontamination of sampling equipment, and that the
filter apparatus and/or de-ionized water were not
impacting the groundwater quality sampling.7
Equipment blank samples for major ion and nutrient
analyses were collected by filling unpreserved and
sulfuric acid preserved bottles with de-ionized water.
Equipment blank samples for trace element analyses
were collected with de-ionized water that had been
filtered into nitric acid preserved bottles.
Systematic contamination was judged to occur if
more than 50 percent of the equipment blank samples
contained measurable quantities of a particular
groundwater quality constituent. The equipment
blanks contained specific conductivity (SC)-lab and
turbidity contamination at levels expected due to
impurities in the source water used for the samples.
The blank results indicated systematic contamination
with SC (detected in 3 equipment blanks) and
turbidity (detected in 3 equipment blanks). A single
detection of phosphorus (0.020 mg/L) also occurred.
For SC, the three equipment blanks had a mean (4.9
uS/cm) which was less than 1 percent of the SC mean
concentration for the study and were not considered
significantly affecting the sample results. The SC
detections may be explained in two ways: water
10
passed through a de-ionizing exchange unit will
normally have an SC value of at least 1 uS/cm, and
carbon dioxide from the air can dissolve in de-ionized
water with the resulting bicarbonate and
hydrogen ions imparting the observed conductivity.20
For turbidity, equipment blanks had a mean level
(0.05 ntu) less than 1 percent of the turbidity median
level for the study and were not considered
significantly affecting the sample results. Testing
indicates turbidity is present at 0.01 ntu in the de-ionized
water supplied by the ADHS laboratory, and
levels increase with time due to storage in ADEQ
carboys.20
Duplicate Samples - Duplicate samples are identical
sets of samples collected from the same source at the
same time and submitted to the same laboratory. Data
from duplicate samples provide a measure of
variability from the combined effects of field and
laboratory procedures.7 Duplicate samples were
collected from sampling sites that were believed to
have elevated constituent concentrations as judged by
SC-field values.
Two duplicate samples were collected in this study.
Analytical results indicate that of the 36 constituents
examined, 17 had concentrations above the MRL.
The maximum variation between duplicates was less
than 10 percent (Table 2). The only exceptions were
TKN (76 percent), turbidity (67 percent), nitrate (37
percent), potassium (15 percent) and sulfate (12
percent). However, constituents with a high
percentage variation of concentrations often have a
low difference in actual concentrations.
Split Samples - Split samples are identical sets of
samples collected from the same source at the same
time that are submitted to two different laboratories
to check for laboratory differences.7 Three inorganic
split samples were collected and analytical results
were evaluated by examining the variability in
constituent concentrations in terms of absolute levels
and as the percent difference.
Analytical results indicate that of the 36 constituents
examined only 15 had concentrations above MRLs
for both ADHS and Test America laboratories (Table
3). The maximum variation between splits was 10
percent. Split samples were also evaluated using the
non-parametric Sign test to determine if there were
any significant differences between ADHS laboratory
and Test America laboratory analytical results.16
There were no significant differences in constituent
concentrations between the labs (Sign test, p ≤ 0.05).
Based on the results of blanks, duplicates and the
split sample collected for this study, no significant
QA/QC problems were apparent with the
groundwater quality collected for this study.
Data Validation
The analytical work for this study was subjected to
five QA/QC correlations and considered valid based
on the following results. 17
Cation/Anion Balances - In theory, water samples
exhibit electrical neutrality. Therefore, the sum of
milliquivalents per liter (meq/L) of cations should
equal the sum of meq/L of anions. However, this
neutrality rarely occurs due to unavoidable variation
inherent in all water quality analyses. Still, if the
cation/anion balance is found to be within acceptable
limits, it can be assumed there are no gross errors in
concentrations reported for major ions.17 Overall,
cation/anion meq/L balances of Dripping Springs
Wash basin samples were significantly correlated
(regression analysis, p ≤ 0.01). Of the 12 samples, all
were within +/-12 percent. Because of high
cation/low anion sums, 9 samples had +/- 5 to 12
percent differences. These samples with high cation
sums were collected on the first two of three field
trips conducted for the study. The ADHS laboratory
was alerted but found no reason for the differences. 20
SC/TDS - The SC and TDS concentrations measured
by contract laboratories were significantly correlated
as were SC-field and TDS concentrations (regression
analysis, r = 0.99, p ≤ 0.01). The TDS concentration
in mg/L should be from 0.55 to 0.75 times the SC in
μS/cm for groundwater up to several thousand TDS
mg/L.17 Groundwater high in bicarbonate and
chloride will have a multiplication factor near the
lower end of this range; groundwater high in sulfate
may reach or even exceed the higher factor. The
relationship of TDS to SC becomes undefined for
groundwater with very high or low concentrations of
dissolved solids.17
Hardness - Concentrations of laboratory-measured
and calculated values of hardness were significantly
correlated (regression analysis, r = 0.99, p ≤ 0.01).
Hardness concentrations were calculated using the
following formula: [(Calcium x 2.497) +
(Magnesium x 4.118)]. 17
SC - The SC measured in the field at the time of
sampling was significantly correlated with the SC
measured by contract laboratories (regression
analysis, r = 0.99, p ≤ 0.01).
11
Table 1. Laboratory Water Methods and Minimum Reporting Levels Used in the Study
Constituent Instrumentation ADHS / Test America
Water Method
ADHS / Test America
Minimum Reporting Level
Physical Parameters and General Mineral Characteristics
Alkalinity Electrometric Titration SM2320B / M2320 B 2 / 6
SC (uS/cm) Electrometric EPA 120.1/ M2510 B -- / 2
Hardness Titrimetric, EDTA SM 2340 C / SM2340B 10 / 1
Hardness Calculation SM 2340 B --
pH (su) Electrometric SM 4500 H-B 0.1
TDS Gravimetric SM2540C 10 / 10
Turbidity (NTU) Nephelometric EPA 180.1 0.01 / 0.2
Major Ions
Calcium ICP-AES EPA 200.7 1 / 2
Magnesium ICP-AES EPA 200.7 1 / 0.25
Sodium ICP-AES EPA 200.7 1 / 2
Potassium Flame AA EPA 200.7 0.5 / 2
Bicarbonate Calculation Calculation / / M2320 B 2
Carbonate Calculation Calculation / / M2320 B 2
Chloride Potentiometric Titration SM 4500 CL D / E300 5 / 2
Sulfate Colorimetric EPA 375.4 / E300 1 / 2
Nutrients
Nitrate as N Colorimetric EPA 353.2 0.02 / 0.1
Nitrite as N Colorimetric EPA 353.2 0.02 / 0.1
Ammonia Colorimetric EPA 350.1/ EPA 350.3 0.02 / 0.5
TKN Colorimetric EPA 351.2 / M4500-
NH3 0.05 / 1.3
Total Phosphorus Colorimetric EPA 365.4 / M4500-PB 0.02 / 0.1
All units are mg/L except as noted
Source 13, 20
12
Table 1. Laboratory Water Methods and Minimum Reporting Levels Used in the Study--Continued
Constituent Instrumentation ADHS / Test America
Water Method
ADHS / Test America
Minimum Reporting Level
Trace Elements
Aluminum ICP-AES EPA 200.7 0.5
Antimony Graphite Furnace AA EPA 200.8 0.005 / 0.003
Arsenic Graphite Furnace AA EPA 200.9 / EPA 200.8 0.005 / 0.001
Barium ICP-AES EPA 200.8 / EPA 200.7 0.005 to 0.1 / 0.01
Beryllium Graphite Furnace AA EPA 200.9 / EPA 200.8 0.0005 / 0.001
Boron ICP-AES EPA 200.7 0.1 / 0.2
Cadmium Graphite Furnace AA EPA 200.8 0.0005 / 0.001
Chromium Graphite Furnace AA EPA 200.8 / EPA 200.7 0.01 / 0.01
Copper Graphite Furnace AA EPA 200.8 / EPA 200.7 0.01 / 0.01
Fluoride Ion Selective Electrode SM 4500 F-C 0.1 / 0.4
Iron ICP-AES EPA 200.7 0.1 / 0.05
Lead Graphite Furnace AA EPA 200.8 0.005 / 0.001
Manganese ICP-AES EPA 200.7 0.05 / 0.01
Mercury Cold Vapor AA SM 3112 B / EPA 245.1 0.0002 / 0.0002
Nickel ICP-AES EPA 200.7 0.1 / 0.01
Selenium Graphite Furnace AA EPA 200.9 / EPA 200.8 0.005 / 0.002
Silver Graphite Furnace AA EPA 200.9 / EPA 200.7 0.001 / 0.01
Thallium Graphite Furnace AA EPA 200.9 / EPA 200.8 0.002 / 0.001
Zinc ICP-AES EPA 200.7 0.05
Radionuclides
Gross alpha beta Gas flow proportional
counter EPA 900.0 varies
Co-Precipitation Gas flow proportional
counter EPA 00.02 varies
Radium 226 Gas flow proportional
counter EPA 903.0 varies
Radium 228 Gas flow proportional
counter EPA 904.0 varies
Uranium Kinnetic phosphorimeter EPA Laser
Phosphorimetry varies
All units are mg/L
Source 3, 13, 20
13
Table 2. Summary Results of Dripping Springs Wash Basin Duplicate Samples from the ADHS
Laboratory
Difference in Percent Difference in Concentrations
Parameter
Number
of Dup.
Sites Minimum Maximum Median Minimum Maximum Median
Physical Parameters and General Mineral Characteristics
Alk., Total 2 0 % 1 % - 0 6 -
SC (uS/cm) 2 0 % 0 % - 0 0 -
Hardness 2 1 % 2 % - 10 10 -
pH (su) 2 0 % 0 % - 0 0 -
TDS 2 0 % 0 % - 0 0 -
Turb. (ntu) 2 10 % 67 % - 0.8 1.1 -
Major Ions
Bicarbonate 2 0 % 1 % - 0 10 -
Calcium 2 0 % 2 % - 0 3 -
Magnesium 2 0 % 2 % - 0 1.5 -
Sodium 2 0 % 4 % - 0 2 -
Potassium 2 7 % 15 % - 0.3 0.5 -
Chloride 2 0 % 3 % - 0 1 -
Sulfate 2 2 % 12 % - 2 14 -
Nutrients
Nitrate (as N) 2 5 % 37 % - 0.027 0.1 -
TKN 1 - - 76 % - - 1.12
Trace Elements
Barium 2 0 % 0 % - 0 0 -
Fluoride 2 0 % 1 % - 0 0.02 -
All concentration units are mg/L except as noted with certain physical parameters.
Iron was detected at 0.41 mg/L in one duplicate sample and not detected in the other duplicate sample at an MRL of 0.1 mg/L.
TKN was detected at 0.28 mg/L in one duplicate sample and not detected in the other duplicate sample at an MRL of 0.10 mg/L
14
Table 3. Summary Results of Dripping Springs Wash Basin Split Samples From the ADHS/Test
America Labs
Difference in Percent Difference in Levels
Constituents Number of
Split Sites Minimum Maximum Minimum Maximum
Significance
Physical Parameters and General Mineral Characteristics
Alkalinity, total 3 0 % 0 % 0 0 ns
SC (uS/cm) 3 0 % 4 % 0 50 ns
Hardness 3 0 % 4 % 0 10 ns
pH (su) 3 1 % 5 % 0.09 0.57 ns
TDS 3 0 % 2 % 0 10 ns
Turbidity (ntu) 1 0 % 0 % 0 0 ns
Major Ions
Calcium 3 0 % 3 % 0 1 ns
Magnesium 3 0 % 6 % 0 4 ns
Sodium 3 0 % 6 % 0 2 ns
Potassium 4 4 % 10 % 0.1 0.5 ns
Chloride 3 1 % 4 % 0.1 1 ns
Sulfate 3 2 % 9 % 0.2 5 ns
Nutrients
Nitrate as N 3 3 % 10 % 0.2 0.5 ns
Trace Elements
Chromium 1 0 % 0 % 0.007 0.007 ns
Fluoride 3 4 % 9 % 0.2 0.4 ns
Zinc 1 4 % 4 % 0.008 0.008 ns
ns = No significant (p ≤ 0.05) difference
* = Significant (p ≤ 0.05) difference
** = Significant (p ≤ 0.05) difference
All units are mg/L except as noted
Zinc was detected at 0.055 mg/L in the Test America split and not detected in the ADHS split at an MRL of 0.05 mg/L
15
pH - The pH value is closely related to the
environment of the water and is likely to be altered
by sampling and storage.17 Thus, the pH values
measured in the field using a YSI meter at the time of
sampling were not significantly correlated with
laboratory pH values (regression analysis, r = 0.39, p
≤ 0.05).
Temperature / GW Depth /Well Depth –
Groundwater temperature measured in the field was
compared to well depth and groundwater depth.
Groundwater temperature should increase with depth,
approximately 3 degrees Celsius with every 100
meters or 328 feet. 8 Well depth was not significantly
correlated with temperature (regression analysis, r =
0.44, p ≤ 0.05).
GROUNDWATER SAMPLING RESULTS
Water Quality Standards/Guidelines
The ADEQ ambient groundwater program
characterizes regional groundwater quality. An
important determination ADEQ makes concerning
the collected samples is how the analytical results
compare to various drinking water quality standards.
ADEQ used three sets of drinking water standards
that reflect the best current scientific and technical
judgment available to evaluate the suitability of
groundwater in the basin for drinking water use:
Federal Safe Drinking Water (SDW)
Primary Maximum Contaminant Levels
(MCLs). These enforceable health-based
standards establish the maximum
concentration of a constituent allowed in
water supplied by public systems.23
State of Arizona Aquifer Water Quality
Standards. These apply to aquifers that are
classified for drinking water protected use.
All aquifers within Arizona are currently
classified and protected for drinking water
use. These enforceable State standards are
identical to the federal Primary MCLs. 2
Federal SDW Secondary MCLs. These non-enforceable
aesthetics-based guidelines
define the maximum concentration of a
constituent that can be present without
imparting unpleasant taste, color, odor, or
other aesthetic effects on the water.23
Health-based drinking water quality standards (such
as Primary MCLs) are based on the lifetime
consumption (70 years) of two liters of water per day
and, as such, are chronic not acute standards.23
Inorganic Constituent Results - Of the 12 sites
sampled for the full suite of inorganic constituents in
the Dripping Springs Wash study, none exceeded any
SDW Primary (health-based) MCLs or Secondary
(aesthetics-based) MCLs (Map 3).2, 23
Radiochemical Constituent Results – Of the 7 sites
sampled for radionuclides in the Dripping Springs
Wash study none exceeded any SDW Primary
(health-based) MCLs.2, 23
Radon Results - Of the 7 sites sampled for radon
none exceeded the proposed 4,000 picocuries per liter
(pCi/L) standard that would apply if Arizona
establishes an enhanced multimedia program to
address the health risks from radon in indoor air. Six
(6) sites exceeded the proposed 300 pCi/L standard
that would apply if Arizona doesn’t develop a
multimedia program. 23
Suitability for Irrigation
The groundwater at each sample site was assessed as
to its suitability for irrigation use based on salinity
and sodium hazards. Excessive levels of sodium are
known to cause physical deterioration of the soil and
vegetation. Irrigation water may be classified using
specific conductivity (SC) and the Sodium
Adsorption Ratio (SAR) in conjunction with one
another. 24
Groundwater sites in the Dripping Springs Wash
basin display a narrow range of irrigation water
classifications. The 12 sample sites are divided into
the following salinity hazards: low or C1 (1), medium
or C2 (10), high or C3 (1), and very high or C4 (0).
The 12 sample sites are divided into the following
sodium or alkali hazards: low or S1 (12), medium or
S2 (0), high or S3 (0), and very high or S4 (0).
Analytical Results
Analytical inorganic and radiochemistry results of the
Dripping Springs Wash basin sample sites are
summarized (Table 4) using the following indices:
minimum reporting levels (MRLs), number of sample
sites over the MRL, upper and lower 95 percent
confidence intervals (CI95%), median, and mean.
Confidence intervals are a statistical tool which
indicates that 95 percent of a constituent’s population
lies within the stated confidence interval.25 Specific
constituent information for each groundwater site is
in Appendix B.
16
17
Table 4. Summary Statistics for Dripping Springs Wash Basin Groundwater Quality Data
Constituent
Minimum
Reporting
Limit (MRL)
# of Samples /
Samples
Over MRL
Median
Lower 95%
Confidence
Interval
Mean
Upper 95%
Confidence
Interval
Physical Parameters
Temperature (C) 0.1 12 / 11 20.1 15.8 18.8 21.8
pH-field (su) 0.01 12 / 12 7.23 7.03 7.24 7.46
pH-lab (su) 0.01 12 / 12 8.00 7.70 7.89 8.09
Turbidity (ntu) 0.01 12 / 12 0.23 0.12 0.32 0.52
General Mineral Characteristics
T. Alkalinity 2.0 12 / 12 299 194 251 308
Phenol. Alk. 2.0 12 / 0 > 50% of data below MRL
SC-field (uS/cm) N/A 12 / 12 627 443 559 674
SC-lab (uS/cm) N/A 12 / 12 620 440 557 673
Hardness-lab 10.0 12 / 12 280 195 255 315
TDS 10.0 12 / 12 375 272 339 406
Major Ions
Calcium 5.0 12 / 12 68 46 61 76
Magnesium 1.0 12 / 12 31 21 27 33
Sodium 5.0 12 / 12 25 17 22 26
Potassium 0.5 12 / 12 1.5 1.4 1.7 2.1
Bicarbonate 2.0 12 / 12 368 237 306 376
Carbonate 2.0 12 / 0 > 50% of data below MRL
Chloride 1.0 12 / 12 13 10 13 15
Sulfate 10.0 12 / 12 28 21 32 43
Nutrients
Nitrate (as N) 0.02 12 / 12 1.9 1.0 1.6 2.3
Nitrite (as N) 0.02 0 / 0 > 50% of data below MRL
TKN 0.05 12 / 6 > 50% of data below MRL
T. Phosphorus 0.02 12 / 3 > 50% of data below MRL
18
Table 4. Summary Statistics for Dripping Springs Wash Basin Groundwater Quality Data
Constituent
Minimum
Reporting
Limit (MRL)
# of Samples /
Samples
Over MRL
Median
Lower 95%
Confidence
Interval
Mean
Upper 95%
Confidence
Interval
Trace Elements
Antimony 0.005 12 / 0 > 50% of data below MRL
Arsenic 0.01 12 / 0 > 50% of data below MRL
Barium 0.1 12 / 2 > 50% of data below MRL
Beryllium 0.0005 12 / 0 > 50% of data below MRL
Boron 0.1 12 / 0 > 50% of data below MRL
Cadmium 0.001 12 / 0 > 50% of data below MRL
Chromium 0.01 12 / 1 > 50% of data below MRL
Copper 0.01 12 / 2 > 50% of data below MRL
Fluoride 0.20 12 / 12 0.29 0.23 0.34 0.45
Iron 0.1 12 / 0 > 50% of data below MRL
Lead 0.005 12 / 0 > 50% of data below MRL
Manganese 0.05 12 / 0 > 50% of data below MRL
Mercury 0.0005 12 / 0 > 50% of data below MRL
Nickel 0.1 12 / 0 > 50% of data below MRL
Selenium 0.005 12 / 0 >50% of data below MRL
Silver 0.001 12 / 0 > 50% of data below MRL
Thallium 0.002 12 / 0 > 50% of data below MRL
Zinc 0.05 12 / 4 > 50% of data below MRL
Radiochemical Constituents
Radon* Varies 4 / 4 377 221 361 500
Gross Alpha* Varies 7 / 4 1.5 - 0.9 2.1 5.1
Gross Beta* Varies 7 / 7 1.7 1.2 1.8 2.3
Ra-226+228* Varies 7 / 0 > 50% of data below MRL
Uranium** Varies 7 / 0 > 50% of data below MRL
Isotopes
Oxygen-18*** Varies 12 / 12 - 9.7 - 10.4 - 9.9 - 9.4
Deuterium*** Varies 12 / 12 - 69.5 - 73.1 - 70.8 - 68.5
All units mg/L except where noted or * = pCi/L, ** = ug/L, and *** = 0/00
19
GROUNDWATER COMPOSITION
General Summary
Groundwater in the Dripping Springs Wash basin
was predominantly of calcium-bicarbonate or mixed-bicarbonate
(Map 4) (Diagram 1). The water
chemistry at the 12 sample sites, in decreasing
frequency, includes calcium-bicarbonate (6 sites),
mixed-bicarbonate (5 sites) and magnesium-bicarbonate
(1 site) (Diagram 1 – middle diagram).
Of the 12 sample sites in the Dripping Springs Wash
basin, the dominant cation was calcium at 6 sites and
magnesium at 1 site; at 5 sites, the composition was
mixed as there was no dominant cation (Diagram 1 –
left diagram).
The dominant anion was bicarbonate at 12 sites
(Diagram 1 – right diagram).
Diagram 1 – The Piper trilinear diagram shows that all the samples have a similar
chemistry and consist mainly of calcium-bicarbonate or mixed-bicarbonate.
20
21
Levels of pH-field were slightly alkaline (above 7 su)
at 9 sites and slightly acidic (below 7 su) at 3 sites.15
Of the 9 sites above 7 su, no sites had pH-field levels
over 8 su.
TDS concentrations were considered fresh (below
1,000 mg/L) at 12 sites (Map 5).15
Hardness concentrations were soft (below 75 mg/L)
at 1 site, moderately hard (75 – 150 mg/L) at 1 site,
hard (150 – 300 mg/L) at 6 sites, and very hard
(above 300 mg/L) at 4 sites (Diagram 2 and Map 6).12
Nitrate (as nitrogen) concentrations at most sites may
have been influenced by human activities. Nitrate
concentrations were divided into natural background
(0 sites at <0.2 mg/L), may or may not indicate
human influence (11 sites at 0.2 – 3.0 mg/L), may
result from human activities (1 site at 3.0 – 10 mg/L),
and probably result from human activities (0 sites
>10mg/L).18
Most trace elements such as antimony, arsenic,
barium, beryllium, boron, cadmium, chromium,
copper, iron, lead, manganese, mercury, nickel,
selenium, silver, and thallium were rarely–if ever—
detected. Only fluoride and zinc were detected at
more than 20 percent of the sites.
Constituent Co-Variation - TDS concentrations are
best predicted among major ions by calcium
concentrations (standard coefficient = 0.42), among
cations by calcium concentrations (standard
coefficient = 0.61) and among anions, bicarbonate
(standard coefficient = 0.84) (multiple regression
analysis, p≤ 0.01).
Hardness Concentrations in the
Dripping Springs Wash Basin
soft
8%
moderately hard
8%
hard
51%
very hard
33%
soft
moderately hard
hard
very hard
Diagram 2 – Samples collected from springs issuing from consolidated rocks in the
upgradient areas of the basin had variable hardness concentrations. The two samples
collected from the highest elevation springs had the two lowest hardness concentrations;
the other upgradient spring samples typically had very hard water.
22
23
24
Isotope Comparison
Groundwater characterizations using oxygen and
hydrogen isotope data may be made with respect to
the climate and/or elevation where the water
originated, residence within the aquifer, and whether
or not the water was exposed to extensive
evaporation prior to collection.11 This is
accomplished by comparing oxygen-18 isotopes
(δ18O) and deuterium (δD), an isotope of hydrogen,
data to the Global Meteoric Water Line (GMWL).
The GMWL is described by the linear equation:
δD = 8 δ18O + 10
where δD is deuterium in parts per thousand (per
mil, 0/00), 8 is the slope of the line, δ18O is oxygen-18
0/00, and 10 is the y-intercept.11 The GMWL is the
standard by which water samples are compared and
represents the best fit isotopic analysis of numerous
worldwide water samples.
Isotopic data from a region may be plotted to create a
Local Meteoric Water Line (LMWL) which is
affected by varying climatic and geographic factors.
When the LMWL is compared to the GMWL,
inferences may be made about the origin or history of
the local water.11 The LMWL created by δ18O and
δD values for samples collected at sites in the
Dripping Springs Wash basin were compared to the
GMWL. The δD and δ18O data lie to the right of the
GMWL. Meteoric waters exposed to evaporation
characteristically plot increasingly below and to the
right of the GMWL. Evaporation tends to
preferentially contain a higher percentage of lighter
isotopes in the vapor phase and causes the water that
remains behind to be isotopically heavier.11
Groundwater from arid environments is typically
subject to evaporation, which enriches δD and δ18O,
resulting in a lower slope value (usually between 3
and 6) as compared to the slope of 8 associated with
the GMWL.11
The data for the Dripping Springs Wash basin
conforms to this theory, having a slope of 4.4, with
the LMWL described by the linear equation:
δD = 4.4 δ 18O - 27.2
The LMWL for the Dripping Springs Wash basin
(4.4) is lower than most other basins in Arizona. 22
-12 -11 -10 -9 -8
Delta Oxygen-18 (0/00)
-80
-75
-70
-65
Delta Deuterium(0/00)
13
10/11
8
18
4
14/15
17
2/3
9 1
6/7
5
19/20
16
Diagram 3 – Two distinct clusters
of isotope values were found in the
basin with each group represented
by both up-gradient springs and
down-gradient wells (Kruskal-
Wallis test, p ≤ 0.05). However,
examining other constituents for
concentration differences using
these groupings found no
significant patterns (Kruskal-Wallis
test, p ≤ 0.05). The two surface
water samples are represented by
Kellner Canyon (#13) and Pioneer
Creek (#18). The extreme
25
Groundwater Quality Variation
Among Aquifers - Twenty-five (25) groundwater
quality constituent concentrations were compared
between six sites (all wells) located in down-gradient
alluvium along the Dripping Springs Wash and six
sites (5 springs and 1 well) located in up-gradient
hard rock areas.
Significant concentration differences were found with
four constituents (Kruskal-Wallis test, p ≤ 0.05).
Temperature, sodium (Diagram 4) and nitrate
(Diagram 5) were significantly higher at sites located
down-gradient in alluvium than at sites located up-gradient
in hard rock; the opposite pattern occurs
with potassium.
Complete results are found in Table 5. Summary
statistics in the form of 95% confidence intervals are
provided for those constituents with significant
concentration differences between aquifers in Table
6.
Alluvial Hard rock
Aquifer
0
10
20
30
Sodium (mg/L)
Alluvial Hard rock
Aquifer
0
1
2
3
4
Nitrate as N (mg/L)
Diagram 5. Sample sites collected from
wells located along the alluvium of the
Dripping Springs Wash in down-gradient
areas of the basin had significantly higher
sodium concentrations than sample sites
collected from springs located in hard
rock in up-gradient areas of the basin
(Kruskal-Wallis test, p ≤ 0.05).
There is more development in down-gradient
area and impacts from domestic
septic systems and livestock likely affect
this trend. However, nitrate
concentrations at all sites were all well
below the health-based 10 mg/L Primary
MCL.
Diagram 4. Sample sites collected from
wells located along the alluvium of the
Dripping Springs Wash in down-gradient
areas of the basin had significantly higher
sodium concentrations than sample sites
collected from springs located in hard
rock in up-gradient areas of the basin
(Kruskal-Wallis test, p ≤ 0.05). In
downgradient areas, the dominant cation
often evolves from calcium to sodium. 21
26
Table 5. Variation in Groundwater Quality Constituent Concentrations Using Kruskal-Wallis Test
Constituent Significance Significant Differences Among Aquifers
Well Depth ns -
Groundwater Depth ns -
Temperature - field * Alluvium > Hard rock
pH – field ns -
pH – lab ns -
SC - field ns -
SC - lab ns -
TDS ns -
Turbidity ns -
Hardness ns -
Calcium ns -
Magnesium ns -
Sodium * Alluvium > Hard rock
Potassium * Hard rock > Alluvium
Bicarbonate ns -.
Chloride ns -
Sulfate ns -
Nitrate (as N) ** Alluvium > Hard rock
Fluoride ns -
Oxygen ns -
Deuterium ns -.
Gross Alpha ns -
Gross Beta ns -
Radon ns -
ns = not significant
* = significant at p ≤ 0.05 or 95% confidence level
** = significant at p ≤ 0.01 or 99% confidence level
27
Table 6. Summary Statistics (95% Confidence Intervals) for Groundwater Quality Constituents
With Significant Concentration Differences Between Aquifers
Constituent Significant
Differences Alluvial Hard Rock
Well Depth (feet) ns - -
Groundwater Depth (feet) ns - -
Temperature – field (C) * 19.3 to 23.6 10.1 to 21.2
pH – field (su) ns - -
pH – lab (su) ns - -
SC – field (uS/cm) ns - -
SC – lab (uS/cm) ns - -
TDS ns - -
Turbidity (ntu) ns - -
Hardness ns - -
Calcium ns - -
Magnesium ns - -
Sodium * 21 to 30 9 to 26
Potassium * 0.9 to 2.0 1.4 to 2.5
Bicarbonate ns - -
Chloride ns - -
Sulfate ns - -
Nitrate (as N) ** 1.9 to 3.0 0 to 1.7
Fluoride ns - -
Oxygen (0/00) ns - -
Deuterium (0/00) ns - -
Gross Alpha ns - -
Gross Beta ns - -
Radon (pCi/L) ns - -
All units in milligrams per liter (mg/L) unless otherwise noted
ns = not significant
* = significant at p ≤ 0.05 or 95% confidence level
** = significant at p ≤ 0.01 or 99% confidence level
28
SUMMARY AND CONCLUSIONS
The Dripping Springs Wash groundwater basin is a
sparsely populated, remote area. Little about the
hydrology of the Dripping Springs area was
previously known as this is the first study that
comprehensively examines the groundwater quality
of the basin. Roughly the eastern half of the basin lies
within the lands of the San Carlos Apache tribe and
was not sampled as part of this study. 4
The western portion consists of a combination of
Bureau of Land Management, State Trust, Forest
Service and private lands. 6 The little groundwater
development in this area consists of domestic and
stock wells mostly located along the alluvium of
Dripping Springs Wash. 5 Half of the dozen sample
sites consisted of wells located in this area. Springs
located up-gradient to the north in the consolidated
rock of the surrounding mountains constituted the
remainder of the sampled sites.
Interpretation of the analytical results from the
samples indicates that groundwater in the Dripping
Springs Wash basin meets drinking water standards
and is suitable for domestic, stock, municipal, and
irrigation purposes. Samples from all 12 sites met all
health and aesthetics based water quality standards. 2,
23
The few groundwater quality patterns found in the
basin appear to be of minor importance and probably
result from both natural and anthropogenic causes. 18,
21 In down-gradient areas of alluvial basins, the
dominant cation often evolves from calcium to
sodium. This would explain the significantly higher
sodium concentrations found along Dripping Springs
Wash compared to sampled springs located up-gradient
in consolidated rock.21 There is more
residential and ranch development in down-gradient
alluvial areas along Dripping Springs Wash; impacts
from domestic septic systems and livestock likely
affect the significantly higher nitrate concentrations
found in this area. 18
29
REFERENCES
1 Arizona Department of Environmental Quality, 1991,
Quality Assurance Project Plan: Arizona Department
of Environmental Quality Standards Unit, 209 p.
2 Arizona Department of Environmental Quality, 2009-
2010, Arizona Laws Relating to Environmental
Quality: St. Paul, Minnesota, West Group Publishing,
§49-221-224, p 134-137.
3 Freeland, Gary, 2008, Personal communication from
ARRA staff.
4 Arizona State Land Department, 1997, “Land Ownership
- Arizona” GIS coverage: Arizona Land Resource
Information Systems, downloaded, 4/7/07.
5 Arizona Department of Water Resources, 1994, Arizona
Water Resources Assessment – Volume II, Hydrologic
Summary, Hydrology Division, pp. 62-63.
6 Arizona Department of Water Resources, 2010,
www.azwater.gov/azdwr/StatewidePlanning/WaterAtlas/SEArizon
a/documents/Volume_3_DSW_final.pdf, accessed 05/25/10.
7 Arizona Water Resources Research Center, 1995, Field
Manual for Water-Quality Sampling: Tucson,
University of Arizona College of Agriculture, 51 p.
8 Bitton, G. and Gerba, C.P., 1994, Groundwater Pollution
Microbiology: Malabar, FL: Krieger Publishing
Company 377 p.
11 Craig, H., 1961, Isotopic variations in meteoric waters.
Science, 133, pp. 1702-1703.
12 Crockett, J.K., 1995. Idaho statewide groundwater
quality monitoring program–Summary of results, 1991
through 1993: Idaho Department of Water Resources,
Water Information Bulletin No. 50, Part 2, p. 60.
13 Test America Laboratory, 2009, Personal
communication from Test America staff.
14 Graf, Charles, 1990, An overview of groundwater
contamination in Arizona: Problems and principals:
Arizona Department of Environmental Quality
seminar, 21 p.
15 Heath, R.C., 1989, Basic ground-water hydrology: U.S.
Geological Survey Water-Supply Paper 2220, 84 p.
16 Helsel, D.R. and Hirsch, R.M., 1992, Statistical methods
in water resources: New York, Elsevier, 529 p.
17 Hem, J.D., 1985, Study and interpretation of the
chemical characteristics of natural water [Third
edition]: U.S. Geological Survey Water-Supply Paper
2254, 264 p.
18 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.
19 Richard, S.M., Reynolds, S.J., Spencer, J.E. and
Pearthree, Pa, P.A., 2000, Geologic map of Arizona:
Arizona Geological Survey Map 35, scale
1:1,000,000.
20 Roberts, Isaac, 2008, Personal communication from
ADHS staff.
21 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 1406-C, 90 p.
22 Towne, D.C., 2010, Ambient groundwater quality of the
McMullen Valley basin: A 2008-2009 baseline study:
Arizona Department of Environmental Quality Open
File Report 10-??, 99 p.
23 U.S. Environmental Protection Agency website,
www.epa.gov/waterscience/criteria/humanhealth/,
accessed 3/05/10.
24 U.S. Salinity Laboratory, 1954, Diagnosis and
improvement of saline and alkali soils: U.S.
Department of Agriculture, Agricultural Research
Service, Agriculture Handbook No. 60, 160 p.
[reprinted, 1969].
25 Wilkinson, L., and Hill, M.A., 1996. Using Systat 6.0
for Windows, Systat: Evanston, Illinois, p. 71-275.
30
Appendix A. Data for Sample Sites, Dripping Springs Basin, 2004-05
Site # Cadastral /
Pump Type Latitude -
Longitude ADWR # ADEQ # Site
Name Samples
Collected Well
Depth Water
Depth Geology
1st Field Trip, December 15-17, 2004 - Towne & Aguilar (Equipment Blank, GV-85)
DSW-1 D(4-16)08ddd
submersible 33°05'34.404"
110°43'46.218" 602062 64263 Bibbs Well Inorganic, Radiochem
Radon, O & H Isotopes 60' 20' Alluvial
DSW-2/3
split D(3-15)29ba
submersible 33°08'48.780"
110°50'04.077" 502917 64264 Windspirit
Well Inorganic, Radon
O, H isotopes 365' 160' Alluvial
DSW-4 D(3-14)25adc
spring 33°08'32.58"
110°51'46.74" - 64322 Dripping
Springs Inorganic, Radiochem,
O, H isotopes - - Hard Rock
DSW-5 D(4-15)01cdb
submersible 33°06'35.552"
110°46'10.516" - 64265 Hoover
Well Inorganic, Radon,
O, H isotopes 110' 40' Alluvial
2nd Field Trip, March 24, 2005 - Towne & Brunley (Equipment Blank, DSW-12)
DSW-6/7
duplicate D(2-14)29dda
spring 33°13'27.663"
110°56'04.213" - 64689 Walnut
Spring Inorganic, Radiochem,
O, H isotopes - - Hard Rock
DSW-8 D(2-14)09dd
spring 33°13'55.452"
110°52'38.727" - 64690 Stone
Cabin Spr. Inorganic, Radiochem
O, H isotopes - - Hard Rock
DSW-9 D(3-14)4aca
windmill 33°12'07.695"
110°55'05.888" 632798 64691 Challenger
Windmill Inorganic, Radiochem
Radon, O, H isotopes 392’ 175' Hard Rock
DSW-10/11
split D(2-15)4c
spring 33°16'51."
110°48'58." - 64692 Squaw
Spring Inorganic, Radiochem
O, H isotopes - - Hard Rock
DSW-13
surface H20 at Pinal Peak Road -- -- Kellner
Canyon O, H isotopes -- -- -
3rd Field Trip, May 19, 2005 - Towne (Equipment Blank, DSW-21)
DSW-14/15
split D(4-15)01cca
submersible 33°06'33.282"
110°46'13.012" 644487 64867 Evans Well Inorganic, Radon
O, H isotopes 89’ 79’ Alluvial
DSW-16 D(4-16)7add
submersible 33°05'58.903"
110°44'41.113" 519967 64868 Teague
Well
Inorganic, Radon
O, H isotopes 90’ - Alluvial
DSW-17 D(4-16)8dca
submersible 33°05'42.740"
110°43'55.209" -- 64869 Kishbaugh
Well
Inorganic, Radon
O, H isotopes 60’ 47’ Alluvial
DSW-18
surface H2o At FS Road -- -- Pioneer
Creek O, H isotopes - - -
DSW-19/20
duplicate D(2-15)20dda
spring 33°15'05.7"
110°50'21.9" -- 64870 Green-house
Spr.
Inorganic, Radiochem
O, H isotopes - - Hard Rock
31
Appendix B. Groundwater Quality Data, Dripping Springs Basin, 2004-05
Site # MCL
Exceedances
Temp
(oC)
pH-field
(su)
pH-lab
(SU)
SC-field
(μS/cm)
SC-lab
(μS/cm)
TDS
(mg/l)
Hard
(mg/l)
Hard - cal
(mg/l)
Turb
(ntu)
DSW-1 - 17.9 6.96 8.0 647 660 390 290 310 0.30
DSW-2/3 - 21.3 7.71 8.16 406 395 235 175 190 ND
DSW-4 - 20.1 7.56 7.9 702 730 420 360 370 ND
DSW-5 - 20.4 7.21 7.9 624 640 370 280 290 0.21
DSW-6/7 - 17.0 6.49 7.9 726 760 440 355 360 0.06
DSW-8 - 13.8 7.15 8.0 276 280 180 110 140 0.78
DSW-9 - 18.4 7.28 8.0 574 600 360 260 260 0.84
DSW-10/11 - 8.8 7.22 7.01 154 160 110 53 56 0.25
DSW-14/15 - 22.9 6.94 7.65 661 645 395 302.5 300 0.03
DSW-16 - 23.5 7.24 8.0 629 590 380 280 290 0.65
DSW-17 - 22.7 7.56 8.1 610 570 370 270 280 0.08
DSW-19/20 - -- 7.61 8.1 695 650 420 320 310 0.59
italics = constituent exceeded holding time
Appendix B. Groundwater Quality Data, Dripping Springs Basin, 2004-05--Continued
Site #
Calcium
(mg/l)
Magnesium
(mg/l)
Sodium
(mg/l)
Potassium
(mg/l)
T. Alk
(mg/l)
Bicarbonate
(mg/l)
Carbonate
(mg/l)
Chloride
(mg/l)
Sulfate
(mg/l)
DSW-1 71 31 29 1.1 300 370 ND 14 25
DSW-2/3 19.5 33 17 2.55 190 230 ND 8.75 5.5
DSW-4 85 38 14 2.0 300 370 ND 20 60
DSW-5 66 31 26 1.2 300 370 ND 12 20
DSW-6/7 93 32 23 2.3 340 410 ND 17.5 46
DSW-8 37 11 8.2 2.8 100 120 ND 5.8 24
DSW-9 68 22 24 1.5 240 290 ND 16 42
DSW-10/11 16.5 3.4 9.45 1.55 57 70 ND 4.3 12.5
DSW-14/15 69 32 27 1.25 310 370 ND 12.5 28.5
DSW-16 67 30 27 1.2 300 370 ND 13 28
DSW-17 64 28 26 1.4 280 340 ND 12 30
DSW-19/20 72.5 32.75 27 1.65 297 365 ND 14 60
32
Appendix B. Groundwater Quality Data, Dripping Springs Basin, 2004-05--Continued
Site #
Nitrate-Nitrite-N
(mg/l)
Nitrate-N
(mg/l)
Nitrite-N
(mg/l)
TKN
(mg/l)
Ammonia
(mg/l)
Total Phosphorus
(mg/l)
SAR
(value)
Irrigation
Quality
DSW-1 1.9 1.9 ND 0.076 ND 0.022 0.7 C2-S1
DSW-2/3 3.2 3.2 ND 0.10 ND ND 0.6 C2- S1
DSW-4 1.1 1.1 ND ND ND ND 0.3 C2- S1
DSW-5 1.9 1.9 ND ND ND 0.026 0.7 C2- S1
DSW-6/7 1.05 1.05 ND ND ND ND 0.5 C3- S1
DSW-8 0.26 0.26 ND 0.16 ND 0.036 0.3 C2- S1
DSW-9 2.2 2.2 ND ND ND ND 0.6 C2- S1
DSW-10/11 0.35 0.35 ND 0.11 ND ND 0.6 C1- S1
DSW-14/15 2.55 2.55 ND ND ND ND 0.7 C2- S1
DSW-16 2.5 2.5 ND ND ND ND 0.7 C2- S1
DSW-17 2.6 2.6 ND 0.10 ND ND 0.7 C2- S1
DSW-19/20 0.036 0.036 ND 1.55 ND ND 0.7 C2- S1
italics = constituent exceeded holding time
Appendix B. Groundwater Quality Data, Dripping Springs Basin, 2004-05--Continued
Site #
Antimony
(mg/l)
Arsenic
(mg/l)
Barium
(mg/l)
Beryllium
(mg/l)
Boron
(mg/l)
Cadmium
(mg/l)
Chromium
(mg/l)
Copper
(mg/l)
Fluoride
(mg/l)
DSW-1 ND ND ND ND ND ND ND 0.063 0.45
DSW-2/3 ND ND ND ND ND ND 0.0145 ND 0.25
DSW-4 ND ND ND ND ND ND ND 0.066 0.18
DSW-5 ND ND ND ND ND ND ND ND 0.32
DSW-6/7 ND ND 0.14 ND ND ND ND ND 0.31
DSW-8 ND ND ND ND ND ND ND ND 0.18
DSW-9 ND ND ND ND ND ND ND ND 0.23
DSW-10/11 ND ND ND ND ND ND ND ND 0.165
DSW-14/15 ND ND ND ND ND ND ND ND 0.27
DSW-16 ND ND ND ND ND ND ND ND 0.44
DSW-17 ND ND ND ND ND ND ND ND 0.51
DSW-19/20 ND ND 0.17 ND ND ND ND ND 0.74
33
Appendix B. Groundwater Quality Data, Dripping Springs Basin, 2004-05--Continued
Site #
Iron
(mg/l)
Lead
(mg/l)
Manganese
(mg/l)
Mercury
(mg/l)
Nickel
(mg/l)
Selenium
(mg/l)
Silver
(mg/l)
Thallium
(mg/l)
Zinc
(mg/l)
DSW-1 ND ND ND ND ND ND ND ND 0.060
DSW-2/3 ND ND ND ND ND ND ND ND ND
DSW-4 ND ND ND ND ND ND ND ND ND
DSW-5 ND ND ND ND ND ND ND ND ND
DSW-6/7 ND ND ND ND ND ND ND ND ND
DSW-8 ND ND ND ND ND ND ND ND ND
DSW-9 ND ND ND ND ND ND ND ND 1.2
DSW-10/11 ND ND ND ND ND ND ND ND 0.055
DSW-14/15 ND ND ND ND ND ND ND ND 0.091
DSW-16 ND ND ND ND ND ND ND ND ND
DSW-17 ND ND ND ND ND ND ND ND ND
DSW-19/20 ND ND ND ND ND ND ND ND ND
Appendix B. Groundwater Quality Data, Dripping Springs Basin, 2004-05--Continued
Site # Radon-222
(pCi/L) Alpha
(pCi/L) Beta
(pCi/L) Ra-226
(pCi/L) Uranium
(μg/l) 18 O
(0/00)
D
(0/00) Type of Chemistry
DSW-1 358 0.4 1.2 - - - 9.3 - 68 calcium-bicarbonate
DSW-2/3 444 - - - - - 8.85 -66 magnesium-bicarbonate
DSW-4 - 1.6 2.7 - - -10.4 -74 calcium-bicarbonate
DSW-5 385 - - - - - 9.4 - 68 mixed-bicarbonate
DSW-6/7 - 4.8 1.7 - - - 9.5 - 67.5 calcium-bicarbonate
DSW-8 - < LLD 2.1 - - - 11.0 -77 calcium-bicarbonate
DSW-9 449 <LLD 1.3 - - -9.5 -68 calcium-bicarbonate
DSW-10/11 - <LLD 1.1 - - - 11.5 - 75 calcium-bicarbonate
DSW-13 - - - - - - 11.6 - 78 -
DSW-14/15 377 - - - - - 10.2 - 73 mixed-bicarbonate
DSW-16 377 - - - - - 9.7 -70 mixed-bicarbonate
DSW-17 239 - - - - -10.1 -74 mixed-bicarbonate
DSW-18 - - - - - -10.6 -75 -
DSW-19/20 - 1.4 2.3 - - - 9.6 - 69 mixed-bicarbonate
LLD = Lower Limit of Detection
34
