U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2012–3035

January 2013 Printed on recycled paper

U.S. Geological Survey and the California State Water Resources Control Board

Groundwater Quality in the Indian Wells Valley, 

California

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital 

resource, the State of California created the Groundwater Ambient Monitoring and Assessment 

(GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive 

assessment of the State’s groundwater quality and increases public access to groundwater-quality 

information. Indian Wells Valley is one of the study areas being evaluated. 

The Indian Wells Study Area Overview of Water Quality

GAMA’s Priority Basin Project evaluates the quality of untreated groundwater. 

However, for context, benchmarks established for drinking-water quality are used 

for comparison. Benchmarks and definitions of high, moderate, and low concentrations are discussed in the inset box on 

page 3. The USGS sampled 13 wells for 

this assessment; data from the California 

Department of Public Health database were 

used to supplement USGS data.

Many inorganic constituents occur 

naturally in groundwater. The concentrations of the inorganic constituents can be 

affected by natural processes as well as by 

human activities. In the Indian Wells study 

area, one or more inorganic constituents 

were present at high concentrations in 62% 

of the primary aquifers and at moderate 

concentrations in 23%.

Organic constituents are present 

in products used in the home, business, 

industry, and agriculture. Organic 

constituents can enter the groundwater 

system through normal usage, spills, or 

improper disposal. In the Indian Wells 

study area, no organic constituents were 

present at high or moderate concentrations 

in the primary aquifers.

The Indian Wells study area is approximately 600 square miles (1,554 square kilometers) and includes the Indian Wells Valley groundwater basin (California Department of Water 

Resources, 2003). Indian Wells Valley has an arid climate and is part of the Mojave Desert. 

Average annual rainfall is about 6 inches (15 centimeters). The study area has internal drainage, with runoff from the surrounding mountains draining towards dry lake beds in the lower 

parts of the valley. Land use in the study area is approximately 97.0 percent (%) natural, 0.4% 

agricultural, and 2.6% urban. The primary natural land cover is shrubland. The largest urban 

area is the city of Ridgecrest (2010 population of 28,000).

Groundwater in this basin is used for public and domestic water supply and for irrigation. The main water-bearing units are gravel, sand, silt, and clay derived from the Sierra 

Nevada to the west and from the other surrounding mountains. Recharge to the groundwater 

system is primarily runoff from the Sierra Nevada and to the west and from the other surrounding mountains. 

Recharge to the groundwater system is primarily runoff from the 

Sierra Nevada and direct 

infiltration from irrigation and septic systems. 

The primary sources of 

discharge are pumping 

wells and evapotranspiration near the dry 

lakebeds. The primary 

aquifers in the Indian 

Wells study area are 

defined as those parts of 

the aquifers corresponding to the perforated 

intervals of wells listed 

in the California Department of Public Health 

database. Public-supply 

wells in Indian Wells 

Valley are completed 

to depths between 240 

and 800 feet (73 to 

244 meters), consist of 

solid casing from the 

land surface to a depth 

of 180 to 260 feet (55 

to 79 meters), and are 

screened or perforated 

below the solid casing.

High Moderate

CONSTITUENT CONCENTRATIONS

Low or not detected 

Pie charts illustrate the proportion of the primary 

aquifers, on an areal basis, with concentrations in the

three specified categories.

62 23

15

Organic

constituents

Inorganic

constituents

Number analyzed: 27 Number analyzed: 79

100

118° 117°50’ 117°40’

36°

35°50’

35°40’

35°30’

35°20’

117°30’

INYO COUNTY

KERN COUNTY

SAN BERNARDINO COUNTY

Los Angeles Aqueduct Los Angeles Aqueduct

Sierra Nevada Mountains

Indian Wells Study Area

EXPLANATION

Lake

Dry lake bed

Urban area

Alluvium

Hard rock

Study area 

boundary

0 5 10 MILES

0 5 10 KILOMETERS

Ridgecrest
RESULTS: Groundwater Quality in the Indian Wells Study Area

Inorganic Constituents with Human-Health Benchmarks

Trace elements are naturally present in the minerals in rocks and soils and in the 

water that comes into contact with those materials. In the Indian Wells study area, trace 

elements with human-health benchmarks were present at high concentrations in 54% 

of the primary aquifers, on an areal basis, and at moderate concentrations in 31%. Of 

the 17 trace elements with human-health benchmarks analyzed in this study, 5 were 

detected at high concentrations: arsenic, boron, molybdenum, strontium, and vanadium. 

Chromium and fluoride were detected at moderate concentrations.

Radioactivity is the release of energy or energetic particles during structural 

changes in the nucleus of an atom. Most of the radioactivity in groundwater comes 

from decay of naturally occurring isotopes of uranium and thorium that are present 

in minerals in the aquifer. In the Indian Wells study area, radioactive constituents 

were detected at concentrations above benchmarks in 15% of the primary aquifers, 

and at moderate concentrations in 8%. Six radioactive constituents were analyzed; of 

these, uranium and gross alpha radioactivity were detected at concentrations above 

benchmarks. 

Nutrients, such as nitrate and nitrite, are naturally present at low concentrations in 

groundwater. High and moderate concentrations generally occur as a result of human 

activities, such as fertilizer application, livestock waste, or septic-system seepage. 

Of the three nutrients with health-based benchmarks analyzed, none were detected at 

concentrations above benchmarks.

Inorganic Constituents with Non-Health Benchmarks

(Not included in water-quality overview charts shown on the front page)

Other inorganic constituents, such as total dissolved solids and manganese, affect 

the aesthetic properties of water, such as taste, color, or odor. In the Indian Wells study 

area, these constituents were present at high concentrations in 23% of the primary 

aquifers, and at moderate concentrations in 31%. Of the seven constituents with nonhealth-based benchmarks that were analyzed, three (chloride, manganese, and total 

dissolved solids) were detected at concentrations above benchmarks. Sulfate was 

detected at moderate concentrations.

Special Interest: Perchlorate

Perchlorate is an inorganic constituent which has been regulated in California 

drinking water since 2007. It is an ingredient in rocket fuel, fireworks, safety flares, 

may be present in some fertilizers, and also occurs naturally at low to moderate 

concentrations in groundwater. In the Indian Wells study area, perchlorate was found at 

moderate concentrations in 15% of the primary aquifer.

Other

inorganic

constituents

Perchlorate

54

15

31

77

100

46

15

23

31

85

8

15

Trace 

elements

Radioactive

constituents 

Nutrients

INORGANIC CONSTITUENTS
RESULTS: Groundwater Quality in the Indian Wells Study Area

Organic Constituents with Human-Health Benchmarks

The Priority Basin Project uses laboratory methods that can detect the presence 

of volatile organic compounds (VOCs) and pesticides at low concentrations, far below 

human-health benchmarks. VOCs and pesticides detected at these low concentrations 

can be used to help trace water from the land surface into the aquifer system.

Volatile Organic Compounds

VOCs are present in many household, commercial, industrial, and agricultural 

products and are characterized by their tendency to volatilize into the air. In the Indian 

Wells study area, VOCs were not detected or were only detected at low concentrations. 

Of 56 VOCs with health-based benchmarks analyzed, none were detected at high or 

moderate concentrations in the primary aquifers.

Pesticides

Pesticides are used on lawns, in gardens, around buildings, along roads, and in 

agriculture to help control unwanted vegetation (weeds), insects, fungi, and other pests. 

In the Indian Wells study area, pesticides were not detected or were only detected at low 

concentrations. Of the 20 pesticides with health-based benchmarks that were analyzed, 

none were detected at high or moderate concentrations in the Indian Wells primary 

aquifers.

BENCHMARKS FOR EVALUATING GROUNDWATER QUALITY

GAMA’s Priority Basin Project uses benchmarks established for drinking 

water to provide context for evaluating the quality of untreated groundwater. After 

withdrawal, groundwater may be disinfected, filtered, mixed, or exposed to the 

atmosphere before being delivered to consumers. Federal and California regulatory 

benchmarks for protecting human health (Maximum Contaminant Level, MCL) are 

used when available. Otherwise, nonregulatory benchmarks for protecting human 

health (Notification Level, NL, and Lifetime Health Advisory, HAL) and nonregulatory 

benchmarks for protecting aesthetic properties such as taste and odor (Secondary 

Maximum Contaminant Level, SMCL) are used. 

High, moderate, and low concentrations are defined relative to benchmarks

Concentrations are considered high if they are greater than a benchmark. For inorganic constituents, concentrations are moderate

if they are greater than one-half of a benchmark. For organic and special-interest constituents, concentrations are considered moderate

if they are greater than one-tenth of a benchmark; this lower threshold was used because organic constituents are generally less prevalent and have smaller concentrations relative to benchmarks than inorganic constituents. Low concentrations include non-detections 

and values less than moderate concentrations. Methods for evaluating water quality are discussed by Milby Dawson and Belitz (2012).

ORGANIC CONSTITUENTS

Pesticides

Volatile

organic

compounds

100

100

High

Moderate

EX

Low or not detected

AMPLE Values are a percentage of the area of the primary aquifers 

with concentrations in the three specified categories.

CONSTITUENT CONCENTRATIONS
Trace Element Concentrations Throughout the 

California Desert Region

Trace elements were present at high concentrations in all of the Desert primary 

aquifers. In Indian Wells, trace elements were high in 54% of the primary aquifers, on 

an areal basis, which is the highest percentage in the Desert Region study areas (Milby 

Dawson and Belitz, 2012). The trace elements with the highest percentages were boron 

(high concentrations in 38% of the primary aquifers) and arsenic (15%). These two 

constituents were detected at high concentrations in all of the Desert Region primary 

aquifers. Boron was detected at high concentrations in a larger portion of the Indian 

Wells primary aquifers than in any of the other Desert Region study areas.

Priority Basin Assessments 

GAMA’s Priority Basin Project 

(PBP) assesses water quality in that part 

of the aquifer system used for drinking 

water, primarily public supply. Water 

quality in shallower and deeper parts 

may differ from water quality in the 

primary aquifers. GAMA’s Domestic 

Well Project assesses water quality 

in the shallower parts of the aquifer 

system. Ongoing assessments are being 

conducted in more than 120 basins 

throughout California.

The PBP assessments are based on a 

comparison of constituent concentrations 

in untreated groundwater with benchmarks established for the protection of 

human health and for aesthetic concerns. 

The PBP does not evaluate the quality of 

drinking water delivered to consumers.

The PBP uses two approaches for 

assessing groundwater quality. The first 

approach uses a network of wells to 

provide a statistically based assessment 

of the status of groundwater quality. The 

second approach uses additional wells 

to help assess the factors that affect 

water quality. Both approaches use 

data routinely collected for regulatory 

compliance, as well as data collected 

by the PBP. The PBP includes chemical 

analyses not generally available 

as part of regulatory compliance 

monitoring, including measurements at 

concentrations much lower than humanhealth benchmarks, and measurement of 

constituents that can be used to trace the 

sources and movement of groundwater.

By Barbara J. Milby Dawson and Kenneth Belitz

SELECTED REFERENCES

California Department of Water Resources, 2003, California’s groundwater: California 

Department of Water Resources Bulletin 118, 246 p., available at

http://www.water.ca.gov/groundwater/bulletin118/update2003.cfm/

Densmore, J.N., Fram, M.S., and Belitz, K., 2009, Ground-water quality data in the 

Owens and Indian Wells Valleys study unit, 2006—Results from the California 

GAMA Program: U.S. Geological Survey Data Series 427, 86 p., available at 

http://pubs.usgs.gov/ds/427

Milby Dawson, B.J., and Belitz, K., 2012, Status of groundwater quality in the 

 California Desert Region, 2006–2008—California GAMA Program Priority Basin 

 Project: U.S. Geological Survey Scientific Investigations Report 2012-5040, 100 p. 

For more information

Technical reports and hydrologic 

data collected for the GAMA Program 

may be obtained from:

GAMA Program Unit

U.S. Geological Survey

California Water Science Center

4165 Spruance Road, Suite 200

San Diego, CA 92101

Telephone number: (619) 225-6100

WEB: http://ca.water.usgs.gov/gama

GAMA Program Unit

State Water Resources Control Board

Division of Water Quality

PO Box 2231, Sacramento, CA 95812

Telephone number: (916) 341-5779

WEB: http://www.waterboards.ca.gov/gama/

0 25 50

0 25 50 100 KILOMETERS

100 MILES

Owens

Valley

Indian Wells

Mojave

Coachella

Antelope

NEVADA

ARIZONA

MEXICO

CALIFORNIA

Colorado

River

Desert Region Study Areas

0%

20%

40%

60%

80%

100%

0%

20%

40%

60%

80%

100%

0%

20%

40%

60%

80%

100%

Owens

Indian Wells

Coachella

Colorado River

Antelope

Mojave

High aquifer proportion

EXPLANATION

Moderate aquifer proportion

Trace Elements

Boron

Arsenic

Percentage of area of primary aquifers with concentrations in the specified categories