U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2013–1221

October 2013

Prepared in cooperation with U.S. Bureau of Land Management, California Desert District

Chuckwalla Valley Multiple-well Monitoring Site, 

Chuckwalla Valley, Riverside County, California

Printed on recycled paper

78

86

177

62

111

10

95

San Bernardino

County

Riverside

County

San Diego

County

Imperial County

La Paz

County

Airport

City

Dry lake

Multiple-well

 monitoring site

 (CWV1)

County boundary

Chuckwalla Valley

Groundwater basin boundaries

Arroyo Seco Valley

Cadiz Valley

Chocolate Valley

Orocopia Valley

Palo Verde Mesa

Pinto Valley

Rice Valley

Ward Valley

0

0 5 10 15 20 Kilometers

5 10 15 20 Miles

116° 115°30’ 115° 114°30’

34°

34°

30’

Salton

Sea

ARIZONA

CALIFORNIA

COLORADO

 RIVER

CWV1

Blythe

Palm

Springs

Mule Mts

McCoy Mts

CHUCKWALLA

VALLEY

PALEN

VALLEY

EXPLANATION

Chuckwalla

Vallley

study area

C

A L I F O R N I A

Pacific Ocean

Shaded relief base created from 30-m 

digital elevation model from USGS 

National Elevation Dataset (NED); 

North America Vertical Datum 1988 

(NAVD88)

Hydrology sourced from 1:24,000-

scale National Hydrography Dataset, 

1974 -2009

Place names sourced from USGS 

Geographic Names Information 

System, 1974 -2009

Albers Projection, NAD83

The U.S. Geological Survey (USGS), in cooperation with 

the Bureau of Land Management, is evaluating the geohydrology and water availability of the Chuckwalla Valley, California (fig. 1). As part of this evaluation, the USGS installed the 

Chuckwalla Valley multiple-well monitoring site (CWV1) in 

the southeastern portion of the Chuckwalla Basin (fig. 1). Data 

collected at this site provide information about the geology, 

hydrology, geophysics, and geochemistry of the local aquifer 

system, thus enhancing the understanding of the geohydrologic 

framework of the Chuckwalla Valley. This report presents construction information for the CWV1 multiple-well monitoring 

site and initial geohydrologic data collected from the site.

Study Area

The Chuckwalla Valley groundwater basin underlies the 

Palen and Chuckwalla Valleys, is located primarily in eastern 

Riverside County, California, and covers approximately 940 

square miles (fig. 1). The basin is mostly surrounded by mountains and highlands. Its water-bearing units consist of Quaternary to Pliocene-aged deposits that are classified into three 

major formations: the Quaternary alluvium (of Holocene and 

Pleistocene age), the Pleistocene-age Pinto Formation, and the 

Pliocene-age Bouse Formation (California Department of Water 

Resources, 1979). The maximum thickness of the deposits is 

about 1,200 feet (ft), and the average specific yield is estimated 

to be 10 percent (California Department of Water Resources, 

1979). The basin receives subsurface inflow from the Pinto 

Valley, Cadiz Valley, and Orocopia groundwater basins and 

is recharged by the combined percolation of runoff from the 

surrounding mountains and precipitation on the valley floor 

(California Department of Water Resources, 1979 and 2003). 

Average annual precipitation in the basin is about 4 inches, and 

there are no perennial streams (Rantz, 1969; California Department of Water Resources, 1979). Data from the meteorological 

station BLH (http://www.cnrfc.noaa.gov/rainfall_data.php, 

accessed November 26, 2012) at the Blythe Airport (fig. 1), 

east of the Chuckwalla Valley, indicated that annual precipitation from 2002 through 2012 ranged from 0.73 to 7.93 inches 

and averaged 3.12 inches. Groundwater flows southeastward 

from the basin’s boundary with the Cadiz Valley and Pinto 

Figure 1. The Chuckwalla 

Valley in Riverside County, 

southeast California.
100

0

200

300

400

500

600

700

800

900

1,000

0 126

Caliper,

in inches

0 15075 0 500

Natural

gamma,

in counts

per second

Temperature,

in degrees

Fahrenheit

Sonic

(Delta T),

in microseconds per foot

0 105 400

Resistivity,

in ohm-meters

(16N-Short normal,

64N-Long normal)

0 800 0 300150

Electromagnetic

conductivity,

in millimhos

per meter

Spontaneous

potential,

in millivolts

NO DATA

Depth, in feet below land surface

92 98

Summary

lithology

Well

construction

( is depth to water,

January 23, 2012)

Clay

Clay

Clay

Clay

Clay

Clay with interbedded silty

sand (VF-M) and marl

Clay

Silt and clay

Silty gravelly sand (VF to VC)

Sandy (VF to M) silt

Sandy (VF to VC) silt

Sandy (VF to VC) silt

Silty sand (VF to C)

Silty sand (VF to VC)

Silty sand (VF to F)

Silty sand (VF to F) with clay

Silty sand (VF to VC) with

minor gravel

Sandy (VF to F) silt

Sand (VF to M)

Sand (VF to M)

Gravelly sand (VF to VC) 

Sand (VF to M) with

interbedded clay

Silty sand (VF to M) with

interbedded clay

Gravelley sand (VF to VC)

Sandy (VF to F) silty clay

with marl

Silty sand (VF to F) with marl

Silty sand (VF to VC) with marl

Sandy (VF to M) silt with marl

Sandy (VF to VC) clayey silt

Sandy clay

100

200

300

400

500

600

700

800

900

1,000

16N

64N

0

Alluvium Pinto Formation Bouse Formation

CWV1 #3CWV1 #2 GROUT

GROUT SAND

SAND

CWV1 #1
Common well USGS Site ID Construction information Sampling information

name (hyperlinked to 

NWISWeb)

Well depth Depth to Depth to bot- Depth to top Depth to Altitude of Date Time

(ft below top perfora- tom perfora- sand pack bottom sand LSD sampled sampled LSD) tion (ft tion (ft below (ft below pack (ft (ft above- (m/d/yyyy) (hhhh) below LSD) LSD) LSD) below LSD) NAVD 88)

CWV1 #1 333527114511901 993 973 993 943 1,000 417.7 6/6/12 1650

CWV1 #2 333527114511902 505 485 505 459 523 417.7 6/6/12 1200

CWV1 #3 333527114511903 230 210 230 177 243 417.7 6/6/12 1330

Valley Basins through the narrows between the McCoy and 

Mule Mountains and into the adjacent Palo Verde Mesa Basin 

(Steinemann, 1989). Measured groundwater levels range from 

an altitude of 500 ft in the western portion of the basin to less 

than 275 ft near the eastern outlet of the basin (Steinemann, 

1989). The California Department of Water Resources reports 

that groundwater levels in the basin were generally stable 

between the early 1950s and 1962 (California Department of 

Water Resources, 1963), indicating that discharge and recharge 

were roughly balanced during that period.

The Chuckwalla Valley is an area with high potential for 

solar energy development. Two large-scale solar energy projects 

are being constructed, and at least nine additional projects are 

approved or proposed in this basin, which is the largest number of solar projects in any single basin in California (Godfrey 

and others, 2012). Water needs associated with proposed solar 

energy projects within the basin have generated concern about 

potential detrimental effects on local groundwater resources and 

phreatophytic-vegetation habitats.

Well Completion

The CWV1 borehole was drilled to a depth of 1,000 ft 

below land surface (ft bls) using standard mud-rotary drilling 

techniques. Drill cuttings were collected at 10-ft intervals during the drilling process to determine the lithology (fig. 2). To 

assist in the identification of lithologic and stratigraphic units, 

geophysical logging of the borehole was done prior to well 

construction by using techniques described in USGS Techniques of Water-Resources Investigations Reports (Keys and 

MacCary, 1971; Shuter and Teasdale, 1989; Keys, 1990). Three 

2-inch-diameter wells were installed with screened intervals 

from 973 to 993 (CWV1 #1), 485 to 505 (CWV1 #2), and 

210 to 230 (CWV1 #3) ft bls (fig. 2, table 1). A filter pack of #3 

sand was installed around each screen, and a low-permeability 

bentonite grout was placed in the depth intervals between the 

filter packs to isolate each of the wells. Installation of multiple 

wells within a single borehole allows for analysis of the hydrologic properties of discrete vertical zones within the aquifer system, as well as the collection of depth-specific water-chemistry 

samples and the determination of vertical hydraulic gradients.

Geology at the CWV1 site

Geologic units beneath the CWV1 site include Pliocene- to 

Quaternary-age continental deposits that are divided into three 

formations: alluvium composed of fine to coarse sand interbedded with gravel, silt, and clay; the Pinto Formation composed 

of coarse fanglomerate containing boulders and lacustrine clay; 

and the Bouse Formation composed of a basal limestone overlain by interbedded clay, silt, and sand, and a tufa (California 

Department of Water Resources, 1963 and 2003; Metzger and 

others 1974). The drill cuttings and geophysical logs indicated 

that the CWV1 borehole penetrated mostly fine-grained sediments, which are interbedded with coarse-grained sediments 

(fig. 2). Interpretation of the geophysical logs and observed 

changes in the lithology indicated that the borehole encountered undifferentiated alluvium from the land surface to about 

285 ft bls, the Pinto Formation from about 285 to 700 ft bls, and 

the Bouse Formation from 700 ft bls to the bottom of the hole 

at 1,000 ft bls. Several thick clay units (238–320, 595–630, and 

900–950 ft bls) were encountered throughout the borehole. 

Hydrology

The clay units likely isolate, to a degree, the water-bearing 

units of the formations from those vertically adjacent. Although 

the lateral extents of these clays are unknown, their thicknesses 

indicate they extend some distance from the site, and differences in water-level elevations among wells were consistent 

with restricted hydraulic connections between water-bearing 

units. Manual depth-to-water measurements made in late January 2012, and again in early May, showed vertical hydraulic 

gradients were downward and that water levels were stable, 

changing by a maximum of 0.2 ft during this period. 

Slug tests were performed on each of the wells to estimate 

the hydraulic conductivity of the aquifer material next to the 

screened interval. The tests were performed by using techniques 

described by Stallman (1971). Computations were performed by 

using spreadsheet-based tools (Halford and Kuniansky, 2002) 

and were analyzed by using methods developed by Butler and 

others (2003) for formations of high hydraulic conductivity. The 

Table 1. Identification, construction, and sampling information 

for the CWV1 multiple-well monitoring site, Chuckwalla Valley, 

Riverside County, California.

Figure 2. Well construction, summary lithology, and geophysicallog data from multiple-well monitoring site CWV1, Chuckwalla 

Valley, California. Abbreviations: VF, very fine; F, fine; M, medium; 

C, coarse; VC, very coarse.

The fifteen-digit U.S. Geological Survey (USGS) Site ID is used to uniquely identify the well. The common name is used throughout the report for quick reference. 

Land-surface datum (LSD) is a datum plane that is approximately at land surface at each well. The altitude of the LSD is described in feet above the North AmericanVertical Datum of 1988 (NAVD 88). Abbreviations: NWISWeb, National Water Information System Web page; ft, feet; m, month; d, day; yyyy, year; hhhh, hour. 
Common well Dissolved pH, field Specific con- Arsenic Chloride Fluoride Sulfate Nitrate, as Total dissolved 

name oxygen, field (standard ductance, field (μg/L) (mg/L) (mg/L) (mg/L) nitrogen solids

(mg/L) units) (μS/cm at 25C) (01000) (00940) (00950) (00945) (mg/L) (mg/L)

(00300) (00400) (00095) (00618) (70300)

Threshold type na SMCL-US SMCL-CA1 MCL-US SMCL-US SMCL-US SMCL-US MCL-US SMCL-US

Threshold level na 6.50–8.5 900 10 250 2 250 10 500

CWV1 #1 1.6 8.2 3700 17.3 944 7.47 324 <0.04 2100

CWV1 #2 4.1 7.9 16000 11.6 4090 2.47 2500 32.0 10700

CWV1 #3 1.1 7.9 5800 27.0 927 2.75 1570 20.5 4160

shallowest well (CWV1 #3) had the lowest estimated hydraulic 

conductivity (K) value at 1.8 feet per day (ft/day); the middle 

well (CWV1 #2) had the highest estimated K value at 7.5 ft/day. 

The deepest well (CWV1 #1) had an estimated K value of 

6.9 ft/day. The hydraulic conductivity estimates were consistent with the lithology in the screened intervals; CWV1 #3 was 

completed in sandy silty clay, whereas the other two wells were 

completed in silty sand (CWV1 #2) and sandy silt (CWV1 #1).

Geochemistry

To delineate the chemical characteristics and source of the 

groundwater, water samples were collected in accordance with 

the protocols established by the USGS National Field Manual 

(U.S. Geological Survey, variously dated, book 9) and analyzed 

for major-ion chemistry; selected minor and trace elements; 

nutrients; organic carbon; the stable isotopes of hydrogen (deuterium) and oxygen (oxygen-18) in water, and of carbon (carbon-13) in dissolved inorganic carbon; and carbon-14 activities. 

Analyses were performed by the USGS National Water Quality Laboratory in Lakewood, Colorado, and the USGS Stable 

Isotope Laboratory in Reston, Virginia, by following standard 

methods outlined by Fishman and Friedman (1989); Coplen 

and others (1991); Patton and Truitt (1992, 2000); Brenton and 

Arnett (1993); Fishman (1993); Coplen (1994); Struzeski and 

others (1996); Garbarino (1999); Garbarino and others (2006); 

and Patton and Kryskalla (2011). Carbon-13 and carbon-14 

analyses were performed by Woods Hole Oceanographic 

Institute under contract with the USGS using standard methods 

described by Vogel and others (1987) and Donahue and others 

(1990). Results presented in this report are limited to those that 

exceed threshold concentrations for drinking water or aid in 

understanding the source of the groundwater.

The water samples from the CWV1 wells had total dissolved solids concentrations ranging from 2,100 to 10,700 milligrams per liter (mg/L; table 2), which is greater than the U.S. 

Environmental Protection Agency (EPA) secondary maximum 

contaminant level (SMCL-US) of 500 mg/L (http://water.epa.

gov/drink/contaminants/secondarystandards.cfm, accessed 

January 3, 2013). Chloride, fluoride, and sulfate concentrations 

also were greater than their respective SMCL-USs in all of the 

samples. In addition, to protect human health, fluoride has a 

maximum contaminant level (MCL-US) of 4 mg/L; the water 

sample from CWV1-1 had a concentration above this MCL. 

Concentrations of arsenic were greater than the MCL-US of 

10 micrograms per liter in all samples.

Nitrate concentrations, reported as nitrogen (NO3

−

-N), in 

the shallower wells (CWV1 #2, and CVW1 #3) were greater 

than the U.S. EPA maximum contaminant level (MCL-US) of 

10 mg/L (table 2). The NO3

−

-N in the shallower wells is hypothesized to be from natural sources or processes, rather than fertilizers in irrigation return flow, because there is little agricultural 

activity in the vicinity.

The stable isotopes oxygen-18 (18O) and deuterium (2H) 

in groundwater reflect the altitude, latitude, and temperature 

of recharge and the extent of evaporation before water entered 

the groundwater system. The isotopic values of water samples 

from the three wells were progressively lighter (more negative) 

with depth (fig. 3, table 3). The isotopic compositions from the 

two shallower wells were similar to each other, indicating that 

these zones could have similar sources of recharge. The isotopic 

composition of the sample from the deeper well (CWV1 #1) 

was much lighter than the shallower wells, indicating that the 

source of recharge for this zone was higher in altitude, lower 

in temperature, or both, compared to the shallower wells. The 

differences in isotopic and chemical compositions measured in 

the wells indicated that hydraulic communication between the 

geologic formations is limited.

Carbon-14 is a radioactive isotope of carbon with a halflife of about 5,700 years (Godwin, 1962). Carbon-14 activities 

are used to determine the age (time since recharge) of groundwater on time scales ranging from recent to more than 20,000 

years before present (Izbicki and Michel, 2003). Carbon-14 

ages presented in this report do not account for changes in 

carbon-14 activities resulting from chemical reactions or mixing and, therefore, are considered uncorrected ages. In general, 

uncorrected carbon-14 ages are older than the actual ages of the 

water after correction. Uncorrected ages (in years before present) were calculated by using the following equation (Stuiver 

and Polach, 1977): Estimated age = 8,033 * natural log (percent 

modern carbon / 100 percent). Uncertainties concerning the 

Table 2. Water-quality indicators (field parameters), selected trace elements and major ions, nitrate, and total dissolved solids, detected in 

samples collected from the CWV1 multiple-well monitoring site, Chuckwalla Valley, Riverside County, California.

1 The SMCL-CA for specific conductance has recommended and upper threshold values. The upper value is shown in parentheses.

The five-digit U.S. Geological survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. Threshold

type: MCL-US, U.S. Environmental Protection Agency maximum contaminant level; SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Abbreviations: mg/L, milligrams per liter; na, not available;

μS/cm, microsiemens per centimeter; °C, degrees Celsius; μg/L, micrograms per liter; <, less than.
–80

–75

–70

–65

–60

–55

–50

–45

–40

delta Oxygen-18, in per mil

delta Deuterium, in per mil

 CWV1 #3

 CWV1 #2

 CWV1 #1

Global meteroic water line

(Craig, 1961)

–11 –10.5 –10 –9.5 –9 –8.5 –8 –7.5 –7 –6.5

sac13-0479_Figure 03 Isotopes

Common δ18O δ2H δ13C Carbon-14 Carbon-14 Estimated age since

well name (per mil) (per mil) (per mil) (percent modern) (counting error) recharge based on

(82085) (82082) (82081) (49933) (49934) uncorrected carbon-14,

years before present

CWV1 #1 -9.78 -74.20 -8.58 9.920 .070 18,600

CWV1 #2 -7.21 -62.30 -10.00 19.05 .110 13,300

CWV1 #3 -6.70 -55.60 -11.62 30.86 .130 9,400

initial value of carbon-14 in recharge waters add uncertainties 

to the groundwater-age estimations made using carbon-14 data; 

without more comprehensive geochemical modeling, the carbon-14 ages are treated as relative estimates of age rather than 

accurate absolute estimates of age. Estimated carbon-14 ages 

for the three wells ranged from 9,400 to 18,600 years before 

present (table 3).

Accessing Data

Users of the data presented in this report are encouraged to 

access information through the USGS National Water Information System (NWIS) web page (NWISWeb) located at http://

waterdata.usgs.gov/nwis/. NWISWeb serves as an interface to 

a database of site information and groundwater, surface-water, 

water-chemistry and real-time data collected from locations 

throughout the 50 states and elsewhere. NWISWeb is updated 

from the database on a regular basis.

Data can be retrieved by category and geographic area, and 

the retrieval can be selectively refined by location or parameter 

field. NWISWeb can output water-level and water-chemistry 

graphs, site maps, and data tables (in HTML and ASCII format) 

and can develop site-selection lists.

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and infrared spectrometry: U.S. Geological Survey Open-File Report 

92–480, 12 p., Method ID: O-1122-92

Butler, J.J., Jr., Garnett, E.J., and Healey, J.M., 2003, Analysis of slug 

tests in formations of high hydraulic conductivity: Ground Water, 

v. 41, no. 5, p. 620-630.

California Department of Water Resources, 1963, Data on water 

wells and springs in the Chuckwalla Valley area, Riverside County, 

California: California Department of Water Resources Bulletin 

No. 91-7, p. 77.

Figure 3. Isotopic 

composition of 

groundwater 

collected from the 

Chuckwalla Valley 

multiple-well 

monitoring site 

CWV1, Chuckwalla 

Valley, Riverside 

County, California

Table 3. Results for analyses of stable isotopes, carbon-14 activities, and estimated age since recharge in samples collected from the 

CWV1 multiple-well monitoring site, Chuckwalla Valley, Riverside County, California.

The five-digit U.S. Geological survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. Threshold type: MCL-US,

U.S. Environmental Protection Agency maximum contaminant level; SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California 

Department of Public Health secondary maximum contaminant level.
By R.R. Everett, A.A. Brown, and G.A. Smith

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91-24, 55 p.

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For more information, contact:

Rhett R. Everett

U.S. Geological Survey

4165 Spruance Road, Suite 200

San Diego, CA 92101

e-mail: reverett @usgs.gov

Phone: (619) 225-6100 Fax: (619) 225-6101

USGS California Water Science Center 

website: http://ca.water.usgs.gov