U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2006–3055

May 2006 Printed on recycled paper

The Willcox and Douglas Basins, 

about 1,910 mi2 and 750 mi2, 

respectively, are in Cochise and Graham 

Counties in southeastern Arizona (fig. 1). 

The majority of the population in the two 

basins resides in the cities of Willcox and 

Douglas where the population in 2000 

was 3,733 and 14,312, respectively (U.S. 

Census Bureau, 2005). The projected 

population in 2025 for the city of Willcox 

is 3,981 and for Douglas is 16,642 

(Arizona Department of Economic 

Security, 2005).

Ground water is the main source of 

water in this area owing to the sparse 

surface-water resources. The Willcox and 

Douglas Basins are the primary areas of 

agriculture in Cochise County, and 90 

percent of the ground-water pumpage is 

for agriculture. According to the National 

Agricultural Statistics Service, irrigated 

land increased 25 percent from 52,000 

acres in 1992 to 65,000 acres in 2002 

(U.S. Department of Agriculture, 1999, 

2004).

There is concern in the Willcox 

and Douglas Basins about the future 

availability of water for all uses, 

including agriculture, municipal and 

domestic, and thermoelectric power. 

Comprehensive monitoring of the 

ground-water system and identification 

of the areas of change will help 

managers with future resource decisions. 

Ground-water pumping commonly 

causes declines in ground-water levels. 

When declines become widespread and 

persistent, further negative consequences 

such as increased pumping lift, land 

subsidence, and deterioration in water 

quality can occur. The combined

estimated ground-water pumpage in both Figure 1.  Physiography and location of water-level monitoring sites in Willcox and Douglas Basins.

Prepared in cooperation with the

ARIZONA DEPARTMENT OF WATER RESOURCES

Investigation of the Hydrologic Monitoring Network of the 

Willcox and Douglas Basins of Southeastern Arizona: 

A Project of the Rural Watershed Initiative

110o15’

110o

45’

109o30’

32o30’

45’

31o30’

15’

Douglas

Bisbee

Willcox

Playa

UNITED STATES

MEXICO

ARIZONA

SONORA

32o

Willcox

Basin

Douglas

Basin

MOUNTAINS

PERILLA

SULFUR

SPRING

VALLEY

Willcox

Tucson

ARIZONA

Willcox and Douglas

basins

G

River

ila

UNITED STATES

MEXICO

Base from U.S. Geological Survey

digital data, 1:100,000, 1982

Universal Transverse Mercator

projection, Zone 12

0 10 MILES

0 10 KILOMETERS

PINALENO

MOUNTAINS

GALIURO

MOUNTAINS

MULE MOUNTAINS

WINCHESTER MOUNTAINS

BLACK HILLS

191

10

DRAGOON

MOUNTAINS

PEDROGOSA

MOUNTA NI S

SWISSHELM

MOUNTAINS

CHIRICAHUA

MOUNTA NI S

181

186

DOS CABEZAS MOUNTAINS

80

Area

enlarged

in fig. 3

GRAHAM CO

COCHISE CO
basins from 1915 to 2000 was more than 

12 million acre-feet. These withdrawals 

have resulted in large declines in groundwater levels in both basins (fig. 2).

In 1965, the State Land Commission 

declared much of the Douglas Basin 

a Critical Groundwater area because 

the large withdrawals for irrigation 

resulted in large water-level declines. 

The commission prohibited drilling new 

irrigation wells except to replace existing 

wells. The Critical Groundwater area 

became the Douglas Irrigated NonExpansion Area (INA) with the passage 

of the 1980 Groundwater Management 

Act. The INA designation means that 

only land irrigated any time between 

1975 and 1980 can be irrigated with 

ground water (Rascona, 1993). There is 

no such limitation on irrigation in the 

Willcox Basin.

In 2005, the U.S. Geological Survey 

(USGS), in cooperation with the Arizona 

Department of Water Resources (ADWR), 

began an investigation of the geology and 

hydrology of the Willcox and Douglas 

Basins (primarily focusing on the 

hydrologic monitoring network) as part 

of the Rural Watershed Initiative (RWI). 

The RWI is a program established by the 

State of Arizona in 1999 and managed 

by the ADWR. Other RWI investigations 

that started in 2005 are the middle San 

Pedro Basin in southeastern Arizona, and 

the Detrital, Hualapai, and Sacramento 

Valleys in northwestern Arizona. RWI 

studies in the Coconino Plateau, the 

Mogollon Highlands, and the upper and 

middle Verde River watersheds (http://

az.water.usgs.gov/rwi-ii/) began in 1999.

The purpose of this study is to 

evaluate the data-collection network that 

is used to monitor hydrologic conditions 

and ground-water storage changes in the 

Willcox and Douglas Basins. The study 

will be conducted in two phases. The 

Willcox Basin will be studied in the first 

phase, and the Douglas Basin will be 

studied in the second phase. The primary 

objectives are to:

1. Assess (a) the current state of 

knowledge of the ground-water flow 

systems, and (b) the existing water-level 

data collection networks and needs for 

improvement.

2. Improve the understanding of the 

hydrogeologic framework of the Willcox 

Basin.

3. Establish a hydrologic monitoring 

network for ongoing assessments and 

changes in aquifer conditions. 

4. Inform the hydrologic community 

and residents of the Willcox and Douglas 

areas about hydrologic conditions in the 

basins.

5. Evaluate historical and current 

estimates of ground-water withdrawal for 

agricultural use.

Physical Setting

The Willcox and Douglas Basins 

form the Sulfur Springs Valley, a 

structural northwest-trending valley 

in southeastern Arizona. The Willcox 

Basin is surrounded by the Dragoon and 

Winchester Mountains on the west, the 

Galiuro Mountains and Black Hills on 

the north, and the Pinaleno, Dos Cabezas, 

and Chiricahua Mountains on the east. 

The southern boundary of the Willcox 

Basin is the Swisshelm Mountains and a 

series of small hills at the northern end of 

the Douglas Basin. The Douglas Basin is 

surrounded by the Swisshelm, Pedrogosa, 

and Perilla Mountains on the east, and 

the Mule and Dragoon Mountains on 

Figure 2.  Hydrographs of depth to water for wells in the Willcox and Douglas Basins.

the west. The Douglas Basin extends 

into northern Mexico, but the southern 

boundary of the study area is the United 

States-Mexican border. The elevation in 

the study area ranges from 10,700 ft in 

the Pinaleno Mountains on the northern 

boundary to 3,900 ft at the international 

boundary.

The Willcox Basin has internal 

drainage where all surface water drains 

to the Willcox Playa, a prominent feature 

of about 50 mi2 in the center of the 

basin. A few streams in the Pinaleno and 

Chiricahua Mountains are perennial. All 

other streams in the basin are ephemeral. 

The Douglas Basin is drained by 

Whitewater Draw, which heads in the 

Chiricahua Mountains in the southern 

part of the Willcox Basin and flows 

westward around the north end of the 

Swisshelm Mountains southward through 

the basin and into Mexico. Most streams 

in the basin, including Whitewater Draw, 

are ephemeral. Leslie Creek, which 

originates in the Pedrogosa Mountains 

and the southern end of the Chiricahua 

Mountains, has a perennial reach.

Climate

The climate in both basins is semiarid 

and characterized by cool winters and 

hot summers. The average annual daily 

minimum and maximum temperatures 

in the city of Willcox are 41oF and 77oF, 

respectively (Western Regional Climate 

Center, 2005). The minimum temperature 

recorded in Willcox was -7oF and the 

maximum temperature was 110oF. In the 

city of Douglas, the average annual daily 

minimum and maximum temperatures 

are 45oF and 79oF, respectively (Western 

Regional Climate Center, 2005). The 

minimum temperature recorded in 

Douglas was 2oF and the maximum 

temperature was 109oF.

Average annual precipitation in 

the two basins ranges from 12 in. on 

the basin floor to more than 35 in. in 

the surrounding mountains (Spatial 

Climate Analysis Service, Oregon State 

University, 2004). Precipitation occurs 

during two seasons. During the winter 

months frontal storms bring widespread 

rainfall, and during summer months 

thunderstorms may produce localized, 

heavy rainfall of short duration. Average 

annual snowfall ranges from about 1 to 

4 in. on the basin floor to 13 in. in the 

higher elevations. Native vegetation in 

DEPTH TO WATER, IN FEET

Douglas

Willcox

19401945195019551960196519701975198019851990199520002005

100

150

200

50

0
Figure 3.  Annual ground-water pumpage in the Willcox and Douglas Basins, 1915–2000.

the noncultivated areas on the basin floor 

and foothills in the two basins is mainly 

mesquite and sagebrush with some 

cactus. Vegetation in the higher elevations 

is primarily pine. The Willcox Playa, an 

alkali flat, is devoid of vegetation.

Hydrology and Water Use

Ground water from the basin-fill 

aquifer is the primary source of water for 

the Willcox and Douglas Basins. In the 

Willcox Basin, the basin fill or alluvial 

deposits consist of stream deposits and 

lake-bed deposits (Brown and Schumann, 

1969). The stream deposits are the most 

productive water-bearing units and are 

composed of gravel, sand, silt, and clay. 

The lake-bed deposits, composed mostly 

of clay, can function as a confining layer 

to the water in the underlying stream 

deposits, creating artesian conditions, or 

can cause ground water to be perched 

above them where they underlie the 

stream deposits (Mann and others, 1978). 

In the Douglas Basin the basin fill is 

composed of sand and gravel lenses 

interbedded with silt and clay lenses. 

The sand and gravel lenses are the main 

source of water. There are no large scale 

confining layers in the Douglas Basin; 

however, there are localized areas with 

confined or perched water conditions 

(Arizona Department of Water Resources, 

1994). The surrounding mountains are 

composed of igneous, metamorphic and 

sedimentary rocks.

There was a large range in the depth 

to ground water in the monitoring wells 

measured by the ADWR in 2003. Depth 

to ground water in the Willcox Basin 

ranged from 30 ft to more than 400 

ft below land surface. In the Douglas 

Basin, depth to ground water ranged 

from 60 ft to more than 300 ft below 

land surface. Prior to development, the 

ground-water flow was similar to the 

surface drainage, but large scale groundwater pumping has created cones of 

depression that have changed groundwater flow in parts of the two basins. 

Several large cones of depression have 

developed in the Willcox Basin. One 

is southeast of the Willcox Playa, and 

the other is about 6 mi northwest of the 

city of Willcox (Mann and others, 1978; 

Oram, 1993). In the Douglas Basin, a 

large cone of depression has formed in 

the northern part of the basin (Mann and 

English, 1980; Rascona, 1993).

Ground-water storage in the upper 

1,200 ft of the basin fill in the Willcox 

Basin in 1989 was estimated to be 45.3 

million acre-ft (Arizona Department 

of Water Resources, 1994). Freethey 

and Anderson (1986) estimated that the 

amount of recoverable water to a depth 

of 1,200 ft in the Douglas Basin is 32 

million acre-ft. Recharge in both basins is 

primarily along the mountain front. There 

is additional recharge from irrigation 

water and from runoff in stream channels. 

Estimated recharge in the Douglas Basin 

is 22,000 acre-ft per year (Coates and 

Cushman, 1955; Freethey and Anderson, 

1986). Estimated recharge in the Willcox 

Basin is 47,000 acre-ft per year on the 

basis of a numerical ground-water model 

(Anderson and Freethey, 1995).

Prior to 1945, the estimated annual 

ground-water pumpage in both basins 

was less than 5,000 acre-ft. After 1945, 

ground-water pumpage increased and the 

maximum annual pumpage in both basins 

was reached in 1974 at 339,000 acre-ft 

in the Willcox Basin and 138,000 acre-ft 

in the Douglas Basin (Anning and Duet, 

1994). Reduction of irrigated acreage 

resulted in a decline in annual pumpage 

in both basins between 1974 and the early 

1980s. Pumpage stabilized between 1991 

and 2000 and averaged 41,000 acre-ft per 

year in the Douglas Basin and 132,000 

acre-ft per year in the Willcox Basin 

(fig. 3).

Ground-water withdrawals have 

resulted in large declines in ground-water 

levels in both basins and may be the 

cause of land subsidence in the Willcox 

Basin. Water levels declined more than 

200 ft in nine wells in the Willcox 

Basin between 1954 and 1975 (Mann 

and others, 1978). Subsidence occurs 

when there is significant ground-water 

withdrawal and resulting compaction of 

the unconsolidated aquifer. Holzer (1980) 

Willcox

Douglas

191519201925193019351940194519501955196019651970197519801985199019952000

300

200

100

0

GROUND-WATER PUMPAGE, IN

ACRE-FEETx 1,000

400

Figure 4.  Earth crack south of Willcox, August 2005.
reported that about 5 ft of subsidence had 

been measured between 1937 and 1974 

northwest of Willcox. Some of the earth 

cracks and fissures found in the Willcox 

Basin could be related to the subsidence 

and to the declines in water levels 

(Holzer, 1980; fig. 4).

Planned Approach of Investigation

The initial task of the investigation 

will be to compile hydrologic data and 

information. Data and information will be 

compiled first for the Willcox Basin and 

then for the Douglas Basin.

Ground-water level monitoring 

networks in the two basins will be 

evaluated to determine if sufficient 

data are being collected to document 

ground-water conditions and changes 

in the ground-water system. The areal 

distribution of the sites in the networks 

will be evaluated on the basis of land 

use and ground-water withdrawals. 

Time series water-level data will be 

plotted to determine if data from the 

network are representing changes in 

the hydrologic conditions as noted in 

published literature. In 2004, there 

were 46 wells in the ADWR groundwater level monitoring network in the 

Willcox Basin and 27 in the Douglas 

Basin (fig. 1). If it is determined that 

additional sites are needed to augment 

the current network, the new sites will be 

selected on the basis of well-construction 

information documented in various 

databases, lithology from well logs, field 

inventories, and statistical techniques.

A ground-water storage-change 

monitoring network using gravity methods 

will be established to complement the 

ground-water level monitoring network. 

Gravity monitoring locations will be 

selected throughout the basins, with 

special emphasis on areas where groundwater levels can not be obtained.

A preliminary assessment of 

subsidence in the Willcox Basin will be 

done by using remote sensing techniques. 

A spatial database of the surface cracks 

and earth fissures will be created. Some 

will be mapped in the field by using the 

Global Positioning System (GPS). 

A major portion of the water budget 

in the Willcox and Douglas Basins is 

ground-water pumpage for irrigation 

of crops. The pumpage for irrigation 

of crops in 2006 will be estimated by 

mapping irrigated acreage, crop type, and 

irrigation method (fig. 5). Estimates of 

pumpage for previous years also will be 

evaluated. This information will be used 

to develop a spatial database.

References Cited

Anderson, T.W., and Freethey, G.W., 1995, 

Simulations of ground-water flow in alluvial 

basins in south-central Arizona and parts 

of adjacent States: U.S. Geological Survey 

Professional Paper 1406–D, 78 p.

Anning, D.W., and Duet, N.R., 1994, Summary of 

ground-water conditions in Arizona 1987–90: 

U.S. Geological Survey Open-File Report 

94–476, 1 sheet.

For further information, contact:

A. D. Konieczki 

U.S. Geological Survey

Arizona Water Science Center

520 North Park Avenue, Suite 221

Tucson, Arizona, 85719-5035

Email: alicek@usgs.gov or visit home page 

at http://az.water.usgs.gov

Figure 5.  Aerial photograph of irrigated area

in the northern part of the Willcox Basin, July

2005 (see fig. 1).

Reconnaissance geophysical surveys 

will be done in the Willcox Basin. These 

surveys will provide some information on 

the distribution and properties of basinfill sediments.

—A.D. Konieczki

Arizona Department of Economic Security, 2005, 

2004 Estimates – Population growth, accessed 

November 11, 2005, at http://www.workforce.

az.gov.us

Arizona Department of Water Resources, 1994, 

Arizona Water Resources Assessment, Volume 

I, Inventory and Analysis, and Volume II, 

Hydrologic Summary: Arizona Department of 

Water Resources, 236 p.

Brown, S.G., and Schumann, H.H., 1969, 

Geohydrology and water utilization in the 

Willcox Basin, Graham and Cochise Counties, 

Arizona: U.S. Geological Survey Water-Supply 

Paper 1859–F, 32 p.

Coates, F.T., and Cushman, R.L., 1955, Geology 

and ground-water resources of the Douglas 

basin, Arizona: U.S. Geological Survey WaterSupply Paper 1354, 56 p.

Freethey, G.W., and Anderson, T.W., 1986, 

Predevelopment hydrologic conditions in the 

alluvial basins of Arizona and adjacent parts of 

California and New Mexico: U.S. Geological 

Survey Hydrologic Investigations Atlas HA-664, 

3 sheets.

Holzer, Thomas L., 1980, Reconnaissance maps of 

earth fissures and land subsidence, Bowie and 

Willcox areas, Arizona: U.S. Geological Survey 

Map MF–1156, 2 sheets, scale 1:24,000.

Mann, Larry J., and English, C.S., 1980, Maps 

showing ground-water conditions in the Douglas 

basin area, Cochise County, Arizona—1978: 

U.S. Geological Survey Water-Resources 

Investigations Open-File Report 80–700, 3 

sheets.

Mann, L.J., White, N.D., and Wilson, R.P., 1978, 

Maps showing ground-water conditions in the 

Willcox area, Cochise and Graham Counties, 

Arizona—1975: U.S. Geological Survey WaterResources Investigations Open-File Report 

78–60, 3 sheets.

Oram, Paul III, 1993, Maps showing groundwater 

conditions in the Willcox Basin Graham and 

Cochise Counties, Arizona—1990: Arizona 

Department of Water Resources Hydrologic Map 

Series Report Number 25, 2 sheets.

Rascona, S.J., 1993, Maps showing groundwater 

conditions in the Douglas Basin, Cochise 

County, Arizona—1990: Arizona Department of 

Water Resources Hydrologic Map Series Report 

Number 26, 2 sheets.

Spatial Climate Analysis Service, Oregon 

State University, 2004, Analysis of annual 

precipitation: Spatial Climate Analysis Service, 

Oregon State University, accessed January 10, 

2006, at http://www.ocs.orst.edu/prism/products/

matrix.phtml?vartype=ppt

U.S. Census Bureau, 2005, City & Town Population 

Estimates, accessed February 10, 2006, at http://

www.census.gov/popest/cities/.

U.S. Department of Agriculture, 1999, 1997 

Census of Agriculture—Volume 1: National, 

state, and county tables, accesses January 12, 

2006, at http://www.nass.usda.gov/Census_of_

Agriculture/index.asp

U.S. Department of Agriculture, 2004, 2002 

Census of Agriculture—Volume 1: National, 

state, and county tables, accesses January 12, 

2006, at http://www.nass.usda.gov/Census_of_

Agriculture/index.asp

Western Regional Climate Center, 2005, Arizona 

Climate Summaries, 2005, accessed November 

21, 2005, at http://www.wrcc.dri.edu/summary/

climsmaz.html

Photograph courtesy of United States Department of

Agriculture–National Agriculture Imagery Program