U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2007–3102

January 2008

Monitoring of Sparta Aquifer Recovery in Southern Arkansas 

and Northern Louisiana, 2003–07

Printed on recycled paper

Prior to 2004, the Sparta aquifer supplied all water for 

industrial and municipal uses in Union County, Arkansas, and 

continues to provide the majority of water for industrial and 

municipal purposes in the surrounding southern Arkansas counties 

and northern Louisiana parishes. In Union County, the Sparta 

aquifer has been used increasingly since development began in the 

early 1920s, resulting in water-level declines of more than 360 feet 

(ft) near El Dorado, Arkansas (Scheiderer and Freiwald, 2006). 

In addition, water quality in some areas of the Sparta aquifer has 

degraded with increased withdrawals (Scheiderer and Freiwald, 

2006).

In 1996, in response to declining water levels and degraded 

water quality in the Sparta aquifer, the Arkansas Natural Resources 

Commission designated a “Critical Ground-Water Area” in five 

southern Arkansas counties—Bradley, Calhoun, Columbia, 

Ouachita, and Union. U.S. Geological Survey (USGS) ground-water 

flow models indicated that Sparta aquifer withdrawals in Union 

County would need to be reduced to 28 percent of 1997 withdrawals, 

about 6 million gallons per day (Mgal/d), to recover and maintain 

the aquifer’s sustainable yield resulting in water levels at or above 

the top of the Sparta Sand (Hays, 2000). Figure 1.  Welcome Center real-time well southeast of El Dorado,

Arkansas (photograph by David Freiwald, U.S. Geological Survey).

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El Dorado #17

Junction City

D'Arbonne

Farmerville

Spencer

Huttig

Magnolia

Emerson

Smackover

Harrell

Louisiana

Arkansas

OUACHITA

CALHOUN

BRADLEY

COLUMBIA

UNION

CLAIBORNE

UNION

LINCOLN

Shumaker

Union School

Marysville

Airport

Monsanto

Welcome 

Center

Lawson-Urbana

Hampton

Warren

Camden

El Dorado

Homer

Bastrop

Strong

WEBSTER

ASHLEY

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0 1 5 0 20Kilometers

Stephens

Hilo

Truxno

MOREHOUSE

DREW

Study

Area

33°30'

93°00' 92°00'

33°00'

El Dorado Water Users 

Monitoring Well

Union County Conservation

District Automatic Data 

Logger Well

U.S. Geological Survey

Real-Time Well

U.S. Geological Survey 

Water-Quality Monitoring Well

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EXPLANATION

El 

Dorado #8

Figure 2.  Location of water-level and water-quality monitoring wells.
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J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

2003 2004 2005 2006 2007

DEPTH TO WATER, IN FEET

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J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Smackover

Spencer

Magnolia

Junction City

Union School

Monsanto

Airport

Welcome Center Welcome Center

El Dorado ChemicalConversion

ChemturaConversion

Lion Oil Conversion

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Background

To prevent further Sparta aquifer water-level declines, 

stakeholders in Union County initiated conservation and ground-water 

reuse and tapped a surface-water supply as an alternative source for 

Union County’s three largest industrial users. A pumping station 

and pipeline completed in 2004 supplies approximately 4.8 Mgal/d 

of Ouachita River surface water to the three industrial users that 

previously relied solely on Sparta aquifer water: El Dorado Chemical, 

Chemtura, and Lion Oil. 

With a reduction in Sparta aquifer ground-water withdrawals, 

ground-water models projected that water levels would rise and water 

quality should improve or stabilize. Formed in 1999 as authorized 

by Act 1050 of 1999 of the Arkansas General Assembly, the Union 

County Water Conservation Board (UCWCB) has authority over 

ground water. The UCWCB built the surface-water infrastructure, 

the Ouachita River Alternative Water Supply Project (Reynolds and 

others, 2006), and in 2002 implemented a cooperative study with the 

USGS, U.S. Environmental Protection Agency (EPA), Union County 

Conservation District (UCCD), and Burns & McDonnell engineering 

firm to monitor Sparta aquifer water-level recovery. The study 

measures, through monitoring and reporting of water levels in Sparta 

aquifer wells throughout the study area, the impact of conservation and 

alternative water efforts on water level and water quality (Yeatts, 2004; 

Scheiderer and Freiwald, 2006).

This study provides continuous real-time water-level data at 

http://ar.water.usgs.gov and www.ucwcb.org from eight USGS wells 

that are part of a network of 29 monitoring wells in southern Arkansas 

and northern Louisiana (figs. 1 and 2), and periodically reports results 

of semi-annual water-quality sampling. In addition to the eight USGS 

real-time wells, the UCCD maintains and posts water-level data from 

eight wells with automated (computerized measurements) data loggers 

in the five-county/three-parish study area. All data were reported in 

semi-annual reports to EPA and are available at www.ucwcb.org. This 

fact sheet describes ground-water level and water-quality monitoring 

activities for the Sparta aquifer recovery study and results for 2003–07.

Ground-Water Level Monitoring

The USGS conducts real-time water-level monitoring in eight 

wells and updates water-level data on the USGS and UCWCB 

Web sites four times per day. Ground-water level monitoring wells 

were selected from six existing and two drilled wells in and around 

Union County in 2003 to form the ground-water level monitoring 

network (fig. 2). 

One of the three criteria for Critical Ground-Water Area 

designation occurs when water levels fall below the top of the 

formation (Pugh and others, 1998; Brantly and others, 2002) for a 

confined aquifer. Water levels for seven of the eight real-time wells 

continue to meet these Critical Ground-Water Area criteria. As of May 

2007, water levels in the Sparta aquifer range from 64 ft above the top 

of the Sparta Sand in the Spencer well in southeastern Union Parish, 

Louisiana, to 85 ft below the top of the Sparta Sand in the Airport 

well near El Dorado where the lowest water levels historically have 

occurred (Schrader and Jones, 2007). 

However, water levels have risen in all eight real-time wells 

since monitoring began in the summer of 2003 (fig. 3), and the 

Ouachita River Alternative Water Supply Project was completed in 

September 2004. In December 2004, Lion Oil converted from using 

ground water to surface water from the Ouachita River. In February 

and October 2005, the UCWCB supplied surface water to El Dorado 

Chemical and Chemtura, respectively (fig. 3). Combined with 

previous conservation efforts, the industrial users’ conversion to 

surface water reduced Union County ground-water withdrawals by 

approximately 7.5 Mgal/d. The largest water-level rises occurred 

between October 2004 and April 2007 in the Monsanto well (49.0 ft 

rise) just north of El Dorado, and the Welcome Center well (36.1 ft 

rise) southeast of El Dorado (fig. 4). The Spencer, Louisiana, well 

had the smallest rise (1.6 ft) during the October 2004 and April 2007 

period. Seasonal fluctuations in water levels occur as a result of 

increased ground-water withdrawals in the summer (fig. 3). Groundwater levels generally are highest in the spring and lowest in the 

summer.

Figure 3.  Hydrograph showing water levels for U.S. Geological Survey real-time wells and industrial conversion to surface-water supplies.
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Emerson

Smackover

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Arkansas

10.0

1.6

3.5

9.2

49.0 20.2

OUACHITA

CALHOUN

BRADLEY

COLUMBIA

UNION

CLAIBORNE

UNION

LINCOLN

Shumaker

Union School

Marysville

Airport

Monsanto

Welcome 

Center

Lawson-Urbana

Hampton

Warren

Camden

El Dorado

Homer

Bastrop

Strong

WEBSTER

ASHLEY

0 5 10 20 Miles

0 1 5 0 20 Kilometers

Stephens

Hilo

Truxno

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Study

Area

33°30'

93°00' 92°00'

33°00'

EXPLANATION

24.1

36.1

Rise in water level,

in feet, between October

2004 and April 2007

36.1

El Dorado Water Users 

Monitoring Well

Union County Conservation

District Automatic Data 

Logger Well

U.S. Geological Survey

Real-Time Well

U.S. Geological Survey 

Water-Quality Monitoring Well

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Water-Quality Monitoring

Another concern in the study area is water-quality degradation, 

or a threat of degradation. Between 2003 and 2007, water-quality 

samples were collected from 12 existing public or industrial supply 

wells throughout the study area selected as water-quality monitoring 

wells (fig. 2). Wells were sampled semi-annually (January and July) 

for specific conductance and chloride concentration. Changes in 

specific conductance and chloride concentration in ground water 

are useful in determining areas affected by saltwater (high-salinity 

water) encroachment. If enough freshwater is withdrawn from a 

ground-water system, water with higher salinity can flow into the 

system to replace the withdrawn freshwater. The higher salinity water 

may flow upward from deeper systems as well as laterally from areas 

containing saltwater (Scheiderer and Freiwald, 2006).

Results of semi-annual water-quality samples collected from 

January 2003 to July 2007 show no trends or major changes through 

time (fig. 5). Water-quality data from the Farmerville, Louisiana, 

well did show some extremes, however, with specific conductance 

ranging from 753 microsiemens per centimeter at 25 degrees Celsius 

(μS/cm) to 1,780 μS/cm, and chloride concentrations ranging from 

90 milligrams per liter (mg/L) to 221 mg/L. 

Specific conductance and chloride concentration increases toward 

the southeast in the study area. Average specific conductance from 

individual wells ranges from 216 in the northwest to 1,157 μS/cm in 

the southeast and average chloride concentration ranges from 3.2 to 

214 mg/L. The highest maximum and average specific conductance 

and chloride concentrations occur in samples from Farmerville, 

Louisiana, and Huttig, Arkansas, in the southeastern part of the study 

area with average specific conductance greater than 1,150 μS/cm 

and average chloride concentrations greater than 175 mg/L. The 

results coincide with more regional specific conductance and chloride 

concentration results (Schrader and Jones, 2007). The EPA’s National 

Secondary Drinking Water Regulation for chloride concentration in 

public water supply is 250 mg/L. There is no standard or regulation for 

specific conductance.

Wells sampled in the northwestern part of the study area 

(Shumaker, Marysville, Magnolia, and Emerson, Arkansas) have 

average specific conductance values less than 400 μS/cm and average 

chloride concentration less than 10 mg/L. The minimum specific 

conductance was 162 μS/cm at Shumaker, and the minimum chloride 

concentration was 3.0 mg/L at Emerson.

References

Brantly, J.A., Seanor, R.C., and McCoy, K.L., 2002, Louisiana 

ground-water map no. 13: Hydrogeology and potentiometric surface, 

October 1996, of the Sparta aquifer in northern Louisiana: U.S. 

Geological Survey Water-Resources Investigations Report 02–4053, 

3 plates.

Hays, P.D., 2000, Sustainable yield estimation for the Sparta aquifer in 

Union County, Arkansas: U.S. Geological Survey Water-Resources 

Investigations Report 99–4272, 17 p.

Pugh, A.L., Westerfield, P.W., Gonthier, G.J., and Poynter, D.T., 1998, 

Altitude of the top of the Sparta Sand in three areas of Arkansas: 

U.S. Geological Survey Water-Resources Investigations Report 

98–4002, 5 p.

Figure 4.  Water-level change for U.S. Geological Survey real-time wells between October 2004 and April 2007.
Reynolds, R.M., Johnson, S.F., and Union County (Arkansas) Water 

Conservation Board, 2006, Ouachita River Alternative Water Supply 

Project: http://argis.ualr.edu/website/unionCoGraph/images/

ProjectDescriptionJan06.pdf, 10 p.

Scheiderer, R.M. and Freiwald, D.A., 2006, Monitoring the recovery 

of the Sparta aquifer in southern Arkansas and northern Louisiana: 

U.S. Geological Survey Fact Sheet 2006–3090, 4 p.

Schrader, T.P. and Jones, J.S., 2007, Status of water levels and selected 

water-quality conditions in the Sparta-Memphis aquifer in Arkansas 

and the status of water levels in the Sparta aquifer in Louisiana, 

spring 2005: U.S. Geological Survey Scientific Investigations Report 

2007–5029, 66 p.

Yeatts, D.S., 2004, Monitoring water-level and water-quality response 

to conservation measures in the Sparta aquifer of the Union County, 

Arkansas area: U.S. Geological Survey Fact Sheet 2004–3086, 4 p. 

—David A. Freiwald, U.S. Geological Survey and Sherrel F. Johnson, 

Union County Water Conservation Board

Information on technical reports and hydrologic data related to 

this study can be obtained from:

Director

USGS Arkansas Water Science Center

401 Hardin Road 

Little Rock, AR 72211

http://ar.water.usgs.gov/ 

E-mail: dc_ar@usgs.gov 

Phone: (501) 228–3600

Fax: (501) 228–3601

For additional information on the Union County study contact:

Cindy Woolsey, Administrative Assistant

Union County Water Conservation Board 

E-mail: cindywoolsey@suddenlink.net 

Phone: (870) 862–1244 

http//www.ucwcb.org

Figure 5.  Specific conductance and chloride concentration results for U.S. Geological Survey water-quality monitoring wells.

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HARRELL

EL DORADO 17

FARMERVILLE

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIU

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CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER