Paul W. McKee and Phillip D. Hays

(ASWCC) has established “thresholds of concern” to be used as criteria for designating a “Critical Ground-Water Area” (CGWA). For 

a confined aquifer like the Sparta aquifer, the criteria include: (1) 

water levels in wells must be above the top of the aquifer formation; 

or (2) the rate of decline in water levels in wells must not be more 

than 1 foot per year over a 5-year period. If these criteria are violated, 

the ASWCC may designate the area in question a “CGWA” (fig. 8).

Can the Sparta aquifer be a sustainable resource without violating conditions defined by the CGWA designation? Management 

of the aquifer as a sustainable resource without violating established 

constraints is possible through the use of computer optimization 

modeling currently under development. This modeling will provide 

an optimal solution of pumping rates called sustainable yield

designed to maximize water production without violating CGWA 

constraints. The sustained yield from the Sparta aquifer, designed to 

protect the aquifer indefinitely, can then be compared to total water 

demand to determine any “unmet demand” needed from alternate 

water sources. 

References Cited

Alley, W.M., Reilly, T.E., and Franke, O.L., 1999, Sustainability of 

ground-water resources: U.S. Geological Survey Circular 1186, 

79 p.

Baker, R.C., Hewitt, F.A., and Billingsley, G.A., 1948, Ground-water 

resources of the El Dorado area, Union County, Arkansas: 

Arkansas University Bureau Research, Research Series 14, 39 

p.

Broom, M.E., Kraemer, T.F., and Bush, W.V., 1984, A reconnaissance study of saltwater contamination in the El Dorado aquifer, Union County, Arkansas: U.S. Geological Survey WaterResources Investigations Report 84-4012, 47 p.

Fitzpatrick, D.J., Kilpatrick, J.M., and McWreath, Harry, 1990, Geohydrologic characteristics and simulated response to pumping 

stresses in the Sparta aquifer in east-central Arkansas: U.S. 

Geological Survey Water-Resources Investigations Report 88-

4201, 50 p.

Freeze, R.A., and Cherry, J.A., 1979, Groundwater: Englewood 

Cliffs, New Jersey, Prentice-Hall, 604 p.

Galloway, D.L., Jones, D.R., and Ingebritsen, S.E., 2000, Land subsidence in the United States: U.S. Geological Survey Fact Sheet 

087-00.

Halberg, H.N., and Stephens, J.W., 1966, Use of water in Arkansas, 

1965: Arkansas Geological Commission Water Resources 

Summary 5, 12 p.

For more information on ground-water conditions in the Sparta aquifer, contact the District Chief, U.S. Geological Survey, 401 Hardin Rd., 

Little Rock, AR 72211; phone: 501-228-3611. Website: http://ar.water.usgs.gov

Figure 8. Eleven counties are currently designated as Critical Ground-Water Areas. 

Optimization modeling can determine pumping rates that are sustainable for all 

Sparta aquifer users.

Hays, P.D., and Fugitt, D.T., 1999, The Sparta aquifer in Arkansas’ 

critical ground-water areas—Response of the aquifer to supplying future water needs: U.S. Geological Survey WaterResources Investigations Report 99-4075, 6 p.

Hays, P.D., Lovelace, J.K., and Reed, T.B., 1998, Simulated response 

to pumping stress in the Sparta aquifer of southeastern Arkansas 

and north-central Louisiana, 1998-2027: U.S. Geological Survey Water-Resources Investigations Report 98-4121, 25 p.

Hosman, R.L., Long, A.T., Lambert, T.W., and others, 1968, Tertiary 

aquifers in the Mississippi embayment, with discussions of 

quality of the water, by Jeffery, H.G.: U.S. Geological Survey 

Professional Paper 448-D, 29 p.

Joseph, R.L., 2000, Status of water levels and selected water-quality 

conditions in the Sparta and Memphis aquifers in eastern and 

south-central Arkansas, 1999: U.S. Geological Survey WaterResources Investigations Report 00-4009, 34 p.

Klein, Howard, Baker, R.C., and Billingsley, G.A., 1950, Groundwater resources of Jefferson County, Arkansas: Arkansas University Institute Science and Technology Research Services 19, 

44 p.

Payne, J.N., 1968, Hydrologic significance of the lithofacies of the 

Sparta Sand in Arkansas, Louisiana, Mississippi, and Texas: 

U.S. Geological Survey Professional Paper 569-A, 17 p.

WHITE

PRAIRIE

LONOKE

PULASKI

ARKANSAS

JEFFERSON

OUACHITA

CALHOUN

BRADLEY

UNION COLUMBIA

El Dorado

Camden

Stuttgart

Pine

Bluff

Magnolia

EXPLANATION

Mississippi Embayment Aquifer

 System Boundary

Critical Ground Water Area

Approximate Extent of Sparta-

 Memphis Aquifer

0

0

25

50

Miles

Kilometers

50

25
have increased from 106 Mgal/d in 1965 to an estimated 265 

Mgal/d in 2000 (Halberg and Stephens, 1966; T.W. Holland, U.S. 

Geological Survey, written commun., 2002). The majority of 

ground-water withdrawals in Arkansas County is from the more 

shallow and transmissive alluvial aquifer for rice and soybean 

crop irrigation because it is more cost effective to pump. However, 

where water-level declines in the alluvial aquifer are causing 

decreased well yields, the Sparta aquifer is increasingly used to 

supplement supplies needed for crop irrigation. In 2000, approximately 85 percent of total ground-water use in Arkansas County 

came from the alluvial aquifer with the remaining 15 percent from 

the Sparta aquifer. Withdrawals from the Sparta aquifer in Arkansas County (fig. 4) increased from 17 Mgal/d in 1965 to 97

Mgal/d in 2000, a 471 percent increase. 

Effects of Pumping

In Arkansas, long-term pumping stresses in the Sparta aquifer have resulted in reduced amounts of water in storage, decreased 

well yields (Hays and others, 1998), regionally extensive waterlevel declines, and the formation of regional-scale cones of depression such as the cone that has formed between El Dorado, Arkansas, 

and Monroe, Louisiana. Additionally, cones of depression have 

formed in Union and Jefferson Counties and continue to grow; a 

recent cone of depression has formed in Arkansas County (Joseph, 

1997; Joseph, 2000).

In a ground-water flow system, water flows downgradient 

from potentiometric high areas to potentiometric lows. Pumping 

wells cause cones of depression in the potentiometric surface that 

alter the direction of ground-water flow (fig. 5). Extreme drawdowns have resulted in increased chloride concentrations of some 

Sparta aquifer wells in Union County (Broom and others, 1984) 

because of upconing of brackish water from below. 

The response of water levels within the Sparta aquifer to 

heavy pumping stress can be substantial over large areas because of 

the confined condition of the aquifer. For example, an aquifer test 

near El Dorado resulted in a 6 ft water-level decline at a distance of 

2,400 ft from the pumping well after 3 days of pumping at a rate of 

approximately 460 gal/min. 

Figure 4. Ground-water use in Arkansas County for the Sparta and alluvial

aquifers from 1965 to 2000.

Figure 5. Schematic of cross-section A-A’ showing a well completed in the Sparta aquifer, 

observed potentiometric surface for 1997, and model simulated potentiometric surface for 

2027.

sands of the Sparta Sand. Water enters (recharges) the Sparta aquifer from the outcrop areas and adjacent geologic units. The outcrop areas provide hydraulic connection between the aquifer and 

surface-water sources such as rivers, lakes, and percolation of 

rainfall. Before development of the aquifer as a water resource 

(predevelopment), flow in the aquifer was predominantly from the 

topographically high outcrop areas downdip to the east and southeast. The aquifer in Arkansas County is confined by the Cook 

Mountain confining unit. Depth to the Sparta aquifer in Arkansas 

County ranges from 300 to 700 feet below land surface, with 

thickness varying from 500 to 800 feet.

Storativity and hydraulic conductivity are used to quantify 

the ability of an aquifer to store and transmit water. Hydraulic conductivity affects the yield of water to wells. For the Sparta aquifer, 

hydraulic conductivity generally ranges from 10 to 200 feet per 

day (ft/d) with an average of about 70 ft/d over the extent of the 

Mississippi embayment (Hosman and others, 1968). Individual 

wells completed in the Sparta aquifer (excluding those wells 

located within areas of large drawdowns) generally yield 100 to 

500 gallons per minute (gal/min). The amount of water that can be 

released from storage in a confined aquifer is measured as storativity and is dependent on aquifer thickness and changes in hydraulic head (decline in potentiometric surface or “water level”). For 

equal declines in water level, the amount of water released from 

storage in the Sparta aquifer (assuming confined conditions are 

maintained) is about 1,000 times less in comparison with that 

released from an unconfined aquifer like the Mississippi River 

Valley alluvial aquifer (commonly referred as the alluvial aquifer). 

Therefore, large water-level declines over extensive areas would 

be required to achieve equivalent water yields.

Water Use

Many industries are located in eastern and southeastern 

Arkansas because of the availability of abundant water of excellent quality from the Sparta aquifer. Many cities and communities 

rely exclusively upon the Sparta aquifer for their public water supply and use the water with minimal treatment. However, high 

salinity, iron, and manganese concentrations limit the usefulness 

of water from the aquifer in some areas (Hosman and others, 

1968). 

Withdrawal of ground water from the Sparta aquifer began 

in the early 1900’s primarily for industry and public supply. Total 

ground-water withdrawals from the Sparta aquifer in Arkansas 
have increased from 106 Mgal/d in 1965 to an estimated 265 

Mgal/d in 2000 (Halberg and Stephens, 1966; T.W. Holland, U.S. 

Geological Survey, written commun., 2002). The majority of 

ground-water withdrawals in Arkansas County is from the more 

shallow and transmissive alluvial aquifer for rice and soybean 

crop irrigation because it is more cost effective to pump. However, 

where water-level declines in the alluvial aquifer are causing 

decreased well yields, the Sparta aquifer is increasingly used to 

supplement supplies needed for crop irrigation. In 2000, approximately 85 percent of total ground-water use in Arkansas County 

came from the alluvial aquifer with the remaining 15 percent from 

the Sparta aquifer. Withdrawals from the Sparta aquifer in Arkansas County (fig. 4) increased from 17 Mgal/d in 1965 to 97

Mgal/d in 2000, a 471 percent increase. 

Effects of Pumping

In Arkansas, long-term pumping stresses in the Sparta aquifer have resulted in reduced amounts of water in storage, decreased 

well yields (Hays and others, 1998), regionally extensive waterlevel declines, and the formation of regional-scale cones of depression such as the cone that has formed between El Dorado, Arkansas, 

and Monroe, Louisiana. Additionally, cones of depression have 

formed in Union and Jefferson Counties and continue to grow; a 

recent cone of depression has formed in Arkansas County (Joseph, 

1997; Joseph, 2000).

In a ground-water flow system, water flows downgradient 

from potentiometric high areas to potentiometric lows. Pumping 

wells cause cones of depression in the potentiometric surface that 

alter the direction of ground-water flow (fig. 5). Extreme drawdowns have resulted in increased chloride concentrations of some 

Sparta aquifer wells in Union County (Broom and others, 1984) 

because of upconing of brackish water from below. 

The response of water levels within the Sparta aquifer to 

heavy pumping stress can be substantial over large areas because of 

the confined condition of the aquifer. For example, an aquifer test 

near El Dorado resulted in a 6 ft water-level decline at a distance of 

2,400 ft from the pumping well after 3 days of pumping at a rate of 

approximately 460 gal/min. 

Figure 4. Ground-water use in Arkansas County for the Sparta and alluvial

aquifers from 1965 to 2000.

Figure 5. Schematic of cross-section A-A’ showing a well completed in the Sparta aquifer, 

observed potentiometric surface for 1997, and model simulated potentiometric surface for 

2027.

sands of the Sparta Sand. Water enters (recharges) the Sparta aquifer from the outcrop areas and adjacent geologic units. The outcrop areas provide hydraulic connection between the aquifer and 

surface-water sources such as rivers, lakes, and percolation of 

rainfall. Before development of the aquifer as a water resource 

(predevelopment), flow in the aquifer was predominantly from the 

topographically high outcrop areas downdip to the east and southeast. The aquifer in Arkansas County is confined by the Cook 

Mountain confining unit. Depth to the Sparta aquifer in Arkansas 

County ranges from 300 to 700 feet below land surface, with 

thickness varying from 500 to 800 feet.

Storativity and hydraulic conductivity are used to quantify 

the ability of an aquifer to store and transmit water. Hydraulic conductivity affects the yield of water to wells. For the Sparta aquifer, 

hydraulic conductivity generally ranges from 10 to 200 feet per 

day (ft/d) with an average of about 70 ft/d over the extent of the 

Mississippi embayment (Hosman and others, 1968). Individual 

wells completed in the Sparta aquifer (excluding those wells 

located within areas of large drawdowns) generally yield 100 to 

500 gallons per minute (gal/min). The amount of water that can be 

released from storage in a confined aquifer is measured as storativity and is dependent on aquifer thickness and changes in hydraulic head (decline in potentiometric surface or “water level”). For 

equal declines in water level, the amount of water released from 

storage in the Sparta aquifer (assuming confined conditions are 

maintained) is about 1,000 times less in comparison with that 

released from an unconfined aquifer like the Mississippi River 

Valley alluvial aquifer (commonly referred as the alluvial aquifer). 

Therefore, large water-level declines over extensive areas would 

be required to achieve equivalent water yields.

Water Use

Many industries are located in eastern and southeastern 

Arkansas because of the availability of abundant water of excellent quality from the Sparta aquifer. Many cities and communities 

rely exclusively upon the Sparta aquifer for their public water supply and use the water with minimal treatment. However, high 

salinity, iron, and manganese concentrations limit the usefulness 

of water from the aquifer in some areas (Hosman and others, 

1968). 

Withdrawal of ground water from the Sparta aquifer began 

in the early 1900’s primarily for industry and public supply. Total 

ground-water withdrawals from the Sparta aquifer in Arkansas 
Paul W. McKee and Phillip D. Hays

(ASWCC) has established “thresholds of concern” to be used as criteria for designating a “Critical Ground-Water Area” (CGWA). For 

a confined aquifer like the Sparta aquifer, the criteria include: (1) 

water levels in wells must be above the top of the aquifer formation; 

or (2) the rate of decline in water levels in wells must not be more 

than 1 foot per year over a 5-year period. If these criteria are violated, 

the ASWCC may designate the area in question a “CGWA” (fig. 8).

Can the Sparta aquifer be a sustainable resource without violating conditions defined by the CGWA designation? Management 

of the aquifer as a sustainable resource without violating established 

constraints is possible through the use of computer optimization 

modeling currently under development. This modeling will provide 

an optimal solution of pumping rates called sustainable yield

designed to maximize water production without violating CGWA 

constraints. The sustained yield from the Sparta aquifer, designed to 

protect the aquifer indefinitely, can then be compared to total water 

demand to determine any “unmet demand” needed from alternate 

water sources. 

References Cited

Alley, W.M., Reilly, T.E., and Franke, O.L., 1999, Sustainability of 

ground-water resources: U.S. Geological Survey Circular 1186, 

79 p.

Baker, R.C., Hewitt, F.A., and Billingsley, G.A., 1948, Ground-water 

resources of the El Dorado area, Union County, Arkansas: 

Arkansas University Bureau Research, Research Series 14, 39 

p.

Broom, M.E., Kraemer, T.F., and Bush, W.V., 1984, A reconnaissance study of saltwater contamination in the El Dorado aquifer, Union County, Arkansas: U.S. Geological Survey WaterResources Investigations Report 84-4012, 47 p.

Fitzpatrick, D.J., Kilpatrick, J.M., and McWreath, Harry, 1990, Geohydrologic characteristics and simulated response to pumping 

stresses in the Sparta aquifer in east-central Arkansas: U.S. 

Geological Survey Water-Resources Investigations Report 88-

4201, 50 p.

Freeze, R.A., and Cherry, J.A., 1979, Groundwater: Englewood 

Cliffs, New Jersey, Prentice-Hall, 604 p.

Galloway, D.L., Jones, D.R., and Ingebritsen, S.E., 2000, Land subsidence in the United States: U.S. Geological Survey Fact Sheet 

087-00.

Halberg, H.N., and Stephens, J.W., 1966, Use of water in Arkansas, 

1965: Arkansas Geological Commission Water Resources 

Summary 5, 12 p.

For more information on ground-water conditions in the Sparta aquifer, contact the District Chief, U.S. Geological Survey, 401 Hardin Rd., 

Little Rock, AR 72211; phone: 501-228-3611. Website: http://ar.water.usgs.gov

Figure 8. Eleven counties are currently designated as Critical Ground-Water Areas. 

Optimization modeling can determine pumping rates that are sustainable for all 

Sparta aquifer users.

Hays, P.D., and Fugitt, D.T., 1999, The Sparta aquifer in Arkansas’ 

critical ground-water areas—Response of the aquifer to supplying future water needs: U.S. Geological Survey WaterResources Investigations Report 99-4075, 6 p.

Hays, P.D., Lovelace, J.K., and Reed, T.B., 1998, Simulated response 

to pumping stress in the Sparta aquifer of southeastern Arkansas 

and north-central Louisiana, 1998-2027: U.S. Geological Survey Water-Resources Investigations Report 98-4121, 25 p.

Hosman, R.L., Long, A.T., Lambert, T.W., and others, 1968, Tertiary 

aquifers in the Mississippi embayment, with discussions of 

quality of the water, by Jeffery, H.G.: U.S. Geological Survey 

Professional Paper 448-D, 29 p.

Joseph, R.L., 2000, Status of water levels and selected water-quality 

conditions in the Sparta and Memphis aquifers in eastern and 

south-central Arkansas, 1999: U.S. Geological Survey WaterResources Investigations Report 00-4009, 34 p.

Klein, Howard, Baker, R.C., and Billingsley, G.A., 1950, Groundwater resources of Jefferson County, Arkansas: Arkansas University Institute Science and Technology Research Services 19, 

44 p.

Payne, J.N., 1968, Hydrologic significance of the lithofacies of the 

Sparta Sand in Arkansas, Louisiana, Mississippi, and Texas: 

U.S. Geological Survey Professional Paper 569-A, 17 p.

WHITE

PRAIRIE

LONOKE

PULASKI

ARKANSAS

JEFFERSON

OUACHITA

CALHOUN

BRADLEY

UNION COLUMBIA

El Dorado

Camden

Stuttgart

Pine

Bluff

Magnolia

EXPLANATION

Mississippi Embayment Aquifer

 System Boundary

Critical Ground Water Area

Approximate Extent of Sparta-

 Memphis Aquifer

0

0

25

50

Miles

Kilometers

50

25