This report describes the thickness and areal extent of the Sparta aquifer, identifies sands within the fresh-water extent of the aquifer, and presents data and a map that illustrate the generalized potentiometric surface (water levels) during October 1996. The report includes a detailed geophysical log, structure contour maps, hydrogeologic sections, and hydrographs of water levels in selected wells. The potentiometric surface-map can be used for determining direction of ground-water flow, hydraulic gradients, and the effects of withdrawals on the aquifer.

This report describes the thickness and areal extent of the Sparta aquifer, identifies sands within the fresh-water extent of the aquifer, and presents data and a map that illustrate the generalized potentiometric surface (water levels) during October 1996. The report includes a detailed geophysical log, structure contour maps, hydrogeologic sections, and hydrographs of water levels in selected wells. The potentiometric surface-map can be used for determining direction of ground-water flow, hydraulic gradients, and the effects of withdrawals on the aquifer.

This report describes the thickness and areal extent of the Sparta aquifer, identifies sands within the fresh-water extent of the aquifer, and presents data and a map that illustrate the generalized potentiometric surface (water levels) during October 1996. The report includes a detailed geophysical log, structure contour maps, hydrogeologic sections, and hydrographs of water levels in selected wells. The potentiometric surface-map can be used for determining direction of ground-water flow, hydraulic gradients, and the effects of withdrawals on the aquifer.

This report describes the thickness and areal extent of the Sparta aquifer, identifies sands within the fresh-water extent of the aquifer, and presents data and a map that illustrate the generalized potentiometric surface (water levels) during October 1996. The report includes a detailed geophysical log, structure contour maps, hydrogeologic sections, and hydrographs of water levels in selected wells. The potentiometric surface-map can be used for determining direction of ground-water flow, hydraulic gradients, and the effects of withdrawals on the aquifer.

This report describes the thickness and areal extent of the Sparta aquifer, identifies sands within the fresh-water extent of the aquifer, and presents data and a map that illustrate the generalized potentiometric surface (water levels) during October 1996. The report includes a detailed geophysical log, structure contour maps, hydrogeologic sections, and hydrographs of water levels in selected wells. The potentiometric surface-map can be used for determining direction of ground-water flow, hydraulic gradients, and the effects of withdrawals on the aquifer.

The Sparta aquifer is the principal source of ground water in north-central Louisiana. In 1985, the aquifer was extensively pumped for public supply (25 Mgal/d) and industrial use (29 Mgal/d and 7 Mgal/d for 1989). More than 100 public supply systems, in 8 parishes, contain water from the Sparta aquifer. Large industrial pumpage from the Sparta aquifer began in 1922 at Bastrop (Sanford, 1973a, p. 60) and in about 1923 at West Monroe. Water levels in wells in the Sparta aquifer have been declining in these arease and in other parts of north-central Louisiana since the early 1920's, when industries began withdrawing large amounts of water. However, in Morehouse Parish the water levels in wells have been recovering since 1982 as a result of a 5 Mgal/d reduction in pumpage at Bastrop (J.K. Lovelace, U.S. Geological Survey, written commun., 1989). Additional knowledge about ground-water flow and the effects of withdrawals on the Sparta aquifer is needed for assessment of ground-water development potential and protection of the resource. Potentiometric contour maps are used to determine direction of ground-water flow, ground-water gradients, and the effects of pumping on an aquifer system. The rate of ground-water movement can be estimated when the hydraulic conductivity of an aquifer is known. This report presents data and maps that illustrate the potentiometric surface and water-level changes for the Sparta aquifer and is the third in a series of map reports that show potentiometric surface and water-level changes of aquifers in Louisiana (Fendick, 1989; Fendick and Nyman, 1987). These maps were prepared in cooperation with the Louisiana Department of Transportation and Development. Reports prepared as part of previous studies of northern Louisiana with emphasis on the Sparta aquifer are included in the Selected References. These maps show the potentiometric surface in the spring of 1989 and water-level changes from 1980 to 1989 for the Sparta aquifer. The regional potentiometric surface of the Sparta aquifer, based on water-level measurements made during May through June 1989, is shown in figure 1. Ground-water flow directions are normal to the contours, from higher to lower head. Water-level changes in wells in the Sparta aquifer from May 1980 to May 1989 are shown in figure 2. Three hydrographs (figs. 3-5) show general water-level trends for periods 1920-89, 1946-89, and 1970-89.

The Sparta aquifer is the principal source of ground water in north-central Louisiana. In 1985, the aquifer was extensively pumped for public supply (25 Mgal/d) and industrial use (29 Mgal/d and 7 Mgal/d for 1989). More than 100 public supply systems, in 8 parishes, contain water from the Sparta aquifer. Large industrial pumpage from the Sparta aquifer began in 1922 at Bastrop (Sanford, 1973a, p. 60) and in about 1923 at West Monroe. Water levels in wells in the Sparta aquifer have been declining in these arease and in other parts of north-central Louisiana since the early 1920's, when industries began withdrawing large amounts of water. However, in Morehouse Parish the water levels in wells have been recovering since 1982 as a result of a 5 Mgal/d reduction in pumpage at Bastrop (J.K. Lovelace, U.S. Geological Survey, written commun., 1989). Additional knowledge about ground-water flow and the effects of withdrawals on the Sparta aquifer is needed for assessment of ground-water development potential and protection of the resource. Potentiometric contour maps are used to determine direction of ground-water flow, ground-water gradients, and the effects of pumping on an aquifer system. The rate of ground-water movement can be estimated when the hydraulic conductivity of an aquifer is known. This report presents data and maps that illustrate the potentiometric surface and water-level changes for the Sparta aquifer and is the third in a series of map reports that show potentiometric surface and water-level changes of aquifers in Louisiana (Fendick, 1989; Fendick and Nyman, 1987). These maps were prepared in cooperation with the Louisiana Department of Transportation and Development. Reports prepared as part of previous studies of northern Louisiana with emphasis on the Sparta aquifer are included in the Selected References. These maps show the potentiometric surface in the spring of 1989 and water-level changes from 1980 to 1989 for the Sparta aquifer. The regional potentiometric surface of the Sparta aquifer, based on water-level measurements made during May through June 1989, is shown in figure 1. Ground-water flow directions are normal to the contours, from higher to lower head. Water-level changes in wells in the Sparta aquifer from May 1980 to May 1989 are shown in figure 2. Three hydrographs (figs. 3-5) show general water-level trends for periods 1920-89, 1946-89, and 1970-89.

The Sparta aquifer is used in 15 parishes in north-central Louisiana, primarily for public supply and industrial purposes. Of those parishes, eight (Bienville, Claiborne, Jackson, Lincoln, Ouachita, Union, Webster, and Winn) rely on the Sparta aquifer as their principal source of groundwater. In 2010, withdrawals from the Sparta aquifer in Louisiana totaled 63.11 million gallons per day (Mgal/d), a reduction of more than 11 percent from 1995, when the highest rate of withdrawals (71.32 Mgal/d) from the Sparta aquifer were documented. The Sparta aquifer provides water for a variety of purposes which include public supply (34.61 Mgal/d), industrial (25.60 Mgal/d), rural domestic (1.50 Mgal/d), and various agricultural (1.40 Mgal/d). Of the 13 major aquifers or aquifer systems in Louisiana, the Sparta aquifer is currently (2012) the sixth most heavily pumped. The Sparta aquifer is the second most heavily pumped aquifer in Arkansas, which borders Louisiana to the north. In 2005, 170 Mgal/d were withdrawn from the Sparta aquifer in eastern and southern Arkansas; of that total, about 15.55 Mgal/d were withdrawn from the aquifer in Union County, which borders Claiborne and Union Parishes to the north. By 1997, a large cone of depression (a cone-shaped depression in the potentiometric surface caused by and centered on a pumping well or wells) in the Sparta aquifer centered over Union County had merged with the cone of depression at West Monroe. In 2004, the rate of withdrawal from the Sparta aquifer in Union County began to decline and water levels in the aquifer began to rise in nearby areas of Arkansas and Louisiana.

The Sparta aquifer is used in 15 parishes in north-central Louisiana, primarily for public supply and industrial purposes. Of those parishes, eight (Bienville, Claiborne, Jackson, Lincoln, Ouachita, Union, Webster, and Winn) rely on the Sparta aquifer as their principal source of groundwater. In 2010, withdrawals from the Sparta aquifer in Louisiana totaled 63.11 million gallons per day (Mgal/d), a reduction of more than 11 percent from 1995, when the highest rate of withdrawals (71.32 Mgal/d) from the Sparta aquifer were documented. The Sparta aquifer provides water for a variety of purposes which include public supply (34.61 Mgal/d), industrial (25.60 Mgal/d), rural domestic (1.50 Mgal/d), and various agricultural (1.40 Mgal/d). Of the 13 major aquifers or aquifer systems in Louisiana, the Sparta aquifer is currently (2012) the sixth most heavily pumped. The Sparta aquifer is the second most heavily pumped aquifer in Arkansas, which borders Louisiana to the north. In 2005, 170 Mgal/d were withdrawn from the Sparta aquifer in eastern and southern Arkansas; of that total, about 15.55 Mgal/d were withdrawn from the aquifer in Union County, which borders Claiborne and Union Parishes to the north. By 1997, a large cone of depression (a cone-shaped depression in the potentiometric surface caused by and centered on a pumping well or wells) in the Sparta aquifer centered over Union County had merged with the cone of depression at West Monroe. In 2004, the rate of withdrawal from the Sparta aquifer in Union County began to decline and water levels in the aquifer began to rise in nearby areas of Arkansas and Louisiana.

The U.S. Geological Survey in cooperation with the Arkansas Natural Resources Commission, the Arkansas Geological Commission, and the Louisiana Department of Transportation and Development has monitored water levels in the Sparta Sand of Claiborne Group and Memphis Sand of Claiborne Group since the 1920's. Ground-water withdrawals have increased while water levels have declined since monitoring was initiated. This report has been produced to describe ground-water levels in the aquifers in the Sparta Sand and Memphis Sand and provide information for the management of this valuable resource. The 2005 potentiometric-surface map of the aquifers in the Sparta Sand and Memphis Sand was constructed using water-level data collected in 333 wells in Arkansas and 120 wells in Louisiana during the spring of 2005. The highest water-level altitude measured in Arkansas was 327 feet above National Geodetic Vertical Datum of 1929 located in Grant County in the outcrop at the western boundary of the study area; the lowest water-level altitude was 189 feet below National Geodetic Vertical Datum of 1929 in Union County. The highest water-level altitude measured in Louisiana was 246 feet above National Geodetic Vertical Datum of 1929 located in Bossier Parish in the outcrop area near the western boundary of the study area; the lowest water-level altitude was 226 feet below National Geodetic Vertical Datum of 1929 in central Ouachita Parish.Three large depressions centered in Columbia, Jefferson, and Union Counties in Arkansas are the result of large withdrawals for industrial and public supplies. In Louisiana, three major pumping centers are in Ouachita, Jackson, and Lincoln Parishes. Water withdrawals from these major pumping centers primarily is used for industrial and public-supply purposes. Withdrawals from Ouachita and Lincoln Parishes and Union County, Arkansas, primarily for industrial purposes, have caused the resulting cones of depression to coalesce so that the -40 foot potentiometric contour encircles the three pumping centers. Seven smaller depressions are evident on the 2005 Sparta-Memphis potentiometric-surface map located in Webster and Winn Parishes, Louisiana, and Calhoun, Cleveland, western Columbia, Desha, and Lafayette Counties, Arkansas. The depression in Calhoun County initially was shown in the 1996-1997 potentiometric surface. The depression in Desha County initially was shown in the 1999 potentiometric surface. The depressions in Webster and Winn Parishes were shown as early as 1975. The depressions in Cleveland, western Columbia, and Lafayette Counties initially were shown in the 2003 potentiometric surface. A map of differences in water-level measurements between 2001 and 2005 was constructed using the difference between water-level measurements from 294 wells in Arkansas and 29 wells in Louisiana. The difference in water levels between 2001 and 2005 ranged from -30.1 to 44.6 feet. The largest rise of 44.6 feet in water level measured was in Union County in Arkansas. The largest decline of 30.1 feet in water level measured was in Columbia County in Arkansas. Areas with a general rise in water levels in Arkansas are shown in Arkansas, Columbia, Craighead, Jefferson, Prairie, and the western half of Union Counties. The area around west-central Union County had rises as much as 44.6 feet, with seven wells showing a rise of 20 feet or greater, which is an annual rise of 5 feet or greater. Areas in Arkansas with a general decline in water level are shown in western Bradley, eastern Calhoun, Cleveland, Cross, Desha, Drew, Lafayette, Lee, Lincoln, Lonoke, Poinsett, and the eastern half of Union Counties. In Louisiana, the water-level difference map showed a general rise in water levels in northern Claiborne, northern Webster, and northwestern Union Parishes mainly because of a decrease in industrial withdrawals in southern Arkansas, particularly Union County. Another rise in water level was indicated in western Jackson Parish