During the spring of 2001, water levels were measured in 427 wells in the Sparta-Memphis aquifer in Arkansas and the Sparta aquifer in Louisiana. Water-quality samples were collected for temperature and specific-conductance measurements during the spring and summer of 2001 from 150 wells in Arkansas in the Sparta-Memphis aquifer. Dissolved chloride samples were collected and analyzed for 87 of the 150 wells. Water-quality samples were not collected in Louisiana. Maps of areal distribution of potentiometric surface, difference in water-level measurements from 1997 to 2001, and specific conductance generated from these data reveal spatial trends across the study area. The highest water-level altitude measured in Arkansas was 328 feet above National Geodetic Vertical Datum of 1929 (NGVD of 1929) in Grant County; the lowest water-level altitude was 197 feet below NGVD of 1929 in Union County. The highest water-level altitude measured in Louisiana was 235 feet above NGVD of 1929 in Bienville Parish; the lowest water-level altitude was 218 feet below NGVD of 1929 in Ouachita Parish. The regional direction of ground-water flow in the Sparta-Memphis aquifer in Arkansas generally is to the south-southwest in the northern half of Arkansas and to the east and south in the southern half of Arkansas; the ground-water flow in the Sparta aquifer in northern Louisiana generally is in an easterly direction toward the Mississippi River. Four cones of depression are shown in the 2001 potentiometric-surface map, centered in Columbia, Jefferson, and Union Counties in Arkansas and Ouachita Parish in Louisiana as a result of large withdrawals for industrial and public supplies. A broad depression exists in western Poinsett, Cross, and St. Francis Counties in Arkansas. A map for water-level changes from 1997 to 2001 was constructed using water-level measurements from 278 wells. The largest rise in water level measured in Arkansas was about 35 feet in Prairie County. The largest decline in water level measured in Arkansas was about 93 feet in Columbia County. The largest rise in water level measured in Louisiana was about 23 feet in Jackson Parish. The largest decline in water level measured in Louisiana was about 33 feet in Claiborne Parish. Hydrographs were constructed for wells with a minimum of 25 years of water-level measurements. A trend line using a linear regression was calculated for the period of record from spring of 1976 to spring of 2001 to determine the annual decline or rise in feet per year for water levels in each well. The hydrographs were grouped by county or parish. The median values for county and parish annual water-level decline or rise ranged from -1.57 to 0.29 foot per year. Specific conductance ranged from 16.8 microsiemens per centimeter at 25 degrees Celsius in Ouachita County to about 1,470 microsiemens per centimeter at 25 degrees Celsius in Lee County. The median specific conductance was 340 microsiemens per centimeter at 25 degrees Celsius. Dissolved chloride concentrations ranged from 1.4 milligrams per liter at a well in Lincoln County to 250 milligrams per liter at a well in Lee County. The median dissolved chloride concentration was 7.7 milligrams per liter.

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

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

These datasets provide the locations of and groundwater-level altitudes from 273 wells that were used to construct a 2015 potentiometric contour surface of the Sparta-Memphis aquifer. Measurements were made from January through June 2015 and represent synoptic conditions. All wells were cased completely in and screened in the Sparta-Memphis aquifer. Groundwater-level data are also available from the USGS National Water Information System (U.S. Geological Survey, 2017). The groundwater-level change maps for the Sparta-Memphis aquifer are constructed as a point-to-point comparison with wells measured in both 2011 and 2013 and both 2013 and 2015. Wells not measured in both 2011 and 2013 and both 2013 and 2015 were not included in the change maps construction. The 2011-2013 change map contains 261 corresponding wells. The 2013-2015 change map contains 241 corresponding wells.

These datasets provide the locations of and groundwater-level altitudes from 273 wells that were used to construct a 2015 potentiometric contour surface of the Sparta-Memphis aquifer. Measurements were made from January through June 2015 and represent synoptic conditions. All wells were cased completely in and screened in the Sparta-Memphis aquifer. Groundwater-level data are also available from the USGS National Water Information System (U.S. Geological Survey, 2017). The groundwater-level change maps for the Sparta-Memphis aquifer are constructed as a point-to-point comparison with wells measured in both 2011 and 2013 and both 2013 and 2015. Wells not measured in both 2011 and 2013 and both 2013 and 2015 were not included in the change maps construction. The 2011-2013 change map contains 261 corresponding wells. The 2013-2015 change map contains 241 corresponding wells.

These datasets provide the locations of and groundwater-level altitudes from 273 wells that were used to construct a 2015 potentiometric contour surface of the Sparta-Memphis aquifer. Measurements were made from January through June 2015 and represent synoptic conditions. All wells were cased completely in and screened in the Sparta-Memphis aquifer. Groundwater-level data are also available from the USGS National Water Information System (U.S. Geological Survey, 2017). The groundwater-level change maps for the Sparta-Memphis aquifer are constructed as a point-to-point comparison with wells measured in both 2011 and 2013 and both 2013 and 2015. Wells not measured in both 2011 and 2013 and both 2013 and 2015 were not included in the change maps construction. The 2011-2013 change map contains 261 corresponding wells. The 2013-2015 change map contains 241 corresponding wells.

Dataset contains 20-ft contours for the 2015 Sparta-Memphis aquifer potentiometric-surface map, in Arkansas. The potentiometric-surface shows altitudes at which the water levels would have risen in tightly-cased wells and represents conditions during the period from January through June 2015. Groundwater-level data from wells cased completely in and with the screened interval open to the Sparta-Memphis aquifer are publicly available from the U.S. Geological Survey’s National Water Information System.

Dataset contains 20-ft contours for the 2015 Sparta-Memphis aquifer potentiometric-surface map, in Arkansas. The potentiometric-surface shows altitudes at which the water levels would have risen in tightly-cased wells and represents conditions during the period from January through June 2015. Groundwater-level data from wells cased completely in and with the screened interval open to the Sparta-Memphis aquifer are publicly available from the U.S. Geological Survey’s National Water Information System.

Dataset contains 20-ft contours for the 2015 Sparta-Memphis aquifer potentiometric-surface map, in Arkansas. The potentiometric-surface shows altitudes at which the water levels would have risen in tightly-cased wells and represents conditions during the period from January through June 2015. Groundwater-level data from wells cased completely in and with the screened interval open to the Sparta-Memphis aquifer are publicly available from the U.S. Geological Survey’s National Water Information System.

The groundwater-level change maps for the Sparta-Memphis aquifer are constructed as a point-to-point comparison between wells measured in both 2011 and 2013. Wells not measured in both 2011 and 2013 were not included in the change maps construction. The 2011-2013 change map contains 261 corresponding wells. Groundwater-level differences were calculated by subtracting 2011 groundwater-level measurements, in ft below land surface from the 2013 groundwater-level measurements, in feet below land surface.