USGS Science⌕ Search

Geology topics

T. P. Schrader

Publications and source records attributed to T. P. Schrader.

At least 19 recordsLinked to original sources
USGS2014

Water levels and water quality in the Sparta-Memphis aquifer (middle Claiborne aquifer) in Arkansas, spring-summer 2011

The U.S. Geological Survey, in cooperation with the Arkansas Natural Resources Commission and the Arkansas Geological Survey, has monitored water levels in the Sparta Sand of Claiborne Group and Memphis Sand of Claiborne Group (herein referred to as “the Sparta Sand” and “the Memphis Sand,” respectively) since the 1920s. Groundwater withdrawals have increased while water levels have declined since monitoring was initiated. Herein, aquifers in the Sparta Sand and Memphis Sand will be referred to as “the Sparta-Memphis aquifer” throughout Arkansas. During the spring of 2011, 291 water levels were measured in wells completed in the Sparta-Memphis aquifer and used to produce a regional potentiometric-surface map. During the summer of 2011, groundwater-quality samples were collected and measured from 61 wells for specific conductance, pH, and temperature. In the northern half of Arkansas, the regional direction of groundwater flow in the Sparta-Memphis aquifer is generally to the south-southeast and flows east and south in the southern half of Arkansas. The groundwater in the southern half of Arkansas flows away from the outcrop area except where affected by large depressions in the potentiometric surface. The highest and lowest water-level altitudes measured in the Sparta-Memphis aquifer were 326 feet above and 120 feet below National Geodetic Vertical Datum of 1929 (NGVD 29), respectively. Five depressions are located in the following counties: Arkansas, Cleveland, Jefferson, Lincoln, and Prairie; Union; Cross, Poinsett, St. Francis, and Woodruff; Columbia; and Bradley. Two large depressions, centered in Jefferson and Union Counties, are the result of large withdrawals for industrial, irrigation, or public supply. The depression centered in Jefferson County has expanded in recent years into Arkansas and Prairie Counties as a result of large withdrawals for irrigation and public supply. The lowest water-level altitude measured in this depression is approximately 20 feet (ft) higher in 2011 than in 2009. The area enclosed within the 40-ft contour on the 2011 potentiometric-surface map has decreased in area, shifting north in Lincoln County and west in Arkansas County when compared with the 2009 potentiometric-surface map. The depression in Union County is roughly circular within the -60-ft contour. The lowest water-level altitude measurement was 157 ft below NGVD 29 in 2009, with a 37-ft rise to 120 ft below NGVD 29 in 2011. The depression in Union County has diminished and encloses a smaller area than in recent years. In 1993, the -60-ft contour enclosed 632 square miles (mi 2 ). In 2011, the -60-ft contour enclosed 375 mi 2 , a decrease of 41 percent from 1993. The lowest water-level altitude measurement during 2011 in the center of the depression in Union County represents a rise of 79 ft since 2003. The area enclosed by the lowest altitude contour, 120 ft below NGVD 29, on the 2011 potentiometric-surface map is less than 10 percent of the area enclosed by that same contour on the 2009 potentiometric-surface map. A broad depression in western Poinsett and Cross Counties was first shown in the 1995 potentiometric-surface map. In 2011, the lowest water-level altitude measurement in this depression, 129 ft above NGVD 29, is 2 ft lower than in 2009. The 140-ft contour has extended southwest into northwestern St. Francis and east-central Woodruff Counties in 2011. In Columbia County in 2011, the area of the depression has decreased, with water levels rising about 1 ft since 2005 in the well with the lowest water-level altitude measurement. The depression in Bradley County in 2011 has decreased in area compared to 2007. A water-level difference map was constructed using the difference between water-level measurements made during 2007 and 2011 at 247 wells. The differences in water level between 2007 and 2011 ranged from -17.3 to 45.4 ft, with a mean of 4.1 ft. Water levels generally declined in the northern half of the study area and generally increased in the southern half of the study area. Areas with a general decline in water levels include Lonoke and western Prairie Counties; northern Arkansas County; Miller County; and Craighead, Poinsett, Cross, and Woodruff Counties. Areas with a general rise in water levels include Lafayette, Columbia, Union, Calhoun, and Bradley Counties; Grant, Jefferson, southern Arkansas, Lincoln, Drew, and Desha Counties; and Phillips County. Hydrographs from 183 wells with a minimum of 25 years of water-level measurements were constructed. During the period 1987–2011, county mean annual water levels generally declined. Mean annual declines were between 0.5 foot per year (ft/yr) and 0.0 ft/yr in Ashley, Chicot, Crittenden, Drew, Grant, Jefferson, Lafayette, Mississippi, Monroe, Ouachita, Phillips, Pulaski, St. Francis, and Woodruff Counties. Mean annual declines were between 1.0 ft/yr and 0.5 ft/yr in Bradley, Calhoun, Cleveland, Craighead, Cross, Desha, Lonoke, Miller, Poinsett, and Prairie Counties. Mean annual declines were between 1.5 ft/yr and 1.0 ft/yr in Arkansas, Lee, and Lincoln Counties. The county mean annual water level rose in Columbia, Dallas, and Union Counties about 0.3 ft/yr, 0.1 ft/yr, and 1.2 ft/yr, respectively. Water samples were collected in the summer of 2011 from 61 wells completed in the Sparta-Memphis aquifer and measured onsite for specific conductance, temperature, and pH. Although there is a regional increase in specific conductance to the east and south, anomalous increases occur in some parts of the study area. Specific conductance ranged from 35 microsiemens per centimeter (μS/cm) in Ouachita County to 1,380 μS/cm in Monroe County. Relatively large specific conductance values (greater than 700 mS/cm) occur in samples from wells in Arkansas, Ashley, Clay, Monroe, Phillips, and Union Counties.

Arkansas↗
USGS2013

Drought and deluge: Effects of recent climate variability on groundwater levels in eastern Arkansas

Arkansas experienced wide extremes in climate variability during the period of 2005 to 2010, recording the largest annual precipitation ever recorded in the State (100.05 inches) in 2009. Many weather stations across the State reported between 80 to 90 inches of rainfall in 2009. For comparison, the average annual precipitation in Little Rock, Arkansas, for the period 1878 to 2010 was 47.1 inches. In contrast, 2005 and 2010 were the 7th and 14th driest years on record in Little Rock with 34.55 and 36.52 inches, respectively; both tied as the hottest years ever recorded in Arkansas. The wettest year on record in Little Rock (2009) was interspersed within these dry years, with a total of 81.79 inches. Fifteen weather stations within the State ranked 2009 as the wettest year on record. Extremes in annual precipitation rates may lead to greater variability in groundwater recharge rates and water use, particularly in the agricultural areas in eastern Arkansas that rely heavily on groundwater produced from the Mississippi River Valley alluvial aquifer (hereafter referred to as the alluvial aquifer). How does this variability affect the groundwater system and water use therein? Are the effects of this variability discernable in measured water levels in wells? Czarnecki and Schrader examined these questions and provided some insights, the results of which are presented here.

Arkansas↗
USGS2013

Effects of recent climate variability on groundwater levels in eastern Arkansas

Water-level fluctuations in wells completed in the Mississippi River Valley alluvial aquifer in eastern Arkansas were compared to variability in annual precipitation, an indicator of climate variability. The wettest year on record in Little Rock, Arkansas, occurred in 2009 with 81.79 inches of precipitation compared to an average of 47.1 inches per year. In contrast, 2005 and 2010 were the 7th and 14th driest years on record with 34.55 and 36.52 inches per year, respectively. This variability in precipitation was reflected in water-level altitude changes between 2004 and 2008 and 2006 and 2010. Generally, drier conditions between 2004 and 2008 led to an average decline in water levels of 1.62 feet, whereas wetter conditions between 2006 and 2010 led to an average rise in water levels of 1.36 feet. Drier periods likely resulted in less recharge compared to wetter periods. Groundwater use from the alluvial aquifer peaked in 2000 and has since declined, in part, because of conservation measures and substantial reduction in aquifer saturated thickness. Groundwater-flow model results showed some areas of the alluvial aquifer simulated as dry in 2010, indicating a reduced capacity of the alluvial aquifer to produce water in those areas. Additional factors affecting groundwater use include the types of crops grown in an area and the availabitiliy of crop subsidies. Real-time continuous water-level measurements in wells allow for a more accurate assessment of the effect of variability in precipitation and water use than periodic water-level measurements.

Arkansas↗
USGS2013

Water levels and water quality in the Sparta-Memphis aquifer (middle Claiborne aquifer) in Arkansas, spring-summer 2009

The U.S. Geological Survey in cooperation with the Arkansas Natural Resources Commission and the Arkansas Geological Survey has monitored water levels in the Sparta Sand of Claiborne Group and Memphis Sand of Claiborne Group (herein referred to as the Sparta Sand and the Memphis Sand, respectively) since the 1920s. Groundwater withdrawals have increased while water levels have declined since monitoring was initiated. Herein, aquifers in the Sparta Sand and Memphis Sand will be referred to as the Sparta-Memphis aquifer throughout Arkansas. During the spring of 2009, 324 water levels were measured in wells completed in the Sparta-Memphis aquifer and used to produce a regional potentiometric-surface map. During the summer of 2009, 64 water-quality samples were collected and measured for specific conductance, temperature, and pH from wells completed in the Sparta-Memphis aquifer. The regional direction of groundwater flow in the Sparta-Memphis aquifer is generally to the south-southeast in the northern half of Arkansas and to the east and south in the southern half of Arkansas, away from the outcrop area except where affected by large groundwater withdrawals. The highest and lowest water-level altitudes measured in the Sparta-Memphis aquifer were 325 feet above and 157 feet below National Geodetic Vertical Datum of 1929, respectively. Eight depressions (generally represented by closed contours) are located in the following counties: Bradley; Ashley; Calhoun; Cleveland; Columbia; Arkansas, Jefferson, Lincoln, and Prairie; Cross and Poinsett; and Union. Two large depressions shown on the 2009 potentiometric-surface map, centered in Jefferson and Union Counties, are the result of large withdrawals for industrial, irrigation, or public supply. The depression centered in Jefferson County deepened and expanded in recent years into Arkansas and Prairie Counties. The area enclosed within the 40-foot contour on the 2009 potentiometric-surface map has expanded south to the Drew County line and moved west from the intersection of Arkansas, Jefferson, and Lincoln Counties when compared with the 2007 potentiometric-surface map. To the north, east, and west, the 40-foot contour is comparable to the 2007 potentiometric-surface map. The lowest water-level altitude measurement during 2009 in the center of the depression in Union County represents a rise of 42 feet since 2003. The area enclosed by the lowest altitude contour, 140 feet below National Geodetic Vertical Datum of 1929, on the 2009 potentiometric-surface map is about half the area on the 2007 potentiometric-surface map. In the depression in western Poinsett and Cross Counties, the 140-foot contour extended north to the Poinsett-Craighead County line and south across Cross County about two-thirds of the distance to the St. Francis County line. A water-level difference map was constructed using water-level measurements made during 2005 and 2009 from 309 wells. The difference in water level between 2005 and 2009 ranged from -74.6 to 60.2 feet. Areas with a general rise in water levels occur in central Columbia County, southern Jefferson County, and most of Union County. In the area around west-central Union County, water levels rose as much as 60.2 feet with water levels in 18 wells rising 20 feet or more, representing an average annual rise of 5 feet or more. Water levels generally declined throughout most of the rest of Arkansas. Hydrographs were constructed using a minimum of 25 years of water-level measurements at each of 206 wells. During the period 1985–2009, mean annual water levels rose in Calhoun, Columbia, Lafayette, and Union Counties, about 1.3 feet per year (ft/yr), 0.2 ft/yr, 0.1 ft/yr, and 0.6 ft/yr, respectively. Mean annual water-level declines between 0.0 and 2.3 ft/yr occurred in all other counties. In western Arkansas County, water-level altitudes in a continuously monitored well declined 60 feet during the irrigation season (April to September). Specific conductance ranged from 43 microsiemens per centimeter at 25 degrees Celsius (μS/cm) in Ouachita County to 1,230 μS/cm in Phillips County. The mean specific conductance was 392 μS/cm. Although there is a regional increase in specific conductance to the east and south, specific conductance values greater than 700 μS/cm occurred in samples from wells in Arkansas, Ashley, Monroe, Phillips, and Union Counties.

Arkansas↗
USGS2013

Water levels in the aquifers of the Nacatoch Sand of southwestern and northeastern Arkansas and the Tokio Formation of southwestern Arkansas, February–March 2011

The aquifers in the Nacatoch Sand and Tokio Formation in southwestern Arkansas and the Nacatoch Sand in northeastern Arkansas are sources of water for industrial, public supply, domestic, and agricultural uses. Potentiometric-surface maps were constructed from water-level measurements made in 47 wells completed in the Nacatoch Sand and 45 wells completed in the Tokio Formation during February and March 2011. Aquifers in the Nacatoch Sand and Tokio Formation are hereafter referred to as the Nacatoch aquifer and the Tokio aquifer, respectively. The direction of groundwater flow in the Nacatoch aquifer in southwestern Arkansas is towards the southeast in Hempstead, Little River, and Miller Counties and east-southeast in Clark and Nevada Counties. A potentiometric high is located within the outcrop area of north-central Hempstead County. Two cones of depression exist in the Nacatoch aquifer, one at Hope in southeastern Hempstead County and one in Clark County. The direction of groundwater flow in the Nacatoch aquifer in northeastern Arkansas generally is towards the southeast. A potentiometric high in the study area is located along the north and northwestern boundaries of the area, but water levels may be higher outside the study area. In northeastern Arkansas, groundwater withdrawals from the Nacatoch aquifer increased by 564 percent from 1965 to 2010. In southwestern Arkansas, groundwater withdrawals from the Nacatoch Sand increased by 125 percent from 1965 to 1980, and withdrawals decreased by 85 percent from 1980 to 2010. In southwestern Arkansas, groundwater withdrawals from the Tokio aquifer increased by 201 percent from 1965 to 1980, and withdrawals decreased by 81 percent from 1980 to 2000. Withdrawals from the Tokio aquifer increased by 291 percent from 2000 to 2005, and withdrawals decreased by 32 percent from 2005 to 2010. The direction of groundwater flow in the Tokio aquifer in southwestern Arkansas generally is towards the south or southeast. The potentiometric high is within the outcrop area in the northern part of the area. Artesian flow exists or is inferred in southeastern Pike, northeastern Hempstead, and northwestern Nevada Counties. One apparent cone of depression might exist northwest of Hope in Hempstead County.

Arkansas↗
USGS2010

Water levels and selected water-quality conditions in the Mississippi River Valley alluvial aquifer in Eastern Arkansas, 2008

During the spring of 2008, the U.S. Geological Survey, in cooperation with the Arkansas Natural Resources Commission and the Arkansas Geological Survey, measured 670 water levels in 659 wells completed in the Mississippi River Valley alluvial aquifer in eastern Arkansas. Groundwater levels are affected by groundwater withdrawals resulting in potentiometric-surface depressions. In 2008, the lowest water-level altitude was 69 feet above National Geodetic Vertical Datum of 1929 in the center of Arkansas County. The highest water-level altitude was 288 feet above National Geodetic Vertical Datum of 1929 in northeastern Clay County on the west side of Crowleys Ridge. Two large depressions in the potentiometric surface are located in Arkansas, Lonoke, and Prairie Counties and west of Crowleys Ridge in Craighead, Cross, Lee, Monroe, Poinsett, St. Francis, and Woodruff Counties. The elongated depression in Arkansas, Lonoke, and Prairie Counties has two areas that have changed in horizontal area or depth when compared to previous conditions of the aquifer. The area in Arkansas County in the southeastern half of the depression has not expanded horizontally from recent years, although the center of the depression has deepened. The area in Lonoke and Prairie Counties in the northwestern half of the depression has not expanded and water level in the deeper part of the depression has risen. In Lonoke and Prairie Counties in the northwestern half of the depression, the 90-foot contour shown on the 2006 potentiometric-surface map is not shown on the 2008 potentiometric-surface map. Along the west side of Crowleys Ridge, the area enclosed by 140-foot contour in Cross and Poinsett Counties has expanded further south into Cross County. The 130-foot contour in Poinsett County expanded north in 2008. The 130-foot contour is shown in Cross County, which was not evident in previous years. The 130-foot contour in St. Francis, Monroe, and Woodruff Counties in 2006 is not shown on the 2008 potentiometric-surface map. A map showing the difference in water level was constructed using 595 differences in water levels measured in 585 wells during 2008 and 2004. The difference in measured water levels from 2004 to 2008 ranged from -20.6 feet to 25.9 feet, with a mean of -1.6 feet. The largest decline of -20.6 feet occurred in Randolph County and the largest rise of 25.9 feet occurred in Prairie County. Out of the 595 differences, 442 were declines (74.3 percent), 10 were no difference (values of 0.0 ft) (1.7 percent), and 143 were rises (24.0 percent). Five areas are dominated by declines that are west of Crowleys Ridge; in eastern Craighead County; in southern Mississippi and Crittenden Counties; in eastern Lonoke and western Prairie Counties; and in Arkansas, Ashley, Chicot, Desha, Drew, and Lincoln Counties. Long-term water-level changes were evaluated using hydrographs from 173 wells in the Mississippi River Valley alluvial aquifer for the period 1984 to 2008. The mean annual rise or decline in water level for the entire study area was -0.38 feet per year (ft/yr) with a range of -4.86 to 0.58 ft/yr. Independence and White Counties are the only counties with a mean annual rise from 1984 to 2008. Mean annual declines between -0.50 ft/yr and 0.00 ft/yr occurred in Arkansas, Chicot, Clay, Craighead, Crittenden, Drew, Greene, Jefferson, Mississippi, Monroe, Phillips, Poinsett, Prairie, Pulaski, Randolph, and Woodruff Counties. Mean annual declines between -1.00 ft/yr and -0.50 ft/yr occurred in Ashley, Desha, Jackson, Lee, Lincoln, and St. Francis Counties. Mean annual declines between -1.50 ft/yr and -1.00 ft/yr occurred in Cross and Lonoke Counties. The analysis of long-term water-level changes in Arkansas, Lonoke, and Prairie Counties shows the elongation of the depression in these three counties. Arkansas and Prairie Counties have two different rates of annual decline for the two hydrographs shown for each county. Water levels in the two we

Scientific Investigations Report↗
USGS2010

Water levels in aquifers in the Nacatoch Sand of southwestern and northeastern Arkansas and the Tokio Formation of southwestern Arkansas, spring 2008

The Nacatoch Sand and Tokio Formation aquifers in southwestern Arkansas and the Nacatoch Sand in northeastern Arkansas are sources of water for industrial, public supply, domestic, and agricultural uses. Potentiometric-surface maps were constructed from water-level measurements made in 61 wells completed in the Nacatoch Sand and in 50 wells completed in the Tokio Formation during spring 2008. Aquifers in the Nacatoch Sand and Tokio Formation are hereafter referred to as the Nacatoch aquifer and the Tokio aquifer, respectively. The direction of groundwater flow in the Nacatoch aquifer in northeastern Arkansas generally is towards the southeast. A potentiometric high is located along the north and northwestern boundaries of the area. The direction of groundwater flow in the Nacatoch aquifer in southwestern Arkansas is towards the south-southeast in Little River, Miller, and Hempstead Counties and to the east-southeast in Nevada and Clark Counties. A potentiometric high is located within the outcrop area in north-central Hempstead County. A cone of depression exists in the Nacatoch aquifer at Hope in southeastern Hempstead County. The direction of groundwater flow in the Tokio aquifer in southwestern Arkansas generally is towards the south or southeast. A potentiometric high is located within the outcrop area. Artesian conditions exist in southeastern Pike, northeastern Hempstead, and northwestern Nevada Counties. One apparent cone of depression might exist northwest of Hope in Hempstead County. In northeastern Arkansas, groundwater withdrawals from the Nacatoch aquifer increased by 480 percent from 1965 to 2005. In southwestern Arkansas, withdrawals from the Nacatoch aquifer and Tokio aquifer increased by 125 percent and 201 percent, respectively, from 1965 to 1980 and decreased by 93 percent and 80 percent, respectively, from 1980 to 2000. Withdrawals from Nacatoch aquifer and Tokio aquifer increased by 690 percent and 291 percent, respectively, from 2000 to 2005. Long-term hydrographs were prepared for 10 wells in the study areas. Changes in water levels in some wells may be associated with changes in withdrawals from the respective aquifers.

Scientific Investigations Report↗
USGS2009

Water Levels and Selected Water-Quality Conditions in the Sparta-Memphis Aquifer (Middle Claiborne Aquifer) in Arkansas, Spring-Summer 2007

The U.S. Geological Survey in cooperation with the Arkansas Natural Resources Commission and the Arkansas Geological Survey has monitored water levels in the Sparta Sand of Claiborne Group and Memphis Sand of Claiborne Group (herein referred to as the Sparta Sand and the Memphis Sand, respectively), since the 1920s. Groundwater withdrawals have increased while water levels have declined since monitoring was initiated. Herein, aquifers in the Sparta Sand and Memphis Sand will be referred to as the Sparta-Memphis aquifer throughout Arkansas. During the spring of 2007, 309 water levels were measured in wells completed in the Sparta-Memphis aquifer. During the summer of 2007, 129 water-quality samples were collected and measured for temperature and specific conductance and 102 were collected and analyzed for chloride from wells completed in the Sparta-Memphis aquifer. Water-level measurements collected in wells screened in the Sparta-Memphis aquifer were used to produce a regional potentiometric-surface map. The regional direction of groundwater flow in the Sparta-Memphis aquifer is generally to the south-southeast in the northern half of Arkansas and to the east and south in the southern half of Arkansas, away from the outcrop area except where affected by large ground-water withdrawals. The highest water-level altitude measured in the Sparta-Memphis aquifer was 326 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 161 feet below National Geodetic Vertical Datum of 1929 in Union County near the southern boundary of the study area. Eight cones of depression (generally represented by closed contours) are located in the following counties: Bradley, Drew, and Ashley; Calhoun; Cleveland; Columbia; Crittenden; Arkansas, Jefferson, and Lincoln; Cross and Poinsett; and Union. Two large depressions are shown on the 2007 potentiometric-surface map, centered in Jefferson and Union Counties, as a result of large withdrawals for industrial and public supplies. The depression centered in Jefferson County deepened and expanded in recent years into Arkansas and Prairie Counties as a result of large withdrawals for irrigation and public supply. The area enclosed within the 40-foot contour has expanded on the 2007 potentiometric-surface map when compared with the 2005 potentiometric-surface map. In 2003, the depression in Union County was elongated east and west and beginning to coalesce with the depression in Columbia County. The deepest measurement during 2007 in the center of the depression in Union County has risen 38 feet since 2003. The area enclosed by the deepest contour, 160 feet below National Geodetic Vertical Datum of 1929, on the 2007 potentiometric-surface map is less than 10 percent of the area on the 2005 potentiometric-surface map. A broad depression in western Poinsett and Cross Counties was first shown in the 1995 potentiometric-surface map caused by withdrawals for irrigation extending north to the Poinsett-Craighead County line, and south into Cross County. A water-level difference map was constructed using the difference between water-level measurements made during 2003 and 2007 from 283 wells. The difference in water level between 2003 and 2007 ranged from -49.8 to 60.0 feet. Areas with a general rise in water levels are shown in northern Arkansas, Columbia, southern Jefferson, and most of Union Counties. In the area around west-central Union County, water levels rose as much as 60.0 feet with water levels in 15 wells rising 20 feet or more, which is an average annual rise of 5 feet or more. Water levels generally declined throughout most of the rest of Arkansas. Hydrographs from 157 wells were constructed with a minimum of 25 years of water-level measurements. During the period 1983-2007, the county mean annual water level rose in Calhoun, Columbia, Hot Spring, and Lafayette Counties. Mean an

Scientific Investigations Report↗
USGS2008

Potentiometric Surface in the Sparta-Memphis Aquifer of the Mississippi Embayment, Spring 2007

The most widely used aquifer for industry and public supply in the Mississippi embayment in Arkansas, Louisiana, Mississippi, and Tennessee is the Sparta-Memphis aquifer. Decades of pumping from the Sparta-Memphis aquifer have affected ground-water levels throughout the Mississippi embayment. Regional assessments of water-level data from the aquifer are important to document regional water-level conditions and to develop a broad view of the effects of ground-water development and management on the sustainability and availability of the region's water supply. This information is useful to identify areas of water-level declines, identify cumulative areal declines that may cross State boundaries, evaluate the effectiveness of ground-water management strategies practiced in different States, and identify areas with substantial data gaps that may preclude effective management of ground-water resources. A ground-water flow model of the northern Mississippi embayment is being developed by the Mississippi Embayment Regional Aquifer Study (MERAS) to aid in answering questions about ground-water availability and sustainability. The MERAS study area covers parts of eight states including Alabama, Arkansas, Illinois, Kentucky, Louisiana, Mississippi, Missouri, and Tennessee and covers approximately 70,000 square miles. The U.S. Geological Survey (USGS) and the Mississippi Department of Environmental Quality Office of Land and Water Resources measured water levels in wells completed in the Sparta-Memphis aquifer in the spring of 2007 to assist in the MERAS model calibration and to document regional water-level conditions. Measurements by the USGS and the Mississippi Department of Environmental Quality Office of Land and Water Resources were done in cooperation with the Arkansas Natural Resources Commission; the Arkansas Geological Survey; Memphis Light, Gas and Water; Shelby County, Tennessee; and the city of Germantown, Tennessee. In 2005, total water use from the Sparta-Memphis aquifer in the Mississippi embayment was about 540 million gallons per day (Mgal/d). Water use from the Sparta-Memphis aquifer was about 170 Mgal/d in Arkansas, about 68 Mgal/d in Louisiana, about 97 Mgal/d in Mississippi, and about 205 Mgal/d in Tennessee. The author acknowledges, with great appreciation, the efforts of the personnel in the U.S. Geological Survey Water Science Centers of Arkansas, Kentucky, Louisiana, Mississippi, Missouri, and Tennessee, and the Mississippi Department of Environmental Quality Office of Land and Water Resources that participated in the planning, water-level measurement, data evaluation, and review of the potentiometric-surface map. Without the contribution of data and the technical assistance of their staffs, this report would not have been completed.

Scientific Investigations Map↗
USGS2008

Water Levels and Selected Water-Quality Conditions in the Mississippi River Valley Alluvial Aquifer in Eastern Arkansas, 2006

During the spring of 2006, the U.S. Geological Survey, in cooperation with the Arkansas Natural Resource Commission and the Arkansas Geological Survey, measured water levels in 707 wells completed in the Mississippi River Valley alluvial aquifer in eastern Arkansas. Ground-water levels are affected by ground-water withdrawals resulting in depressions. In 2006, the lowest water-level altitude was 76 feet above the National Geodetic Vertical Datum of 1929 in the center of Arkansas County. The highest water-level altitude was 289 feet above the National Geodetic Vertical Datum of 1929 in northeastern Clay County on the west side of Crowleys Ridge. Two large depressions in the potentiometric surface are located in Arkansas, Lonoke, and Prairie Counties and west of Crowleys Ridge in Craighead, Cross, Lee, Monroe, Poinsett, St. Francis, and Woodruff Counties. The elongated depression in Arkansas, Lonoke, and Prairie Counties has changed in areal extent or depth when compared to previous conditions of the aquifer. The area in Arkansas County at the southeastern half of the depression has not expanded horizontally during recent years, although the center of the depression has deepened. The area in Lonoke and Prairie Counties in the northwestern half of the depression has expanded horizontally in the deeper part of the depression. The 90-foot contour has expanded north and east in Lonoke County when compared with the 2004 potentiometric surface. Along the west side of Crowleys Ridge the 2006 potentiometric-surface map shows very little change in the area of this depression, although the deeper areas within the depression have expanded. A map showing the difference in water level was constructed using 645 differences in water-levels measured in 633 wells during 2002 and 2006. The difference in measured water levels from 2002 to 2006 ranged from -24.0 feet to 25.0 feet, with a mean of -2.0 feet. The largest decline of -24.0 feet occurred in Poinsett County and the largest rise of 25.0 feet occurred in Randolph County. Out of the 645 differences, 481 were declines (74.6 percent), 12 were no difference (values of 0.0 ft) (1.8 percent), and 152 were rises (23.6 percent). Long-term water-level trends were evaluated using hydrographs from 152 wells completed in the Mississippi River Valley alluvial aquifer for the period 1982 to 2006. The mean annual rise or decline in water level for the entire study area was -0.32 feet per year with a range of -1.28 to 0.77 feet per year. Independence and White Counties are the only counties with a mean annual rise from 1982 to 2006. Mean annual declines between -0.50 feet per year and 0.00 feet per year occurred in Arkansas, Ashley, Chicot, Clay, Craighead, Crittenden, Drew, Jefferson, Lee, Mississippi, Monroe, Phillips, Poinsett, Prairie, Pulaski, Randolph, and Woodruff Counties. Mean annual declines between -1.00 feet per year and -0.50 feet per year occurred in Cross, Desha, Greene, Jackson, Lincoln, Lonoke, and St. Francis Counties. The analysis of long-term water-level changes in Arkansas, Lonoke, and Prairie Counties shows the elongation of the depression in these three counties. Both Arkansas and Prairie Counties have two different rates of annual decline for the two hydrographs shown for each county. Water levels in the two wells near the Arkansas and White Rivers either have risen or declined at a slower rate than in the three wells in the center, northern, and western part of the depression. These rates of water-level change indicate that this depression is expanding in an elongated direction north and west into Lonoke and Prairie Counties. The depression west of Crowleys Ridge has five wells with hydrographs in or near the depression that can be used to characterize the rates of water-level change within the depression. Water samples were collected from 65 wells completed in the Mississippi River Valley alluvial aquifer and measured onsite for specific conductance and tempera

Scientific Investigations Report↗
USGS2007

Status of water levels in aquifers in the Nacatoch Sand of southwestern and northeastern Arkansas and the Tokio Formation of southwestern Arkansas, February 2005

The Nacatoch Sand and Tokio Formation aquifers in southwestern Arkansas and the Nacatoch Sand aquifer in northeastern Arkansas are sources of water for industrial, public supply, domestic, and agricultural uses. Potentiometric-surface maps were constructed from water-level measurements made in 60 wells completed in the Nacatoch Sand and 50 wells completed in the Tokio Formation during February 2005. Aquifers in the Nacatoch Sand and Tokio Formation are hereafter referred to as the Nacatoch aquifer and Tokio aquifer, respectively. The direction of ground-water flow in the Nacatoch aquifer in northeastern Arkansas generally is towards the southeast. The potentiometric high is located along the north and northwestern boundaries of the area. The direction of ground-water flow in the Nacatoch aquifer in southwestern Arkansas is towards the south-southeast in Little River, Miller, and Hempstead Counties and to the east-southeast in Nevada and Clark Counties. The potentiometric high is located within the outcrop area in north-central Hempstead County. A cone of depression exists in the Nacatoch aquifer at Hope in southeastern Hempstead County. The direction of ground-water flow in the Tokio aquifer in southwestern Arkansas generally is towards the south or southeast. The potentiometric high is within the outcrop area. An area of artesian flow exists in southeastern Pike, northeastern Hempstead, and northwestern Nevada Counties. One apparent cone of depression might exist northwest of Hope in Hempstead County. In northeastern Arkansas, withdrawals from the Nacatoch aquifer increased by 516 percent from 1965 to 2000. In southwestern Arkansas, withdrawals from Nacatoch aquifer and Tokio aquifer increased by 125 percent and 201 percent, respectively, from 1965 to 1980 and decreased by 93 percent and 80 percent, respectively, from 1980 to 2000. Long-term hydrographs were prepared for 10 wells in the study areas. Changes in water levels in some wells may be associated with changes in withdrawals from the respective aquifers.

Arkansas↗
USGS2007

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

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

Scientific Investigations Report↗
USGS2007

Potentiometric Surfaces and Water-Level Trends in the Cockfield and Wilcox Aquifers of Southern and Northeastern Arkansas, 2006

The Cockfield Formation of Claiborne Group and the Wilcox Group contain aquifers that provide sources of ground water in southern and northeastern Arkansas. In 2000, about 9.9 million gallons per day was withdrawn from the Cockfield Formation of Claiborne Group and about 22.2 million gallons per day was withdrawn from the Wilcox Group. Major withdrawals from the aquifers were for industrial and public water supplies. A study was conducted by the U.S. Geological Survey in cooperation with the Arkansas Natural Resources Commission and the Arkansas Geological Survey to determine the water level associated with the aquifers in the Cockfield Formation of Claiborne Group and the Wilcox Group in southern and northeastern Arkansas. During February and March 2006, 56 water-level measurements were made in wells completed in the Cockfield aquifer and 59 water-level measurements were made in wells completed in the Wilcox aquifer, 16 in southwestern and 43 in northeastern Arkansas. This report presents the results as potentiometric-surface maps and as long-term water-level hydrographs. The regional direction of ground-water flow in the Cockfield Formation of Claiborne Group generally is towards the east and southeast, away from the outcrop, except in areas of intense ground-water withdrawals, such as western Drew County, southeastern Lincoln County, southwestern Calhoun County, and near Crossett in Ashley County. There are three cones of depression indicated by relatively low water-level altitudes in southeastern Lincoln County, southwestern Calhoun County, and near Crossett in Ashley County. The lowest water-level altitude measured was 44 feet above the National Geodetic Vertical Datum of 1929 in Lincoln County; the highest water-level altitude measured was 346 feet above the National Geodetic Vertical Datum of 1929 in Columbia County at the outcrop area. Hydrographs from 40 wells with historical water levels from 1986 to 2006 were evaluated using linear regression to calculate the annual rise or decline. Calhoun and Cleveland Counties have mean annual rises from 0.01 to 0.07 feet per year. Arkansas, Ashley, Bradley, Chicot, Columbia, Drew, Lincoln, and Union Counties have mean annual declines from 0.4 to 0.55 feet per year. Desha County has a mean annual decline of about 1.35 feet per year. The direction of ground-water flow in the southwestern study area of the Wilcox Group generally is south and east. The lowest water-level altitude measured in southwestern Arkansas was 147 feet above the National Geodetic Vertical Datum of 1929 near the Ouachita River in Clark County; the highest water-level altitude measured was 397 feet above the National Geodetic Vertical Datum of 1929 in the outcrop area of Hempstead County. The direction of ground-water flow in the northeastern study area of the Wilcox Group generally is south and east. The lowest water-level altitude measured in northeastern Arkansas was 120 feet above the National Geodetic Vertical Datum of 1929 near West Memphis in Crittenden County; the highest water-level altitude measured was 368 feet above the National Geodetic Vertical Datum of 1929 on Crowleys Ridge in Clay County. Hydrographs from 28 wells with historical water levels from 1986 to 2006 were evaluated using linear regression to calculate the annual rise or decline. All 28 wells showed an annual decline from 1986 to 2006. Craighead, Greene, Mississippi, and Poinsett Counties have mean annual declines from 0.27 to 1.00 feet per year. Crittenden, Lee, and St. Francis Counties have mean annual declines from 1.39 to 1.64 feet per year.

Scientific Investigations Report↗
USGS2006

Status of water levels and selected water-quality conditions in the Sparta-Memphis aquifer in Arkansas, Spring-Summer 2003

During the spring of 2003, water levels were measured in 341 wells in the Sparta-Memphis aquifer in Arkansas. Waterquality samples were collected for temperature and specificconductance measurements during the spring-summer of 2003 from 70 wells in Arkansas in the Sparta-Memphis aquifer. Maps of areal distribution of potentiometric surface, change in waterlevel measurements from 1999 to 2003, and specific-conductance 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 Craighead County; the lowest water-level altitude was 199 feet below NGVD of 1929 in Union County. Three large cones of depression are shown in the 2003 potentiometric surface map, centered in Columbia, Jefferson, and Union Counties in Arkansas as a result of large withdrawals for industrial and public supplies. A broad depression exists in western Poinsett County in Arkansas. The potentiometric surface indicates that large withdrawals have altered or reversed the natural direction of flow in most areas. In the northern third of the study area the flow is from the east, west, and north towards the broad depression in Poinsett County. In the central third of the study area the flow is dominated by the cone of depression centered in Jefferson County. In the southern third of the study area the flow is dominated by the two cones of depression in Union and Columbia Counties. A map of water-level changes from 1999 to 2003 was constructed using water-level measurements from 281 wells. The largest rise in water level measured was about 57.8 feet in Columbia County. The largest decline in water level measured was about -71.6 feet in Columbia County. Areas with a general rise are shown in Arkansas, Bradley, Calhoun, Cleveland, Columbia, Ouachita, and Union Counties. Areas with a general decline are shown in Craighead, Crittenden, Cross, Desha, Drew, Jefferson, Lonoke, Phillips, Poinsett, Prairie, and Woodruff Counties. 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 1978 to spring of 2003 to determine the annual decline or rise in feet per year for water levels in each well. The hydrographs were grouped by county. The mean values for county annual water-level decline or rise ranged from -1.42 to 0.27 foot per year. Specific conductance ranged from 82 microsiemens per centimeter at 25 degrees Celsius in Jefferson County to about 1,210 microsiemens per centimeter at 25 degrees Celsius in Lee County. The mean specific conductance was 400 microsiemens per centimeter at 25 degrees Celsius.

Scientific Investigations Report↗
USGS2006

Status of Water Levels and Selected Water-Quality Conditions in the Mississippi River Valley Alluvial Aquifer in Eastern Arkansas, 2004

During the spring of 2004, water levels were measured in 684 wells completed in the Mississippi River Valley alluvial aquifer in eastern Arkansas. Ground-water levels are affected by intense ground-water withdrawals resulting in extensive potentiometric depressions. In 2004, the highest water-level altitude measured was 293 feet above National Geodetic Vertical Datum of 1929 in northeastern Clay County. The lowest water-level altitude measured was 76 feet above National Geodetic Vertical Datum of 1929 in the center of Arkansas County. A large depression in the potentiometric surface was located in Arkansas, Lonoke, and Prairie Counties during 1998 and persisted to 2002. The area enclosed in the 100-foot contour in Arkansas County in 2004 is about the same as in 2002, however, the area enclosed in the 100-foot contour in Lonoke and Prairie Counties in 2004 has receded. Two shallower cones of depressions were located in Craighead, Cross, and Poinsett Counties and St. Francis, Woodruff, Lee, and Monroe Counties west of Crowleys Ridge during 1998. The 2004 potentiometricsurface map shows that the areas enclosed by the 140-foot contour have continued to expand. A map of changes in water-level measurements between 2000 and 2004 was constructed using the difference between water-level measurements from 625 wells reported in this report and the 2000 Mississippi River Valley alluvial aquifer report. Water-level changes between 2000 and 2004 ranged from -31.1 feet to 16.3 feet, with a mean of -0.7 feet (negative changes indicating water-level declines, positive changes indicating water-level rises). The largest rise of 16.3 feet is in Arkansas County and the largest decline of -31.1 feet is in Prairie County. Long-term water-level changes were calculated for 134 wells in the alluvial aquifer for the period from 1980 to 2004. The mean annual decline in water level for the entire study area was -0.31 feet per year with a range of -1.35 feet per year to 0.84 feet per year. The analysis of long-term water-level changes (1980-2004) in the depression in Arkansas and Prairie Counties shows the effects of the elongation of this depression. Water samples were collected from 138 wells completed in the alluvial aquifer and measured onsite for specific conductance and temperature. Samples were collected at 71 wells for dissolved chloride analysis at the U.S. Geological Survey National Water Quality Laboratory. Specific conductance ranged from 205 microsiemens per centimeter at 25 degrees Celsius at a well in Lonoke County to 1,440 microsiemens per centimeter at 25 degrees Celsius at a well in Monroe County.

Scientific Investigations Report↗
USGS2005

Potentiometric surface of the Ozark aquifer in northern Arkansas, 2004

The Ozark aquifer in northern Arkansas comprises dolomites, limestones, sandstones, and shales of Late Cambrian to Middle Devonian age, and ranges in thickness from approximately 1,100 feet to more than 4,000 feet. Hydrologically, the aquifer is complex, characterized by discrete and discontinuous flow components with large variations in permeability. The potentiometric-surface map, based on 59 well and 5 spring water-level measurements collected in 2004 in Arkansas and Missouri, indicates maximum water-level altitudes of about 1,188 feet in Benton County and minimum water-level altitudes of about 116 feet in Randolph County. Regionally, the flow within the aquifer is to the south and southeast in the eastern and central part of the study area and to the northwest and north in the western part of the study area. Comparing the 2004 potentiometric- surface map with a predevelopment potentiometricsurface map indicates general agreement between the two surfaces. Potentiometric-surface differences could be attributed to differences in pumping related to changing population from 1990 to 2000, change in source for public supplies, processes or water use outside the study area, or differences in data-collection or map-construction methods.

Scientific Investigations Report↗
USGS2005

Water resources data, Arkansas, 2004

The U.S. Geological Survey Arkansas Water Science Center, in cooperation with State, Federal, and other local governmental agencies, obtains a large amount of data pertaining to the water resources of Arkansas each year. These data, accumulated during many water years, constitute a valuable database for developing an improved understanding of the water resources of the State. Water resources data reported for the 2004 water year for Arkansas consist of records of discharge and water quality (physical measurements and chemical concentrations) of streams, water quality of lakes, and ground-water levels and ground-water quality. Data from selected sites in Louisiana, Missouri, and Oklahoma also are included. This report contains daily discharge records for 104 surface-water gaging stations, 82 peak-discharge partial-record stations, 8 stage-only stations, water-quality data for 79 surface-water stations and 16 wells, and water levels for 47 observation wells. Additional water data were collected at various sites, not part of the systematic data-collection program, and are published as miscellaneous measurements.

Water Data Report↗