(Upper Claiborne) Aquifer in Southern Arkansas and the Wilcox (Lower Wilcox) Aquifer of Northeastern and Southern Arkansas, 2012

Prepared in cooperation with the Arkansas Natural Resources Commission and the Arkansas Geological Survey

Potentiometric Surfaces and Water-Level Trends in the Cockfield (Upper Claiborne) Aquifer in Southern Arkansas and the Wilcox (Lower Wilcox) Aquifer of Northeastern and Southern Arkansas, 2012

94º 93º MISSOURI 92º 91º

ARKANSAS CLAY

GREENE 90º 36º OZARK PLATEAUS CRAIGHEAD TENNESSEE MISSISSIPPI POINSETT OKLAHOMA Arkansas Valley S CROSS D N LA OUACHITA H G ST. FRANCIS I CRITTENDEN 35º PROVINCE IN H A PL LEE L A Mississippi Alluvial Plain INTERIORST Ouachita Mountains OA C Mississippi River

HOT SPRING ARKANSAS GRANT MISSISSIPPI JEFFERSON

34º DALLAS CLEVELAND CLARK LINCOLN

DESHA

OUACHITA NEVADA DREW HEMPSTEAD CALHOUN TEXAS BRADLEY West Gulf Coastal Plain CHICOT ASHLEY COLUMBIA UNION

LOUISIANA Scientific Investigations Report 2014–5232

U.S. Department of the Interior U.S. Geological Survey

Potentiometric Surfaces and Water- Level Trends in the Cockfield (Upper Claiborne) Aquifer in Southern Arkansas and the Wilcox (Lower Wilcox) Aquifer of Northeastern and Southern Arkansas, 2012

By Kirk D. Rodgers

Prepared in cooperation with the Arkansas Natural Resources Commission and the Arkansas Geological Survey

Scientific Investigations Report 2014–5232

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

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Suggested citation: Rodgers, K.D., 2015, Potentiometric surfaces and water-level trends in the Cockfield (upper Claiborne) aquifer in southern Arkansas and the Wilcox (lower Wilcox) aquifer of northeastern and southern Arkansas, 2012: U.S. Geological Survey Scientific Investigations Report 2014–5232, 46 p., http://dx.doi.org/10.3133/sir20145232.

ISSN 2328-0328 (online) iii

Contents

Abstract ...... 1 Introduction ...... 2 Methods ...... 4 Water-Level Measurements ...... 4 Linear Regression ...... 4 Geographic Information Systems ...... 4 Cockfield (Upper Claiborne) Aquifer ...... 6 Hydrogeologic Setting ...... 6 Hydraulic Properties ...... 6 Water Use ...... 8 Potentiometric Surface ...... 9 Water-Level Trends ...... 9 Water-Level Difference from 2006 to 2012 ...... 9 Long-Term Hydrographs ...... 12 Wilcox (Lower Wilcox) Aquifer ...... 19 Hydrogeologic Setting ...... 19 Hydraulic Properties ...... 20 Water Use ...... 20 Potentiometric Surface ...... 20 Water-Level Trends ...... 23 Water-Level Difference from 2006 to 2012 ...... 23 Long-Term Hydrographs ...... 23 Summary ...... 33 References Cited ...... 34 Appendixes 1. Water-level data collected during February 2012 from wells completed in the Cockfield aquifer in southern Arkansas ...... 39 2. Difference in depth to water from 2006 to 2012 in the Cockfield aquifer in southern Arkansas ...... 41 3. Water-level data collected during February and March 2012 from wells completed in the Wilcox aquifer in northeastern Arkansas ...... 42 4. Water-level data collected during February and March 2012 from wells completed in the Wilcox aquifer in southern Arkansas ...... 43 5. Difference in depth to water from 2006 to 2012 in the Wilcox aquifer in northeastern Arkansas ...... 44 6. Difference in depth to water from 2006 to 2012 in the Wilcox aquifer in southern Arkansas ...... 45 iv

Figures

1. Map showing location of study area of Cockfield aquifer in southern Arkansas and Wilcox aquifer in northeastern and southern Arkansas ...... 3 2. Diagram showing well-numbering system ...... 5 3. Diagram showing generalized section of the hydrogeologic and geologic units within the Mississippi Embayment ...... 8 4. Bar graph showing water use from the Cockfield aquifer in southern Arkansas, 1975–2010 ...... 8 5. Map showing potentiometric surface of the Cockfield aquifer in southern Arkansas, 2012 ...... 10 6. Map showing water-level difference for the Cockfield aquifer in southern Arkansas, 2006–12 ...... 11 7. Water-level hydrographs for selected wells completed in the Cockfield aquifer in southern Arkansas ...... 13 8. Bar graph showing water use from the Wilcox aquifer in Arkansas, 1975–2010 ...... 20 9. Map showing potentiometric surface of the Wilcox aquifer in northeastern Arkansas, 2012 ...... 21 10. Map showing potentiometric surface of the Wilcox aquifer in southern Arkansas, 2012 ...... 22 11. Map showng water-level difference for the Wilcox aquifer in northeastern Arkansas, 2006–12 ...... 24 12. Map showng water-level difference for the Wilcox aquifer in southern Arkansas, 2006–12 ...... 25 13. Water-level hydrographs for selected wells completed in the Wilcox aquifer in northeastern Arkansas ...... 26 14. Water-level hydrographs for selected wells completed in the Wilcox aquifer in southern Arkansas ...... 30

Tables

1. Hydrogeologic and geologic units within the Mississippi Embayment of Arkansas ...... 7 2. Range, mean, and median of annual rise or decline in water level by county for wells with 20 or more years of record completed in the Cockfield aquifer in Arkansas ...... 19 3. Range, mean, and median of annual rise or decline in water level by county for wells with 20 or more years of record completed in the Wilcox aquifer in Arkansas ...... 32 v

Conversion Factors

Inch/Pound to International System of Units

Multiply By To obtain Length foot (ft) 0.3048 meter (m) mile (mi) 1.609 kilometer (km) Flow rate foot per year (ft/yr) 0.3048 meter per year (m/yr) gallon per minute (gal/min) 0.06309 liter per second (L/s) million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s) Specific capacity gallon per minute per foot 0.2070 liter per second per meter [(gal/min)/ft)] [(L/s)/m] Transmissivity* foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d)

Datum

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD of 1929) Horizontal coordinate information is referenced to North American Datum of 1983 (NAD 83).

Supplemental Information

Altitude, as used in this report, refers to distance above the vertical datum. *Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot squared per day (ft2/d), is used for convenience.

Potentiometric Surfaces and Water-Level Trends in the Cockfield (Upper Claiborne) Aquifer in Southern Arkansas and the Wilcox (Lower Wilcox) Aquifer of Northeastern and Southern Arkansas, 2012

By Kirk D. Rodgers

Abstract Arkansas is defined by observation wells completed in the Wilcox aquifer or by areas that contain outcrops of the Wilcox The Cockfield aquifer, located in southern Arkansas, is Group, or both. composed of Eocene-age sand beds found near the base of the The potentiometric-surface map of the Cockfield Cockfield Formation of Claiborne Group. The Wilcox aquifer, aquifer shows the regional direction of groundwater flow located in northeastern and southern Arkansas, is composed was generally toward the east-southeast, except in areas of of Paleocene-age sand beds found in the middle to lower part intense groundwater withdrawals such as southwestern Ashley of the Wilcox Group. The Cockfield and Wilcox aquifers are County, where groundwater flows toward the town of Crossett. primary sources of groundwater. In 2010, withdrawals from The highest water-level altitude measured was 350 feet (ft) the Cockfield aquifer in Arkansas totaled 19.2 million gallons above National Geodetic Vertical Datum of 1929 (NGVD 29) per day (Mgal/d), and withdrawals from the Wilcox aquifer in central Columbia County. The lowest water-level altitude totaled 36.5 Mgal/d. measured was 40 ft above NGVD 29 in southeastern Lincoln A study was conducted by the U.S. Geological Survey in County. cooperation with the Arkansas Natural Resources Commission The water-level difference map for the Cockfield and the Arkansas Geological Survey to measure water levels aquifer in Arkansas was constructed using 42 water-level associated with the Cockfield aquifer and the Wilcox aquifer measurements made during 2006 and 2012. The difference in in northeastern and southern Arkansas. Water levels were water levels for the Cockfield aquifer ranged from 27.4 ft to measured at 43 wells completed in the Cockfield aquifer -10.4 ft. The largest water-level rise was in Calhoun County, and 47 wells completed in the Wilcox aquifer in February and the largest water-level decline was 10.4 ft in Union and March 2012. Measurements from 2012 are presented County. Of the 42 wells, 13 wells had a rise in water level, and as potentiometric-surface maps and in combination with the remaining 29 wells had a decline in water level. measurements from 2006 as water-level difference maps. Hydrographs for 32 wells in the Cockfield aquifer Trends in water-level change over time within the Cockfield with historical water-level data were evaluated using linear and Wilcox aquifers were determined using the water-level regression to calculate the annual rise or decline for each difference maps and selected well hydrographs. well. These data were aggregated by county and statistically The Cockfield aquifer study area in southern Arkansas evaluated for the range, mean, and median of water-level is bounded on the east by the Mississippi River and on the change in each county. Hydrographs for Bradley, Calhoun, west by the area that contains outcrops and subcrops of the Chicot, Columbia, and Union Counties indicated both rising Cockfield Formation. The northern boundary of the Cockfield and declining water levels. The mean annual water-level rise aquifer study area is defined by the area that contains or decline for Calhoun County was 0.00 foot per year (ft/yr) or observation wells completed in the Cockfield aquifer and the unchanged. The mean annual water-level for Ashley, Bradley, southern boundary is the Louisiana State line. Chicot, Cleveland, Columbia, Lincoln, and Union Counties The Wilcox aquifer study area in northeastern Arkansas show declines ranging from -0.02 to -1.10 ft/yr. is bounded on the east by the Mississippi River and on the Two potentiometric-surface maps, one for the southern north by the Missouri State line. The southern and western area and one for the northeastern area, were constructed to boundaries are defined by areas containing observation wells show the altitude of the water surface in the Wilcox aquifer. completed in the Wilcox aquifer or by outcrop areas on or near The direction of groundwater flow in the northeastern area was Crowleys Ridge. The Wilcox aquifer study area in southern generally towards the south-southwest except for some areas 2 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012 immediately adjacent to the Mississippi River where the flow withdrawals from the Cockfield aquifer in Arkansas totaled was more eastward towards the river. The highest water-level 19.2 million gallons per day (Mgal/d), and withdrawals from altitude was 219 ft in northern Mississippi County, and the the Wilcox aquifer totaled 36.5 Mgal/d. In 2010, the Cockfield lowest water-level altitude was 123 ft near West Memphis in aquifer in Arkansas ranked fifth in combined usage for the Crittenden County. The direction of groundwater flow in the State, and the Wilcox aquifer ranked third. northern part of the southern area was generally towards the A study was conducted by the U.S. Geological Survey southwest. The direction of groundwater flow in the southern (USGS) in cooperation with the Arkansas Natural Resources part was in all directions because of two cones of depression Commission and the Arkansas Geological Survey to determine and two water-level mounds. The highest water-level altitude water levels associated with the Cockfield aquifer in southern measured was 394 ft at the center of a water-level mound Arkansas and the Wilcox aquifer in northeastern and southern in eastern Hot Spring County and a water-level mound in Arkansas. In February and March 2012, water levels were southwestern Hempstead County. The lowest water-level measured at 43 wells completed in Cockfield aquifer and altitude measured was 145 ft at the center of the cone of 47 wells completed in the Wilcox aquifer. These water-level depression in Clark County. measurements are presented as potentiometric-surface maps, Water-level difference maps for the Wilcox aquifer in in combination with measurements from 2006 as water-level Arkansas were constructed using 47 water-level measurements difference maps, and in long-term hydrographs. made during 2006 and 2012. The difference in water levels The study areas of the Cockfield and Wilcox aquifers for the Wilcox aquifer in the northeastern area ranged from are part of the Mississippi Embayment that includes much 22.0 ft to -17.9 ft. The largest rise in water level occurred in of the West Gulf Coastal Plain and the Mississippi Alluvial Crittenden County, and the largest decline occurred in Lee Plain in Arkansas (fig. 1). The Mississippi Embayment is a County. Twenty-one wells had rising water levels, and 10 north-northeast trending syncline, plunging south-southwest, wells had declining water levels. The difference in water levels and is filled with Cretaceous and younger-age sediments. for the Wilcox aquifer in the southern area ranged from 18.1 ft The study area of the Cockfield aquifer in southern Arkansas to -4.2 ft. The largest rise and the largest decline in water level is bounded on the east by the Mississippi River and on the occurred in Nevada County. Twelve wells had rising water west by the area that contains outcrops and subcrops of the levels, and 4 wells had declining water levels. Cockfield Formation (Hosman, 1982). The northern boundary Linear regression analysis of long-term hydrographs was of the Cockfield aquifer study area is defined by the locations used to determine the mean annual water-level rise and decline of observation wells completed in the Cockfield aquifer, and in the Wilcox aquifer in the northeastern and southern areas the southern boundary is the Louisiana State line (fig. 1). of Arkansas. In the northeastern area, the mean annual water The Wilcox aquifer study area in northeastern Arkansas is level declined in all seven counties. The mean annual declines bounded on the east by the Mississippi River and on the ranged from -0.55 ft/yr in Craighead County to -1.46 ft/yr in north by the Missouri State line. The southern and western St. Francis County. In the southern area, the annual rise and boundaries are defined by areas containing observation decline calculations for wells with over 20 years of records wells completed in the Wilcox aquifer or by outcrop areas indicate rising and declining water levels in Clark, Hot Spring, in or near Crowleys Ridge. Crowleys Ridge is an erosional and Nevada Counties. The mean annual water level declined remnant of Cretaceous- and Tertiary-age rocks that ranges in all counties except Hot Spring County. from 0.5 to 12 miles (mi) wide, rises 250 to 550 feet (ft) above the surrounding Mississippi Alluvial Plain, and extends about 150 mi from southeastern Missouri to east-central Introduction Arkansas. The Wilcox aquifer study area in southern Arkansas is defined by observation wells completed in the Wilcox The Cockfield aquifer (recognized nationally as the aquifer or by areas that contain outcrops of the Wilcox Group, Upper Claiborne aquifer), located in southern Arkansas, is or both. composed of Eocene-age sand beds found near the base of This is the sixth in a series of triennial reports discussing the Cockfield Formation of Claiborne Group. The Middle the potentiometric surfaces of the Cockfield and Wilcox and Lower Wilcox aquifer (recognized nationally as the aquifers in Arkansas. Earlier reports, with water-level lower Wilcox aquifer), located in northeastern and southern measurements made in 1991, 1996–97, 2000, 2003, 2006, Arkansas, is composed of Paleocene-age sand beds found in and 2009 are reported in Westerfield (1994), Joseph (1998), the lower part of the Wilcox Group. The Cockfield and Wilcox Schrader and Joseph (2000), Yeatts (2004), Schrader (2007), aquifers are sources of groundwater for local use. In 2010, and Pugh (2010). Introduction 3

94º 93º MISSOURI 92º 91º

ARKANSAS CLAY

HOT SPRING ARKANSAS GRANT MISSISSIPPI JEFFERSON

34º DALLAS CLEVELAND CLARK LINCOLN

DESHA

OUACHITA NEVADA DREW HEMPSTEAD CALHOUN TEXAS BRADLEY West Gulf Coastal Plain CHICOT ASHLEY COLUMBIA UNION

LOUISIANA

Base from U.S. Geological Survey Physiographic division boundaries digital data, 1:100,000 from Fenneman and Johnson (1946) 0 20 40 MILES

0 20 40 KILOMETERS

EXPLANATION

Aquifer Crowleys Ridge

Cockfield aquifer in southern Arkansas Physiographic division boundary Major Division Wilcox aquifer in southern Arkansas Province Wilcox aquifer in northeastern Arkansas Section

Figure 1. Location of study area of Cockfield aquifer in southern Arkansas and Wilcox aquifer in northeastern and southern Arkansas. 4 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

Methods Water-level difference maps for the Cockfield and Wilcox aquifers in Arkansas were constructed using the differences The well-numbering system used in this report is based between depth-to-water measurements made during 2006 on location of wells according to the Public Land Survey and 2012. The difference in water level was calculated by System used in Arkansas (U.S. Geological Survey, 2014). subtracting the 2012 depth-to-water value from the 2006 The component parts of a well number are the township depth-to-water value for each individual well. Positive number, the range number, the section number, three letters difference values indicate a rise in water level, and negative which indicate, respectively, the quarter section, the quarter- difference values indicate a decline in water level. quarter section, and the quarter-quarter-quarter section in which the well is located, and a sequence number. The letters Linear Regression are assigned counterclockwise, beginning with “A” in the northeast quarter, quarter-quarter, or quarter-quarter-quarter A linear regression analysis was used to determine the section in which the well is located. For example, well annual rise or decline of water level in selected wells using 01S03W04BBD16 (fig. 2) is located in Township 1 South, the well hydrograph. Water-level measurements made yearly Range 3 West, and in the southeast quarter of the northwest during March, April, and May of the minimum 20-year period quarter of the northwest quarter of section 4. This well is the of record were used in the linear regression analysis. The 16th well in this quarter-quarter-quarter section of section 4 equation of the regression line or line of best fit is Y = MX from which data were collected (Pugh, 2010). + B. The slope, M from the equation, represents the daily The horizontal coordinate information (latitude and rise or decline in water level, B is the water level measured longitude) of a well was determined using a global positioning in feet at the y-intercept and X is the year in which the system, and land-surface altitude information was determined measurement was made. Five assumptions are associated using a USGS 7.5-minute, 1:24,000 quadrangle topographic with linear regression: (1) Y is linearly related to X, (2) data map. The horizontal coordinate information is based on the used to fit the linear regression are representative of data of North American Datum of 1983 and is accurate to about one- interest, (3) variance of the residuals is constant and does tenth of a second (approximately 10–20 ft). The location of not depend on X or on anything else, (4) the residuals are the well was then plotted on the corresponding topographic independent, and (5) the residuals are normally distributed. map and the land-surface altitude at that point was determined The assumption of a normal distribution is involved only when by interpolation of the topographic contours. This altitude testing hypotheses, requiring the residuals from the regression is accurate to about one-half the contour interval of the equation to be normally distributed (Helsel and Hirsch, topographic map, which is based on the National Geodetic 1992). Water-level measurements collected during February Vertical Datum of 1929 (NGVD 29). and March of 2006 and 2012 were used for linear regression analysis.

Water-Level Measurements Geographic Information Systems

Water levels were measured by USGS personnel at Longitudes, latitudes, and measured water-level altitudes public water-supply, industrial, commercial, domestic, and of the Cockfield and Wilcox aquifer wells were obtained observation wells completed in the Cockfield or Wilcox from NWIS and geocoded using ArcGIS (Esri, 2011), which aquifers. Measurements were made using steel or electric is a computer-based application used to visually represent field tapes graduated to hundredths of a foot. The steel and spatially based data using geographic coordinates. These data electric tapes used by USGS personnel were calibrated during points were then interpolated using the kriging method of January 2010, prior to collecting water-level measurements. interpolation to construct potentiometric-surface maps of the Calibration of steel and electric tapes was performed by Cockfield and Wilcox aquifers. This process produces a raster comparing the field steel or electric tape to a standardized image in which each color represents a range of water-level steel tape used only for calibration of field tapes. The water- values. The raster images were then converted to contour lines level data are stored in the USGS National Water Information using the ArcGIS Contour tool. Upon conversion, the contour System (NWIS) (U.S. Geological Survey, 2002). polylines were corrected and refined using the Polynomial Potentiometric-surface maps for the Cockfield and Approximation with Exponential Kernel (PAEK) method of Wilcox aquifers in Arkansas were constructed by plotting smoothing (Bodansky and others, 2002). The PAEK method well positions with their respective water-level altitude uses a maximum allowable offset to smooth lines. PAEK is using ArcGIS (Esri, 2011). The altitude of the water level a smoothing algorithm that sets a tolerance by which lines in each well was determined by subtracting the measured are smoothed. A higher tolerance preserves less detail from depth to water from the land-surface altitude. The direction the original interpolated contour line, and a lower tolerance of groundwater flow is perpendicular to the contours in the preserves more detail. This method allows for the preservation direction of decreasing water level. of end points. Methods 5

B WELL 01S03W04BBD16 C B A D C B A B D B C C A C A A D B D SECTION: 04 C DD A D

6 7 5 18 8 4 19 17 9 3 30 20 16 10 2 31 29 21 15 11 1 32 28 22 14 12 RANGE: 3303 West 27 23 13 34 26 24 35 25 36 TOWNSHIP: 01 South

N W

S E

BASE LINE

4N 5W 3N 4W 2N 3W 1N 2W PRINCIPAL MERIDIAN 1S 1W 2S 3S 1E WEST EAST 4S 2E SOUTH NORTH 5S 3E 6S 4E 7S 5E RANGES 8S 6E TOWNSHIPS

Figure 2. Well-numbering system. 6 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

Cockfield (Upper Claiborne) Aquifer alluvium overlies the formation in some of the larger river valleys A generalized section of the hydrogeologic and geologic units within the Mississippi Embayment are shown in Hydrogeologic Setting figure 3. Most of the Cockfield aquifer recharge occurs by The Cockfield aquifer generally consists of discontinuous infiltration of rainfall on the upland outcrop areas and by fine- to medium-grained sand units interbedded with silt, inflow from the overlying alluvium or rivers that have eroded clay, and lignite of nonmarine origin. Most of the sand beds through the overburden connecting them hydrologically with of the Cockfield aquifer are located near the base of the the aquifer. Discharge from the aquifer is to hydrologically Cockfield Formation of Claiborne Group (hereafter referred connected rivers in the outcrop areas, vertically to adjacent to as Cockfield Formation) (table 1). The Cockfield Formation hydrogeologic units where the aquifer is confined, and to wells ranges from 100 to 400 ft thick in the outcrop areas and completed in the aquifer (Ackerman, 1987). In the outcrop thickens downdip to about 625 ft in northeastern Chicot areas, well depths in the aquifer are less than 200 ft and well County (Onellion and Criner, 1955). The Cockfield Formation yields are small, usually less than 30 gallons per minute (gal/ dips to the south and east towards the synclinal axis of the min), but in areas downdip from the outcrop areas, wells Mississippi Embayment (fig. 3). Thicknesses of the sand screening the full thickness of the aquifer may yield from 100 beds of the Cockfield aquifer generally range from 20 to 150 to 500 gal/min (Westerfield, 1994). ft. Throughout the study area, the Cockfield Formation is underlain by calcareous and sandy marl, carbonaceous clay, Hydraulic Properties and limestone of the Cook Mountain Formation of Claiborne Group (table 1). In much of the study area, the Cockfield Values for specific capacity and transmissivity vary Formation is overlain by silty clays of the Jackson Group. within the Cockfield aquifer. Specific capacity values The potentiometric surface can be near or above land range from 0.15 gallon per minute per foot [(gal/min)ft)] surface in the confined part of the Cockfield aquifer. Sand beds to 23.7 (gal/min)/ft with a median of 0.76 (gal/min)/ft. at the base of the overlying Jackson Group in parts of southern Transmissivity values range from 325 feet squared per day Arkansas may be in hydraulic connection with the Cockfield (ft2/d) to 6,280 ft2/d with a median of 3,350 ft2/d and a mean of aquifer (Ackerman, 1987). The Cockfield Formation and 3,300 ft2/d. Hydraulic conductivity values were not provided aquifer outcrop in Bradley, Calhoun, Cleveland, Columbia, for any of the well tests completed in the Cockfield aquifer. Dallas, Grant, and Union Counties and dips to the southeast. An estimated hydraulic conductivity value for the Cockfield In the subcrop area, Quaternary-age terrace deposits and aquifer was determined by dividing the mean transmissivity alluvium overlie the Cockfield Formation. The thickness value (3,300 ft2/d) by the maximum aquifer thickness (400 ft), of terrace deposits may reach 40 ft, and as much as 60 ft of resulting in a value of 8.33 ft/d (Pugh, 2008). Cockfield (Upper Claiborne) Aquifer 7

Table 1. Hydrogeologic and geologic units within the Mississippi Embayment of Arkansas (modified from Hosman and Weiss, 1991; Hart and others, 2008).

[Dashed lines indicate the approximate location where hydrogeologic units begin and end]

Geologic unit Hydrogeologic

Group unit Series Southern Northeastern System Erathem Arkansas Arkansas Holocene Mississippi River Valley Alluvium and terrace deposits alluvial aquifer Quaternary Pleistocene

Not present in study areas Vicksburg Oligocene Vicksburg-Jackson confining unit

Jackson Formation Jackson

Upper Claiborne aquifer Cockfield Formation (Cockfield aquifer)

Middle Claiborne Cook Mountain Formation confining unit Cenozoic Sparta Sand Eocene

Lower Claiborne Cane River Claiborne Middle Tertiary Formation confining Memphis Sand Claiborne unit aquifer

Lower Carrizo Sand Claiborne aquifer

Flour Island Middle Wilcox aquifer Formation

Undifferentiated Fort Pillow Sand Wilcox Lower Wilcox aquifer Old Breastworks Formation Upper Paleocene

Midway Group Midway confining unit 8 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

WEST EAST

OUTCROP OUTCROP MISSISSIPPI RIVER VALLEY AREA ALLUVIAL AQUIFER AREA GRAVEL DEPOSITS LOESS, SILT, SAND, UNIT V NING IC NFI KSB CO URG–JACKSON

UPPER CLAIBORNE AQUIFER M T I (Cockfield aquifer) I D UN DL G E NIN CLA NFI IBORN E CO

MIDDLE CLAIBORNE AQUIFER MIDWAY MIDWAY CONFINING UNIT CONFINING UNIT LOW ER IT C UN LA G IBO IN RNE FIN LO CON ER WE UIF EXPLANATION R CLAIBORNE AQ Generalized groundwater LOWER WILCOX AQUIFER flow direction

NOT TO SCALE Geology modified from Arthur and Taylor (1990)

Figure 3. Generalized section of the hydrogeologic and geologic units within the Mississippi Embayment.

Water Use U.S. Geological Survey, written commun., 2009) and decreased by 50 percent between 2005 and 2010 (D.E. Burt, Withdrawals from the Cockfield aquifer during 2010 U.S.Geological Survey, written commun., 2013). The large totaled about 19.2 Mgal/d (Terrance W. Holland, U.S. amount of water withdrawn in Mississippi from the aquifer Geological Survey written commun., 2013) (fig. 4). These probably contributed to lower water levels in southeastern withdrawals were primarily for industrial and public supply Arkansas (Ackerman, 1987; Joseph, 1998; Schrader and use, but withdrawals for agricultural, commercial, and Joseph, 2000; Yeatts, 2004; Pugh, 2010). domestic use are important locally. Withdrawals from the Cockfield aquifer rose from 1975 to 2010, with the exception of 1985. Withdrawals were 5.2 Mgal/d in 1975, 7.2 Mgal/d in 1980, 5.0 Mgal/d in 1985, 8.1 Mgal/d in 1990, 9.8 Mgal/d in 22

1995, 9.9 Mgal/d in 2000, and 16.1 Mgal/d in 2005 (Halberg 20 19.2 and Johnson, 1977; Holland and Ludwig, 1981; Holland, 18 1987, 1993, 1999, 2004, 2007). The increase in withdrawals 16.1 from the Cockfield aquifer between 2000 (9.9 Mgal/d) and 16 2005 (16.1 Mgal/d) are associated with increased use of 14 water by public water-supply systems in eastern Arkansas 12 (Holland, 2004, 2007; Pugh, 2010), and the increase in 9.9 withdrawals from the aquifer between 2005 (16.1 Mgal/d) and 10 9.8 8.1 2010 (19.2 Mgal/d) are associated with increased industrial 8 7.2 use of water in eastern Arkansas (Terrance W. Holland, U.S. 6 Geological Survey written commun., 2013). Most wells 5.2 5.0 completed in the study area provide small volumes of water Water use, in million gallons per day 4 for domestic and livestock use, but in some locations, the 2 aquifer yields volumes large enough to supply industrial and 0 public-supply systems. 1975 1980 1985 1990 1995 2000 2005 2010 In 2010, the State of Mississippi withdrew 22.8 Mgal/d Year of water from the Cockfield aquifer. Across the State line from Data compiled from Halberg and Johnson (1977), Holland and Ludwig (1981), and Holland (1987, Chicot County, Ark., the city of Greenville, Miss., withdrew 1993, 1999, 2004, 2007, Terrance W. Holland, 10.4 Mgal/d of water for public supply from the Cockfield U.S. Geological Survey, written commun., 2010) aquifer in 2010 (D.E. Burt, U.S. Geological Survey, written commun., 2013). Withdrawals from the aquifer in Mississippi Figure 4. Water use from the Cockfield aquifer in southern rose 170 percent between 1999 and 2005 (D.E. Burt, Arkansas, 1975–2010. Cockfield (Upper Claiborne) Aquifer 9

Potentiometric Surface short-term (6 years) changes in water levels (fig. 6). The map was constructed using the difference between water-level The potentiometric-surface map shows the altitude of the measurements made in 2006 and 2012 in 42 wells (app. 2). water surface in tightly cased wells screened in the Cockfield Positive values, represented with blue, upward pointing aquifer in the study area (fig. 5). Water-level data used to triangles, indicate a rise in water levels between 2006 and construct the map are shown in appendix 1. 2012; negative values, represented with red, downward The potentiometric surface of the Cockfield aquifer pointing triangles, indicate a decline in water levels between in 2012 shows the regional direction of groundwater flow 2006 and 2012. The triangles are scaled in size to the relative generally is towards the east-southeast, except in areas of value of rise or decline. The 2006 to 2012 water-level intense groundwater withdrawals, such as southwestern difference map indicates short-term changes and may not Ashley County where groundwater flows toward the town represent long-term trends. of Crossett. In southern Columbia County, a trough in the The 2006 to 2012 difference in water levels for the potentiometic surface exists, which locally alters the flow Cockfield aquifer ranged from 27.4 to -10.4 ft (fig. 6). The of groundwater. This trough may indicate the formation of a largest water-level rise was in Calhoun County, and the largest cone of depression. In northeastern Drew County and northern water-level decline was in Union County (app. 2). Of the Chicot County, groundwater flow is towards the northeast, and 42 wells, 13 wells had a rise in water levels, and the remaining in southeastern Lincoln County, groundwater flow is towards 29 wells had a decline in water levels from 2006 to 2012. the east. The highest water-level altitude measured was 350 ft Rises in water levels occurred in Ashley, Bradley, Calhoun, above NGVD 29 in central Columbia County. This elevated Chicot, Cleveland, Columbia, Drew, and Union Counties and water-level altitude is the result of the well being located on ranged from 27.4 ft in Calhoun County to 0.2 ft in Bradley a higher land-surface altitude in the outcrop area. The lowest County. Declines in water levels ranged from -0.3 ft in water-level altitude measured was 40 ft above NGVD 29 in Calhoun and Columbia Counties to -10.4 ft in Union County, southeastern Lincoln County. and most were less than -5.0 ft. East of the Saline River, water levels declined in 12 of the 16 wells between 2006 and 2012. In Ashley County, 6 of Water-Level Trends the 7 wells had declines in water levels. Eleven of the 15 wells located between the Saline and Ouachita Rivers had declines in water levels, and 6 of the 11 wells west of the Ouachita Water-Level Difference from 2006 to 2012 River had declines in water levels for the period between 2006 A water-level difference map for the Cockfield aquifer and 2012. in the study area was constructed to spatially evaluate

10 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

s i M Greenville, Mississippi 91°00' 40 MILES D 91 86 73 DESHA CHICOT 83 66 75 81 ARKANSAS 84 A 88 80 84 91°30' 60 C 40 40

E 60 34°30' 99 98

80 ASHLEY LINCOLN 0 10 20 30 0 10 20 30 40 KILOMETERS DREW 61 80 Crossett B 92°00'

JEFFERSON 102 100

F 95

120

268 140 111

BRADLEY 108 160 107

CLEVELAND 180 232 200

G 220

240 140 260 131 175 209 194 Moro Creek 257

Saline River J 124 H GRANT 153 193 133 92°30' UNION 119 160 192

180 199 CALHOUN

DALLAS 200 K

220 230

Ouachita River 240

260

222 34°00' 280

93°00' OUACHITA

300

320 340 290 L 33°30'

350 280 260 256 260 308 COLUMBIA Base modified from U.S. Geological Survey digital data Area enlarged EXPLANATION P otentiometric surface of the Cockfield aquifer in southern Arkansas, 2012. General direction of groundwater flow Outcrop of the Cockfield Formation (modified from Hosman, 1988) Well completed in Cockfield aquifer —Number Well where present, altitude. Letter, is water-level corresponds to hydrograph in ﬁgure 7 Potentiometric contour —Shows altitude at which water level would have stood in tightly cased wells. Dashed where approximately located. Contour interval 20 feet. Datum is Datum of 1929 National Geodetic Vertical

ARKANSAS ARKANSAS 81 200 A Figure 5.

Cockfield (Upper Claiborne) Aquifer 11

s i M Greenville, Mississippi 91°00' 40 MILES 1.8 DESHA -9.8 -0.9 CHICOT -0.5 -3.6 -5.6 ARKANSAS 1.5 -8.0 91°30' -5.7 -5.4 -5.0 -4.0 34°30' 3.4 -3.6 ASHLEY LINCOLN 0 10 20 30 0 10 20 30 40 KILOMETERS DREW -7.3 Crossett 92°00' JEFFERSON -0.9 -1.7 2.2 9.6 BRADLEY -3.0 -3.1 -0.9 -1.6 CLEVELAND 4.7 0.2 0.6 -1.3 Saline River Moro Creek -0.4 -0.6 -1.2 -1.9 -0.3 GRANT 92°30' 27.4 UNION 18.5 CALHOUN -1.4 DALLAS 0.9

Ouachita River -10.4 34°00' 93°00' OUACHITA 4.4 -0.3 33°30' 3.2 -2.0 -2.3 COLUMBIA Base modified from U.S. Geological Survey digital data Area enlarged EXPLANATION ater-level difference for the Cockfield aquifer in southern Arkansas, 2006–12. ater-level W Outcrop of Cockfield Formation (modified from Hosman, 1988) completed in Cockﬁeld aquifer —Value Well is rise in water level from 2006 to 2012, feet. Symbols are scaled to value completed in Cockﬁeld aquifer —Value Well is decline in water level from 2006 to 2012, in feet. Symbols are scaled to value

ARKANSAS ARKANSAS * 2.2 -1.7 Figure 6. 12 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

Long-Term Hydrographs in figures 7A–E. These hydrographs indicate changes in water levels ranging from a rise of approximately 0.5 ft (well Two methods were used to evaluate long-term water-level 18S02W25ABB3, fig. 7D) to a decline of approximately 57 ft trends for the Cockfield aquifer in Arkansas. The first method (well 10S05W06CAC1, fig. 7E) over the period of record. was to use the hydrograph for a well with a minimum of 20 Hydrographs for wells located in Bradley, Calhoun, and years of record and plot the water levels in relation to time. part of Cleveland Counties, the area between the Saline and Hydrographs of selected wells are shown in figure A7 –L. The Ouachita Rivers, are shown in figures F7 –I. These wells are selected well locations are plotted on figure 5. The second screened in confined and unconfined areas of the Cockfield method evaluated the annual rise or decline in water levels aquifer. The hydrographs indicate rises and declines in water over a 20-year or more period through 2012, using the line levels ranging from a decline of approximately 23 ft (well of best fit (Y = MX + B) and residual (R2). The coefficient of 14S10W31DBA1, fig 7F) to a rise of approximately 1 ft (well determination (R2) is a measure of how close the data are to 15S12W11CAB1, fig. 7G) over the period of record. the line of best fit. Hydrographs for wells located in Union and Columbia Hydrographs for 32 wells with historical water-level data Counties, the area west of the Ouachita River, are shown in in the Cockfield aquifer with a minimum of 20 years of water- figures 7J–L. The hydrographs indicate rises and declines level data were constructed and evaluated. The annual rise or over the period of record from a decline of approximately 5 ft decline in water levels was aggregated by county. The values (well 17S16W33BBA2, fig. K7 ) to a rise of approximately 2 ft for the range, mean, and median of water-level change were (well 17S13W17DDC1, fig. 7J). computed for each county (table 2). Hydrographs for the 32 wells with historical water- Analysis of selected hydrographs is divided into level data were evaluated using linear regression to calculate three geographic regions: the area east of the Saline River the annual rise or decline for each well, and the data were (Ashley, Chicot, Desha, Drew, Lincoln, and part of Cleveland aggregated by county and statistically evaluated for the range, Counties), the area between the Saline and Ouachita Rivers mean, and median of water-level change in each county (Bradley, Calhoun, and part of Cleveland Counties), and (table 2). Cleveland and Lincoln Counties had only one well the area west of the Ouachita River (Columbia and Union with a minimum of 20 years of record. Annual rise or decline Counties). The area east of the Saline River is confined by calculations associated with wells with more than 20 years of the overlying Jackson Group. The central area between the record in Ashley and Chicot Counties indicated a decline in Saline and Ouachita Rivers is a mixed area, the northern part water levels. Bradley, Calhoun, Columbia, and Union Counties is an outcrop area, the eastern part is confined by the Jackson indicate rising and declining water levels. The mean annual Group, and the southern part underlies Quaternary-age terrace water-level rise or decline for Calhoun County was 0.00 ft/yr deposits. The area west of the Ouachita River is in an outcrop or unchanged. The mean annual water-level data for Ashley, area with overlying Quaternary-age terrace deposits. Bradley, Chicot, Cleveland, Columbia, Lincoln, and Union Hydrographs for wells located in Ashley, Chicot, and Counties show declines ranging from -0.02 to -1.10 ft/yr. Lincoln Counties, east of the Saline River and screened within the confined part of the Cockfield aquifer, are shown Cockfield (Upper Claiborne) Aquifer 13

A. ASHLEY COUNTY 17S04W10BCD2 110

105

100

NO DATA 90 Geodetic Vertical Datum of 1929Datum of Geodetic Vertical Water level, in feet above above Nationalinlevel, feet Water 85

80 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013

Year

B. ASHLEY COUNTY 18S08W04BBC1 110

100

70 Geodetic Vertical Datum of 1929 of Datum Geodetic Vertical

Water level, in feet aboveNational aboveNational feet in level, Water NO DATA 60

50 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 7. Water-level hydrographs for selected wells completed in the Cockfield aquifer in southern Arkansas. 14 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

C. ASHLEY COUNTY 19S05W12CAC1 110

100

80 NO DATA

70 Geodetic Vertical Datum of 1929Datum of GeodeticVertical Water level, in feet above above Nationalin level, feet Water 60

50 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

D. CHICOT COUNTY 18S02W25ABB3 110

100

90 NO DATA

70 Geodetic Vertical Datum of 1929Datum of Geodetic Vertical Water level, in feet above above Nationalin level, feet Water

50 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 7. Water-level hydrographs for selected wells completed in the Cockfield aquifer in southern Arkansas.—Continued Cockfield (Upper Claiborne) Aquifer 15

E. LINCOLN COUNTY 10S05W06CAC1 110

100

60 NO DATA Geodetic Vertical Datum of 1929Datum of GeodeticVertical

Water level , in feet above feet ,above Nationallevel in Water 50

30 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

F. BRADLEY COUNTY 14S10W31DBA1 140

130

120

110

100 Geodetic Vertical Datum of 1292Datum of GeodeticVertical Water level, in feet above above Nationalin level, feet Water NO DATA 90

80 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 7. Water-level hydrographs for selected wells completed in the Cockfield aquifer in southern Arkansas.—Continued 16 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

G. BRADLEY COUNTY 15S12W11CAB1 150

140

130

NO DATA 120

110 Geodetic Vertical Datum of 1929Datum of Geodetic Vertical Water level, in feet above above Nationalin level, feet Water 100

90 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

H. CALHOUN COUNTY 14S13W29ADA1 180

170

160

150 NO DATA 140

Geodetic Vertical Datum of 1929Datum of GeodeticVertical 130 Water level, in feet above above Nationalin level, feet Water

120 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 7. Water-level hydrographs for selected wells completed in the Cockfield aquifer in southern Arkansas.—Continued Cockfield (Upper Claiborne) Aquifer 17

I. CLEVELAND COUNTY 11S11W23BBD1

250

240

230

NO DATA 220

210 Geodetic Vertical Datum of 1929Datum of GeodeticVertical Water level, in feet above above Nationalinlevel, feet Water 200

190 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

J. UNION COUNTY 17S13W17DDC1

180

170

160

150

NO DATA 140 Geodetic Vertical Datum of 1929Datum of GeodeticVertical Water level, in feet above above Nationalinlevel, feet Water 130

120 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 7. Water-level hydrographs for selected wells completed in the Cockfield aquifer in southern Arkansas.—Continued 18 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

K. UNION COUNTY 17S16W33BBA2 260

250

240

230

NO DATA 220 Geodetic Vertical Datum of 1929Datum of GeodeticVertical Water level, in feet above above Nationalin level, feet Water

210

200 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

L. COLUMBIA COUNTY 17S20W35BBD1

410

390

370

350

330 NO DATA Geodetic 1929Datum of Vertical Water level, in feet above feet above NationalWaterin level, 310

290 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 7. Water-level hydrographs for selected wells completed in the Cockfield aquifer in southern Arkansas.—Continued Wilcox (Lower Wilcox) Aquifer 19

Table 2. Range, mean, and median of annual rise or decline in water level by county for wells with 20 or more years of record completed in the Cockfield aquifer in Arkansas.

[Annual rise or decline in water level for each well is calculated using linear regression; negative value indicates decline; positive value indicates rise; R2, coefficient of determination]

Range of values of Mean annual rise (+) Median annual rise (+) annual rise (+) or Number or decline (-) in or decline (-) in Range of R2 values County decline (-) in of wells water level water level for trend lines water level (feet/year) (feet/year) (feet/year)

Ashley 6 -0.55 to -0.11 -0.32 -0.31 0.08 to 0.90 Bradley 4 -0.51 to 0.40 -0.04 -0.03 0.04 to 0.97 Calhoun 6 -0.11 to 0.22 0.00 -0.01 0.07 to 0.70 Chicot 3 -0.33 to -0.11 -0.19 -0.15 0.40 to 0.70 Cleveland 1 -0.04 -0.04 -0.04 0.16 Columbia 5 -0.11 to 0.04 -0.02 0.01 0.01 to 0.26 Lincoln 1 -1.10 -1.10 -1.10 0.84 Union 6 -0.18 to 0.11 -0.03 -0.02 0.001 to 0.85

Wilcox (Lower Wilcox) Aquifer In northeastern Arkansas, the Wilcox aquifer is overlain by a clay bed of the Wilcox Group and is underlain by a clay bed of the Wilcox Group or the Midway Group. Part of Hydrogeologic Setting the Wilcox aquifer, within Crowleys Ridge, is perched and hydrologically separated from the aquifer in the surrounding The Wilcox aquifer, in northeastern and southern Mississippi Alluvial Plain (fig. 1) (Petersen and others, Arkansas, is composed of the Wilcox Group and is distributed 1985). throughout the Mississippi Embayment. The Wilcox Group The Wilcox Group is composed of interbedded layers is part of a syncline approximately centered beneath the of clay, sandy clay, sand, and lignite in the southern area. Mississippi River that plunges to the south-southeast (fig. 3). The Wilcox Group overlies the Midway Group and underlies In the northeast part of Arkansas, the Wilcox Group is Quaternary-age terrace deposits and alluvium or crops out. composed of three units: the Flour Island Formation, the Fort The outcrop is generally thin and discontinuous over large Pillow Sand, and the Old Breastworks Formation; in southern areas. Downslope from the outcrop, the Wilcox Group Arkansas, the formation is undifferentiated (table 1). In central becomes thicker, ranging from a few feet in the outcrop areas Arkansas, the Wilcox aquifer is not extensively used, and to about 750 ft at the center of the syncline (Albin, 1964). water-level data are not sufficient to determine potentiometric Recharge to the Wilcox aquifer in the northeastern area surfaces. Because of the discontinuous nature of water-level occurs through infiltration of precipitation in outcrop areas data, the potentiometric-surface map of the Wilcox aquifer is along the western side of Crowleys Ridge. Discharge occurs divided into two areas—one in northeastern Arkansas and the mainly through well withdrawals (Westerfield, 1994). The second in southern Arkansas. depth of wells in this area ranged from 462 ft in Greene The Wilcox Group is composed of thin interbedded layers County to 1,885 ft in Lee County. Well yield ranged from of lignitic sand and clays in most of the northeastern area. The 100 to 2,000 gal/min (Schrader and Joseph, 2000). Wilcox Group crops out at or near Crowleys Ridge in Clay, Recharge to the Wilcox aquifer in the southern area Craighead, and Greene Counties (Broom and Lyford, 1981). occurs through infiltration of precipitation in outcrop areas East of Crowleys Ridge, the Wilcox Group (including the Fort and inflow from overlying alluvial and terrace deposits. Pillow Sand and the Old Breastworks Formation) contains Discharge occurs from flows into overlying formations, into a sand bed 200 ft or more in thickness (Petersen and others, streams in the outcrop area, and to wells (Westerfield, 1994). 1985) in the middle to lower part of the unit which is referred Well depths ranged from 14 ft within the recharge area in to as the “1,400-foot sand” (Ryling, 1960; Plebuch, 1961) Hempstead County to 533 ft in Ouachita County. Well yields or the “lower Wilcox aquifer” (Hosman and others, 1968). ranged from 10 to 100 gal/min (Schrader and Joseph, 2000). 20 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

Hydraulic Properties attributed to withdrawals by a power generation plant that was operating during this time period (Terrance W. Holland, U.S. Values for specific capacity and transmissivity vary Geological Survey written commun., 2009). The rise in water within the Wilcox aquifer. Pugh (2008) reported the following use from 2005 to 2010 was attributed to increased withdrawals values based on multiple-well aquifer tests and single-well for industry, irrigation, and public supply (Aaron L. Pugh, pump tests. Specific capacity values ranged from 0.25 (gal/ U.S. Geological Survey written commun., 2014). In the min)/ft to 641 (gal/min)/ft with a median of 21.1 (gal/min)/ft. northeastern area, the majority of water withdrawn from the Transmissivity values ranged from 30 ft2/d to 32,000 ft2/d with Wilcox aquifer was for public supply. The aquifer is also an a median of 8,170 ft2/d and a mean of 10,700 ft2/d. Hydraulic important source of water locally for agricultural, commercial, conductivity values could not be determined based on well and domestic use. In the southern area, the majority of water tests completed in the Wilcox aquifer. Pugh (2008) calculated withdrawn from the aquifer was for domestic use. an estimated hydraulic conductivity value of 9.7 ft/d for the Wilcox aquifer by dividing the mean transmissivity value (10,700 ft2/d) by the maximum aquifer thickness (1,100 ft). Potentiometric Surface Two potentiometric-surface maps, one for the Water Use northeastern area and one for the southern area, show the altitude of the water surface in the Wilcox aquifer (figs. 9 The majority of water withdrawals from the Wilcox and 10). The maps were constructed using water-level data aquifer were for industrial and public supply. Withdrawals collected in February and March 2012 from 47 wells; 31 wells for agricultural, commercial, and domestic use were less than in the northeastern area (app. 3) and 16 wells in the southern those for industrial and public supply but important locally. area (app. 4). Reported withdrawals from the Wilcox aquifer in Arkansas The direction of groundwater flow in the Wilcox aquifer totaled 36.5 Mgal/d during 2010 (fig. 8), most of which in the northeastern area in 2012 (fig. 9) was towards the south- occurred in the northeastern study area (Terrance W. Holland, southwest except for some areas immediately adjacent to the U.S. Geological Survey, written commun., 2012). Withdrawals Mississippi River where the flow was more eastward towards from 1975 through 2005 remained relatively constant, between the river. Groundwater withdrawals have altered the direction 21.0 Mgal/d and 27.0 Mgal/d, with the exception of 1990 and of flow near West Memphis (Joseph, 1998). The highest water- 1995 when 30.9 Mgal/d and 41.0 Mgal/d were withdrawn, level altitude was 219 ft in northern Mississippi County, and respectively. The rise in water use from 1990 to 1995 was the lowest water-level altitude was 123 ft near West Memphis in Crittenden County. In Greene County, a water-level altitude of 182 ft was measured near Crowleys Ridge. Within

50 Crowleys Ridge, the waters of the Wilcox aquifer are perched at higher altitudes than the surrounding Mississippi Alluvial 45 Plain and have too few control points for contouring. 41.0 40 The direction of groundwater flow in the southern area 36.5 (fig. 10) was generally towards the southwest in the northern 35 part. The direction of groundwater flow in the southern part 30.9 30 was in all directions because of two cones of depression and 27.0 25.7 two water-level mounds. The cones of depression are located 25 24.3 22.2 21.0 in southeastern Clark County and central Nevada County, 20 and the water-level mounds are located in Hot Spring County and Hempstead County (fig. 10). The water-level mounds are 15 the result of the higher land-surface altitudes in the outcrop 10 Water use, in million gallons per day Water area. Groundwater flow toward the cone of depression in southeastern Clark County was generally from the north, 5 south, and west; water flows toward the cone of depression in 0 1975 1980 1985 1990 1995 2000 2005 2010 Nevada County from all directions. Groundwater flow from Year the water-level mound in eastern Hot Spring County was

Data compiled from Halberg and Johnson (1977), generally to the north, south, and east; groundwater flows Holland and Ludwig (1981), and Holland (1987, from the water-level mound in southern Hempstead County 1993, 1999, 2004, 2007, Terrance W. Holland, to the south, east, and west. The highest water-level altitude U.S. Geological Survey, written commun., 2010) measured was 394 ft at the centers of the water-level mounds in eastern Hot Spring County and southwestern Hempstead Figure 8. Water use from the Wilcox aquifer in Arkansas, County. The lowest water-level altitude measured was 145 ft 1975–2010. at the center of the cone of depression in Clark County. Wilcox (Lower Wilcox) Aquifer 21

EXPLANATION

90° 30’ Crowleys Ridge (from Hosman, 1988) 36° 30’ 180 Potentiometric contour—Shows altitude at which water level would have stood in tightly cased wells. Dashed where approximately located. Contour interval 10 feet. CLAY Datum is National Geodetic Vertical Datum of 1929

General direction of groundwater flow

M ! Well completed in Wilcox aquifer, northeastern 200 Arkansas—Number is water-level altitude. Letter, GREENE where present, corresponds to hydrograph in figure 13

Paragould 182 O 90°00’ 36°00’ 219 197 205 206 91°00’ Q 210 M 205 200 200 193 197 203 CRAIGHEAD MISSISSIPPI 190 196 204 183 R 191 180

179 178 189 POINSETT 187 170 35° 30’ 166

165

163 CROSS CRITTENDEN ARKANSAS 170 176 N 148 Area enlarged 123 160

West Memphis 150 141

ST. FRANCIS 145 35°00’ 140 143 136 S 135 127 130

LEE

136 P 0 10 20 MILES

0 10 20 KILOMETERS

Figure 9. Potentiometric surface of the Wilcox aquifer in northeastern Arkansas, 2012. 22 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

34°30'

93°00' 342 V

340 394 360 HOT SPRING 380 360 340 320 267 92°30' 300 232 280

CLARK 260 34°00' 240 93°30' DALLAS L 210 i U tt le

M 160 is so 145T u ri Riv er 180 200 NEVADA 220 240 HEMPSTEAD 313 260 O u a 251 282 c 345 h 394 i 280 ta

260242 R 380 iv e 360 r 341 319 300 320 OUACHITA

334 340 33°30' W X 329

0 10 20 MILES

0 10 20 KILOMETERS

EXPLANATION

Outcrop of Wilcox Group (from Hosman, 1988)

180 Potentiometric contour—Shows altitude at which water level ARKANSAS would have stood in tightly cased wells. Hachures indicate depression. Dashed where approximately located. Contour interval 20 feet. Datum is National Geodetic Vertical Datum of 1929

General direction of groundwater flow Area enlarged ! Well completed in Wilcox aquifer, southern Arkansas—Number T 145 is water-level altitude. Letter, where present, corresponds to hydrograph in figure 14

Figure 10. Potentiometric surface of the Wilcox aquifer in southern Arkansas, 2012. Wilcox (Lower Wilcox) Aquifer 23

Water-Level Trends Wilcox aquifer. The well locations for the corresponding hydrographs are plotted on figures 9 and 10 and designated by the letters M–X positioned next to the well. These Water-Level Difference from 2006 to 2012 hydrographs are shown on figure 13 (northeastern, area) and figure 14 (southern area). Hydrographs for 36 wells (24 wells Water-level difference maps (figs. 11 and 12) for the in the northeastern area of the Wilcox aquifer and 12 wells Wilcox aquifer in Arkansas were constructed using 47 water- in the southern area) were used to calculate the annual rise level measurements made during 2006 and 2012. Difference or decline in water levels over a period of 20 or more years values were obtained from water levels measured in 31 wells using linear regression. The annual rise or decline in water in the northeastern area of the Wilcox aquifer and 16 wells levels was aggregated by county, and values for the range, measured in the southern area. mean, and median of water-level change were computed for The 2006 to 2012 difference in water levels for the each county (table 3). The summary for Greene, Lee, and St. Wilcox aquifer in the northeastern area (fig. 11, app. 5) ranged Francis Counties was for a single well. from 22.0 to -17.9 ft. The largest rise in water levels occurred Selected hydrographs for the northeastern area in Crittenden County, and the largest decline was in Lee (figs. 13M–S) all show declining water levels. Water- County. Twenty-one wells in the northeastern area had rising level changes in selected wells ranged from a decline of water levels, and 10 wells had declining water levels. Wells approximately 23 ft in well 14N07E17DCB1 (fig. M7 ) in the northern part of this area had rising water levels, and in Craighead County to a decline of approximately 60 ft wells in the southern part had declining water levels. In the in well 04N06E21BAD2 (fig. 7S) in St. Francis County. central part of the area, water levels in all wells measured in Hydrographs in the southern area (figs. 14T–X) show rising Craighead County rose, and water levels rose in all but one and declining water levels. Water-level changes in selected well in Poinsett County and one well in Mississippi County. wells ranged from a decline of approximately 20 ft in well Water levels in wells in Crittenden County rose and declined. 10S18W10DDB1 (fig. 7T) in Clark County to a rise of All water levels in wells measured in Lee and St. Francis approximately 14 ft in well 14S22W19AAA1 (fig. X7 ) in Counties declined. Nevada County. The 2006 to 2012 difference in water levels for the Linear regression analysis of long-term hydrographs Wilcox aquifer in the southern area (fig. 12, app. 6) ranged was used to determine the mean annual water-level rise from 18.1 to -4.2 ft. The largest rise and the largest decline in and decline in the Wilcox aquifer in the northeastern and water levels occurred in Nevada County. Water-levels rose in southern areas of Arkansas. In the northeastern area, the 12 wells in the southern area and declined in 4 wells. Water mean annual water level declined in all seven counties. The levels in wells in the northern area rose and declined in wells mean annual declines ranged from -0.55 ft/yr in Craighead in the central part of the area (Clark County). Water levels in County to -1.46 ft/yr in St. Francis County. Greene, Lee, and wells in the southern part of the area rose and declined. St. Francis Counties had only one well with a minimum of 20 years of record. Long-Term Hydrographs In the southern area, the annual rise or decline calculations for wells with over 20 years of record indicate Hydrographs for 12 wells with a minimum of 20 years rising and declining water levels in Clark, Hot Spring, and of record (7 wells in the northeastern area and 5 wells in the Nevada Counties. The mean annual water level declined in southern area) were used to evaluate long-term trends of the all counties except Hot Spring County. 24 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

EXPLANATION

Crowleys Ridge (from Hosman, 1988)

90° 30’ * Well completed in Wilcox aquifer, northeastern 36° 30’ 0.5 Arkansas—Value is rise in water level from

2006 to 2012, in feet. Symbols are scaled to

value CLAY * Well completed in Wilcox aquifer, northeastern -3.4 Arkansas—Value is decline in water level from 2006 to 2012, in feet. Symbols are scaled to value

GREENE

Paragould

0.8 90°00’ 36°00’

11.0 1.3 91°00’ 15.6 6.5 3.1 3.4 1.7 0.6 17.2 CRAIGHEAD MISSISSIPPI 2.2 16.1

7.6 -1.2

2.9 1.5 POINSETT 7.5 -0.6 2.5 35° 30’

r e iv R -4.5 i p ip s s i s s i M CROSS CRITTENDEN ARKANSAS 1.6 -5.0 Area enlarged 22.0 3.7 -0.1 West Memphis 6.8

ST. FRANCIS 35°00’ -5.0 -7.3 -17.9 -3.7

LEE -5.3

0 10 20 MILES

0 10 20 KILOMETERS

Figure 11. Water-level difference for the Wilcox aquifer in northeastern Arkansas, 2006–12. Wilcox (Lower Wilcox) Aquifer 25

34°30'

93°00'

1.5 HOT SPRING 3.3

92°30' 12.0 1.8 CLARK 34°00' 93°30' DALLAS L -2.1 i tt le

M -1.7 i ss ou ri River

NEVADA HEMPSTEAD O u a c 7.9 h -3.0 0.8 it -4.2 a R 0.4 iv e 0.2 r OUACHITA 1.6 0.7

33°30' 4.6 18.1

0 10 20 MILES

0 10 20 KILOMETERS

EXPLANATION

Outcrop of Wilcox Group (from Hosman, 1988)

Well completed in Wilcox aquifer, southern Arkansas— ARKANSAS 3.3 Value is rise in water level from 2006 to 2012, in feet. Symbols are scaled to value

Well completed in Wilcox aquifer, southern Arkansas— -1.7 Value is decline in water level from 2006 to 2012, in feet. Area enlarged Symbols are scaled to value

Figure 12. Water-level difference for the Wilcox aquifer in southern Arkansas, 2006–12. 26 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

M. CRAIGHEAD COUNTY 14N07E17DCB1

240

230

220

210

200 Geodetic Vertical Datum of 1929Datum of GeodeticVertical

Water level, in feet above above Nationalin level, feet Water NO DATA

190

180 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

N. CRITTENDEN COUNTY 08N06E33CBD1 210

200

190

180

170 Geodetic Vertical Datum of 1929Datum of GeodeticVertical

Water level, in feet above above Nationalin level, feet Water NO DATA 160

150 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 13. Water-level hydrographs for selected wells completed in the Wilcox aquifer in northeastern Arkansas. Wilcox (Lower Wilcox) Aquifer 27

O. GREENE COUNTY 17N06E31DCB1

220

210

200

190

NO DATA

Geodetic Vertical Datum of 1929Datum of GeodeticVertical 180 Water level, in feet above above Nationalin level, feet Water

170

160 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

P. LEE COUNTY 01N04E09DCC1

200

190

180

170

160 Geodetic Vertical Datum of 1929Datum of GeodeticVertical

Water level, in feet above above Nationalin level, feet Water 150

140

130 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 13. Water-level hydrographs for selected wells completed in the Wilcox aquifer in northeastern Arkansas.—Continued 28 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

Q. MISSISSIPPI COUNTY 15N09E31ACD1 240

230

220

210

NO DATA 200 Geodetic Vertical Datum of 1929Datum of GeodeticVertical Water level, in feet above above Nationalin level, feet Water

190

180 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

R. POINSETT COUNTY 12N05E13BBB1 230

220

210

200

190 Geodetic Vertical Datum of 1929Datum of GeodeticVertical Water level, in feet above above Nationalin level, feet Water

NO DATA 180

170 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 13. Water-level hydrographs for selected wells completed in the Wilcox aquifer in northeastern Arkansas.—Continued Wilcox (Lower Wilcox) Aquifer 29

S. ST. FRANCIS COUNTY 04N06E21BAD2 200

190

180

170

160 NO DATA 150

Geodetic Vertical Datum of 1929Datum of GeodeticVertical 140 Water level, in feet above above Nationalin level, feet Water

130

120 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 13. Water-level hydrographs for selected wells completed in the Wilcox aquifer in northeastern Arkansas.—Continued 30 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

T. CLARK COUNTY 10S18W10DDB1 170

160

150 NO DATA

140

130 Geodetic Vertical Datum of 1929Datum of GeodeticVertical Water level, in feet above above Nationalin level, feet Water

120

110 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

U. CLARK COUNTY 09S18W20CBB1 230

220

210

NO DATA 200

190 Geodetic Vertical Datum of 1929Datum of GeodeticVertical Water level, in feet above above Nationalin level, feet Water 180

170 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 14. Water-level hydrographs for selected wells completed in the Wilcox aquifer in southern Arkansas. Wilcox (Lower Wilcox) Aquifer 31

V. HOT SPRING 04S16W20CBB1 370

360

350

340

NO DATA 330 Geodetic Vertical Datum of 1929Datum of GeodeticVertical Water level, in feet above above Nationalin level, feet Water 320

310 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

W. HEMPSTEAD COUNTY 14S24W29BCA1 360

350

340

330

NO DATA 320 Geodetic Vertical Datum of 1929Datum of GeodeticVertical Water level, in feet above above Nationalin level, feet Water 310

300 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 14. Water-level hydrographs for selected wells completed in the Wilcox aquifer in southern Arkansas.—Continued 32 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

X. NEVADA COUNTY 14S22W19AAA1 340

330

320

310 NO DATA 300

290 Geodetic Vertical Datum of 1929Datum of GeodeticVertical Water level, in feet above above Nationalin level, feet Water

280

270 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 Year

Figure 14. Water-level hydrographs for selected wells completed in the Wilcox aquifer in southern Arkansas.—Continued

Table 3. Range, mean, and median of annual rise or decline in water level by county for wells with 20 or more years of record completed in the Wilcox aquifer in Arkansas.

[Annual rise or decline in water level for each well is calculated using linear regression; negative value indicates decline; positive value indicates rise; R2, coefficient of determination]

Range of values of Mean annual rise (+) Median annual rise (+) annual rise (+) Number of or decline (-) in or decline (-) in Range of R2 values County or decline (-) in wells water level water level for trend lines water level (feet/year) (feet/year) (feet/year) Northeastern area Craighead 4 -0.66 to -0.43 -0.55 -0.55 0.67 to 0.92 Crittenden 8 -1.57 to -0.88 -1.15 -1.11 0.78 to 0.98 Greene 1 -0.66 -0.66 -0.66 0.54 Lee 1 -1.31 -1.31 -1.31 0.97 Mississippi 6 -0.95 to -0.55 -0.73 -0.68 0.70 to 0.91 Poinsett 3 -0.91 to -0.80 -0.85 -0.84 0.76 to 0.93 St. Francis 1 -1.46 -1.46 -1.46 0.97 Southern area Clark 3 -0.55 to 0.18 -0.15 -0.07 0.30 to 0.97 Hempstead 3 -0.62 to -0.07 -0.26 -0.07 0.05 to 0.67 Hot Spring 2 -0.01 to 0.11 0.05 0.05 0.01 to 0.88 Nevada 4 -0.11 to 0.03 -0.03 -0.04 0.00 to 0.16 Summary 33

Summary (Ashley, Chicot, Desha, Drew, Lincoln, and part of Cleveland Counties), the area between the Saline and Ouachita Rivers The Cockfield aquifer located in southern Arkansas is (Bradley, Calhoun, and part of Cleveland Counties), and composed of Eocene-age sand beds found near the base of the the area west of the Ouachita River (Columbia and Union Cockfield Formation of Claiborne Group. The Wilcox aquifer Counties). Hydrographs for wells located east of the Saline located in northeastern and southern Arkansas, is composed River and screened within the confined part of the Cockfield of Paleocene-age sand beds found in the middle to lower part aquifer indicated changes in water levels that range from a of the Wilcox Group. The Cockfield and Wilcox aquifers are rise of approximately 0.5 ft to a decline of approximately primary sources of groundwater. In 2010, withdrawals from 57 ft over the period of record. the Cockfield aquifer in Arkansas totaled 19.2 (Mgal/d) and Hydrographs for wells located in the area between the withdrawals from the Wilcox aquifer totaled 36.5 Mgal/d. Saline and Ouachita Rivers were screened in confined and Water levels were measured at 43 wells completed in unconfined areas of the Cockfield aquifer. The hydrographs the Cockfield aquifer and 47 wells completed in the Wilcox indicate rises and declines in water levels that ranged from aquifer in February and March 2012. Measurements from a rise of approximately 1 ft to a decline of approximately 2012 are presented as potentiometric-surface maps and in 23 ft over the period of record. Hydrographs for wells combination with measurements from 2006 as water-level located in the area west of the Ouachita River indicated difference maps. Trends in water-level change over time rises and declines in water levels that ranged from a rise of within the Cockfield and Wilcox aquifers were determined approximately 2 ft to a decline of approximately 5 ft over the using the water-level difference maps and selected well period of record. hydrographs. Hydrogaphs for selected wells were constructed Hydrographs for the 32 wells with historical water-level using 20 or more years of historical water-level data. data in the Cockfield aquifer were evaluated using linear The Cockfield aquifer study area in southern Arkansas regression to calculate the annual rise or decline for each is bounded on the east by the Mississippi River and on the well and the data were aggregated by county and statistically west by the area that contains outcrops and subcrops of the evaluated for the range, mean, and median of water-level Cockfield Formation. The northern boundary of the Cockfield change in each county. Bradley, Calhoun, Columbia, and aquifer study area is defined by the area that contains Union Counties indicate rising and declining water levels. observation wells completed in the Cockfield aquifer and the The mean annual water-level rise or decline for Calhoun southern boundary is the Louisiana State line. The Wilcox County was 0.00 ft/yr or unchanged. The mean annual water- aquifer study area in northeastern Arkansas is bounded on the level data for Ashley, Bradley, Chicot, Cleveland, Columbia, east by the Mississippi River and on the north by the Missouri Lincoln, and Union Counties show declines ranging from State line. The southern and western boundaries are defined by -0.02 to -1.10 ft/yr. areas containing observation wells completed in the Wilcox Two potentiometric-surface maps, one for the aquifer or by outcrop areas on or near Crowleys Ridge. The northeastern area and one for the southern area, were Wilcox aquifer study area in southern Arkansas is defined by constructed to show the altitude of the water surface in the observation wells completed in the Wilcox aquifer or by areas Wilcox aquifer. The maps were constructed using water-level that contain outcrops of the Wilcox Group, or both. data collected in February and March 2012 from 47 wells; The potentiometric surface of the Cockfield aquifer 31 wells in the northeastern area and 16 wells in the southern shows the regional direction of groundwater flow was area. The direction of groundwater flow in the northeastern generally toward the east-southeast, except in areas of intense area was generally towards the south-southwest except groundwater withdrawals such as southwestern Ashley for some areas immediately adjacent to the Mississippi County, where groundwater flows toward the town of Crossett. River where the flow was more eastward towards the river. In southern Columbia County, a trough in the potentiometic The highest water-level altitude was 219 ft in northern surface exists, which locally alters the flow of groundwater. Mississippi County, and the lowest water-level altitude was The highest water-level altitude measured was 350 feet (ft) 123 ft near West Memphis in Crittenden County. In Greene above National Geodetic Vertical Datum of 1929 (NGVD 29) County, a water-level altitude of 182 ft was measured near in central Columbia County. The lowest water-level altitude Crowleys Ridge. Within Crowleys Ridge, water levels in the measured was 40 ft above NGVD 29 in southeastern Lincoln Wilcox aquifer were perched at higher water-level altitudes County. than the aquifer in the surrounding Mississippi Alluvial Plain. The 2006 to 2012 difference in water levels for the The direction of groundwater flow in the southern area was Cockfield aquifer ranged from 27.4 to -10.4 ft. The largest generally towards the southwest in the northern part. The water-level rise was in Calhoun County, and the largest water- direction of groundwater flow in the southern part was in level decline was in Union County. Of the 42 wells, 13 wells all directions because of two cones of depression and two had a rise in water levels, and the remaining 29 wells had a water-level mounds. The water-level mounds are the result decline in water levels from 2006 to 2012. of the higher land-surface altitudes in the outcrop area. The Analysis of selected hydrographs was divided into highest water-level altitude measured was 394 ft at the center three geographic regions: the area east of the Saline River of the water-level mounds in eastern Hot Spring County 34 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012 and southwestern Hempstead County. The lowest water-level Arthur, J.K., and Taylor, R.E., 1990, Definition of the altitude measured was 145 ft at the center of the cone of geohydrologic framework and preliminary simulation on depression in Clark County. ground-water flow in the Mississippi Embayment aquifer Water-level difference maps for the Wilcox aquifer in system, Gulf Coastal Plain, United States: U.S. Geological Arkansas were constructed using 47 water-level measurements Survey Water-Resources Investigations Report 86–4364, made during 2006 and 2012. Difference values were obtained 97 p. from water levels measured in 31 wells in the northeastern Bodansky, Eugene, Gribov, Alexander, and Pilouk, Morakot, area of the Wilcox aquifer and 16 wells measured in the 2002, Smoothing and compression of lines obtained by southern area. The difference in water levels for the Wilcox raster-to-vector conversion: Lecture Notes in Computer aquifer in the northeastern area ranged from 22.0 ft to -17.9 ft. Science Volume 2390, Springer Publishing Co., p. 256–265. The largest rise in water levels occurred in Crittenden County, and the largest decline was in Lee County. Twenty-one wells Broom, M.E., and Lyford, F.P., 1981, Alluvial aquifer of the had rising water levels, and 10 wells had declining water Cache and St. Francis River Basins, northeastern Arkansas: levels. The difference in water levels for the Wilcox aquifer U.S. Geological Survey Open-File Report 81–476, 48 p. in the southern area ranged from 18.1 ft to -4.2 ft. The largest rise and the largest decline in water levels occurred in Nevada Esri, 2011, ArcGIS desktop – Release 10: Redlands, County. Twelve wells had rising water levels, and 4 wells had California, Environmental Systems Research Institute. declining water levels. Fenneman, N.M., and Johnson, D.W., 1946, Physical divisions Hydrographs for the northeastern area showed declining of the United States (map): Washington, D.C., U.S. water levels. Water-level changes in selected wells ranged Geological Survey. from a decline of approximately 23 ft to a decline of approximately 60 ft. Hydrographs in the southern area showed Halberg, H.N., and Johnson, D.W., 1977, Use of water in declining and rising water levels. Water-level changes in Arkansas, 1975: Arkansas Geological Commission Water selected wells ranged from a rise of approximately 14 ft to a Resources Summary Number 9, 28 p. decline of approximately 20 ft. Hart, R.M., Clark, B.R., and Bolyard, S.E., 2008, Digital Linear regression analysis of long-term hydrographs was surfaces and thicknesses of selected hydrogeologic units used to determine the mean annual water-level rise and decline within the Mississippi Embayment Regional Aquifer Study in the Wilcox aquifer in the northeastern area and southern (MERAS): U.S. Geological Survey Scientific Investigations area of Arkansas. In the northeastern area, the mean annual Report 2008–5098, 33 p. water level declined in all seven counties. The mean annual declines ranged from -0.55 ft/yr in Craighead County to -1.46 Helsel, D.R., and Hirsh, R.M., 1992, Statistical methods ft/yr in St. Francis County. in water resources: New York, N.Y., Elsevier Science In the southern area, the annual rise or decline Publishing Co., 522 p. calculations for wells with over 20 years of record indicated rising and declining water levels in Clark, Hot Spring, and Holland, T.W., 1987, Use of water in Arkansas, 1985: Nevada Counties. The mean annual water level declined in all Arkansas Geological Commission Water Resources counties except Hot Spring County. Summary Number 6, 30 p. This is the sixth in a series of triennial reports discussing Holland, T.W., 1993, Use of Water in Arkansas, 1990: U.S. the potentiometric surfaces of the Cockfield and Wilcox Geological Survey Open-File Report 93–48, pamphlet. aquifers. This report and the previous five reports were prepared in cooperation with the Arkansas Natural Resources Holland, T.W., 1999, Water use in Arkansas, 1995: U.G. Commission and the Arkansas Geological Survey. Geological Survey Open-File Report 99–188, 1 sheet. Holland, T.W., 2004, Estimated water use in Arkansas, 2000: U.S. Geological Survey Scientific Investigations Report References Cited 2004–5230, 31 p. Holland, T.W., 2007, Water use in Arkansas, 2005: U.S. Ackerman, D.J., 1987, Generalized potentiometric surface Geological Survey Scientific Investigations Report 2007– of the aquifers in the Cockfield Formation, southeastern 5241, 32 p. Arkansas, spring 1980: U.S. Geological Survey Water- Holland, T.W., and Ludwig, A. H., 1981, Use of water in Resources Investigations Report 87–4214, scale 1:500,000, Arkansas, 1980: Arkansas Geological Commission Water 1 sheet. Resources Summary Number 14, 30 p.

Albin, D.R., 1964, Geology and ground-water resources of Hosman, R.L., 1982, Outcropping Tertiary units in southern Bradley, Clahoun, and Ouachita Counties, Arkansas: U.S. Arkansas: U.S. Geological Survey Miscellaneous Geological Survey Water-Supply Paper 1779–G, 32 p. Investigations Series I–1405, 1 sheet. References Cited 35

Hosman, R.L., 1988, Geohydrologic framework, Gulf Coastal Pugh, A.L., 2010, Potentiometric surfaces and water-level Plain: U.S. Geological Survey Hydrologic Investigations trends in the Cockfield (upper Claiborne) and Wilcox (lower Atlas HA–695, 2 sheets. Wilcox) aquifers of southern and northeastern Arkansas, 2009: U.S. Geological Survey Scientific Investigations Hosman, R.L., Long, A.T., Lambert, T.W., and others, 1968, Report 2010–5014, 47 p. Tertiary aquifers in the Mississippi Embayment: U.S. Geological Survey Professional Paper 448–D, 29 p. Ryling, R.W., 1960, Ground-water potential of Mississippi County, Arkansas: Arkansas Geological and Conservation Hosman, R.L., and Weiss, J.S., 1991, Geohydrologic units Commission Water Resources Circular 7, 87 p. of the Mississippi Embayment and Texas Coastal Uplands aquifer systems, South-Central United States: U.S. Schrader, T.P., 2007, Potentiometric surfaces and water-level Geological Survey Professional Paper 1416–B, 19 p. tends in the Cockfield and Wilcox aquifers of southern and northeastern Arkansas, 2006: U.S. Geological Survey Joseph, R.L., 1998, Potentiometric surface of the Cockfield Scientific Investigations Report 2007–5218, 27 p. aquifer in southeastern Arkansas and the Wilcox aquifers Schrader, T.P., and Joseph, R.L., 2000, Potentiometric in southern and northeastern Arkansas, October 1996– surfaces of aquifers in the Cockfield Formation in July 1997: U.S. Geological Survey Water-Resources southeastern Arkansas and the Wilcox Group in southern Investigations Report 98–4084, 19 p. and northeastern Arkansas, 2000: U.S. Geological Survey Onellion, F.E., and Criner, J.H., Jr., 1955, Ground-water Water-Resources Investigations Report 00–4206, 22 p. resources of Chicot County, Arkansas: Arkansas Geological U.S. Geological Survey, 2002, National Water Information and Conservation Commission Water Resources Circular System: Accessed October 10, 2013, at http://waterdata. No. 3, 27 p. usgs.gov/nwis. Petersen, J.C., Broom, M.E., and Bush, W.V., 1985, U.S. Geological Survey, 2014, National atlas of the United Geohydrologic units of the Gulf Coastal Plain in Arkansas: States: Accessed April 21, 2014 , at http://www.usgs.gov/ U.S. geological Survey Water-Resources Investigations science/cite-view.php?cite=244. Report 85–4116, 20 p. Westerfield, P.W., 1994, Potentiometric-surface maps of the Plebuch, R.O., 1961, Fresh-water aquifers of Crittenden Cockfield and lower Wilcox aquifers in Arkansas, 1991: County, Arkansas: Arkansas Geological and Conservation U.S. Geological Survey Water-Resources Investigations Commission Water Resources Circular 8, 65 p. Report 93–4134, scale 1:500,000, 2 sheets. Yeatts, D.S., 2004, Potentiometric Surfaces in the Cockfield Pugh, A.L., 2008, Summary of aquifer test data for and Wilcox aquifers of southern and northeastern Arkansas, Arkansas—1940–2006: U.S. Geological Survey Scientific 2003: U.S. Geological Survey Scientific Investigations Investigations Report 2008–5149, 33 p. Report 2004–5169, 24 p.

Appendixes

Appendix 1

Appendix 1 39

Appendix 1. Water-level data collected during February 2012 from wells completed in the Cockfield aquifer in southern Arkansas.— AppendixContinued 1. Water-level data collected during February 2012 from wells completed in the Cockfield aquifer in southern Arkansas. [Horizontal datum is North America Datum of 1983; NGVD 29, National Geodetic Vertical Datum of 1929; Letters in parentheses correspond to well locations in [Horizontal datum is North America Datum of 1983; NGVD 29, National Geodetic Vertical Datum of 1929; Letters in parentheses correspond to well locations figure 5 and well hydrographs in figure 7; --, missing data] in figure 5 and well hydrographs in figure 7; --, missing data] Latitude Longitude Water-level Depth to water Land-surface Date of (degrees, (degrees, altitude (feet below datum Well depth Station name measure- minutes, minutes, (feet above land-surface (feet above (feet) ment seconds) seconds) NGVD 29) datum) NGVD 29) Ashley County 15S04W26CBC1 332144 912932 88 40.36 128 409 2/24/2012 17S04W10BCD2 (A) 331417 913030 81 43.58 125 340 2/24/2012 17S04W10CBA1 331406 913033 84 41.34 125 360 2/24/2012 17S06W07ADA1 331442 914510 98 76.43 174 426 2/24/2012 18S04W19DAA2 330710 913247 83 32.61 116 356 2/24/2012 18S08W04BBC1 (B) 331038 915627 61 87.62 149 314 2/24/2012 19S05W12CAC1 (C) 330336 913425 81 34.40 115 320 2/24/2012 Bradley County 12S10W10BCA1 334108 920807 102 125.02 227 425 2/23/2012 12S10W30CAC1 333815 921046 238 2.07 240 58 2/23/2012 14S10W31DBA1 (F) 332658 921025 95 98.12 193 349 2/23/2012 14S11W35CAB1 332656 921251 111 79.03 190 320 2/23/2012 14S11W35DAC1 332650 921233 107 67.32 174 345 2/23/2012 15S12W11CAB1 (G) 332536 921858 131 23.76 155 225 2/23/2012 16S11W11ACA1 332027 921223 109 32.39 141 140 2/23/2012 Calhoun County 11S13W15BBC1 334560 922534 257 53.44 310 70 2/23/2012 13S13W09CBD1 333555 922638 193 38.63 323 147 2/23/2012 13S13W15DBA1 333517 922520 209 22.78 232 122 2/23/2012 14S13W11CAC1 333045 922451 175 29.89 205 105 2/22/2012 14S13W29ADA1 (H) 332829 922722 133 27.22 160 81 2/22/2012 14S13W29DAC1 332815 922729 124 14.69 139 − 2/22/2012 14S14W21ACB1 332931 923249 119 12.87 132 160 2/22/2012 Chicot County 13S03W26BBB1 333247 912301 66 72.96 139 442 2/27/2012 16S02W04BAC1 332027 911857 86 38.98 125 330 2/27/2012 18S02W25ABB3 (D) 330640 911541 91 44.48 135 322 2/27/2012 18S03W14CCC1 330731 912319 83 15.32 98 320 2/27/2012 Cleveland County 09S10W17CDD1 335534 920942 268 2.49 270 361 2/23/2012 11S11W23BBD1 (I) 334449 921258 232 42.93 275 148 2/23/2012 Columbia County 17S20W35BBD1 (L) 331313 930914 350 10.52 361 − 2/22/2012 19S20W34ADC1 330233 930958 290 22.71 313 40 2/22/2012 19S21W17CBB1 330520 931857 260 46.16 306 55 2/22/2012 19S21W35ADC1 330247 931513 256 0.37 256 30 2/22/2012 19S22W36DBB1 330245 932034 308 43.43 351 69 2/22/2012 Desha County 12S03W30ADC1 333747 912611 75 78.54 153 280 2/27/2012 13S02W08CAA1 333504 911921 73 74.29 147 515 2/27/2012 40 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

Appendix 1. Water-level data collected during February 2012 from wells completed in the Cockfield aquifer in southern Arkansas.— Continued

[Horizontal datum is North America Datum of 1983; NGVD 29, National Geodetic Vertical Datum of 1929; Letters in parentheses correspond to well locations in figure 5 and well hydrographs in figure 7; --, missing data] Latitude Longitude Water-level Depth to water Land-surface Date of (degrees, (degrees, altitude (feet below datum Well depth Station name measure- minutes, minutes, (feet above land-surface (feet above (feet) ment seconds) seconds) NGVD 29) datum) NGVD 29) Drew County 14S06W21BDC1 332846 914339 99 117.19 216 − 2/24/2012 11S05W35DDB1 334216 913438 60 119.60 180 500 2/27/2012 Lincoln County 10S05W06CAC1 (E) 335204 913918 40 130.29 170 550 2/27/2012 Union County 16S18W22DCD1 331913 925704 222 25.15 247 36 2/22/2012 17S13W17DDC1 (J) 331402 922746 153 40.52 193 24 2/22/2012 17S15W31DCA2 331144 924116 199 54.41 253 110 2/22/2012 17S16W33BBA2 (K) 331229 924601 230 24.63 255 31 2/22/2012 18S15W21DAC1 330824 923909 192 7.65 200 40 2/22/2012 19S12W28CBA1 330207 922109 194 6.02 200 25 2/22/2012 Appendix 2

Appendix 2 41

Appendix 2. Difference in depth to water from 2006 to 2012 in the Cockfield aquifer in southern Arkansas. Appendix 2. Difference in depth to water from 2006 to 2012 in the Cockfield aquifer in southern Arkansas.—Continued [Horizontal datum is North American Datum of 1983; Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929; positive [Horizontal datum is North American Datum of 1983;Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929; positive differences in depth to water indicate a rise in water levels from 2006 to 2012 whereas negative values indicate a decline in water levels from 2006 to 2012] differences in depth to water indicate a rise in water levels from 2006 to 2012 whereas negative values indicate a decline in water levels from 2006 to 2012] Latitude Longitude Difference in 2006 depth to water 2012 depth to water (degrees, (degrees, water level Station name (feet below land- (feet below land- minutes, minutes, from 2006 to 2012 surface datum) surface datum) seconds) seconds) (feet) Ashley County 15S04W26CBC1 332144 912932 41.88 40.36 1.5 17S04W10BCD2 331417 913030 38.18 43.58 -5.4 17S04W10CBA1 331406 913033 33.30 41.34 -8.0 17S06W07ADA1 331442 914510 72.85 76.43 -3.6 18S04W19DAA2 330710 913247 26.89 32.61 -5.7 18S08W04BBC1 331038 915627 80.30 87.62 -7.3 19S05W12CAC1 330336 913425 29.38 34.40 -5.0 Bradley County 12S10W10BCA1 334108 920807 124.15 125.02 -0.9 12S10W30CAC1 333815 921046 11.66 2.07 9.6 14S10W31DBA1 332658 921025 96.47 98.12 -1.7 14S11W35CAB1 332656 921251 75.89 79.03 -3.1 14S11W35DAC1 332650 921233 65.68 67.32 -1.6 15S12W11CAB1 332536 921858 23.94 23.76 0.2 16S11W11ACA1 332027 921223 29.36 32.39 -3.0 Calhoun County 11S13W15BBC1 334560 922534 53.18 53.44 -0.3 13S13W09CBD1 333555 922638 38.03 38.63 -0.6 13S13W15DBA1 333517 922520 23.40 22.78 0.6 14S13W11CAC1 333045 922451 28.55 29.89 -1.3 14S13W29ADA1 332829 922722 26.02 27.22 -1.2 14S13W29DAC1 332815 922729 14.24 14.69 -0.4 14S14W21ACB1 332931 923249 40.27 12.87 27.4 Chicot County 13S03W26BBB1 333247 912301 69.34 72.96 -3.6 16S02W04BAC1 332027 911857 38.07 38.98 -0.9 18S02W25ABB3 330640 911541 46.27 44.48 1.8 18S03W14CCC1 330731 912319 14.86 15.32 -0.5 Cleveland County 09S10W17CDD1 335534 920942 4.73 2.49 2.2 11S11W23BBD1 334449 921258 42.03 42.93 -0.9 Columbia County 17S20W35BBD1 331313 930914 14.91 10.52 4.4 19S20W34ADC1 330233 930958 22.37 22.71 -0.3 19S21W17CBB1 330520 931857 44.12 46.16 -2.0 19S21W35ADC1 330247 931513 3.54 0.37 3.2 19S22W36DBB1 330245 932034 41.15 43.43 -2.3 42 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

Appendix 2. Difference in depth to water from 2006 to 2012 in the Cockfield aquifer in southern Arkansas.—Continued

[Horizontal datum is North American Datum of 1983;Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929; positive differences in depth to water indicate a rise in water levels from 2006 to 2012 whereas negative values indicate a decline in water levels from 2006 to 2012] Latitude Longitude Difference in 2006 depth to water 2012 depth to water (degrees, (degrees, water level Station name (feet below land- (feet below land- minutes, minutes, from 2006 to 2012 surface datum) surface datum) seconds) seconds) (feet) Desha County 12S03W30ADC1 333747 912611 72.99 78.54 -5.6 13S02W08CAA1 333504 911921 64.48 74.29 -9.8 Drew County 14S06W21BDC1 332846 914339 120.62 117.19 3.4 Lincoln County 10S05W06CAC1 335204 913918 126.3 130.29 -4.0 Union County 16S18W22DCD1 331913 925704 14.71 25.15 -10.4 17S13W17DDC1 331402 922746 38.67 40.52 -1.9 17S15W31DCA2 331144 924116 52.99 54.41 -1.4 17S16W33BBA2 331229 924601 25.54 24.63 0.9 18S15W21DAC1 330824 923909 26.13 7.65 18.5 19S12W28CBA1 330207 922109 10.73 6.02 4.7 Appendix 3

Appendix 3 43

Appendix 3. Water-level data collected during February and March 2012 from wells completed in the Wilcox aquifer in northeastern Arkansas.

[Horizontal datum is North America Datum of 1983; NGVD 29, National Geodetic Vertical Datum of 1929; Letters in parentheses correspond to well locations in figure 9 and well hydrographs in figure 13]

Latitude Longitude Water-level Land-surface Depth to water Date of (degrees, (degrees, altitude datum Well depth Station name (feet below land- measure- minutes, minutes, (feet above (feet above (feet) surface datum) ment seconds) seconds) NGVD 29) NGVD 29) Craighead County 13N07E14BBA2 354526 901911 196 24.72 221 1,028 2/29/2012 14N05E25DCB1 354843 903029 193 40.52 233 890 2/29/2012 14N06E27ACB2 354858 902613 197 30.39 227 999 2/29/2012 14N07E17DCB1 (M) 355008 902202 200 32.17 232 1,070 2/29/2012 15N07E33BAD1 355315 902107 205 26.68 232 1,034 2/29/2012 Crittenden County 04N07E36ADB1 345449 901828 135 66.38 201 1,638 2/28/2012 05N07E29ACC1 350129 902225 145 54.77 200 1,700 2/28/2012 06N07E01ABB1 350520 901807 141 66.16 207 1,541 2/28/2012 06N09E07CAC1 350907 901042 123 86.72 210 1,470 2/28/2012 07N07E14CCC1 351318 901930 176 46.91 223 1,584 2/28/2012 07N08E24CAB1 351238 901148 148 73.36 221 1,540 2/28/2012 08N06E33CBD1 (N) 351614 902752 163 52.41 215 1,750 2/28/2012 09N08E29ADD1 352225 901516 165 60.57 225 1,564 2/28/2012 Greene County 17N06E31DCB1 (O) 360328 902902 182 103.23 285 462 2/29/2012 Lee County 01N04E09DCC1 (P) 344209 904220 136 67.93 204 1,885 2/28/2012 03N05E01BAB1 345413 903136 127 69.06 196 1,702 2/28/2012 Mississippi County 11N09E33AAB1 353214 900739 187 49.77 237 1,560 3/1/2012 11N10E20ADA1 353349 900213 189 45.57 235 1,417 3/1/2012 12N11E17CDD1 353917 895618 191 54.02 245 1,500 3/1/2012 13N11E08DDA1 354528 895547 203 41.82 245 1,445 3/1/2012 13N11E31CCCC1 354221 895807 204 37.37 241 1,500 3/1/2012 14N11E20CCA1 354859 895626 205 34.77 240 1,518 3/1/2012 15N09E31ACD1 (Q) 355306 900952 206 34.19 240 1,158 2/29/2012 15N10E01ADC1 355712 895806 219 28.96 248 1,350 2/29/2012 15N12E23DBC1 355426 894701 197 41.03 238 1,491 3/1/2012 Poinsett County 10N07E16CBB2 352925 902129 166 51.60 218 1,500 3/1/2012 11N05E06CCD1 353622 903618 179 35.21 214 992 3/2/2012 11N07E03BDD1 353629 901955 178 38.15 216 1,456 3/2/2012 12N05E13BBB1 (R) 354038 903059 183 39.66 222 1,071 3/2/2012 St. Francis County 04N06E16CCB1 345712 902830 143 59.35 202 1,615 2/28/2012 04N06E21BAD2 (S) 345649 902815 136 65.48 201 1,740 2/28/2012 Appendix 4

44 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

Appendix 4. Water-level data collected during February and March 2012 from wells completed in the Wilcox aquifer in southern Arkansas.

[Horizontal datum is North America Datum of 1983; NGVD 29, National Geodetic Vertical Datum of 1929; Letters in parentheses correspond to well locations in figure 10 and well hydrographs in figure 14; --, missing data]

Latitude Longitude Water-level Depth to water Land-surface (degrees, (degrees, altitude (feet below datum Well depth Date of Station name minutes, minutes, (feet above land-surface (feet above (feet) measurement seconds) seconds) NGVD 29) datum) NGVD 29) Clark County 07S18W03BBD1 340917 925604 267 2.75 270 47 2/21/2012 07S18W20ABB2 340652 925757 232 9.86 242 19 2/21/2012 09S18W20CBB1 (U) 335611 925905 210 20.10 230 26 2/22/2012 10S18W10DDB1 (T) 335216 925613 145 49.99 195 215 2/21/2012 Hempstead County 13S23W04BDD1 333842 932911 345 4.51 350 14 2/21/2012 13S24W02DCA2 333829 933311 394 51.92 446 63 2/21/2012 13S24W29ACC1 333524 933635 341 29.98 371 60 2/21/2012 14S24W29BCA1 (W) 333017 933704 334 21.04 355 31 2/21/2012 Hot Springs County 04S16W20CBB1 (V) 342144 924532 342 2.73 345 18 2/21/2012 05S17W10AAC1 341836 924853 394 15.57 410 26 2/21/2012 Nevada County 12S22W24CDA1 334046 931941 313 31.21 344 41 2/21/2012 13S21W02DCC1 333754 931426 251 63.53 315 240 2/21/2012 13S21W11BDA1 333738 931432 242 25.91 268 − 2/21/2012 13S21W23ABC1 333556 931423 319 42.56 362 47 2/21/2012 14S22W19AAA1 (X) 333105 932443 329 7.92 337 75 2/21/2012 Ouachita County 12S19W11DCD1 334144 930105 282 5.92 288 533 2/21/2012 Appendix 5

Appendix 5 45

Appendix 5. Difference in depth to water from 2006 to 2012 in the Wilcox aquifer in northeastern Arkansas.

2006 depth 2012 depth Difference Latitude Longitude to water to water in water level Station name (degrees, minutes, (degrees, minutes, (feet below land- (feet below land- from 2006 to 2012 seconds) seconds) surface datum) surface datum) (feet) Craighead County 13N07E14BBA2 354526 901911 26.89 24.72 2.2 14N05E25DCB1 354843 903029 42.24 40.52 1.7 14N06E27ACB2 354858 902613 30.98 30.39 0.6 14N07E17DCB1 355008 902202 35.57 32.17 3.4 15N07E33BAD1 355315 902107 28.00 26.68 1.3 Crittenden County 04N07E36ADB1 345449 901828 59.09 66.38 -7.3 05N07E29ACC1 350129 902225 61.52 54.77 6.8 06N07E01ABB1 350520 901807 66.06 66.16 -0.1 06N09E07CAC1 350907 901042 90.44 86.72 3.7 07N07E14CCC1 351318 901930 68.93 46.91 22.0 07N08E24CAB1 351238 901148 68.37 73.36 -5.0 08N06E33CBD1 351614 902752 53.96 52.41 1.6 09N08E29ADD1 352225 901516 56.03 60.57 -4.5 Greene County 17N06E31DCB1 360328 902902 104.00 103.23 0.8 Lee County 01N04E09DCC1 344209 904220 62.62 67.93 -5.3 03N05E01BAB1 345413 903136 51.18 69.06 -17.9 Mississippi County 11N09E33AAB1 353214 900739 52.29 49.77 2.5 11N10E20ADA1 353349 900213 47.07 45.57 1.5 12N11E17CDD1 353917 895618 52.79 54.02 -1.2 13N11E08DDA1 354528 895547 59.03 41.82 17.2 13N11E31CCCC1 354221 895807 53.51 37.37 16.1 14N11E20CCA1 354859 895626 37.88 34.77 3.1 15N09E31ACD1 355306 900952 40.69 34.19 6.5 15N10E01ADC1 355712 895806 39.93 28.96 11.0 15N12E23DBC1 355426 894701 56.59 41.03 15.6 Poinsett County 10N07E16CBB2 352925 902129 51.03 51.60 -0.6 11N05E06CCD1 353622 903618 42.72 35.21 7.5 11N07E03BDD1 353629 901955 41.03 38.15 2.9 12N05E13BBB1 354038 903059 47.28 39.66 7.6 St. Francis County 04N06E16CCB1 345712 902830 54.36 59.35 -5.0 04N06E21BAD2 345649 902815 61.81 65.48 -3.7 Appendix 6

46 Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012

Appendix 6. Difference in depth to water from 2006 to 2012 in the Wilcox aquifer in southern Arkansas.

2012 depth Difference in Latitude Longitude 2006 depth to water to water water level Station name (degrees, minutes, (degrees, minutes, (feet below land- (feet below land- from 2006 to 2012 seconds) seconds) surface datum) surface datum) (feet) Clark County 07S18W03BBD1 340917 925604 14.72 2.75 12.0 07S18W20ABB2 340652 925757 11.63 9.86 1.8 09S18W20CBB1 335611 925905 18.03 20.10 -2.1 10S18W10DDB1 335216 925613 48.31 49.99 -1.7 Hempstead County 13S23W04BDD1 333842 932911 4.91 4.51 0.4 13S24W02DCA2 333829 933311 48.9 51.92 -3.0 13S24W29ACC1 333524 933635 31.6 29.98 1.6 14S24W29BCA1 333017 933704 25.68 21.04 4.6 Hot Springs County 04S16W20CBB1 342144 924532 4.25 2.73 1.5 05S17W10AAC1 341836 924853 18.85 15.57 3.3 Nevada County 12S22W24CDA1 334046 931941 32.01 31.21 0.8 13S21W02DCC1 333754 931426 59.31 63.53 -4.2 13S21W11BDA1 333738 931432 26.07 25.91 0.2 13S21W23ABC1 333556 931423 43.28 42.56 0.7 14S22W19AAA1 333105 932443 26.03 7.92 18.1 Ouachita County 12S19W11DCD1 334144 930105 13.82 5.92 7.9

Publishing support provided by Lafayette Publishing Service Center Rodgers—Potentiometric Surfaces and Water-Level Trends in the Cockfield Aquifer and the Wilcox Aquifer, Arkansas, 2012—SIR 2014–5232 ISSN 2328-0328 (online)