U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5238

Prepared in cooperation with the Arkansas Natural Resources Commission 

and the Arkansas Geological Survey

Water Levels in Aquifers in the Nacatoch Sand of 

Southwestern and Northeastern Arkansas and the Tokio 

Formation of Southwestern Arkansas, Spring 2008

36o

35o

34o

94o 93o 92o 91o

90o

Fall

line

West

Gulf

Coastal

Plain

Mississippi

Alluvial

Plain

Ouachita

Mountains

Arkansas Valley

Ozark Plateaus

INTERIOR

HIGHLANDS

COASTAL

PLAIN

SEVIER

HOWARD PIKE

CLARK

HEMPSTEAD LITTLE

RIVER

NEVADA

CLAY

GREENE

MILLER

LAFAYETTE

COLUMBIA TEXAS

LOUISIANA

MISSISSIPPI

TENNESSEE

MISSOURI

OKLAHOMA

Mississippi River

Water Levels in Aquifers in the Nacatoch 

Sand of Southwestern and Northeastern 

Arkansas and the Tokio Formation of 

Southwestern Arkansas, Spring 2008

By T.P. Schrader and Joshua M. Blackstock

Prepared in cooperation with the Arkansas Natural Resources Commission and the

Arkansas Geological Survey

Scientific Investigations Report 2010-5238

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

This and other USGS information products are available at http://store.usgs.gov/

U.S. Geological Survey

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Denver, CO 80225

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Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Schrader, T.P., and Blackstock, J.M., 2010, Water levels in aquifers in the Nacatoch Sand of southwestern and northeastern Arkansas and the Tokio Formation of southwestern Arkansas, spring 2008: U.S. Geological Survey Scientific 

Investigations Report 2010-5238, 22 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Methods...........................................................................................................................................................3

Nacatoch Sand...............................................................................................................................................3

Hydrogeologic Setting .........................................................................................................................3

Water Use ..............................................................................................................................................4

Potentiometric Surface........................................................................................................................5

Long-Term Water-Level Changes.....................................................................................................10

Tokio Formation ............................................................................................................................................14

Hydrogeologic Setting .......................................................................................................................14

Water Use ............................................................................................................................................14

Potentiometric Surface......................................................................................................................14

Long-Term Water-Level Changes.....................................................................................................15

Summary........................................................................................................................................................21

Selected References...................................................................................................................................22

Figures

1. Map showing location of study areas.......................................................................................2

2. Diagram showing well-numbering system...............................................................................3

3. Graph showing withdrawals for the Nacatoch aquifer for the northeastern area in

 Arkansas ........................................................................................................................................4

4. Graph showing withdrawals for the Nacatoch aquifer for the southwestern area in

 Arkansas ........................................................................................................................................5

5. Map showing potentiometric surface of the Nacatoch aquifer, northeastern

 Arkansas, spring 2008 ..................................................................................................................6

6. Map showing potentiometric surface of the Nacatoch aquifer, southwestern

 Arkansas, spring 2008 ..................................................................................................................7

7. Water-level hydrographs (A to F) for selected wells completed in the Nacatoch

 aquifer..........................................................................................................................................11

8 Graph showing withdrawals for the Tokio aquifer for the southwestern area

 in Arkansas ..................................................................................................................................15

9. Map showing potentiometric surface of the Tokio aquifer, southwestern

 Arkansas, spring 2008 ................................................................................................................16

10. Water-level hydrographs (G to J) for selected wells completed in the Tokio aquifer.....19
iv

Tables

1. Water-level data collected during spring 2008 from wells completed in the

 Nacatoch Sand .............................................................................................................................8

2. Water-level data collected during spring 2008 from wells completed in the

 Tokio Formation...........................................................................................................................17

Conversion Factors Vertical Datums, and Abbreviations

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)

gallon per day (gal/d) 0.003785 cubic meter per day (m3

/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD of 1929).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 1983).

Altitude as used in this report, refers to distance above the vertical datum.
Water Levels in Aquifers in the Nacatoch Sand of 

Southwestern and Northeastern Arkansas and the Tokio 

Formation of Southwestern Arkansas, Spring 2008

By T.P. Schrader and Joshua M. Blackstock

Abstract

The Nacatoch Sand and Tokio Formation aquifers in 

southwestern Arkansas and the Nacatoch Sand in northeastern 

Arkansas are sources of water for industrial, public supply, 

domestic, and agricultural uses. Potentiometric-surface maps 

were constructed from water-level measurements made in 61 

wells completed in the Nacatoch Sand and in 50 wells completed in the Tokio Formation during spring 2008. Aquifers in 

the Nacatoch Sand and Tokio Formation are hereafter referred 

to as the Nacatoch aquifer and the Tokio aquifer, respectively.

The direction of groundwater flow in the Nacatoch 

aquifer in northeastern Arkansas generally is towards the 

southeast. A potentiometric high is located along the north and 

northwestern boundaries of the area. 

The direction of groundwater flow in the Nacatoch aquifer in southwestern Arkansas is towards the south-southeast 

in Little River, Miller, and Hempstead Counties and to the 

east-southeast in Nevada and Clark Counties. A potentiometric 

high is located within the outcrop area in north-central Hempstead County. A cone of depression exists in the Nacatoch 

aquifer at Hope in southeastern Hempstead County.

The direction of groundwater flow in the Tokio aquifer 

in southwestern Arkansas generally is towards the south or 

southeast. A potentiometric high is located within the outcrop 

area. Artesian conditions exist in southeastern Pike, northeastern Hempstead, and northwestern Nevada Counties. One 

apparent cone of depression might exist northwest of Hope in 

Hempstead County.

In northeastern Arkansas, groundwater withdrawals 

from the Nacatoch aquifer increased by 480 percent from 

1965 to 2005. In southwestern Arkansas, withdrawals from 

the Nacatoch aquifer and Tokio aquifer increased by 125 

percent and 201 percent, respectively, from 1965 to 1980 and 

decreased by 93 percent and 80 percent, respectively, from 

1980 to 2000. Withdrawals from Nacatoch aquifer and Tokio 

aquifer increased by 690 percent and 291 percent, respectively, 

from 2000 to 2005. Long-term hydrographs were prepared for 

10 wells in the study areas. Changes in water levels in some 

wells may be associated with changes in withdrawals from the 

respective aquifers.

Introduction

Groundwater is a renewable resource important for 

economic growth and quality of life. Aquifers in the Nacatoch 

Sand and Tokio Formation in southwestern Arkansas and the 

Nacatoch Sand in northeastern Arkansas are sources of water 

for industrial, public supply, domestic, and agricultural uses. 

Monitoring of groundwater levels and withdrawals provides 

information to effectively plan and manage the resource. A 

study was conducted by the U.S. Geological Survey in cooperation with the Arkansas Natural Resources Commission and 

the Arkansas Geological Survey to provide potentiometricsurface maps and water-level hydrographs associated with 

aquifers in the Nacatoch Sand and Tokio Formation (hereafter 

referred to as the Nacatoch aquifer and Tokio aquifer, respectively) in southwestern Arkansas and the Nacatoch aquifer in 

northeastern Arkansas. 

The study areas comprise parts of 10 counties in two 

areas of northeastern and southwestern Arkansas. The northeastern area includes most of Clay and Greene Counties in 

the Mississippi Alluvial Plain physiographic province (fig. 

1). This area is bounded on the north and east by the Missouri State line and on the west by the western extent of the 

Nacatoch aquifer. The southern boundary of this area was 

defined by the southern extent of water withdrawals from 

wells screened in the Nacatoch aquifer. The southwestern area 

includes parts of eight counties (Clark, Hempstead, Howard, 

Little River, Miller, Nevada, Pike, and Sevier) in the West 

Gulf Coastal Plain physiographic province (fig. 1). This area is 

bounded on the north approximately by the Fall Line separating the Interior Highlands from the Coastal Plain, on the west 

by the extent of use and the availability of wells, and on the 

east by the eastern borders of Clark and Nevada Counties. The 

southwestern area was limited to the occurrence of freshwater; 

the southern boundary of the area is defined by a freshwater/
2 Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008

saltwater interface. To the south, the groundwater is considered saline (more than 1,000 milligrams per liter of dissolved 

solids) and is not suitable for most uses (Boswell and others, 

1965; Petersen and others, 1985).

This report presents the results of water-level measurements made in 61 wells completed in the Nacatoch aquifer and 

in 50 wells completed in the Tokio aquifer during spring 2008. 

These measurements were used to construct potentiometricsurface maps. All water-level data are stored in the U.S. 

Geological Survey’s Ground-Water Site Inventory (GWSI) 

data storage system (http://waterdata.usgs.gov). Long-term 

water-level hydrographs were prepared for selected wells. 

Withdrawal data for the aquifers in each county collected by 

the U.S. Geological Survey from 1965 to 2005 were related to 

these hydrographs.

Figure 1. Location of study areas.

36o

35o

34o

94o 93o 92o 91o

90o

0 20 40 MILES

0 20 40 KILOMETERS

Fall

line

West

Gulf

Coastal

Plain

Mississippi

Alluvial

Plain

Ouachita

Mountains

Arkansas Valley

Ozark Plateaus

INTERIOR

HIGHLANDS

COASTAL

PLAIN

EXPLANATION

Study areas

Boundary of physiographic major division

Boundary of physiographic province

SEVIER

HOWARD PIKE

CLARK

HEMPSTEAD LITTLE

RIVER

NEVADA

CLAY

GREENE

MILLER

LAFAYETTE

COLUMBIA

TEXAS

LOUISIANA

MISSISSIPPI

TENNESSEE

MISSOURI

OKLAHOMA

Mississippi River

Physiographic division boundaries 

from Fenneman (1938) Base from U.S. Geological Survey

digital data, 1:100,000

The Tokio Formation is stratigraphically below the 

Nacatoch Sand and separated from it by five stratigraphic 

units, listed here in descending stratigraphic order: Saratoga 

Chalk, Marlbrook Marl, Annona Chalk, Ozan Formation, and 

Brownstown Marl. The Saratoga Chalk, Marlbrook Marl, and 

Annona Chalk are nonwater bearing, and the five-unit section 

can obtain a thickness of 900 feet (ft) (Petersen and others, 

1985). These five units rarely are used as water sources and 

are not discussed in this report.

As a well is pumped, water levels decline, forming a cone 

of depression. Pumping rates that exceed recharge rates for 

an extended period of time will cause cones of depression to 

enlarge. Local cones of depression can intersect and coalesce, 

causing a regional decrease in water levels within the aquifer. 

Variations in climatic conditions and resulting recharge rates 

can result in the natural rise or decline of water levels and may 

account for changes shown by long-term hydrographs.
Nacatoch Sand 3

Methods

Personnel from the U.S. Geological Survey (USGS) 

collected water-level measurements during spring 2008 from 

wells screened in the Nacatoch aquifer or Tokio aquifer. 

Measurements by USGS personnel were made with steel or 

electric tapes graduated in hundredths of a foot. The steel 

and electric tapes were calibrated during January 2008 prior 

to collecting measurements from wells. Calibration of steel 

and electric tapes was performed by comparing the field steel 

or electric tape to a standardized steel tape used only for 

calibration.

Well locations were measured using Global Positioning 

System receivers to acquire the horizontal coordinate information (latitude and longitude) based on the North American 

Datum of 1983. Land-surface altitude, feet above National 

Geodetic Vertical Datum of 1929 (NGVD of 1929), was 

determined for each well by superposition of the wells latitude 

and longitude on a topographic map and is accurate to about 

one-half the topographic contour interval of 5 or 10 ft. Herein, 

all water-level and land-surface altitudes are referenced to 

NGVD of 1929.

The well-numbering system used in this report is based 

upon the location of the wells according to the Federal land 

survey used in Arkansas. The component parts of a well number are the township number; the range number; the section 

number; three letters that indicate, respectively, the quarter 

section, the quarter-quarter section, and the quarter-quarterquarter section in which the well is located; and a sequence 

number of the well in the quarter-quarter-quarter section. The 

letters are assigned counterclockwise, beginning with “A” 

in the northeast quarter or quarter-quarter or quarter-quarterquarter section in which the well is located. For example, well 

01S03W04BBD16 (fig. 2) is located in Township 1 South, 

Range 3 West, and in the southeast quarter of the northwest 

quarter of the northwest quarter of section 4. This well is the 

16th well in this quarter-quarter-quarter section of section 4 

from which data were collected. 

Nacatoch Sand

Hydrogeologic Setting

The Nacatoch Sand of Late Cretaceous age is underlain 

by the Saratoga Chalk and overlain by the Arkadelphia Marl. 

In the northeastern area, the Nacatoch Sand subcrops beneath 

Quaternary alluvial and terrace deposits along the western 

boundary. The top of the Nacatoch Sand has an altitude of 

about 50 to 100 ft above NGVD of 1929 along the western 

boundary, dips toward the southeast, and descends to about 

1,200 ft below NGVD of 1929 at the Mississippi River. 

This unit is about 100 ft thick near the subcrop and attains a 

PRINCIPAL MERIDIAN

BASE LINE

TOWNSHIPS

SOUTH NORTH

WEST EAST RANGES

1E

2E

3E

4E

1W 2W 3W 4W 5W

5E

1N 2N 3N 4N

1S

2S

3S

4S 5S

6S

7S

8S

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36 RANGE: 03 West TOWNSHIP: 01 South

DD

C

B

A A

B

C

D

A

B

C

D

A

B

C

D

A

B

C

D

A

B

C D

SECTION: 04

WELL 01S03W04BBD16

N

S

E

W

Figure 2. Well-numbering system.

maximum thickness of about 600 ft downdip (Petersen and 

others, 1985). 

The Nacatoch Sand in the northeastern area consists of 

interbedded clay, limestone, and fine sand in the lower part, 

grading upward to loose fine quartz sand in the upper part 

(Petersen and others, 1985). The Nacatoch aquifer receives 

recharge from precipitation through the overlying alluvium 

and terrace deposits in western Clay and Greene Counties.

In the southwestern area, the Nacatoch Sand outcrops 

in a belt 3 to 8 miles (mi) wide extending from central Clark 

County southwestward to western Hempstead County. The 

belt continues westward as a subcrop below Quaternary alluvial and terrace deposits across Little River County (Boswell 

and others, 1965). The top of the Nacatoch Sand has an 

altitude of about 300 ft above NGVD of 1929 in the outcrop, 

dips towards the southeast, and descends to about 800 ft below 

NGVD of 1929 at the southern boundary of the area. The Nacatoch Sand is about 100 ft thick near the outcrop and attains a 

maximum thickness of 600 ft (Petersen and others, 1985).
4 Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008

The Nacatoch Sand in the southwestern area consists 

of three distinct units. The upper unit is composed of unconsolidated, gray, fine-grained quartz sand that commonly is 

crossbedded. Locally, the sand is massive and contains a few 

hard lenses and beds of fossiliferous sandy limestone. This 

upper sand unit is the main water-bearing unit of the Nacatoch Sand. The middle unit consists of a dark-green sand that 

contains coarse grains of glauconite and weathers to lighter 

shades of green. This unit generally is fossiliferous where it is 

glauconitic. The lower unit consists of interbedded gray clay, 

sandy clay and marl, dark clay-rich fine-grained sand, and 

hard irregular concretionary beds (Counts and others, 1955; 

Plebuch and Hines, 1969).

In the southwestern area, the Nacatoch aquifer receives 

recharge from precipitation in its outcrop areas in Clark, 

Nevada, and Hempstead Counties and through the overlying 

alluvium and terrace deposits in Little River County and in 

northeastern Texas. The Nacatoch aquifer is used in northeastern Greene County, Clay County, southern Clark County, 

northwestern Nevada County, central Hempstead County, 

northern Miller County, and southeastern Little River County. 

Flowing artesian wells produce yields of 1 or 2 gallons per 

minute (gal/min) in the lowest stream valleys in Clark and 

Nevada Counties. Wells in Hempstead County and western 

Nevada County produce yields of 150 to 300 gal/min. In the 

southwestern area, downdip about 2 to 20 mi southeast of 

the outcrop area, groundwater generally is excessively saline 

for most uses. Well yields in Miller County, eastern Nevada 

County, and Clark County generally are small, and the water 

may contain considerable chloride (Counts and others, 1955). 

Aquifer tests of wells completed in the Nacatoch aquifer at 

Hope and Prescott show a transmissivity of 3,600 gallons per 

day per foot (gal/d/ft) (Ludwig, 1972). 

Water Use

Total withdrawals from the Nacatoch aquifer in the 

northeastern area were 0.25 million gallons per day (Mgal/d) 

in 1965 and increased to 2.21 Mgal/d in 1990, an increase 

of 784 percent during the 25-year period (fig. 3). The majority of these withdrawals occurred in Clay County and were 

0.25 Mgal/d in 1965 and increased to 1.98 Mgal/d in 1990, an 

increase of 692 percent. Withdrawals in Greene County were 

0.00 Mgal/d in 1965 and increased to 0.23 Mgal/d in 1990. 

The total amount of withdrawals in the northeastern area in 

2005 was 1.45 Mgal/d, a decrease of 34 percent from 1990. 

This trend is explained by the decrease in withdrawals from 

Clay County from 1.98 Mgal/d in 1990 to 0.97 Mgal/d in 

2005. However, withdrawals have increased in Greene County 

from 0.23 Mgal/d in 1990 to 0.48 Mgal/d in 2005, an increase 

of 200 percent. From 1965 to 2005, withdrawals from the 

Nacatoch aquifer increased by 480 percent. Withdrawals in 

Clay County have increased from 0.25 Mgal/d in 1965 to 0.97 

Figure 3. Withdrawals for the Nacatoch aquifer for the northeastern area in Arkansas.

1965 1970 1975 1980 1985 1990 1995 2000 2005

0

1

2

3

WITHDRAWALS, IN MILLION GALLONS PER DAY

Clay County

Greene County

Total northeastern

 area

EXPLANATION

Water use data from Halberg and Stephens (1966);

Halberg (1972, 1977); Holland and Ludwig (1981); and

Holland (1987, 1993, 1999, 2004, 2007).
Nacatoch Sand 5

Mgal/d in 2005, an increase of 288 percent. Withdrawals in 

Greene County have increased from 0.06 Mgal/d in 1970 to 

0.48 Mgal/d in 2005, an increase of 700 percent (Halberg and 

Stephens, 1966; Holland and Ludwig, 1981; Holland, 1987, 

1993, 1999, 2004, 2007). 

Withdrawals from the Nacatoch aquifer in the southwestern area were 2.11 Mgal/d in 1965 and increased by 125 

percent to 4.75 Mgal/d in 1980 (fig. 4). During this period, 

the largest withdrawals occurred in Hempstead County where 

withdrawals increased from 1.12 Mgal/d in 1965 to 1.98 

Mgal/d in 1980, an increase of 77 percent. Withdrawals in 

Clark County increased from 0.44 Mgal/d in 1965 to 1.73 

Mgal/d in 1980, an increase of 293 percent. Withdrawals in 

Howard, Little River, Miller, and Nevada County were 0.00, 

0.20, 0.14, and 0.21 Mgal/d, respectively, in 1965. In 1980, 

Howard and Nevada County withdrawals increased to 0.24 

and 0.68 Mgal/d, respectively. However, withdrawals in Little 

River and Miller County decreased to 0.06 Mgal/d. Withdrawals from the Nacatoch aquifer in this area were 0.32 Mgal/d in 

2000, a decrease of 93 percent from 1980. In 2000, withdrawals in Clark, Hempstead, and Miller County decreased to 0.02, 

0.27, and 0.03 Mgal/d, respectively. Withdrawals in Howard, 

Little River, and Nevada County decreased to 0.00 Mgal/d 

in 2000. The sharp decrease in withdrawal rates is explained 

by public water supplies in the southwestern area converting 

to a surface-water source and relying less on groundwater 

sources (Halberg and Stephens, 1966; Holland and Ludwig, 

1981; Holland, 1987, 1993, 1999, 2004). However, in 2005, 

groundwater withdrawals increased to 2.53 Mgal/d. Withdrawals increased in Clark, Hempstead, and Nevada County. 

Withdrawals in Clark and Nevada County increased to 0.43 

and 0.18 Mgal/d, respectively, in 2005. In Hempstead County, 

withdrawals increased from 0.27 in 2000 to 1.92 Mgal/d in 

2005, an increase of 711 percent (Holland, 2007). 

Potentiometric Surface

Water-level measurements in 61 wells during spring 2008 

were used to construct potentiometric-surface maps for the 

Nacatoch aquifer (figs. 5 and 6; table 1). The potentiometric 

surface was mapped by calculating the altitude of the water 

levels (table 1) and is represented by contour lines of equal 

water-level altitude value. The general direction of groundwater flow is perpendicular to the contour lines in the direction of downward hydraulic gradient.

1965 1970 1975 1980 1985 1990 1995 2000 2005

0

1

2

3

4

5

WITHDRAWALS, IN MILLION GALLONS PER DAY

Clark County

Hempstead County

Howard County

Little River County

Miller County

Nevada County

Total southwestern

 area

EXPLANATION

Water use data from Halberg and Stephens (1966);

Halberg (1972, 1977); Holland and Ludwig (1981); and

Holland (1987, 1993, 1999, 2004, 2007).

Figure 4. Withdrawals for the Nacatoch aquifer for the southwestern area in Arkansas.
6 Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008

MISSOURI

CLAY MISSOURI

GREENE

T. 20 N.

T. 18 N.

T. 16 N.

R. 4 E. R. 6 E. R. 8 E.

EXPLANATION

Northeastern area

Approximate western limit of Nacatoch aquifer

Potentiometric contour—Shows altitude at which water 

 level would have stood in tightly cased wells. Dashed 

 where approximately located. Contour interval 10 feet. 

 Datum is National Geodetic Vertical Datum of 1929

Control point—Letter, where present, corresponds to 

 hydrograph in figure 7. Number is water level in feet

 above NGVD of 1929

 

250

A 251

36°00’

36°30’

90°40’ 90°10’

236

235 239

269

272

232

241

251

264

235

239 245

269

270

260

250

240

A

B

Base from U.S. Geological Survey

digital data, 1:100,000

0 10 MILES

0 10 KILOMETERS

Figure 5. Potentiometric surface of the Nacatoch aquifer, northeastern Arkansas, spring 2008.
Nacatoch Sand 7

34°00’

33°30’

94°00’ 93°30’

93°00’

T. 6 S.

T. 8 S.

T. 10 S.

T. 12 S.

T. 14 S.

R. 18 W.

R. 30 W. R. 28 W. R. 26 W. R. 24 W. R. 22 W. R. 20 W.

CLARK PIKE

HOWARD

SEVIER

LITTLE

RIVER

HEMPSTEAD

MILLER

NEVADA

LAFAYETTE

COLUMBIA

Prescott

Hope

Ashdown

400

350

300

250

200

175

150

425

325

275

225

175

375

D

F

C

E

208

215 215

223

309

300 283

264

177

178

241

242 236

226

239

259

154

232

186

220

256

314 365 283 393

153

421 294

331

335

442

152

177

244

181 176 145

157

163

182

172

191

320

245

185

197 167

178

Southwestern area

Outcrop of Nacatoch Sand

Approximate northern limit of Nacatoch aquifer

Potentiometric contour—Shows altitude at which water level would 

 have stood in tightly cased wells. Dashed where approximately located. 

 Hachures indicate depression. Contour interval 25 feet. Datum is

 National Geodetic Vertical Datum of 1929

Control point—Letter, where present, corresponds to hydrograph in 

 figure 7. Number is water level in feet above NGVD of 1929

Flowing artesian well—Number is water level in feet above NGVD of 1929

250

197

D 186

EXPLANATION

Base from U.S. Geological Survey

digital data, 1:100,000

0 10 20 MILES

0 10 20 KILOMETERS

Figure 6. Potentiometric surface of the Nacatoch aquifer, southwestern Arkansas, spring 2008.
8 Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008

Table 1. Water-level data collected during spring 2008 from wells completed in the Nacatoch Sand.—Continued

[NGVD of 1929, National Geodetic Vertical Datum of 1929; Horizontal datum is North American Datum of 1983]

Station Name

Latitude

 (degrees,

minutes,

seconds)

Longitude

(degrees,

minutes,

seconds)

Water-level

altitude

(feet above

NGVD of 1929)

Depth to water 

(feet below

land surface)

Land-surface 

datum

(feet above

NGVD of 1929)

Date of

measurement

Clark

08S19W06DCB1 340359 930433 191 78.98 270 2/28/2008

08S19W09ACC1 340323 930228 178 -0.85 177 2/28/2008

08S19W16CAB1 340226 930247 172 0.78 173 2/28/2008

08S20W34DAB1 335954 930744 182 18.47 200 2/28/2008

09S20W16DBD1 335708 930847 163 77.83 241 2/28/2008

09S20W16DDC1 335657 930845 157 75.93 233 2/28/2008

09S20W28DCB1 335516 930901 185 16.93 202 2/28/2008

09S20W31CAD1 335435 931111 145 114.39 259 2/28/2008

09S20W33ABD1 335447 930852 176 33.33 209 2/28/2008

09S20W33BCD2 335446 930926 181 26.22 207 2/28/2008

09S21W21DAD1 335625 931453 244 100.76 345 2/28/2008

10S20W22DCB1 335054 930757 177 83.18 260 2/28/2008

10S21W12BAB1 335321 931225 152 69.26 221 2/28/2008

Clay

19N04E01BDB1 361910 903560 269 11.33 280 3/03/2008

19N07E23BAC1 361602 901748 239 82.64 322 303/2008

19N07E23DBC1 361549 901730 245 37.68 283 3/03/2008

19N07E26AAA1 361532 901703 235 41.18 276 3/03/2008

20N04E36DCC1 361929 903542 264 15.24 279 3/03/2008

20N08E10ABC1 362313 901202 251 88.97 340 3/03/2008

20N08E14BAB2 362227 901120 241 44.63 286 3/03/2008

20N08E15BAA1 362224 901208 232 148.86 381 3/03/2008

21N06E23DAC1 362619 902329 272 28.02 300 3/03/2008

21N07E25AAC1 362550 901607 269 72.77 342 3/03/2008

Greene

18N06E14CCD1 361115 902420 239 48.12 287 3/04/2008

18N06E24ABB2 361112 902256 235 34.69 270 3/04/2008

18N06E24BDA1 361058 902300 236 39.84 276 3/04/2008

Hempstead

11S24W08BDB1 334837 933619 442 28.18 470 2/26/2008

11S24W21ADD1 334641 933449 320 50.29 370 2/26/2008

11S24W21DDD1 334621 933447 335 35.97 371 2/26/2008

11S24W22ADD1 334647 933343 331 34.13 365 2/26/2008

11S24W34CBC1 334444 933438 294 26.28 320 2/26/2008

11S26W27BDD1 334611 934645 421 9.16 430 2/25/2008

12S24W28CDC1 334012 933536 153 200.18 353 2/22/2008

12S25W07ABB1 334346 934340 393 42.14 435 2/25/2008

12S25W15DBC1 334214 934036 283 28.17 311 2/22/2008
Nacatoch Sand 9

Table 1. Water-level data collected during spring 2008 from wells completed in the Nacatoch Sand.—Continued

[NGVD of 1929, National Geodetic Vertical Datum of 1929; Horizontal datum is North American Datum of 1983]

Station Name

Latitude

 (degrees,

minutes,

seconds)

Longitude

(degrees,

minutes,

seconds)

Water-level

altitude

(feet above

NGVD of 1929)

Depth to water 

(feet below

land surface)

Land-surface 

datum

(feet above

NGVD of 1929)

Date of

measurement

Hempstead—Continued

12S25W34BAC1 334002 934055 245 74.80 320 2/26/2008

12S26W21AAC1 334158 934739 365 32.66 398 2/21/2008

12S26W24ABC1 334159 934438 314 0.72 315 2/21/2008

13S25W05ABD1 333915 934232 256 26.23 282 2/22/2008

13S25W18AAB1 333740 934332 220 62.99 283 2/22/2008

13S25W35DDC1 333406 933931 186 187.49 373 2/26/2008

13S26W17DDB1 333705 934845 232 58.57 291 2/21/2008

14S25W04DDD1 333317 934132 154 105.94 260 2/26/2008

Little River

13S28W31BCC1 333509 940251 259 51.81 311 2/19/2008

14S30W01DAA1 333426 940904 239 43.32 282 2/19/2008

Miller

14S27W02AAB1 333419 935121 226 29.23 255 2/20/2008

14S28W13CCB1 333158 935727 236 29.53 266 2/20/2008

14S28W17BBC1 333240 940134 242 28.42 270 2/20/2008

Nevada

10S22W23DCB1 335105 931935 241 0.66 242 2/27/2008

11S20W08DCD1 334727 931037 178 3.18 181 2/27/2008

11S20W15CDC1 334622 930905 167 8.12 175 2/27/2008

11S20W22AAA1 334624 930926 177 -1.76 175 2/27/2008

11S21W14CAB1 334652 931434 197 -1.20 196 2/27/2008

11S22W08DAC2 334760 932314 264 41.70 306 2/26/2008

11S22W08DDB4 334757 932314 283 22.92 306 2/26/2008

11S23W03DCD1 334840 932726 300 85.28 385 2/26/2008

11S23W12ABB1 334837 932541 309 72.40 381 2/26/2008

12S22W09CDD1 334230 932250 223 6.37 229 2/27/2008

12S22W22ACD1 334108 932135 215 126.93 342 2/27/2008

12S22W23CBA1 334102 932057 215 114.00 329 2/27/2008

13S22W07BDC1 333744 932514 208 135.48 343 2/27/2008
10 Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008

In the southwestern area, the direction of groundwater 

flow in the Nacatoch aquifer is generally towards the southsoutheast in Little River, Miller, and Hempstead Counties and 

to the east-southeast in Nevada and Clark Counties (fig. 6). 

This direction of flow may be affected by the increase in clay 

content in the downdip direction (Boswell and others, 1965). 

The highest water-level altitude measured was 442 ft in the 

outcrop area of north-central Hempstead County. The lowest water-level altitude measured was about 145 ft in Clark 

County. 

Three depressions exist in the southwestern area. The 

largest depression exists at Hope in Hempstead County (fig. 

6). Historical water levels indicate a decline of 40 ft from an 

altitude of 185 ft in 1942 to 145 ft in 1969 (Ludwig, 1972). 

The water-level altitude in January 2002 was 119 ft (Schrader 

and Scheiderer, 2004). This depression alters local groundwater-flow directions from the regional direction, with groundwater flowing towards Hope from the west, north, and northeast 

directions. A comparison with the 2002 potentiometric-surface 

maps (Schrader and Scheiderer, 2004) for the Nacatoch aquifer exhibits a substantial rise in water level at Hope from 119 

ft to 153 ft in 2000. Small depressions exist in southern Clark 

County and northeastern Hempstead County. The water level 

in the depression in southern Clark County has declined about 

1 ft from 146 ft in 2005 to 145 ft in 2008. The water level in 

the depression in northeastern Hempstead County has declined 

1 ft from 321 in 2005 to 320 ft in 2008. The rest of the southwestern and northeastern areas have minor variations in water 

level when compared to the 2005 maps.

Long-Term Water-Level Changes

Hydrographs from wells completed in the Nacatoch aquifer with long-term (minimum of 20 years) water-level measurements were constructed (two in the northeastern area and 

four in the southwestern area). A minimum 20-year period was 

used to minimize the effect of short-term variations in climate 

and localized pumping rates on water levels in a single well. 

Two long-term hydrographs are associated with two wells 

(sites A and B, fig. 7) located in the northeastern area (fig. 5). 

Water levels in both of these wells have an annual decline of 

about 1.2 ft/yr. In Clay County, well 20N08E10ABC1 consistently showed declines in water level from 1965 to 1990. 

These declines may be associated with increased withdrawals 

in Clay County during this period from 0.25 Mgal/d in 1965 

to 1.98 Mgal/d in 1990. However, water levels since 1998 

have been relatively stable, which may also be associated with 

withdrawals. Since 1990, withdrawals in Clay County have 

decreased from 1.98 Mgal/d in 1990 to 0.97 Mgal/d in 2005, a 

decrease of 51 percent (Halberg and Stephens, 1966; Holland, 

1993, 2007; Schrader, 2007). In Greene County, water levels 

in well 18N06E14CCD1 show an overall decline from 1977 

until 1990. Water levels have been relatively stable since then. 

Overall declines in both wells may be associated with withdrawals from the Nacatoch aquifer in the northeastern area 

from 1965 to 2005 with the majority of withdrawals occurring 

in Clay County (fig. 3). However, relatively stable water levels 

in Clay County from 1990 to 2005 may also be associated 

with decreased withdrawals.

Four wells with historical water-level measurements 

(sites C-F; fig. 7) are located in the southwestern area (fig. 

6). One well is located in each of the following four counties: 

Clark, Hempstead, Miller, and Nevada Counties. Water-level 

rise and decline varied by county.

Water levels in well 08S19W09ACC1 (site C, figs. 6 and 

7) declined from about 186 ft above NGVD of 1929 in 1962 to 

about 178 ft in 2008, an annual decline of about 0.2 ft/yr. The 

consistent decline in water level does not reflect the changes 

associated with water use from the Nacatoch aquifer in Clark 

County. 

Water levels in well 13S25W35DDC1 (site D, figs. 6 and 

7) declined from 188 ft in 1975 to 175 ft in 1979. Water use 

from the Nacatoch aquifer in Hempstead County increased 

from 1.44 Mgal/d in 1975 to 1.98 Mgal/d in 1980 (Halberg, 

1977; Holland and Ludwig, 1981), an increase of 72 percent 

(fig. 4). Water use declined from 1.98 Mgal/d in 1980 to 0.15 

Mgal/d in 1985. From 1979 to 1999, a general rise in water 

level was observed, but from 1999 to 2002, a sharp decrease 

in water level occurred. From 2005 to 2008, a small decrease 

in water level occurred. Water-use rates from the Nacatoch 

aquifer increased from 0.32 Mgal/d in 2000 to 2.53 Mgal/d 

in 2005, an increase of about 690 percent (Holland, 1987, 

1999, 2004, 2007). These fluctuations in water level can be 

explained by corresponding changes in water use from the 

Nacatoch aquifer in Hempstead County. 

Water levels in well 14S28W13CCB1 (site E, figs. 6 and 

7) ranged from 248 ft to 236 ft from 1962 to 2008. Withdrawals in Miller County were less than 0.10 Mgal/d from 1970 

through 2005 (fig. 4). Water-level changes in this well cannot 

be attributed to a specific factor. 

Water levels in well 11S22W08DAC2 (site F, figs. 6 

and 7), increased from about 179 ft in 1985 to about 267 ft in 

1990, an average rise of about 17.6 ft/yr in the 5-year period 

(Schrader, 2007). This increase in water levels occurred when 

the withdrawal rates from the Nacatoch aquifer in Nevada 

County decreased from 1.11 Mgal/d in 1985 to 0.44 Mgal/d 

in 1990 (Holland, 1987, 1993), a decrease of about 60 percent 

(fig. 4). Water levels declined 2 ft from about 266 in 2005 to 

264 in 2008. 

Although water levels in these six wells located in the 

northeastern and southwestern areas may be associated with 

changes in water use, including localized withdrawals that are 

not apparent in the county totals, other factors also may affect 

water levels such as climatic variations or changes in leakage 

to and from overlying and underlying rock units. 
Nacatoch Sand 11

1953 1957 1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009

220

240

260

280

300

320

340

WATER LEVEL, IN FEET ABOVE NGVD OF 1929

220

240

260

280

300

320

340

A. CLAY COUNTY, WELL 20N08E10ABC1

B. GREENE COUNTY, WELL 18N06E14CCD1

Figure 7. Water-level hydrographs for selected wells completed in the Nacatoch aquifer.
12 Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008

1953 1957 1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009

WATER LEVEL, IN FEET ABOVE NGVD OF 1929

120

140

160

180

200

220

240

140

160

180

200

220

240

260

C. CLARK COUNTY, WELL 08S19W09ACC1

D. HEMPSTEAD COUNTY, WELL 13S25W35DDC1

Figure 7. Water-level hydrographs for selected wells completed in the Nacatoch aquifer.—Continued
Nacatoch Sand 13

1953 1957 1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009

WATER LEVEL, IN FEET ABOVE NGVD OF 1929

180

200

220

240

260

280

300

160

180

200

220

240

260

280

E. MILLER COUNTY, WELL 14S28W13CCB1

F. NEVADA COUNTY, WELL 11S22W08DAC2

Figure 7. Water-level hydrographs for selected wells completed in the Nacatoch aquifer.—Continued
14 Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008

Tokio Formation

Hydrogeologic Setting

The Tokio Formation of Cretaceous age underlies the 

Brownstown Marl and overlies consolidated rocks of Mississippian and Pennsylvanian age in Clark and northeastern 

Nevada Counties (Plebuch and Hines, 1969); the Trinity 

Group of Early Cretaceous age in Pike, Nevada, Miller, and 

most of Hempstead Counties (Petersen and others, 1985); 

and the Woodbine Formation of Late Cretaceous age in Little 

River, Sevier, Howard, and northwestern Hempstead Counties (Boswell and others, 1965). The Tokio Formation outcrops in a southwest-to-northeast trending band from eastern 

Sevier County to west-central Clark County. The outcrop 

attains a maximum width of about 10 mi in Howard County 

and extends approximately 8 mi to the southwest into Sevier 

County. In this area, the Tokio Formation is overlain in several 

places by terrace deposits of Quaternary alluvium. The unit 

also outcrops in northwestern Little River County, west of the 

southwestern area. The unit ranges in thickness from about 

50 ft to more than 300 ft, dips towards the southeast, and is 

composed of discontinuous, interbedded gray clay and poorly 

sorted, crossbedded quartz sands, lignite, and a prevalent basal 

gravel (Counts and others, 1955; Boswell and others, 1965; 

Plebuch and Hines, 1969; Petersen and others; 1985). The 

Tokio Formation does not occur in the northeastern area.

The Tokio aquifer receives recharge from precipitation 

where it outcrops or is overlain by permeable alluvial and terrace deposits. Salinity increases downdip to the south-southeast. The Tokio aquifer yields freshwater to within a few miles 

north of Ashdown in Little River County (fig. 9) and becomes 

slightly to moderately saline downdip (southeast) from near 

Prescott to the fault zone trending across Nevada County 

(Petersen and others, 1985). 

The Tokio aquifer yields potable water to wells in eastern 

Little River County, southeastern Sevier County, southern 

Howard and Pike Counties, western Clark County, northern 

and central Hempstead County, and northwestern Nevada 

County. Wells penetrating the Tokio aquifer range in depth 

from a few feet in the outcrop area to about 1,200 ft at Hope 

and Prescott (Ludwig, 1972). Wells in central Hempstead 

County yield up to 300 gal/min. Wells flowing as much as 90 

gal/min occur in the bottom-land areas adjacent to streams 

(Counts and others, 1955). Historic records indicate that water 

levels in the aquifer did not decline appreciably from 1950 to 

1968, and that water levels had not been greatly affected by 

withdrawal of water at Hope and Prescott during this period 

(Ludwig, 1972). 

Water Use

Water withdrawn from the Tokio aquifer increased by 201 

percent from 2.0 Mgal/d in 1965 to 6.02 Mgal/d in 1980 (fig. 

8). Water withdrawn from the Tokio aquifer was 1.17 Mgal/d 

in 2000, a decrease of 80 percent from 1980. Water withdrawn 

from the Tokio aquifer was 4.58 Mgal/d in 2005, an increase 

of 291 percent from 2000 (Halberg and Stephens, 1966; Holland and Ludwig, 1981; Holland, 1999, 2004, 2007).

Water-use data for the Tokio aquifer by county is variable, with increases or decreases occurring over 5- to 20-year 

periods. Water withdrawals in Hempstead County increased 

by 348 percent from 0.67 Mgal/d in 1965 to 3.0 Mgal/d in 

1980 (fig. 8). Water withdrawn in Hempstead County was 0.76 

Mgal/d in 2000, a decrease of 75 percent from 1980. Water 

withdrawn increased to 2.10 Mgal/d in 2005, an increase of 

213 percent from 2000. By county, Hempstead County was the 

largest user of water from the Tokio aquifer in 2005. In Sevier 

County, water withdrawals were 0.15 Mgal/d in 1965, increasing to 1.15 Mgal/d in 1990, an increase of 667 percent from 

1965. From 1990 to 2000, water withdrawn in Sevier County 

decreased to 0.30 Mgal/d in 2000, a decrease of 74 percent 

from 1990. Water withdrawn in 2005 was 1.73 Mgal/d, an 

increase of 477 percent from 2000. In Howard County, water 

withdrawals were 0.69 Mgal/d in 1965, increasing to 1.11 

Mgal/d in 1980, an increase of 61 percent from 1965. Water 

withdrawals decreased to 0.14 Mgal/d in 1985 and to less than 

0.1 Mgal/d in 1990, 1995, and 2000. In 2005, water withdrawals increased to 0.50 Mgal/d in Howard County. In Nevada 

County, water withdrawals were 0.37 Mgal/d in 1965, increasing to 0.68 Mgal/d in 1980, an increase of 84 percent from 

1965. Water withdrawals decreased to less than 0.1 Mgal/d in 

1990, 1995, 2000, and 2005. In Pike County, water withdrawals were 0.12 Mgal/d in 1965, increasing to 0.82 Mgal/d in 

1980, an increase of 583 percent from 1965. Water withdrawals decreased to less than 0.1 Mgal/d in 1990, 1995, 2000, 

and 2005. Water withdrawls in Clark, Little River, and Miller 

Counties were less than 0.1 Mgal/d from 1965 through 2005 

(Halberg and Stephens, 1966; Holland and Ludwig, 1981; 

Holland, 1999, 2004, 2007). 

Potentiometric Surface

The potentiometric-surface map for the Tokio aquifer 

shows the altitude that water would have stood in tightly cased 

wells screened in the aquifer (fig. 9). Water-level measurements (table 2) in 50 wells during spring 2008 were used to 

construct the map. The surface was mapped by determining the altitude of the water levels and is represented on the 

map by contour lines that connect points of equal value. The 

general direction of groundwater flow is perpendicular to the 

contours in the direction of downward hydraulic gradient.

In the southwestern area, the direction of groundwater flow in the Tokio aquifer generally is towards the south 

or southeast. The potentiometric-surface high is within the 

outcrop area in the northwestern part of the southwestern area. 

The highest water-level altitude measured was 488 ft above 

NGVD of 1929 in the outcrop area of Howard County. The 

lowest water-level altitude measured was 129 ft above NGVD 

of 1929 about 5 mi northwest of Hope in Hempstead County. 
Tokio Formation 15

1965 1970 1975 1980 1985 1990 1995 2000 2005

0

1

2

3

4

5

6

7

WITHDRAWALS, IN MILLION GALLONS PER DAY

Clark County

Hempstead County

Howard County

Nevada County

Pike County

Sevier County

Total Tokio aquifer

EXPLANATION

Water use data from Halberg and Stephens (1966);

Halberg (1972, 1977); Holland and Ludwig (1981); and 

Holland (1987, 1993, 1999, 2004, 2007).

Figure 8. Withdrawals for the Tokio aquifer 

for the southwestern area in Arkansas.

An area of artesian flow exists in southeastern Pike, northeastern Hempstead, and northwestern Nevada Counties as 

evidenced by eight flowing artesian wells (fig. 9).

A cone of depression may exist about 5 mi northwest of 

Hope. The northern half of an apparent cone of depression 

northwest of Hope is shown on figure 9. Water-level data in 

the Tokio aquifer were not available south of this area. No 

other cones of depression were evident in the Tokio aquifer. A 

comparison of the 2008 map with the 2002 and 1999 potentiometric-surface maps for the Tokio aquifer shows one substantial change; the 300-foot contour is positioned further north in 

Howard County. The change in this contour is the result of the 

addition of the measurement at well 10S27W02ACD1, which 

had not been collected prior to 2005. 

Long-Term Water-Level Changes

Four hydrographs from wells completed in the Tokio 

aquifer have long-term (minimum of 20 years) water-level 

altitudes (fig. 10). Two wells are located in Hempstead County 

(sites G and H) and the other two wells are located in Howard 

(site I) and Nevada (site J) Counties (fig. 9). The minimum 

20-year period is used to decrease the effect of short-term 

variations in climate and localized pumping rates on water 

levels in a single well.

The two hydrographs in Hempstead County show differences between water-level trends over long periods. In 

well 09S23W33CDA1 (site G, figs. 9 and 10), water levels 

generally declined from 1958 to 2008. Water levels in well 

12S24W06DAD1 (site H, figs. 9 and 10) fluctuated through a 

range in altitude of about 276 to about 132 ft over a 37-year 

period. Water levels generally declined from 1971 to 1979, 

generally rose from 1979 to 1989, then declined from 1989 

to 1999. The average annual decline in water level at well 

12S24W06DAD1 from 1971 to 2008 was 3.8 ft/yr. Water 

withdrawals in Hempstead County increased from 0.67 Mgal/d 

in 1965 to 3.0 Mgal/d in 1980, then decreased to 0.76 Mgal/d 

in 2000. Water withdrawn increased to 2.10 Mgal/d in 2005. 

The decline and rise in water levels in well 12S24W06DAD1 

may be associated with the fluctuating withdrawals from the 

Tokio aquifer in Hempstead County, whereas water levels 

in well 09S23W33CDA1 do not appear to have a similar 

association.
16 Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008

34°00’

33°30’

94°00’ 93°30’

93°00’

T. 6 S.

T. 8 S.

T. 10 S.

T. 12 S.

T. 14 S.

R. 18 W.

R. 30 W. R. 28 W. R. 26 W. R. 24 W. R. 22 W. R. 20 W.

CLARK

PIKE

HOWARD

SEVIER

LITTLE

RIVER

HEMPSTEAD

MILLER

NEVADA

LAFAYETTE

COLUMBIA

Prescott

Hope

Ashdown

287 282 258

351

279 269

271

251

279

320

364

288

429

214 213

235 220

263

315

337 306 283

467

368

396

413

426

197

259

260

129 132

323

300

366

319

292

401 421

436

283 373 220

201

205

271

358

435

489

219

425

400

375

350

325

300

275

250

225

200

175

150

450

475

J

H

I

G

Base from U.S. Geological Survey

digital data, 1:100,000

0 10 20 MILES

0 10 20 KILOMETERS

Southwestern area

Outcrop of Tokio Formation

Approximate area of artesian flow

Approximate northern limit of Tokio aquifer

Potentiometric contour—Shows altitude at which water level would 

 have stood in tightly cased wells. Dashed where approximately located. 

 Contour interval 25 feet. Datum is National Geodetic Vertical Datum of 1929

Control point—Letter, where present, corresponds to hydrograph in 

 figure 10. Number is water level in feet above NGVD of 1929

Flowing artesian well—Number is water level in feet above NGVD of 1929

250

251

J 214

EXPLANATION

Figure 9. Potentiometric surface of the Tokio aquifer, southwestern Arkansas, spring 2008.
Tokio Formation 17

Table 2. Water-level data collected during spring 2008 from wells completed in the Tokio Formation.—Continued

[NGVD of 1929, National Geodetic Vertical Datum of 1929; Horizontal datum is North American Datum of 1983; a negative depth to water indicates 

a flowing artesian well]

Station name

Latitude

(degrees, minutes, seconds)

Longitude 

(degrees, minutes, seconds)

Water-level

altitude 

(feet above

NGVD of 1929)

Depth to water 

(feet below

land surface)

Land-surface 

datum

(feet above

NGVD of 1929)

Date of

measurement

Clark County

08S22W05CCC1 340408 932256 358 31.63 390 2/27/2008

08S22W15ABB2 340313 932018 271 53.59 325 2/27/2008

09S22W05BBB1 335951 932259 205 107.18 312 2/28/2008

09S22W05BCA1 335936 932257 201 33.60 235 2/28/2008

09S22W10DBA1 335832 932022 219 142.93 362 2/27/2008

09S22W16ACA1 335754 932120 220 13.23 233 2/27/2008

Hempstead County

09S23W20BDA1 335710 932859 251 -1.23 250 2/21/2008

09S23W33CDA1 335457 932802 271 -0.95 270 2/21/2008

09S24W25BBB1 335633 933132 269 -0.50 268 2/21/2008

09S24W28ACC1 335617 933415 279 -2.11 277 2/21/2008

09S24W30DCC1 335556 933607 373 17.04 390 2/21/2008

09S24W33ADC1 335526 933356 283 45.87 329 2/21/2008

09S26W08ADA2 335920 934717 435 2.53 438 2/21/2008

09S26W08ADD1 335918 934717 436 0.73 437 2/21/2008

09S26W09CDC1 335846 934656 421 3.89 425 2/21/2008

09S26W18CBB1 335815 934921 401 23.54 425 2/21/2008

10S25W09CDB1 335329 934052 292 69.48 361 2/21/2008

10S25W30CCD1 335048 934310 319 69.32 388 2/21/2008

10S26W03BBA1 335507 934612 366 1.18 367 2/25/2008

11S26W08BBB1 334909 934903 300 71.58 372 2/25/2008

11S26W23BBB1 334720 934602 323 95.74 419 2/25/2008

12S24W06DAD1 334360 933701 132 222.56 355 2/25/2008

12S25W02DDD1 334341 933902 129 237.92 367 2/22/2008

12S27W04BBC1 334450 935358 260 174.83 435 2/25/2008

12S27W05AAC1 334449 935421 259 176.22 435 2/25/2008

12S27W36DBC1 333958 935024 197 63.61 261 2/21/2008

Howard County

09S27W03DBD1 340000 935153 488 73.52 562 2/20/2008

09S27W10BCB1 335930 935232 426 108.06 534 2/20/2008

09S27W18ADB1 335840 935453 413 78.62 492 2/20/2008

09S27W32BDB1 335606 935424 396 54.57 451 2/20/2008

09S27W32BDB2 335606 935424 368 81.58 450 2/20/2008

09S28W20DAC1 335740 940014 467 12.64 480 2/20/2008

10S27W02ACD1 335454 935056 283 75.49 358 2/20/2008

10S27W04BBD1 335512 935330 337 55.48 392 2/20/2008

10S27W12CAB1 335356 935021 306 76.98 383 2/20/2008

10S27W18BAC1 335336 935535 315 106.87 422 2/20/2008
18 Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008

Table 2. Water-level data collected during spring 2008 from wells completed in the Tokio Formation.—Continued

[NGVD of 1929, National Geodetic Vertical Datum of 1929; Horizontal datum is North American Datum of 1983; a negative depth to water indicates 

a flowing artesian well]

Station name

Latitude

(degrees, minutes, seconds)

Longitude 

(degrees, minutes, seconds)

Water-level

altitude 

(feet above

NGVD of 1929)

Depth to water 

(feet below

land surface)

Land-surface 

datum

(feet above

NGVD of 1929)

Date of

measurement

Little River County

11S30W25DDC1 334618 940852 263 22.16 285 2/19/2008

Nevada County

09S22W33DCC1 335437 932130 220 5.47 225 2/26/2008

10S23W12AAA1 335345 932421 235 21.14 256 2/26/2008

11S22W08DAC1 334758 932315 213 92.17 305 2/26/2008

11S22W08DAC8 334757 932312 214 91.47 305 2/26/2008

Pike County

08S23W19ADC1 340213 932931 351 -1.01 350 2/20/2008

08S23W35DCA1 340004 932530 258 -1.15 257 2/20/2008

08S24W14AAC1 340324 933134 429 94.41 523 2/20/2008

09S23W17BBC2 335804 932925 282 -1.83 280 2/20/2008

09S24W14AAD1 335810 933139 287 -1.63 285 2/20/2008

Sevier County

10S28W31DCC1 335026 940145 288 41.84 330 2/19/2008

11S29W05DCA1 334949 940653 364 116.33 480 2/19/2008

11S29W08DBB1 334907 940704 320 144.83 465 2/19/2008

11S29W13CCD1 334750 940317 279 81.42 360 2/19/2008
Tokio Formation 19

1953 1957 1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009

WATER LEVEL, IN FEET ABOVE NGVD OF 1929

220

240

260

280

300

320

340

120

140

160

180

200

220

240

260

280

G. HEMPSTEAD COUNTY, WELL 09S23W33CDA1

H. HEMPSTEAD COUNTY, WELL 12S24W06DAD1

Figure 10. Water-level hydrographs for selected wells completed in the Tokio aquifer.
20 Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008

1953 1957 1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009

WATER LEVEL, IN FEET ABOVE NGVD OF 1929

420

440

460

480

500

520

540

120

140

160

180

200

220

240

I. HOWARD COUNTY, WELL 09S28W20DAC1

J. NEVADA COUNTY, WELL 11S22W08DAC1

Figure 10. Water-level hydrographs for selected wells completed in the Tokio aquifer.—Continued
Summary 21

In Howard County, water levels in well 09S28W20DAC1 

(site I, figs. 9 and 10) range from about 476 ft to about 464 ft 

over a 51-year period from 1957 to 2008. No substantial rises 

or declines in water levels were observed. In Howard County, 

water withdrawals were 0.69 Mgal/d in 1965, increasing to 

1.11 Mgal/d in 1980. Water withdrawals decreased to 0.14 

Mgal/d in 1985 and less than 0.1 Mgal/d in 1990, 1995, and 

2000. In 2005, water withdrawals increased to 0.50 Mgal/d in 

Howard County. There does not appear to be any association 

between water levels in this well and withdrawals from the 

Tokio aquifer (fig. 8).

In Nevada County, water levels in well 11S22W08DAC1 

(site J, figs. 9 and 10) declined from about 211 ft in 1972 to 

about 150 ft in 1985, with a minimum of 135 ft in 1981. This 

is an annual decline of about 4.7 ft/yr. Water withdrawals from 

the Tokio aquifer for Nevada County increased from 0.37 

Mgal/d in 1965 to 0.68 Mgal/d in 1980 (fig. 8). From 1985 

to 1987, a rise in water level to about 225 ft was observed, 

which is an approximately 37.5 ft/yr rise. From 1998 to 2008, 

there was a decline in water level from about 225 ft to about 

213 ft, respectively. Water withdrawals from Nevada County 

decreased to less than 0.10 Mgal/d by 1985 and continued 

at this rate through 1990, 2000, and 2005. The decline and 

rise in water levels may be associated with the increased and 

decreased withdrawals from the Tokio aquifer.

Although water levels in these four wells may be associated with changes in water use, other factors also may affect 

water levels such as climatic variations or changes in leakage 

to and from overlying and underlying rock units. 

Summary

Aquifers in the Nacatoch Sand and Tokio Formation in 

southwestern Arkansas and the Nacatoch Sand in northeastern 

Arkansas are sources of water for industrial, public supply, 

domestic, and agricultural uses. A study was conducted by 

the U.S. Geological Survey in cooperation with the Arkansas 

Natural Resources Commission and the Arkansas Geological 

Survey to provide potentiometric-surface maps and waterlevel hydrographs associated with aquifers in the Nacatoch 

Sand and Tokio Formation (hereafter referred to as the Nacatoch aquifer and Tokio aquifer, respectively) in southwestern 

Arkansas and the Nacatoch aquifer in northeastern Arkansas. 

Potentiometric-surface maps were constructed from 

water-level measurements made in 61 wells completed in the 

Nacatoch Sand and 50 wells completed in the Tokio Formation during spring 2008. In northeastern Arkansas, withdrawals from the Nacatoch aquifer increased by 480 percent from 

1965 to 2005. In southwestern Arkansas, withdrawals from the 

Nacatoch and Tokio aquifers increased by 125 percent and 201 

percent, respectively, from 1965 to 1980 and decreased by 93 

percent and 80 percent, respectively, from 1980 to 2000. Withdrawals from Nacatoch aquifer and Tokio aquifer increased by 

690 percent and 291 percent, respectively, from 2000 to 2005.

The direction of groundwater flow in the northeastern 

area of the Nacatoch aquifer generally is towards the southeast. The highest water level measured is located in northern 

Clay County along the north and northwestern boundary of 

this area. The lowest water level measured is located in eastern 

Clay County.

The direction of groundwater flow in the southwestern 

area of the Nacatoch aquifer is towards the south-southeast in 

Little River, Miller, and Hempstead Counties and to the eastsoutheast in Nevada and Clark Counties. The highest water 

level measured is located in the outcrop area in north-central 

Hempstead County. A depression exists at Hope in Hempstead 

County. Small depressions exist in southern Clark County and 

northeastern Hempstead County.

In the northeastern area of the Nacatoch aquifer, water 

levels in two wells declined during a period of increased withdrawals from the Nacatoch aquifer. Water levels in these wells 

have an annual decline of about 1.2 ft/yr. The Clay County 

well consistently showed declines in water level from 1965 

to 1990. These declines may be associated with increased 

withdrawals in Clay County during this period. However, 

water levels since 1998 have been relatively stable. Withdrawals in Clay County have decreased from 1.98 Mgal/d in 1990 

to 0.97 Mgal/d in 2005. The Greene County well shows an 

overall decline from 1977 until 1990. Water levels have been 

relatively stable since then. 

In the southwestern area of the Nacatoch aquifer, the 

sharp decrease in withdrawal rates is explained by public 

water supplies in the southwestern area converting to surface 

water and relying less on groundwater sources. Four wells 

with historical measurements are located in the southwestern 

area. Water levels in the Hempstead County well show a 

decline from 1975 to 1979, a general rise from 1979 to 1999, 

a sharp decrease from 1999 to 2002, and a small decrease 

from 2005 to 2008. These fluctuations in water level can be 

explained by changes in water use. Water levels in the Nevada 

County well show an increase from 1985 to 1990, an average 

rise of about 17.6 ft/yr. This increase in water levels occurred 

when the withdrawal rates from the Nacatoch aquifer in 

Nevada County decreased from 1985 to 1990. Water levels 

declined from 2005 to 2008. Water levels in the Clark and 

Miller County wells do not reflect the changes associated 

with water use. The variation in water levels in these six wells 

located in the northeastern and southwestern areas could result 

from differences in localized withdrawals, climatic variations, 

or leakage of water from overlying and underlying rock units.

The direction of groundwater flow in the Tokio aquifer 

generally is towards the south or southeast. The highest water 

level measured is located where the aquifer outcrops in the 

northwestern part of the study area. An area of artesian flow 

exists in southeastern Pike, northeastern Hempstead, and 

northwestern Nevada Counties. A cone of depression may 

exist about 5 miles northwest of Hope in Hempstead County.

The hydrographs of two of four wells completed in the 

Tokio aquifer showed a decline and a rise in water levels 
22 Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008

during a period of increased, then decreased withdrawals from 

the Tokio aquifer. Water levels in the two wells in Hempstead County show differences between water-level trends 

over long periods. In well 09S23W33CDA1, water levels 

generally declined from 1958 to 2008. Water levels in well 

12S24W06DAD1 fluctuated over a 37-year period. Water 

levels generally declined from 1971 to 1979, generally rose 

from 1979 to 1989, then declined from 1989 to 1999. The 

decline and rise in water levels in well 12S24W06DAD1 may 

be associated with the fluctuating withdrawals from the Tokio 

aquifer in Hempstead County, whereas water levels in well 

09S23W33CDA1 do not appear to have a similar association. 

In the Howard County well there does not appear to be any 

association between water levels in this well and withdrawals 

from the Tokio aquifer. Water levels in the Nevada County 

well declined from 1972 to 1985 and rose from 1985 to 1987. 

The decline and rise in water levels may be associated with the 

increased and decreased withdrawals from the Tokio aquifer.

Selected References

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1965, Cretaceous aquifers in the Mississippi Embayment: 

U.S. Geological Survey Professional Paper 448- C, 37 p.

Counts, H.B., Tait, D.B., Klein, Howard, and Billingsley, 

G.A., 1955, Ground-water resources in a part of southwestern Arkansas: U.S. Geological Survey Water Resources 

Circular No. 2, 35 p.

Fenneman, N.M., 1938, Physiography of western United 

States: New York, McGraw-Hill Book Co., Inc., 689 p.

Halberg, H.N., 1972, Use of water in Arkansas, 1970: Arkansas Geological Commission Water Resources Summary 

Number 7, 17 p.

Halberg, H.N., 1977, Use of water in Arkansas, 1975: Arkansas Geological Commission Water Resources Summary 

Number 9, 28 p.

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

Arkansas, 1965: Arkansas Geological Commission Water 

Resources Summary Number 5, 12 p.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in 

water resources: New York, NY, Elsevier Science Publishing Co., 522 p.

Holland, T.W., 2007, Estimated water use in Arkansas, 2005: 

U.S. Geological Survey Scientific Investigations Report 

2004-5230, 31 p. 

Holland, T.W., 2004, Estimated water use in Arkansas, 2000: 

U.S. Geological Survey Scientific Investigations Report 

2007-5241, 32 p. 

Holland, T.W., 1999, Water use in Arkansas, 1995: U.S. Geological Survey Open-File Report 99-188, 1 sheet. 

Holland, T.W., 1993, Use of water in Arkansas, 1990: U.S. 

Geological Survey Open-File Report 93-48, pamphlet.

Holland, T.W., 1987, Use of water in Arkansas, 1985: Arkansas Geological Commission Water Resources Summary 

Number 16, 30 p.

Holland, T.W., and Ludwig, A.H., 1981, Use of water in 

Arkansas, 1980: Arkansas Geological Commission Water 

Resources Summary Number 14, 30 p.

Ludwig, A.H., 1972, Water resources of Hempstead, Lafayette, Little River, Miller, and Nevada Counties, Arkansas: 

U.S. Geological Survey Water-Supply Paper 1998, 41 p.

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

of the Sparta Sand in Arkansas, Louisiana, Mississippi, and 

Texas: U.S. Geological Survey Professional Paper 569-A, 

17 p.

Petersen, J.C., Broom, M.E., and Bush, W.V., 1985, Geohydrologic units of the Gulf Coastal Plain in Arkansas: U.S. 

Geological Survey Water-Resources Investigations Report 

85-4116, 20 p.

Plebuch, R.O., and Hines, M.S., 1969, Water resources of 

Clark, Cleveland, and Dallas Counties, Arkansas: U.S. Geological Survey Water-Supply Paper 1879-A, 32 p.

Schrader. T.P., 2007, Status of water levels in aquifers in the 

Nacatoch Sand of southwestern and northeastern Arkansas 

and Tokio Formation of southwestern Arkansas, February 2005: U.S. Geological Survey Scientific Investigations 

Report 2007-5024, 21 p.

Schrader. T.P., and Scheiderer, R.M., 2004, Status of water 

levels in aquifers in the Nacatoch Sand of southwestern and 

northeastern Arkansas and Tokio Formation of southwestern 

Arkansas, 2002: U.S. Geological Survey Water- Resources 

Investigations Report 03-4284, 24 p.
Publishing support provided by:

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For more information concerning the research

described in the report

U.S. Geological Survey

Arkansas Water Science Center

401 Hardin Road

Little Rock, AR 72211-3528

(501) 228-3600

http://ar.water.usgs.gov

Schrader and Blackstock—Water Levels in Aquifers in the Nacatoch Sand and the Tokio Formation, Spring 2008—Scientific Investigations Report 2010–5238

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