Prepared in cooperation with the

Arkansas Soil and Water Conservation Commission and the

Arkansas Geological Commission

STATUS OF WATER LEVELS IN AQUIFERS IN THE 

NACATOCH SAND OF SOUTHWESTERN AND 

NORTHEASTERN ARKANSAS AND THE TOKIO 

FORMATION OF SOUTHWESTERN ARKANSAS, 2002

Water-Resources Investigations Report 03-4284

36

35

34

94 93 92 91

90 O

O

O

O

O

O

O

O

0 20 40 MILES

0 20 40 KILOMETERS

FALL

LINE

FALL

LINE

PLAIN

OZARK PLATEAUS

ARKANSAS VALLEY HIGHLANDS

INTERIOR

COASTAL

OUACHITA

MOUNTAINS

MISSISSIPPI

ALLUVIAL

PLAIN

WEST

GULF

COASTAL

PLAIN

Sevier

Howard Pike

Clark

Hempstead

Little

River

Nevada

Clay

Greene

Miller

Lafayette

Columbia TEXAS

LOUISIANA

MISSISSIPPI

TENNESSEE

MISSOURI

OKLAHOMA

Mississippi

River

Physiographic boundaries

from Fenneman (1938)

Base from U.S. Geological Survey

digital data, 1:100,000

U.S. Department of the Interior

U.S. Geological Survey
STATUS OF WATER LEVELS IN AQUIFERS IN THE 

NACATOCH SAND OF SOUTHWESTERN AND 

NORTHEASTERN ARKANSAS AND THE TOKIO 

FORMATION OF SOUTHWESTERN ARKANSAS, 2002

by T.P. Schrader and Rheannon M. Scheiderer

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 03-4284

Prepared in cooperation with the

Arkansas Soil and Water Conservation Commission

and the Arkansas Geological Commission

Little Rock, Arkansas

2004
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

For additional information Copies of this report can be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey, WRD Branch of Information Services

401 Hardin Road Box 25286

Little Rock, Arkansas 72211 Denver Federal Center

Denver, Colorado 80225

The use of firm, trade, and brand names in this report is for identification purposes only and does not

constitute endorsement by the U.S. Geological Survey.
Contents III

CONTENTS

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

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

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

Nacatoch Sand....................................................................................................................................................4

Hydrogeologic Setting .............................................................................................................................. 4

Potentiometric Surface.............................................................................................................................. 6

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

Tokio Formation...............................................................................................................................................15

Hydrogeologic Setting ............................................................................................................................ 15

Potentiometric Surface............................................................................................................................ 17

Long-Term Water-Level Changes ........................................................................................................... 20

Summary ..........................................................................................................................................................23

References........................................................................................................................................................23

ILLUSTRATIONS

Figure 1. Map showing location of study subareas ........................................................................................ 2

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

3. Graph showing estimated water use by county from the Nacatoch aquifer for the 

northeastern subarea ................................................................................................................... 5

4. Graph showing estimated water use by county from the Nacatoch aquifer for the

southwestern subarea.................................................................................................................. 5

5. Map showing hydrogeologic setting and potentiometric surface of the Nacatoch aquifer,

northeastern Arkansas, January-February 2002 ......................................................................... 6

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

January-February 2002............................................................................................................... 7

7. Water-level altitudes for selected wells completed in the Nacatoch aquifer.................................10

8. Map showing hydrogeologic setting and potentiometric surface of the Tokio aquifer,

southwestern Arkansas, January 2002......................................................................................16

9. Graph showing estimated water use by county from the Tokio aquifer........................................17

10. Water-level altitudes for selected wells completed in the Tokio aquifer.......................................21

TABLES

Table 1. Water-level measurements and well information for wells completed in the Nacatoch

aquifer......................................................................................................................................... 8

2. Water-level measurements and well information for wells completed in the Tokio aquifer...........18
Abstract 1

Status of Water Levels in Aquifers in the Nacatoch Sand 

of Southwestern and Northeastern Arkansas and the 

Tokio Formation of Southwestern Arkansas, 2002

By T.P. Schrader and Rheannon M. Scheiderer

ABSTRACT

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. Potentiometricsurface maps were constructed from water-level 

measurements made in 60 wells completed in the 

Nacatoch Sand and 48 wells completed in the 

Tokio Formation during January and February 

2002.

In northeastern Arkansas, withdrawals from 

the Nacatoch Sand increased by 784 percent from 

1965 to 1990 and decreased by 30 percent from 

1990 to 2000. In southwestern Arkansas withdrawals from aquifers in the Nacatoch Sand and 

Tokio Formation increased by 125 percent and 201 

percent, respectively, from 1965 to 1980 and 

decreased by 93 percent and 81 percent, respectively, from 1980 to 2000. Long-term hydrographs 

were prepared for 13 wells in the study area. 

Changes in water levels in some wells may be 

associated with changes in withdrawals from the 

respective aquifers.

The direction of ground-water flow in the 

aquifer in the Nacatoch Sand in northeastern 

Arkansas generally is towards the southeast. The 

potentiometric high is located along the north and 

northwestern boundaries of the subarea. 

The direction of ground-water flow in the 

aquifer in the Nacatoch Sand in southwestern 

Arkansas is towards the south-southeast in Little 

River, Miller, and Hempstead Counties and to the 

east-southeast in Nevada and Clark Counties. The 

potentiometric high is located within the outcrop 

area in north-central Hempstead County. Cones of 

depression exist in the aquifer in the Nacatoch 

Sand in southeastern Hempstead County and in 

southwestern Clark County.

The direction of ground-water flow in the 

aquifer in the Tokio Formation in southwestern 

Arkansas generally is towards the south or southeast. The potentiometric high 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. One apparent cone of 

depression may exist northwest of Hope in Hempstead County.

INTRODUCTION

Ground water 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 a source of water for industrial, public 

supply, domestic, and agricultural uses. Monitoring of 

ground-water levels and withdrawals provides information needed to effectively plan and manage the 

resource. The U.S. Geological Survey (USGS) conducted this study in cooperation with the Arkansas Soil 

and Water Conservation Commission and the Arkansas 

Geological Commission to provide potentiometric-surface maps and water-level hydrographs associated with 

aquifers in the Nacatoch Sand and Tokio Formation 
2 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation 

of Southwestern Arkansas, 2002

(hereinafter referred to as the Nacatoch aquifer and 

Tokio aquifer, respectively) in southwestern Arkansas 

and the Nacatoch aquifer in northeastern Arkansas. 

The study area comprises parts of 10 counties in 

two subareas of northeastern and southwestern Arkansas. The northeastern subarea includes most of Clay 

and Greene Counties in the Mississippi Alluvial Plain 

physiographic section (fig. 1). This subarea 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 subarea was defined by 

the area of water use in the Nacatoch aquifer. The 

southwestern subarea includes parts of eight counties 

(Clark, Hempstead, Howard, Little River, Miller, 

Nevada, Pike, and Sevier) in the West Gulf Coastal 

Plain physiographic section (fig. 1). This subarea is 

bounded on the north approximately by the Fall Line 

separating the Interior Highlands from the West Gulf 

Coastal Plain, on the southwest by the Texas State line, 

on the west by the western extent of withdrawals in Little River and Sevier Counties, and on the east by the 

eastern borders of Clark and Nevada Counties. The 

southwestern subarea was limited to the occurrence of 

freshwater; the southern boundary of the subarea is 

defined by a freshwater/saltwater interface. To the 

south, the ground water 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 60 wells completed in the Nacatoch aquifer and in 48 wells completed in the Tokio 

aquifer during January and February 2002. These measurements were used to construct potentiometric-surface maps. All water-level data are stored in the USGS 

Ground-Water Site Inventory (GWSI) data storage system. Long-term water-level hydrographs were prepared 

for selected wells. County withdrawal data collected by 

the USGS from 1965 to 2000 are presented and related 

to these hydrographs. The Tokio Formation is stratigraphically below the Nacatoch Sand and separated 

from it by five stratigraphic units, listed here in 

Figure 1. Location of study area.

36

35

34

94 93 92 91

90 O

O

O

O

O

O

O

O

0 20 40 MILES

0 20 40 KILOMETERS

FALL

LINE

FALL

LINE

PLAIN

OZARK PLATEAUS

ARKANSAS VALLEY HIGHLANDS

INTERIOR

COASTAL

OUACHITA

MOUNTAINS

MISSISSIPPI

ALLUVIAL

PLAIN

WEST

GULF

COASTAL

PLAIN

EXPLANATION

Study Area

Boundary of

physiographic

section

Sevier

Howard

Pike

Clark

Little Hempstead

River

Nevada

Clay

Greene

Miller Lafayette

Columbia

TEXAS

LOUISIANA

MISSISSIPPI

TENNESSEE

MISSOURI

OKLAHOMA

Mississippi

River

Physiographic boundaries

from Fenneman (1938)

Base from U.S. Geological Survey

digital data, 1:100,000
Methods 3

descending stratigraphic order: Saratoga Chalk, Marlbrook Marl, Annona Chalk, Ozan Formation, and 

Brownstown Marl. The Saratoga Chalk, Marlbrook 

Marl, and Annona Chalk are non-water bearing and the 

five unit section can obtain a thickness of 900 feet (ft) 

in the study area, which hydraulically separates the 

Nacatoch and Tokio aquifers. These five units rarely 

are used as water sources and are not discussed in this 

report.

Cones of depression within a potentiometric surface are indicators of pumping rates that are exceeding 

the local recharge rates to the aquifer. During pumping, 

water levels are drawn down, forming a local cone of 

depression. Water levels will recover to static conditions if pumping rates do not exceed the recharge rates 

to the aquifer. 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 could account 

for changes shown by long-term hydrographs.

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 which 

indicate, respectively, the quarter section, the quarterquarter section, and the quarter-quarter-quarter 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 quarterquarter-quarter 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. Wells were located using a Global Positioning System (GPS) capable of accuracy to one-tenth 

of a second of latitude and longitude, referenced to 

North American Datum 1983.

Figure 2. Well-numbering system.

METHODS

Personnel from the U.S. Geological Survey collected water-level measurements during January and 

February 2002 from wells screened in either the Nacatoch or Tokio aquifer. Measurements were collected 

using steel or electric tapes graduated in hundredths of 

a foot. The steel and electric tapes were calibrated during January 2002, prior to collecting measurements 

from wells. Well locations were measured using a Global Positioning System receiver to acquire the horizontal coordinate information, latitude and longitude, 

based on the North American Datum of 1983. The latitude and longitude of the well location was transferred 

to the topographic map and the altitude (National Geodetic Vertical Datum of 1929), was determined at the 

location. 

A

B

A

C

D

C

D

B

A

B

A

C

D

C

D

C

D

B

A

B

C A DB

6

3

2

1

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

R-3-W

T-1-S

SECTION 4

WELL 01S03W04BBD16

4S 3S 2S 1S

5W 4W 3W 2W 1W 1E 2E 3E 4E

PRINCIPAL MERIDIAN

BASELINE

WEST

RANGES

EAST SOUTH

TOWNSHIPS

NORTH
4 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation 

of Southwestern Arkansas, 2002

NACATOCH SAND

Hydrogeologic Setting

The Nacatoch Sand of the Upper Cretaceous 

series is overlain by the Arkadelphia Marl and underlain by the Saratoga Chalk. In the northeastern subarea, 

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 the National Geodetic Vertical 

Datum of 1929 (NGVD of 1929) along the western 

boundary, dips toward the southeast (Petersen and others, 1985), and descends to about 500 ft below the 

NGVD of 1929 at the eastern boundary. The unit is 

about 100 ft thick near the subcrop and attains a maximum thickness of about 300 ft downdip. 

The Nacatoch aquifer in the northeastern subarea 

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 alluvial and terrace deposits in 

western Clay and Greene Counties.

In the southwestern subarea, 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 the NGVD of 1929 in the outcrop, dips 

towards the southeast, and descends to about 800 ft 

below the NGVD of 1929 at the southern boundary of 

the subarea (Petersen and others, 1985). The Nacatoch 

Sand is about 100 ft thick near the outcrop and attains 

a maximum thickness of about 300 ft.

The Nacatoch Sand in the southwestern subarea 

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 aquifer. 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 subarea, the Nacatoch aquifer receives recharge from precipitation in its outcrop 

areas in Clark, Nevada, and Hempstead Counties and 

through the overlying alluvial and terrace deposits in 

Little River County and in northeastern Texas.

The Nacatoch aquifer is used in northeastern 

Green County, Clay County, southern Clark County, 

northwestern Nevada County, central Hempstead 

County, northern Miller County, and southeastern Little River County. Flowing 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. The water generally is 

excessively saline for most uses downdip 2 to 20 mi 

southeast from the outcrop area in the southwestern 

subarea. In Miller County, eastern Nevada County, and 

Clark County, yields are generally small and the water 

may contain considerable chloride (Counts and others, 

1955). Aquifer tests made using wells completed in the 

Nacatoch aquifer at the cities of Hope and Prescott 

show a transmissivity of 3,600 gallons per day per foot 

(gal/d/ft) (Ludwig,1972).

Water withdrawn from the Nacatoch aquifer in 

the northeastern subarea was estimated to be 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 amount of water withdrawn in 2000 was 1.54 Mgal/d, a decrease of 30 percent from 1990 (Halberg and Stephens; 1966, Holland, 

1993; T.W. Holland, U.S. Geological Survey, written 

commun., 2002).

Water withdrawn from the Nacatoch aquifer in 

the southwestern subarea was estimated to be 2.11 

Mgal/d in 1965 and increased by 125 percent to 4.75 

Mgal/d in 1980 (fig. 4). Water withdrawn from the 

Nacatoch aquifer in this subarea was estimated to be 

0.32 Mgal/d in 2000, a decrease of 93 percent from 

1980. The sharp decrease in water withdrawal rates is 

explained by counties in the southwestern subarea relying more on surface water during the 1980s and 1990s 

(Halberg and Stephens, 1966; Holland and Ludwig, 

1981; T.W. Holland, U.S. Geological Survey, written 

commun., 2002).
Nacatoch Sand 5

Figure 3. Estimated water use by county from the Nacatoch aquifer for the northeastern subarea.

Figure 4. Estimated water use by county from the Nacatoch aquifer for the southwestern subarea.

EXPLANATION

0.00

1.00

2.00

3.00

1965 1970 1975 1980 1985 1990 1995 2000

Year

WATER USE, IN MILLION GALLONS PER DAY

Clay County

Greene County

Total

northeastern

subarea

EXPLANATION

0.00

1.00

2.00

3.00

4.00

5.00

1965 1970 1975 1980 1985 1990 1995 2000

Year

WATER USE, IN MILLION GALLONS PER DAY

Clark County

Hempstead County

Howard County

Little River County

Miller County

Nevada County

Total southeastern

subarea
6 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation 

of Southwestern Arkansas, 2002

Potentiometric Surface

Water-level measurements in 60 wells during 

January and February 2002 were used to construct 

potentiometric-surface maps for the Nacatoch aquifer 

(figs. 5 and 6; table 1). The surface is mapped by calculating the altitude of the water levels (table 1), plotting 

the values on a map, and representing the surface on the 

figures by contours that connect points of equal elevation. The general direction of ground-water flow is perpendicular to the contours in the direction of downward 

hydraulic gradient.

In the northeastern subarea, the direction of 

ground-water flow in the Nacatoch aquifer generally is 

towards the southeast (fig. 5). The potentiometric high 

is located along the north and northwestern boundary 

of this subarea. The highest water-level altitude measured was about 272 ft in northern Clay County. The 

lowest water-level altitude measured was about 233 ft 

in eastern Clay County. 

In the southwestern subarea the direction of 

ground-water flow in the Nacatoch aquifer is generally 

towards the south-southeast in Little River, Miller, and 

Hempstead Counties and to the east-southeast in 

Nevada and Clark Counties (fig. 6). The direction of 

flow may be affected by the increase in clay content in 

the downdip direction and by a fault system trending 

northeastward from northeastern Texas across Miller, 

Lafayette, and Nevada Counties in Arkansas. The highest water-level altitude measured was about 445 ft in 

the outcrop area of north-central Hempstead County. 

The lowest water-level altitude measured was about 

119 ft at Hope in southeastern Hempstead County.

Figure 5. Potentiometric surface of the Nacatoch aquifer, northeastern Arkansas, January-February 2002.

Clay

Greene

D

A

C

B

EXPLANATION

BOUNDARY OF STUDY SUBAREA

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

250

D

Base from U.S. Geological Survey

digital data, 1:100,000

0 10 20 MILES

0 10 20 KILOMETERS

R.

4

E.

R.

6

E.

R.

8

E.

T. 20 N.

T. 18 N.

T. 16 N.

270

260

250

240
Nacatoch Sand 7

Figure 6. Hydrogeologic setting and potentiometric surface of the Nacatoch aquifer, southwestern Arkansas, JanuaryFebruary 2002.

Clark

Pike

Howard

Sevier

Little River

Hempstead

Miller

Nevada

Lafayette Columbia

I

H

G

F

E

H

150

U

D

EXPLANATION

OUTCROP OF NACATOCH SAND

BOUNDARY OF STUDY AREA

APPROXIMATE NORTHERN LIMIT OF NACATOCH

AQUIFER

FAULT--U, Upthrown side; D, Downthrown side

POTENTIOMETRIC CONTOUR--Shows altitude at

which water level would have stood in tightly cased

wells. Hachures indicate depression. Contour interval

25 feet. Datum is National Geodetic Datum of 1929

CONTROL POINT--Letter, where present, corresponds

to hydrograph in figure 5

FLOWING WELL

0 10 20 MILES

0 10 20 KILOMETERS

U

D

D

U

U

U

U

D

U

D

34o

33 30’ o

94o

93 30’ o

93o

Prescott

Hope

Ashdown

T. 6 S.

T. 8 S.

T. 10 S.

T. 12 S.

T. 14 S.

R.

30

W.

R.

28

W.

R.

26

W.

R.

24

W.

R.

22

W.

R.

20

W.

R.

18

W.

400 350

300

250

200

150

175

175

150
8 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation 

of Southwestern Arkansas, 2002

Table 1. Water-level measurements and well information for wells completed in the Nacatoch aquifer

[ddmmss, degrees, minutes, seconds; NGVD of 1929 is National Geodetic Vertical Datum of 1929]

Local well number

Latitude

(ddmmss)

Longitude

(ddmmss)

Water-level

altitude

(feet above

NGVD of

1929)

Depth to

water level

(feet below

land-surface

datum)

Land-surface

altitude

(feet above

NGVD of

1929)

Date of

measurement

Clark County

08S19W06DDA1 340401 930414 176 8.45 185 1/31/2002

08S19W09ACC1 340323 930228 178 -0.85 177 1/31/2002

08S19W16CAB1 340226 930247 171 1.89 173 1/31/2002

08S20W34DAB1 335954 930744 183 16.77 200 1/31/2002

09S20W16DBD1 335708 930847 164 76.64 241 2/01/2002

09S20W16DDC1 335657 930845 158 75.12 233 2/01/2002

09S20W28DCB1 335516 930901 184 17.53 202 1/31/2002

09S20W31CAD1 335435 931111 140 118.77 259 1/31/2002

09S20W33ABD1 335447 930852 176 32.57 209 1/31/2002

09S20W33BCD2 335446 930926 180 26.87 207 1/31/2002

09S21W21DAD1 335625 931453 242 102.84 345 1/31/2002

10S20W22DCB1 335054 930757 179 81.32 260 1/31/2002

10S21W12BAB1 335321 931225 152 69.02 221 1/31/2002

Clay County

19N04E01BDB1 361910 903560 268 11.78 280 2/05/2002

19N07E23BAC1 361602 901748 239 83.26 322 2/04/2002

19N07E23DBC1 361549 901730 246 36.92 283 2/04/2002

19N07E26AAA1 361532 901703 244 31.99 276 2/04/2002

20N04E36DCC1 361929 903542 264 15.09 279 2/05/2002

20N08E10ABC1 362313 901202 251 88.67 340 2/04/2002

20N08E14BAB2 362227 901120 242 43.78 286 2/05/2002

20N08E15BAA1 362224 901208 233 147.78 381 2/05/2002

21N06E23DAC1 362619 902329 272 27.79 300 2/05/2002

21N07E25AAC1 362550 901607 269 73.00 342 2/04/2002

Greene County

18N06E14CCD1 361115 902420 239 47.94 287 2/04/2002

18N06E24BDA1 361058 902300 234 41.59 276 2/04/2002

Hempstead County

11S24W08BDB1 334837 933619 445 24.89 470 1/30/2002

11S24W21ADD1 334641 933449 323 47.22 370 1/30/2002

11S24W21DDD1 334621 933447 339 32.29 371 1/30/2002

11S24W22ADD1 334647 933343 334 30.64 365 1/30/2002

11S24W34CBC1 334444 933438 297 23.44 320 1/30/2002
Nacatoch Sand 9

11S26W27BDD1 334611 934645 423 6.55 430 1/28/2002

12S24W28CDC1 334012 933536 119 233.66 353 1/29/2002

12S25W07ABB1 334346 934340 395 39.99 435 1/28/2002

12S25W15DBC1 334214 934036 285 25.78 311 1/28/2002

12S25W34BAC1 334002 934055 249 71.23 320 1/28/2002

12S26W21AAC1 334158 934739 366 31.73 398 1/28/2002

12S26W24ABC1 334159 934438 313 2.22 315 1/28/2002

13S25W05ABD1 333915 934232 258 23.79 282 1/28/2002

13S25W18AAB1 333740 934332 223 60.47 283 1/28/2002

13S25W35DDC1 333406 933931 188 185.26 373 1/28/2002

13S26W17DDB1 333705 934845 234 57.04 291 1/28/2002

14S25W04DDD1 333317 934132 156 103.72 260 1/28/2002

Little River County

13S28W31BCC1 333509 940251 259 52.28 311 1/23/2002

14S30W01DAA1 333426 940904 240 42.36 282 1/23/2002

Miller County

14S27W02AAB1 333419 935121 229 26.12 255 1/23/2002

14S28W13CCB1 333158 935727 238 27.88 266 1/23/2002

14S28W17BBC1 333240 940134 244 25.52 270 1/23/2002

Nevada County

10S22W23DCB1 335105 931935 241 0.74 242 1/25/2002

11S20W08DCD1 334727 931037 177 4.36 181 1/25/2002

11S20W15CDC1 334622 930904 166 8.76 175 1/25/2002

11S20W22AAA1 334624 930926 176 -1.10 175 1/25/2002

11S21W14CAB1 334652 931434 197 -1.36 196 1/25/2002

11S22W08DAC2 334760 932314 262 44.08 306 1/25/2002

11S22W08DDB4 334757 932314 281 25.32 306 1/25/2002

11S23W03DCD1 334840 932726 298 86.81 385 1/25/2002

11S23W12ABB1 334837 932538 310 71.31 381 1/25/2002

12S22W09CDD1 334230 932250 225 3.71 229 1/25/2002

12S22W22ACD1 334108 932135 219 122.86 342 1/25/2002

12S22W23CBA1 334102 932057 219 109.58 329 1/25/2002

13S22W07BDC1 333744 932514 211 131.92 343 1/25/2002

Table 1. Water-level measurements and well information for wells completed in the Nacatoch aquifer--Continued

[ddmmss, degrees, minutes, seconds; NGVD of 1929 is National Geodetic Vertical Datum of 1929]

Local well number

Latitude

(ddmmss)

Longitude

(ddmmss)

Water-level

altitude

(feet above

NGVD of

1929)

Depth to

water level

(feet below

land-surface

datum)

Land-surface

altitude

(feet above

NGVD of

1929)

Date of

measurement
10 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation 

of Southwestern Arkansas, 2002

A cone of depression exists at Hope in Hempstead County (fig. 6). Historical water levels indicate a 

decline from 185 ft above the NGVD of 1929 in 1942 

to 145 ft in 1969 (Ludwig, 1972). The water-level altitude from January 2002 was 119 ft above the NGVD of 

1929. This cone of depression alters local ground-water 

flow directions from the regional direction, with 

ground water flowing towards Hope from all directions. A cone of depression also exists in southwestern 

Clark County. This feature has not been noted in previous publications and may be caused by short-term variations in local recharge or pumping. A comparison with 

the 1999 potentiometric-surface maps for the Nacatoch 

aquifer shows no other changes over large areas in the 

southwestern subarea; however, the northeastern subarea shows a general decrease in water levels over the 

subarea (Schrader, 1999). 

Long-Term Water-Level Changes

Nine hydrographs from wells completed in the 

Nacatoch aquifer display long-term (minimum of 20-

year period) water-level altitudes (fig. 7). Linear 

regression was used to determine the average annual 

decline or rise in feet per year for the period from 

spring 1982 to spring 2002 for water levels in each 

well. The minimum 20-year period is used to decrease 

the influence of short-term variations in climate and 

localized pumping rates on water levels in a single well.

Four wells (sites A- D) are located in the northeastern subarea (fig. 5). Water levels in each of these 

wells generally declined over the period an average of 

0.0 to 1.4 feet per year (ft/yr), with a median waterlevel decline of 0.8 ft/yr. The decrease in water levels 

may be associated with the increased withdrawal from 

the Nacatoch aquifer in Greene and Clay Counties (fig. 

3).

Five wells with historical water-level measurements (sites E-I; fig. 7), are located in the southwestern 

subarea (fig. 6). Two wells (sites E and F) are located in 

Clark County and the other three wells are located in 

Hempstead (site H), Miller (site I), and Nevada (site G) 

Counties. The range of values for the annual rise or 

decline for wells in the southwestern subarea over the 

period from spring 1982 to 2002 was 3.8 to

-0.3 ft/yr (positive values represent a water-level rise), 

with a median value of 0.5 ft/yr.

Figure 7. Water-level altitudes for selected wells completed in the Nacatoch aquifer.

A. GREENE COUNTY, WELL 18N06E14CCD1

180

200

220

240

260

280

300

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929
Nacatoch Sand 11

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

B. CLAY COUNTY, WELL 19N07E23DBC1

180

200

220

240

260

280

300

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929

C. CLAY COUNTY, WELL 20N08E10ABC1

180

200

220

240

260

280

300

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929
12 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation 

of Southwestern Arkansas, 2002

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

D. CLAY COUNTY, WELL 21N06E23DAC1

220

240

260

280

300

320

340

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929

E. CLARK COUNTY, WELL 08S19W09ACC1

120

140

160

180

200

220

240

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929
Nacatoch Sand 13

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

F. CLARK COUNTY, WELL 09S20W16DDC1

110

130

150

170

190

210

230

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929

G. NEVADA COUNTY, WELL 11S22W08DAC2

160

180

200

220

240

260

280

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929
14 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation 

of Southwestern Arkansas, 2002

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

H. HEMPSTEAD COUNTY, WELL 13S25W35DDC1

150

170

190

210

230

250

270

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929

I. MILLER COUNTY, WELL 14S28W13CCB1

180

200

220

240

260

280

300

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929
Tokio Formation 15

Water levels in well 08S19W09ACC1 (site E, 

figs. 6 and 7) declined from about 186 ft above the 

NGVD of 1929 in 1962 to about 178 ft in 2002, an 

average decline of about 0.2 ft/yr. There is no apparent 

association between water-level changes and withdrawals. The variation in water levels in this well could 

result from differences in withdrawal rate changes, climatic variations, or leakage of water from overlying 

and underlying rock units.

Water levels in well 09S20W16DDC1 (site F, 

figs. 6 and 7), declined from about 184 ft above the 

NGVD of 1929 in 1975 to about 144 ft in 1981, which 

is a decline of 6.7 ft/yr. Estimated withdrawal rates 

from the Nacatoch aquifer in Clark County increased 

from 0.64 Mgal/d in 1975 to 1.73 Mgal/d in 1980, an 

increase of 170 percent in withdrawals (fig. 4). From 

1981 to 2002, a general rise in water level was observed 

along with a general decrease in water use in Clark 

County. 

Water levels in well 11S22W08DAC2 (site G, 

figs. 6 and 7), rose from about 179 ft above the NGVD 

of 1929 in 1985 to about 267 ft in 1990, an average rise 

of about 17.6 ft/yr. The increase in water levels 

occurred when the estimated withdrawal rates from the 

Nacatoch aquifer in Nevada County decreased from 

1.11 Mgal/d in 1985 to 0.44 Mgal/d in 1990; a decrease 

of about 60 percent (fig. 4). 

Water levels in well 13S25W35DDC1 (site H, 

figs. 6 and 7), declined from 188 ft in 1975 to 175 ft in 

1979. Estimated withdrawal rates from the Nacatoch 

aquifer in Hempstead County increased from 1.44 

Mgal/d in 1975 to 1.98 Mgal/d in 1980, an increase of 

about 38 percent (fig. 4). From 1979 to 1999, a general 

rise in water level was measured, but from 1999 to 

2002, a sharp decrease in water level occurred. Estimated withdrawal rates from the Nacatoch aquifer in 

Hempstead County after 1980 fluctuated from 0.15 

Mgal/d in 1985 to 0.32 Mgal/d in 1995 and decreased 

to 0.27 Mgal/d in 2000. 

Water levels in well 14S28W13CCB1 (site I, 

figs. 6 and 7) ranged from 242 ft above the NGVD of 

1929 to 238 ft from 1969 to 2002. The decline and rise 

in water levels in this well may be associated with the 

increased and decreased withdrawals from the Nacatoch aquifer in Clark, Hempstead, and Nevada Counties (fig. 4).

Although water levels in these nine wells may be 

associated with changes in withdrawals, other factors 

also may affect water levels. Water levels may be 

affected by local factors such as withdrawal rate 

changes, localized recharge, or changes in leakage to 

and from overlying and underlying rock units. 

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 mile-wide 

band in west-central Clark County. The outcrop attains 

a maximum width of about 10 mi in Howard County 

and continues approximately 8 mi southwest into 

Sevier County. In this area, the Tokio Formation is 

overlain in several places by alluvial and terrace deposits of Quaternary age. The unit also outcrops in northwestern Little River County, west of the study area.

The Tokio Formation ranges in thickness from 

about 50 ft to more than 300 ft and dips towards the 

southeast. The unit 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 

subarea.

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 aquifer yields fresh 

water to within a few miles north of Ashdown in Little 

River County (fig. 8). The water in the Tokio aquifer 

becomes slightly to moderately saline downdip (southeast) from near Prescott to the fault zone trending 

across Nevada County. Except in its outcrop area, water 

in the Tokio aquifer is under artesian conditions 

(Petersen and others, 1985). 
16 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation 

of Southwestern Arkansas, 2002

Figure 8. Hydrogeologic setting and potentiometric surface of the Tokio aquifer, southwestern Arkansas, January 2002.

L K

J

M

Clark

Howard Pike

Sevier

Little River

Hempstead

Miller

Nevada

Lafayette Columbia

0 10 20 MILES

0 10 20 KILOMETERS

M

200

U

D

EXPLANATION

OUTCROP OF TOKIO FORMATION

APPROXIMATE AREA OF ARTESIAN FLOW

BOUNDARY OF STUDY SUBAREA

APPROXIMATE NORTHERN LIMIT OF TOKIO

FORMATION

FAULT--U, Upthrown side; D, Downthrown side

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 7

FLOWING WELL

Base from U.S. Geological Survey

digital data, 1:100,000

U

D

D

U

U

U

U

D

U

D

34o

33 30’ o

94o

93 30’ o

93o

Prescott

Hope

Ashdown

R.

30

W.

R.

28

W.

R.

26

W.

R.

24

W.

R.

22

W.

R.

20

W.

R.

18

W.

T. 6 S.

T. 8 S.

T. 10 S.

T. 12 S.

T. 14 S.

425

400

375

350

325

300

275

250

225

200

175

150

450

500

475

Figure 8. Hydrogeologic setting and potentiometric surface of the Tokio aquifer, southwestern Arkansas, January 2002.
Tokio Formation 17

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 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 have not 

been greatly affected by withdrawal of water at Hope 

and Prescott (Ludwig, 1972).

Estimates of 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. 9). Water withdrawn 

from the Tokio aquifer was estimated to be 1.17 Mgal/

d in 2000, a decrease of 81 percent from 1980 (Halberg 

and Stephens, 1966; Holland and Ludwig, 1981; Holland, 1999).

Potentiometric Surface

The potentiometric surface for the Tokio aquifer 

shows the altitude that water would have stood in 

tightly cased wells screened in the aquifer (fig. 8). 

Water-level measurements in 48 wells in January 2002 

(fig. 9; table 2) were used to construct the potentiometric-surface map. The surface is mapped by calculating 

the altitude of the water levels, plotting the values on a 

map, and representing the surface on the figures by 

contours that connect points of equal elevation. The 

general direction of ground-water flow is perpendicular 

to the contours in the direction of downward hydraulic 

gradient.

Figure 9. Estimated water use by county from the Tokio aquifer.

EXPLANATION

0.00

1.00

2.00

3.00

4.00

5.00

6.00

1965 1970 1975 1980 1985 1990 1995 2000

Year

WATER USE, IN MILLION GALLONS PER DAY

Clark County

Hempstead County

Howard County

Little River County

Miller County

Nevada County

Pike County

Sevier County

Total Tokio aquifer
18 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation 

of Southwestern Arkansas, 2002

Table 2. Water-level measurements and well information for wells completed in the Tokio aquifer

[ddmmss, degrees, minutes, seconds; NGVD of 1929; National Geodetic Vertical Datum of 1929]

Local well number

Latitude

(ddmmss)

Longitude

(ddmmss)

Water-level

altitude

(feet above

NGVD of

1929)

Depth to

water level

(feet below

land-surface

datum)

Land-surface

altitude

(feet above

NGVD of

1929)

Date of

measurement

Clark County

08S22W05CCC1 340408 932255 358 31.74 390 1/30/2002

08S22W15ABB2 340313 932018 271 53.97 325 1/30/2002

09S22W05BBB1 335951 932259 205 106.59 312 1/30/2002

09S22W05BCA1 335936 932257 203 31.64 235 1/30/2002

09S22W10DBA1 335832 932021 224 138.18 362 1/30/2002

Hempstead County

09S23W20BDA1 335710 932858 251 -1.2 250 1/30/2002

09S23W33CDA1 335457 932802 271 -0.9 270 1/29/2002

09S24W25BBB1 335633 933132 269 -0.5 268 1/29/2002

09S24W28ACC1 335617 933415 279 -2.1 277 1/29/2002

09S24W30DCC1 335556 933607 375 15.17 390 1/29/2002

09S24W33ADC1 335526 933356 284 45.07 329 1/29/2002

09S26W08ADA2 335920 934717 436 1.63 438 1/29/2002

09S26W08ADD1 335918 934717 437 0.28 437 1/29/2002

09S26W09CDC1 335846 934656 423 2.23 425 1/29/2002

09S26W18CBB1 335815 934921 403 21.91 425 1/29/2002

10S25W09CDB1 335329 934052 291 69.85 361 1/29/2002

10S25W30CCD1 335048 934310 319 69.12 388 1/28/2002

10S26W03BBA1 335507 934612 366 0.68 367 1/29/2002

11S26W08BBB1 334909 934903 302 69.56 372 1/28/2002

11S26W23BBB1 334720 934602 326 93.22 419 1/28/2002

12S24W06DAD1 334360 933701 148 206.87 355 1/29/2002

12S25W02DDD1 334341 933902 134 232.6 367 1/29/2002

12S27W04BBC1 334450 935358 262 172.66 435 1/28/2002

12S27W05AAC1 334449 935421 262 172.61 435 1/28/2002

12S27W36DBC1 333960 935006 228 32.79 261 1/28/2002

Howard County

09S27W03DBD1 340000 935152 491 70.98 562 1/22/2002

09S27W10BCB1 335930 935231 426 108.16 534 1/22/2002
Tokio Formation 19

09S27W18ADB1 335840 935452 415 77.34 492 1/22/2002

09S27W32BDB1 335606 935423 398 53.06 451 1/22/2002

09S27W32BDB2 335606 935423 370 79.98 450 1/22/2002

09S28W20DAC1 335740 940013 469 11.16 480 1/22/2002

10S27W04BBD1 335512 935329 338 53.56 392 1/22/2002

10S27W12CAB1 335356 935020 309 74.18 383 1/22/2002

10S27W18BAC1 335336 935534 317 104.81 422 1/22/2002

Little River County

11S30W25DDC1 334618 940852 264 21.26 285 1/23/2002

Nevada County

09S22W33DCC1 335437 932130 219 5.73 225 1/25/2002

10S23W12AAA1 335345 932421 235 20.87 256 1/25/2002

11S22W08DAC1 334758 932315 214 91.29 305 1/25/2002

11S22W08DAC8 334757 932312 215 90.39 305 1/25/2002

Pike County

08S23W19ADC1 340213 932930 351 -0.85 350 1/24/2002

08S23W35DCA1 340004 932530 258 -1.15 257 1/24/2002

08S24W14AAC1 340324 933134 433 89.84 523 1/24/2002

09S23W17BBC2 335804 932924 282 -1.93 280 1/24/2002

09S24W14AAD1 335810 933138 287 -1.6 285 1/24/2002

Sevier County

10S28W31DCC1 335026 940145 293 37.16 330 1/23/2002

11S29W05DCA1 334949 940653 365 115.06 480 1/23/2002

11S29W08DBB1 334907 940704 321 144.17 465 1/23/2002

11S29W13CCD1 334750 940317 278 82.22 360 1/23/2002

Table 2. Water-level measurements and well information for wells completed in the Tokio aquifer--Continued

[ddmmss, degrees, minutes, seconds; NGVD of 1929; National Geodetic Vertical Datum of 1929]

Local well number

Latitude

(ddmmss)

Longitude

(ddmmss)

Water-level

altitude

(feet above

NGVD of

1929)

Depth to

water level

(feet below

land-surface

datum)

Land-surface

altitude

(feet above

NGVD of

1929)

Date of

measurement
20 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation 

of Southwestern Arkansas, 2002

In the southwestern subarea, the direction of 

ground-water flow in the Tokio aquifer generally is 

towards the south or southeast. The potentiometric high 

is within the outcrop area in the northwestern part of 

the study subarea. The highest water-level altitude 

measured was about 491 ft above the NGVD of 1929 in 

Howard County. The lowest water-level altitude measured was about 134 ft above the NGVD of 1929, about 

5 mi northwest of Hope in Hempstead County. An area 

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

evidenced by eight flowing wells.

A cone of depression may exist about 5 mi northwest of Hope; the northern half of an apparent cone of 

depression is shown on figure 8. 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 2001 potentiometric-surface map with the 1996 and 1999 potentiometric-surface maps for the Tokio aquifer shows no substantial 

changes over large areas (Schrader, 1998; Schrader, 

1999).

Long-Term Water-Level Changes

Four hydrographs from wells completed in the 

Tokio aquifer have long-term (minimum of 20 years) 

water-level altitudes. Two wells are located in Hempstead County (sites J and K) and the other two wells are 

located in Howard (site L) and Nevada (site M) Counties (fig. 10). Linear regression was used to determine 

the average annual decline or rise in feet per year for 

the period from spring 1982 to spring 2002 for water 

levels in each well. The minimum 20-year period is 

used to decrease the influence of short-term variations 

in climate and localized pumping rates on water levels 

in a single well.

The two hydrographs in Hempstead County 

show water-levels decline in one hydrograph and fluctuate over a range in the other. In well 

09S23W33CDA1 (site J, figs. 8 and 10), water levels 

generally declined about 11 ft from 1957 to 2002. 

Water levels in well 09S26W18CBB1 (site K, figs. 8 

and 10), fluctuated through a range of about 15 ft over 

a 45-year period. There does not appear to be an association between water levels in these two wells and the 

general decline in estimated withdrawals from the 

Tokio aquifer for Hempstead County (fig. 9).

In Howard County, water levels in well 

09S28W20DAC1 (site L, figs. 8 and 10) range from 

about 476 ft to about 464 ft above the NGVD of 1929 

over a 45-year period from 1957 to 2002. No significant rises or declines in water levels were observed. 

There does not appear to be any association between 

water levels in this well and estimated withdrawals 

from the Tokio aquifer for Howard County (fig. 9).

In Nevada County, water levels in well 

11S22W08DAC1 (site M, figs. 8 and 10) declined from 

about 211 ft above the NGVD of 1929 in 1972 to about 

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

decline averages approximately 4.7 ft/yr. Estimated 

withdrawal rates from the Tokio aquifer for Nevada 

County increased from 0.45 Mgal/d in 1970 to 0.68 

Mgal/d in 1980, an increase of 51 percent (fig. 9). From 

1985 to 1987, a rise in water level to about 225 ft was 

observed, which is approximately a 37.5 ft/yr rise. 

Water withdrawal rates from the Tokio aquifer for 

Nevada County are estimated to have decreased to zero 

by 1985. Water levels in the Tokio aquifer in Nevada 

County appear to respond to changes in withdrawal 

rates.

Although water levels in these four wells may be 

associated with changes in withdrawals, other factors 

also may affect water levels. Water levels may be 

affected by local factors such as withdrawal rate 

changes, climatic variations, or changes in leakage to 

and from overlying and underlying rock units. The 

range of values for the annual average rise or decline in 

water level for wells in the Tokio aquifer was -1.9 to 2.9 

ft/yr, with a median value of 0.1 ft/yr. 
Tokio Formation 21

Figure 10. Water-level altitudes for selected wells completed in the Tokio aquifer.

J. HEMPSTEAD COUNTY, WELL 09S23W33CDA1

200

220

240

260

280

300

320

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929

K. HEMPSTEAD COUNTY, WELL 09S26W18CBB1

320

340

360

380

400

420

440

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929
22 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation 

of Southwestern Arkansas, 2002

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

L. HOWARD COUNTY, WELL 09S28W20DAC1

420

440

460

480

500

520

540

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929

M. NEVADA COUNTY, WELL 11S22W08DAC1

120

140

160

180

200

220

240

1/1/57 1/1/62 1/1/67 1/1/72 1/1/77 1/1/82 1/1/87 1/1/92 1/1/97 1/1/02

WATER LEVEL, IN FEET ABOVE NGVD OF 1929
Summary 23

SUMMARY

Aquifers in the Nacatoch Sand and Tokio Formation in southwestern Arkansas and the Nacatoch Sand 

in northeastern Arkansas are a source of water for 

industrial, public supply, domestic, and agricultural 

uses. Potentiometric-surface maps were constructed 

from water-level measurements made in 60 wells completed in the Nacatoch aquifer and 48 wells completed 

in the Tokio aquifer during January and February 2002. 

In northeastern Arkansas, withdrawals from the Nacatoch aquifer increased by 784 percent from 1965 to 

1990 and decreased by 30 percent from 1990 to 2000. 

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 81 percent, respectively, 

from 1980 to 2000.

The direction of ground-water flow in the northeastern subarea of the Nacatoch aquifer generally is 

towards the southeast. The potentiometric high is 

located along the north and northwestern boundary of 

this subarea. The potentiometric low is located in eastern Clay County.

The direction of ground-water flow in the southwestern subarea of the Nacatoch aquifer is towards the 

south-southeast in Little River, Miller, and Hempstead 

Counties and to the east-southeast in Nevada and Clark 

Counties. The potentiometric high is located within the 

outcrop area in Hempstead County. Cones of depression exist in southeastern Hempstead County and in 

southwestern Clark County. 

In the northeastern subarea of the Nacatoch aquifer, water levels in four wells declined during a period 

of increased withdrawals from the Nacatoch aquifer. 

Water levels generally declined over the period of 

record an average of 0.0 to 1.4 ft/yr, with a median 

water-level decline of 0.8 ft/yr.

In the southwestern subarea of the Nacatoch 

aquifer, water levels in three of five wells rose during a 

period of decreased withdrawal from the Nacatoch 

aquifer. The range of values for the annual average rise 

or decline for wells in the southwestern subarea (minimum of 20 years) was 3.8 to -0.3 ft/yr, with a median 

value of 0.5 ft/yr. The hydrograph for site E shows no 

apparent association between water-level changes in a 

well completed in the Nacatoch aquifer and withdrawals. The variation in water levels in this well could 

result from differences in withdrawal rate changes, climatic variations, or leakage of water from overlying 

and underlying rock units.

Estimates of water withdrawn from the Tokio 

aquifer increased from 2.0 Mgal/d in 1965 to 6.02 

Mgal/d in 1980. Water withdrawn from the Tokio aquifer was estimated to be 1.17 Mgal/d in 2000, a decrease 

of 81 percent from 1980. 

The direction of ground-water flow in the Tokio 

aquifer is towards the south or southeast. The potentiometric high 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. One apparent cone of depression may exist northwest of Hope in 

Hempstead County.

The range of values for the annual average rise or 

decline in water level for wells in the Tokio aquifer was 

-1.9 to 2.9 ft/yr, with a median value of 0.1 ft/yr. Hydrographs in the Tokio aquifer in Hempstead County show 

water levels declined in one well and fluctuated in the 

other. No significant changes in water levels in Howard 

County were observed. In Nevada County, the 

hydrograph showed a decline and a rise in water levels 

during a period of increased, then decreased, withdrawals from the aquifer. Three hydrographs show no apparent association between water-level changes in wells 

completed in the Tokio aquifer and withdrawals. 

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