EXPLANATION

OUTCROP OF TOKIO FORMATION
APPROXIMATE AREA OF ARTESIAN FLOW

BOUNDARY OF STUDY AREA

# se aie st APPROXIMATE NORTHERN LIMIT OF TOKIO
FORMATION

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

— 200 -- 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 sea
level

M, CONTROL POINT--Letter, where present,
corresponds to hydrograph in figure 6

8 FLOWING WELL

} 10 a
10

20 KILOMETERS

Figure 6. Potentiometric surface of the Tokio aquifer, southwestern Arkansas, April-May 1999.

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

of Southwestern Arkansas, 1999


Site A, GREENE COUNTY, 18NO6E14CCD1

1/1/00

= fo pop yp pp ee ee ee ee eee
8

1/1/90

on ie re een) ane 4
a fir 8 g
job } aI a —j}f og -—l} f 7
=¢ — E F
ee a es ee Cn ce Ge ee ee a
1 a a oe “7695 mone 7 on ee
£ 82
— Sr ee ee ee C ae
on ni oe a eo oe o Bho
>
=3
t= tot ae ae ee ee re
See ee | 2 fo NN
a a ee i a a ~
SS oe
_ roe @ Ho 7 1
2 4 a L jo |. 4
on

= = w a —
e

TT a 1 = = —P 1

= —E - a oe ee ry ee eee ee eee a
o
g

= = ms Fo —l— oe ae

73A31 VaS 3AO8V 1334 NI ‘13A37 YALVM

200

1/1/55

310

2 fo} (=)
3 ge i) a ~
N N Nn a nN

13A31 VaS 3A08V 1334 NI ‘13A37 4ALYM

190

11/60 «(1/1/65 «1/1/70 1/1/75 1/1/80 1/1/85 1/1/90 1/1/95 1/1/00
Figure 5. Water-level altitudes for selected wells completed in the Nacatoch aquifer.

1/1/55

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

of Southwestern Arkansas, 1999


Site K, HEMPSTEAD COUNTY, 09S26W18CBB1

8
ae Lt 4s _ ry 4
= i eee GeO, fees Qe es a eee eee if —_t- ty
\ 8 L
= - = jf 4 5 po} a
a —— 1 i bp t=
+ a Poesy
i ee ee ee a | | 8 4 - _ _ +f. —f
4 ff} 7 et a fj \ | —.
oe a } _. 8 a } = po
— a T] = 8f7
Toe | aoe ie
ee -— Es z
pt Poe ped te
=a se ee 3
an = | wo =
t+ = 8
in or <cn n Fob
an ff os
- t | + |e Sf
= a an a
jf oe on a
a Cen cee Oe ne eee T £
_ oo — 8 oO
— 7 t+ 4s
i | _ - lo |
©
SP NP . bo
red
oO Oo [=] [=] i=] i=} = fo} oO f=} o Oo f=} o
g g g 3 8 3 3 8 3 3 § 8 8 =
13A31 W3S SAOSV 1334 NI ‘13A37 HALYM

73A31 WaS 3AO8V 1334 NI “T3A37 HSLVM

1/1/60 «1/1/65 1/1/70 1/1/75 1/1/80 1/1/85 1/1/90 1/1/95 = 1/1/00
Figure 7. Water-level altitudes for selected wells completed in the Tokio aquifer—Continued.

1/1/55

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

of Southwestern Arkansas, 1999


Status of Water Levels in Aquifers in the Nacatoch Sand
of Southwestern and Northeastern Arkansas and the
Tokio Formation of Southwestern Arkansas, 1999

By T. P. Schrader
ABSTRACT

Nacatoch Sand and Tokio Formation aquifers in
southwestern Arkansas and the Nacatoch Sand aquifer
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 59 wells com-
pleted in the Nacatoch Sand and 45 wells completed in
the Tokio Formation from April through May 1999.

The direction of ground-water flow in the aquifer
in the Nacatoch Sand in northeastern Arkansas gener-
ally is towards the southeast. The potentiometric high
is located along the north and northwestern boundaries.

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 Hemp-
stead County. A cone of depression exists in the aquifer
in the Nacatoch Sand at Hope in southeastern Hemp-
stead County.

The direction of ground-water flow in the aquifer
in the Tokio Formation in southwestern Arkansas gen-
erally is towards the southeast. The potentiometric high
is within the outcrop area. An area of artesian flow
exists in southeastern Pike, northeastern Hempstead,
and northwestern Nevada Counties. One apparent cone
of depression might exist northwest of Hope in Hemp-
stead County.

In northeastern Arkansas, withdrawals from the
Nacatoch Sand increased by 736 percent from 1965 to
1995. 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 78 percent and 63
percent, respectively, from 1980 to 1995. 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.

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 infor-
mation needed to effectively plan and manage the
resource. A study was conducted in cooperation with
the Arkansas Soil and Water Conservation Commis-
sion and the Arkansas Geological Commission to pro-
vide potentiometric-surface maps and water-level
hydrographs associated with aquifers in the Nacatoch
Sand and Tokio Formation (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 Arkan-
sas. The northeastern subarea includes most of Clay
and Greene Counties in the Mississippi Alluvial Plain
physiographic province (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 Naca-
toch 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 province (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 west by the Texas State

Abstract 1


Table 3. Water-level measurements and well information for wells completed in the Tokio aquifer

Water level ater level Land-surface well Date of
Local well number Latitude Longitude ated (feet eet below _aalltitude (feet depth measure-
sea evel a surtace above sealevel) (feet) ment
Clark County
O8S22WO8BBB1 34041439 --932251.93 354 31.04 385 106 4/29/99
08S22W15ABB2 340312.77932017.91 267 $7.54 325 145 4/29/99
O9S22W10DBA1 —335831.65  932021.45 232 129.81 362 500 4/29/99
O9S22W16ACA1 335753.53 932120.02 220 12.84 233 450 4/29/99
Hempstead County
09S23W20BDA1 335710 932858 251 12 250 210 4/21/99
09$23W33CDA1 33545724 932802.43 21 09 270 467 5/03/99
09S24W25BBB1 33563339 —933131.90 269 0.5 268 270 5/03/99
O9S24W28ACC1 335617.26 933414.51 279 21 277 200 5/03/99
09S24W33ADC1 335526.07 933355.97 285 44.04 329 335 5/03/99
O9S26WO8ADA2 —335919.86 934716.71 436 1.89 438 25 4/29/99
O9S26WO8ADD1 —335917.85  934716.84 437 0.49 437 25 4/29/99
O9S26WOICDC1 —335845.81  934656.00 422 3.38 425 16 4/29/99
O9S26W18CBB1 335815.46 934920.92 405 20.32 425 30 4/29/99
10S25WO9CDBI —_335328.56934051.57 305 69.62 375 327 4/30/99
10S25W30CCD1 —-335047.51  934310.18 324 64.19 388 500 = 4/22/99
10S26WO3BBA1- 335506.74 934611.68 366 1 367 162 4/29/99
11S26WO8BBB1 —334909.23 934903.22 305 66.92 372 550 4/29/99
11S26W23BBB1 — 334719.87 934601.93 328 91.28 419 820 4/28/99
12S24WO6DAD1 —334359.68  933701.28 133 221.8 355 1,140 5/05/99
12825W02DDD1 —334341.13 933901.80 138 228.78 367 1,159 5/05/99
12S27WO4BBC1 — 334449.54 935357.50 265 169.52 435 870 4/28/99
12S27WOSAAC1 —334448.86 935421.32 264 170.76 435 906 4/28/99
12827W36DBC1 33395972 935006.34 233 28.35 261 1,156 4/28/99
Howard County
09S27W03DBD1 340000935152 493 68.89 562 220 4/22/99
09827W10BCB1 335930935231 423 110.64 534 195 4/22/99
O9S27W18ADB1 335840 935452 416 75.85 492 200 4/22/99
09S27W32BDB1 335606 935423 400 52.2 452 150 4/23/99
09S27W32BDB2 335606 935423 400 49.92 450 61 4/23/99
09828W20DAC1 335740 (940013 468 12.3 480 27 4/22/99

Tokio Formation 17


REFERENCES

Boswell, E.H., Moore, G.K., MacCary, L.M., and others,
1965, Cretaceous aquifers in the Mississippi Embay-
ment: 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 south-
western Arkansas: U.S. Geological Survey Water
Resources Circular No. 2, 35 p.

Fenneman, N.M., 1938, Physiography of eastern 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.

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.

Holland, T.W., 1987, Use of water in Arkansas, 1985:
Arkansas Geological Commission Water Resources
Summary Number 16, 27 p.

1993, Use of water in Arkansas, 1990: U.S. Geolog-

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

1999, Use of water in Arkansas, 1995: U.S. Geolog-
ical Survey Open-File Report 99-188, | sheet.

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, Lafay-
ette, Little River, Miller, and Nevada Counties, Arkan-
sas: U.S. Geological Survey Water-Supply Paper 1998,
41 p.

Petersen, J.C., Broom, M.E., and Bush, W.V., 1985, Geohy-
drologic units of the Gulf Coastal Plain in Arkansas:
USS. Geological Survey Water-Resources Investiga-
tions 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., 1998, Status of water levels in aquifers in the
Nacatoch Sand and Tokio Formation of southwestern
Arkansas, 1996: U.S. Geological Survey Water-
Resources Investigations Report 98-4130, 14 p.

& U.S. GOVERNMENT PRINTING OFFICE: 1999—755-177 / 40037

References

23


Long-Term Water-Level Changes

Four hydrographs from wells completed in the
Tokio aquifer display long-term (minimum of 20 years)
water-level altitudes (fig. 7). 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. 6).

The two hydrographs in Hempstead County
show differences between water-level trends over long
periods. In well 09S23W33CDAI (site J, figs. 6 and 7),
water levels generally declined from 1957 to 1999.
Water levels in well 09S26W18CBBI (site K, figs. 6
and 7), fluctuated through a range of about 399 to about
414 ftabove sea level over a 43-year period. There does
not appear to be an association between water levels in
these two wells and estimated withdrawals from the
Tokio aquifer for Hempstead County (table 4).

In Howard County, water levels in well
09S28W20DACI (site L, figs. 6 and 7) range from
about 476 ft to about 464 ft above sea level over a 43-
year period from 1957 to 1999. 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 (table 4).

In Nevada County, water levels in well
11S22W08DACI (site M, figs. 6 and 7) declined from
about 211 feet above sea level 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 with-
drawal 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 (table 4). 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 with-
drawal rates from the Tokio aquifer for Nevada County
are estimated to have decreased to zero by 1985. The
decline and rise in water levels may be associated with
the increased and decreased withdrawals from the
Tokio aquifer in Nevada County.

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 pumpage changes, cli-
matic variations, or changes in leakage to and from
overlying and underlying rock units.

Site J, HEMPSTEAD COUNTY, 09S23W33CDA1

340

TTT Th

320

300

280

WATER LEVEL, IN FEET ABOVE SEA LEVEL

260
| po Ht

: i i i Pig) iil
240 + — —— - — — “4 + ——+
: ' I | | 1

| | f it | | | 4

yo r “Th

220 i i pi ji vil ia Li

11/55 1/60 1/1/65 1/1/70 1/75) 1/1/80 1/1/85 1/1/90 1/1/95 1/1/00

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

Tokio Formation 19


Site 1, MILLER COUNTY, 14S28W13CCB1

300

Toth

T
Ji] |
ie \
i

ee 7

280 —

260

240

|
220 L+
i

200

WATER LEVEL, IN FEET ABOVE SEA LEVEL

|

r if

| |

Ak

i T
|

1

L

180

11/55 1/1/60 1/1/65 1/1/70 1/1/75

11/80 1/1/85 1/1/90 1/1/95 1/1/00

Figure 5. Water-level altitudes for selected wells completed in the Nacatoch aquifer—Continued.

Water levels in well 08S19W09ACCI (site E,
figs. 4 and 5) declined from about 186 ft above sea level
in 1962 to about 178 ft in 1999, an average decline of
about 0.2 fi/yr.

Water levels in well 09S20W16DDC1 (site F,
figs.4 and 5), declined from about 184 ftabove sea level
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 (table 2). From 1981 to 1996, a general
rise in water level was observed during a general
decrease in water use in Clark County.

Water levels in well 11S22W08DAC2 (site G,
figs. 4 and 5), rose from about 179 ft above sea level 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 aqui-
fer in Nevada County decreased from 1.11 Mgal/d in
1985 to 0.44 Mgal/d in 1990; a decrease of about 60
percent (table 2).

14
of Southwestern Arkansas, 1999

Water levels in well 13S25W35DDCI (site H,
figs. 4 and 5), 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 (table 2). From 1979 to 1999, a gen-
eral rise in water level was observed. Estimated with-
drawal 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.

Water levels in well 14S28W13CCBI (site I, fig.
4 and 5) ranged from 248 ft above sea level to 234 ft
from 1962 to 1999. The decline and rise in water levels
in these wells may be associated with the increased and
decreased withdrawals from the Nacatoch aquifer in
Clark, Hempstead, and Nevada Counties.

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 pumpage changes, cli-
matic variations, or changes in leakage to and from
overlying and underlying rock units.

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


Ra
=RD
8

rT |
cn “
—

abeseeeeeoe

T1258,

N
} 10 20 MILES
EXPLANATION 10 20 KILOMETERS

OUTCROP OF NACATOCH SAND

smeeeeees BOUNDARY OF STUDY AREA

a8 sf st ae ~~ APPROXIMATE NORTHERN LIMIT OF NACATOCH
SAND

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

—150— POTENTIOMETRIC CONTOUR-Shows altitude at
which water level would have stood in tightly cased
wells. Contour interval 25 feet. Datum is sea level

CONTROL POINT--Letter, where present, corresponds
to hydrograph in figure 4

8 FLOWING WELL

Figure 4. Potentiometric surface of the Nacatoch aquifer, southwestern Arkansas, April-May 1999.

6 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation of
Southwestern Arkansas, 1999


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 quarter-
quarter 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 let-
ters are assigned counterclockwise, beginning with "A"
in the northeast quarter or quarter-quarter or quarter-
quarter-quarter section in which the well is located. For
example, well 01S03W04BBD 16 (fig. 2) is located in
Township 1 South, Range 3 West, and in the southeast
quarter of the northwest quarter of the northwest quar-
ter of section 4. This well is the 16th well in this quar-
ter-quarter-quarter section of section 4 from which data
were collected. Wells were located using a Global Posi-
tioning System (GPS) capable of accuracy to one one-
hundreth of a second of latitude and longitude.

NACATOCH SAND

Hydrogeologic Setting

The Nacatoch Sand of Cretaceous age is under-
lain by the Saratoga Chalk and overlain by the Arkadel-
phia Marl. In the northeastern subarea, the Nacatoch
Sand subcrops beneath Quaternary alluvial and terrace
deposits along the western boundary (fig. 3). The top of
the Nacatoch Sand has an altitude of about 50 to 100
feet (ft) above sea level! along the western boundary,
dips toward the southeast, and descends to about 1,200
ft below sea level at the Mississippi River. The unit is
about 100 ft thick near the subcrop and attains a maxi-
mum thickness of about 600 ft downdip (Petersen and
others, 1985).

The Nacatoch Sand in the northeastern subarea
consists of interbedded clay, limestone, and fine sand in

'n this report, sea level refers to the National Geodetic Verti-
cal Datum of 1992--a geodetic datum derived from a general
adjustment of the First-order level nets of the United States and
Canada, formerly call Sea Level Datum of 1929

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 subarea the Nacatoch Sand
outcrops ina belt 3 to 8 miles (mi) wide extending from
central Clark County southwestward to western Hemp-
stead County (fig. 4). 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 sea level in the outcrop, dips towards the
southeast, and descends to about 800 ft below sea level
at the southern boundary of the subarea. The Nacatoch
Sand is about 100 ft thick near the outcrop and attains
a maximum thickness of 600 ft (Petersen and others,
1985).

The Nacatoch Sand in the southwestern subarea
consists of three distinct units. The upper unit is com-
posed of unconsolidated, gray, fine-grained quartz sand
that commonly is cross bedded. Locally the sand is
massive and contains a few hard lenses and beds of fos-
siliferous 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 inter-
bedded 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).

Inthe southwestern subarea 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
Green County, Clay County, southern Clark County,
northwestern Nevada County, central Hempstead
County, northern Miller County, and southeastern Lit-
tle River County. Flowing wells produce yields of 1 or
2 gallons per minute (gal/min) in the lowest stream val-
leys in Clark and Nevada Counties. Wells in Hemp-
stead County and western Nevada County produce
yields of 150 to 300 gal/min. Downdip 2 to 20 mi

Nacatoch Sand 3


“fom Fanneman (1938)
Figure 1. Location of study area.

line, and on the east by the eastern borders of Clark and
Nevada Counties. The southwestern subarea was lim-
ited to the occurrence of freshwater; the southern
boundary of the subarea is defined by a freshwater/salt-
water interface. To the south, the ground water is con-
sidered 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 59 wells completed in the Naca-
toch aquifer and in 45 wells completed in the Tokio
aquifer during April and May of 1999. These measure-
ments were used to construct potentiometric-surface
maps. All water-level data are stored in the U.S. Geo-
logical Survey’s Ground- Water Site Inventory (GWSI)
data storage system. Long-term water-level hydro-
graphs were prepared for selected wells. County with-

EXPLANATION

Study Area

Boundary of
physiographic
province

drawal data collected by the U.S. Geological Survey
from 1965 to 1995 were related to these hydrographs.

The Tokio Formation is stratigraphically below
the Nacatoch Sand and separated from it by five strati-
graphic units, listed here in descending stratigraphic
order: Saratoga Chalk, Marlbrook Marl, Annona
Chalk, Ozan Formation, and Brownstown Marl. In the
study area, these five units are rarely used as water
sources and are not discussed in this report.

Cones of depression within a potentiometric sur-
face are indicators of pumping rates that are exceeding
the local recharge rates to the aquifer. As a well is
pumped, water levels are drawn down, forming a local
cone of depression. Water levels will recover in time 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

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

of Southwestern Arkansas, 1999


TOKIO FORMATION

Hydrogeologic Setting

The Tokio Formation of Cretaceous age under-
lies 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 Forma-
tion of Late Cretaceous age in Little River, Sevier,
Howard, and northwestern Hempstead Counties
(Boswell and others, 1965). The Tokio Formation out-
crops in a southwest-to-northeast trending mile-wide
band in west-central Clark County (fig. 6). The outcrop
attains a maximum width of about 10 mi in Howard
County and continues southwest into Sevier County
approximately 8 mi. In this area, the Tokio Formation
is overlain in several places by terrace deposits of Qua-
ternary alluvium. The unit also outcrops in northwest-
ern Little River County, west of the study area. The unit
ranges in thickness from about 50 ft to more than 300
ft, dips towards the southeast, and is composed of dis-
continuous, interbedded gray clay and poorly sorted,
cross-bedded 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 precip-
itation where it outcrops or is overlain by permeable
alluvial and terrace deposits. Salinity increases down-
dip to the south-southeast. The aquifer yields freshwa-
ter to within a few miles north of Ashdown in Little
River County (fig. 6). The water in the Tokio aquifer
becomes slightly to moderately saline downdip (south-
east) 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).

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 apprecia-
bly 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 with-
drawn from the Tokio aquifer increased by 201 percent
from 2.0 Mgal/d in 1965 to 6.02 Mgal/d in 1980. Water
withdrawn from the Tokio aquifer was estimated to be
2.23 Mgal/d in 1995, a decrease of 63 percent from
1980 (Halberg and Stephens, 1966; Holland and Lud-
wig, 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. 6).
Water-level measurements in 45 wells from April and
May 1999 were used to construct the map (table 3). The
surface is mapped by determining the altitude of the
water levels and is represented on the map by contours
that connect points of equal value. The general direc-
tion of ground-water flow is perpendicular to the con-
tours in the direction of downward hydraulic gradient.

In the study area, the direction of ground-water
flow in the Tokio aquifer generally is towards the south
or southeast. The potentiometric high is within the out-
crop area in the northwestern part of the study area. The
highest water-level altitude measured was about 493 ft
above sea level in Howard County. The lowest water-
level altitude measured was about 133 ft above sea
level, 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 miles
northwest of Hope. The northern half of an apparent
cone of depression northwest of Hope is shown on fig-
ure 6. Water level data in the Tokio aquifer were not
available south of this area. No other cones of depres-
sion were evident in the Tokio aquifer. A comparison
with the 1996 potentiometric surface map for the Tokio
aquifer shows no substantial changes over large areas
(Schrader, 1998).

Tokio Formation 15


ee ere pint

i 10 2 MILES
10 20 KILOMETERS.

EXPLANATION
seeeeeee= BOUNDARY OF STUDY AREA
aa at as APPROXIMATE WESTERN LIMIT OF NACATOCH
SAND
—250-- 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 sea level

D- CONTROL POINT--Letter, where present, corresponds
to hydrograph in figure 4

Figure 3. Potentiometric surface of the Nacatoch aquifer, northeastern Arkansas, April-May 1999.

southeast from the outcrop area in the southwestern
subarea, the water generally is excessively saline for
most uses. 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 com-
pleted in the Nacatoch aquifer at Hope and Prescott
show a transmissivity of 3,600 gallons per day per foot
(gal/d/ft) (Ludwig,1972).

In the northeastern subarea, water withdrawn
from the Nacatoch aquifer was estimated to be 0.25
million gallons per day (Mgal/d) in 1965 and increased
to 2.09 Mgal/d in 1995, an increase of 736 percent dur-
ing a 30-year period.

In the southwestern subarea, water withdrawn
from the Nacatoch aquifer was estimated to be 2.11
Mgal/d in 1965 and increased by 125 percent to 4.75

Mgal/d in 1980. Water withdrawn from the Nacatoch
aquifer in this subarea was estimated to be 1.02 Mgal/
din 1995, a decrease of 78 percent from 1980 (Halberg
and Stephens; 1966, Holland and Ludwig, 1981; Hol-
land, 1999).

Potentiometric Surface

Water-level measurements in 59 wells from

April and May 1999 were used to construct potentio-
metric-surface maps for the Nacatoch aquifer (figs. 3
and 4; table 1). The surface is mapped by calculating
the altitude of the water levels (table 1) and is repre-
sented on the figures by contours that connect points of
equal value. The general direction of ground-water
flow is perpendicular to the contours in the direction of
downward hydraulic gradient.

Nacatoch Sand 5


Site M, NEVADA COUNTY, 11S22W08DAC1

240 TTT TTT TT
| | |
4 | tpi Lita itt it
a i Perry yt PT TT]
w it poy | pod Ii T |
220 e+ on en ' + <5
a i | | | iid id | !
| | {i | | | | 1
a T ot im ry | |
o LE | eee eee | | meee
w 200 5 ae | — t in an
i, id | | | | ii]
a Litt || | i | i
< r mT ee ' I T TT
= i | hl ' | | | | i | aa
it 180 + tt A - — —
iy | | | |
z Ly | ,__ eee | |
~ ii r| ry | ]
i | id 1 {oq t i i !
@ 160 PP} ++} Vt —
ay Ped | eee \ | |
= a8 een po +4
fi Toy ky SEE
E aceon | LI | ti
se
pio ti tt to4 bait} iy Lit ii
pene Pr ey Sen neeeneen
4290 LU i oe Petit aoe iti

11/55 1/1/60 1/1/65 1/1/70 1/1/75 1/1/80 1/1/85 1/1/90 1/1/95 1/1/00

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

Table 4. Estimated withdrawal rates by county from the Tokio aquifer
(Units are million gallons per day. Data from Holland, 1999; Holland, 1993; Holland, 1987; Holland and Ludwig, 1981; Halberg, 1977;
Halberg, 1972; Halberg and Stephens, 1966]

Estimated withdrawal rate
County 1965 1970 1975 1980 1985, 1990 1995
Clark 0.00 0.00 0.02 0.06 0.04 0.01 0.01
Hempstead 0.67 0.68 2.15 3.00 2.86 1,10 1.66
Howard 0.69 0.62 0.97 111 0.14 0.00 0.00
Little River 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Miller 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Nevada 0.37 0.45 0.55 0.68 0.00 0.00 0.00
Pike 0.12 0.41 0.43 0.82 0.06 0.03 0.02
Sevier 0.15 0.17 0.25 0.35 0.79 1.15 0.54
Total 2.00 2.33 4.37 6.02 3.89 2.29 2.23

Tokio Formation = 21


s)
aUSGS he

science for a changing world

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, 1999

Water-Resources Investigations Report 99-4208

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


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

Depth to

Water level Land-surface

Local well number Latitude Longitude atimude (eet treet below aide (eet aepth measure:

sea level) land-surface level) (feet) ment

datum)
11S24W22ADD1 = 334647.25 — 933342.50 338 31.59 370 100 4/30/99
11S24W34CBC1 —334443.82 — 933437.90 298 22.41 320 31 4/30/99
11826W27BDD1 334610.50  934644.59 425 5.30 430 32 4/28/99
12S24W28CDC1 —-334012.41_—-933535.89 133 220.12 353 620 5/05/99
12S25WO7ABB1 = 334345.67  934340.05 398 36.66 435 100 4/28/99
12S25W15DBC1 —334213.66 + 934035.55 292 18.62 311 202 4/28/99
12S25W34BAC1 —334001.94 934055.44 254 65.62 320 300 4/28/99
12S26W21AAC1 = 334158.03  934739.04 368 30.12 398 60 4/28/99
12S26W24ABC1 = 3334159.15  934438.21 312 3.14 315 108 4/28/99
13S25WOSABD1 —333915.43  934231.85 262 19.68 282 300 4/28/99
13S25W18AAB1 —333739.64 —934331.59 232 51.48 283 335 4/30/99
13S25W35DDC1 —333406.09  —933930.91 220 152.88 373 780 4/30/99
13S26W17DDB1 = 333705.19 934844.69 235 55.72 291 210 4/30/99
14S25WO04DDD1 —(3333317.01_ 934131.68 212 48.31 260 850 4/30/99
Little River County

13S28W31BCC1 —333509.35 —940250.97 259 51.77 311 260 4/22/99
14S30WOIDAA1 —333426.16 — 940904.22 253 29.01 282 375 4/22/99

Miller County
14S27WO2AABI1 —-333419.42—-935121.43 232 22.64 255 390 4/20/99
14S28W13CCB1 —333158.09 — 935726.62 240 25.91 266 416 4/21/99
14S28W17BBC1 —333239.92  940134.07 247 23.39 270 360 4/21/99

Nevada County
10S22W23DCB1 —335105.16 —931934.65 241 1.06 242 45 4/23/99
11S20WO8DCD1 —-.334727.45 —-931037.28 175 5.66 181 525 4/26/99
11S20W22AAA1 —334623.76 + 930925.95 177 -2.05 175 550 4/26/99
11S21W14CAB1 —334652.02  931434.14 197 -1.0 196 550 4/26/99
11S22WO8DAC2 —334759.75 —-932314.18 266 39.58 306 232 4/26/99
11S23W0O3DCD1 —334840.28 +=: 932726.19 306 78.57 385 135 4/23/99
11S23W12ABB1 —334837.00 _ 932538.00 311 70.05 381 300 4/23/99
12S21W27BAC1 —334016.14 — 931547.01 194 5.86 200 890 427199
12S22WO9CDD1 —334229.68 + 932250.19 228 0.98 229 442 4/27/99
12822W22ACD1 =. 334107.66 + 932134.93 225 117.26 342 600 4/27/99
12S22W23CBA1 334102.42 — 932057.36 222 107.28 329 630 4/27/99
13S22WO7BDC1 =. 333744.12  932514.03 227 115.61 343 671 4/27/99

8 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation of
Southwestern Arkansas, 1999


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

Rawle arrived EAMEABETIEE yey ate of

Local well number Latitude —_Longitude above (feet below above sea depth ——_ measure-

sea level) tanaeurtie level) (feet) ment

Clark County
O8S1I9WO6DCA1 = 340359.21  — 930432.34 193 76.93 270 148 5/03/99
O8SI9WO6DDA1 340400.87 930413.83 179 5.84 185 109.5 5/03/99
O8SI9WO9ACC1 340323.35 —930228.33 178 -0.85 177 195 5/03/99
O8SI9W16CAB1 340225.62 —930247.10 171 1.83 173 - 5/03/99
08S20W34DAB1 = 335954.15  930744.35 183 16.69 200 100 5/03/99
O9S20W16DBD1 = 335708.15 —930847.37 162 78.57 241 228 4/30/99
O9S20W16DDC1 335656.77 930844.75 157 76.41 233 241 4/30/99
09S20W28DCB1 = 335516.13  930900.79 182 20.49 202 245 4/30/99
O9S20W31CAD1 —335434.79  931111.15 180 79.49 259 276 4/30/99
09S20W33ABD1 335447.13 930852.09 176 33.39 209 245 4/30/99
09S20W33BCD2  335446.06 930926.02 182 24.75 207 236 4/30/99
09S21W21DAD1 —335625.47 931453.39 240 105.22 345 110 5/03/99
10S20W22DCB1 = 335054.14 —- 930757.21 181 79.25 260 500 4/29/99

Clay County

19N04E01BDB1 361909.66  903559.97 271 9.25 280 - 4/15/99
19NO7E23BAC1 361601.75 —901748.02 242 79.69 322 1,100 4/14/99
19NO7E23DBC1 —-361548.58 ~—901730.31 249 34.36 283 1,114 4/14/99
I9NO7E26AAA1 —361531.66 901702.61 244 32.03 276 1,086 4/14/99
20N04E36DCC1 361928.53  903542.09 266 12.61 279 348 4/15/99
20N08E10ABC1 362312.60 901201.74 253 87.02 340 989 4/15/99
20N08E14BAB2 362227.05 901119.62 242 44.33 286 1,000 4/15/99
20NO8E1SBAA1 —362223.50 901207.70 239 142.32 381 1,062 4/15/99
21NO6E23DAC1 362618.79 — 902329.21 277 22.73 300 462 4/15/99
21NO7E25AAC1 —-362549.74 — 901606.97 274 67.78 342 732 4/15/99

Greene County
18NO06E14CCD1 361114.55  902419.58 243 44.15 287 1,153 4/15/99
18NO6E24BDA 1 361058.18 — 902300.11 251 25.32 276 1,105 4/15/99

Hempstead County

11S24W08BDB1 —-334836.52 _933619.25 447 22.58 470 30 4/30/99
11S24W21ADD1 —334640.64 ~—933448.80 353 48.31 401 50 4/30/99
11S24W21DDD1 —334620.53 933447.12 338 32.64 371 90 4/30/99

Nacatoch Sand

7


©
=
a
a
ao
+
S
s
ise)
f=}
an
=
°
4
=
wi
=

Figure 2. Diagram showing well-numbering system.

of

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

Southwestern

Arkansas, 1999


Table 3. Water-level measurements and well information for wells completed in the Tokio aquifer--Continued

Water level Depth to
water level Land-surface Well Date of

Local well number Latitude ~—Longitude alirade (eet (feet below _ altitude (feet depth —_ measure-

sea level) land-surface above sea level) (feet) ment

datum)

10S27W04BBD1 =: 335512 935329 341 50.97 392 170 4/23/99
10S27W12CAB1 335356 935020 311 72.14 383 416 4/23/99
10S27W18BACI1 335336 935534 341 81.29 422 300 4/23/99

Little River County
11S30W25DDC1 = 334618.44 = 940852.31 266 18.98 285 380 4/29/99

Nevada County
09S22W33DCC1 = 335437.37 = 932130.47 220 4.57 225 677 4/23/99
10S23W12AAA1 —335344.81  932420.89 236 19.78 256 600 4/23/99
11S22WO8DACI —334757.94  932315.14 218 87.49 305 1,052 4/26/99
11S22WO8DAC8 —334756.76 932311.82 218 86.67 305 1,050 4/26/99
Pike County
08S23W19ADC1 340213 932930 351 13 350 105 4/21/99
08S23W35DCAI 340004 932530 259 “15 257 125 4/21/99
O8S24W14AAC1 340324 933134 439 84.11 523 185 4/21/99
09823W17BBC2 335804 932924 283 2.85 280 200 4/21/99
O9S24W14AAD1 335810 —-933138 287 1.6 285 140 4/21/99
Sevier County

10S28W31DCC1 335026.12  940145.37 290 39.55 330 185 4/21/99
11S29WOSDCA1 —334949.30  940652.64 321 159.07 480 400 4/22/99
11S29W13CCD1 —334750.48 940317.44 280 80.27 360 339 4/21/99

18 Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation
of Southwestern Arkansas, 1999


CONTENTS

Abstract...
Introduction
Nacatoch Sand
Hydrogeologic Setting
Potentiometric Surface ........
Long-Term Water-Level Changes
Tokio Formation .....
Hydrogeologic Setting
Potentiometric Surface .
Long-Term Water-Level Changes

ILLUSTRATIONS

Figure 1. Map showing location of study area ...
2. Diagram showing well-numbering system.
3. Map showing potentiometric surface of the Nacatoch aquifer, northeastern Arkansas, April-May 199!
4. Map showing potentiometric surface of the Nacatoch aquifer, southwestern Arkansas, April-May 1999
5. Hydrographs showing water-level altitudes for selected wells completed in the Nacatoch aquifer...
6. Map showing potentiometric surface of the Tokio aquifer, southwestern Arkansas, April-May 199
7. Hydrographs showing water-level altitudes for selected wells completed in the Tokio aquife

SASauUan

TABLES

Table 1. Water-level measurements and well information for wells completed in the Nacatoch aquifer.
2. Estimated withdrawal rates by county from the Nacatoch aquifer ......
3. Water-level measurements and well information for wells completed in the Tokio aquifer.
4, Estimated withdrawal rates by county from the Tokio aquifer

Sten

Contents iii


Site C, CLAY COUNTY, 20NO08E10ABC1

1/1/00

ae a a CO = TI Jl] an
ote ee ee ee a [
= a Ce a ee
Q L
ff] F fateh dtretcte te tet
a ee qe a toh
g
a a 8 }—+ +f F +—--4--+-]
| = 8 oa i - ~ bo : —+—4
ae 8 8 ee ee |
4s Seat
= oot en 458 pope
|g
es ee eS ee oe ed eet
eer 'e) =
eee ee oe ee oe fo
= —o _ re ee on = 8
Pres : ees ee ee

340

§ gs & & 8
ss 8 & & @

13A31 WAS JAO8V 1334 NI “T3A57 HaLVM

220

1/1/55

13A31 WAS SAO@V 1334 NI “13A37 HALVM

1/1/60 «1/1/65 1/1/70 1/1/75 1/1/80 1/1/85 1/1/90 1/1/95 1/1/00
Figure 5. Water-level altitudes for selected wells completed in the Nacatoch aquifer—Continued.

1/1/55

"

Nacatoch Sand


Site G, NEVADA COUNTY, 11S22W08DAC2

a ‘om a —

280

13A31 VaS JAOSV 1334 NI “T3A37 HALVM

W160 «(1/1/65 «1/1/70 1/1/75 1/1/80 1/1/85 1/1/90 1/1/95 — 1/1/00
Site H, HEMPSTEAD COUNTY, 13S25W35DDC1

1/1/55

to

13A31 WAS SAV 1334 NI “13A37 HALVM

150

1/1/60 «1/4/65 «1/1/70 1/4/75 1/1/80) 1/1/85 1/4/90 1/1/95 ~— 1/1/00
Figure 5. Water-level altitudes for selected wells completed in the Nacatoch aquifer—Continued.

1/1/55

13

Nacatoch Sand


U.S. DEPARTMENT OF THE INTERIOR
BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY
Charles G. Groat, Director

For additional information
write to:

District Chief

U.S. Geological Survey, WRD
401 Hardin Road

Little Rock, Arkansas 72211

Copies of this report can be
purchased from:

U.S. Geological Survey

Branch of Information Services
Box 25286

Denver Federal Center
Denver, Colorado 80225


SUMMARY

Aquifers in the Nacatoch Sand and Tokio Forma-
tion 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 59 wells com-
pleted in the Nacatoch Sand and 45 wells completed in
the Tokio Formation from April through May 1999. In
northeastern Arkansas, withdrawals from the Nacatoch
Sand increased by 736 percent from 1965 to 1995, 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 78 percent and 63 percent,
respectively, from 1980 to 1995.

The direction of ground-water flow in the north-
eastern 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 east-
ern Clay County.

The direction of ground-water flow in the south-
western 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 in the out-
crop area in north-central Hempstead County. A cone
of depression exists at Hope in Hempstead County. No
other cones of depression were evident in the Nacatoch
aquifer.

In the northeastern subarea of the Nacatoch aqui-
fer, water levels in four wells declined during a period
of increased withdrawals from the Nacatoch aquifer.
Water withdrawn from the Nacatoch aquifer was esti-
mated to be 0.25 Mgal/d in 1965 and increased to 2.09
Mgal/d in 1995, an increase of 736 percent during a 30-
year period.

In the southwestern subarea of the Nacatoch
aquifer, water levels in four of five wells rose during a
period of decreased withdrawal from the Nacatoch
aquifer. Water withdrawn from the Nacatoch aquifer
was estimated to be 1.02 Mgal/d in 1995, a decrease of
78 percent from 4.75 Mgal/d in 1980. The hydrograph
for site E shows no apparent association between
water-level changes in a well completed in the Naca-
toch aquifer and withdrawals. The variation in water
levels in this well could result from differences in local-
ized withdrawals, climatic variations, or leakage of
water from overlying and underlying rock units.

The direction of ground-water flow in the Tokio
aquifer is towards the southeast. The potentiometric
high is located where the aquifer outcrops in the north-
western 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 might exist northwest of Hope in Hemp-
stead County.

The hydrographs of one of four wells completed
in the Tokio aquifer showed a decline and a rise in
water levels during a period of increased, then
decreased withdrawals from the aquifer in Nevada
County. 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 aqui-
fer was estimated to be 2.23 Mgal/d in 1995, a decrease
of 63 percent from 1980. Three hydrographs show no
apparent association between water-level changes in
wells completed in the Tokio aquifer and withdrawals.
The variation in water levels in these wells could result
from differences in localized withdrawals, climatic
variations, or leakage of water from overlying and
underlying rock units.

22 ‘Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Tokio Formation

of Southwestern Arkansas, 1999


STATUS OF WATER LEVELS IN AQUIFERS IN THE
NACATOCH SAND OF SOUTHWESTERN AND
NORTHEASTERN ARKANSAS AND THE TOKIO
FORMATION OF SOUTHWESTERN ARKANSAS, 1999

By T.P. Schrader

U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 99-4208

Prepared in cooperation with the

Arkansas Soil and Water Conservation Commission
and the Arkansas Geological Commission

Little Rock, Arkansas
1999


In the northeastern subarea, the direction of
ground-water flow in the Nacatoch aquifer generally is
towards the southeast (fig. 3). The potentiometric high
is located along the north and northwestern boundary
of this subarea. The highest water-level altitude mea-
sured was about 277 ft in northern Clay County. The
lowest water-level altitude measured was about 239 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. 4). 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 high-
est water-level altitude measured was about 447 ft in
the outcrop area of north-central Hempstead County.
The lowest water-level altitude measured was about
133 ft at Hope in southeastern Hempstead County.

A cone of depression exists at Hope in Hemp-
stead County (fig. 4). Historical water levels indicate a
decline from 185 ft above sea level in 1942 to 145 ftin
1969 (Ludwig, 1972). The water-level altitude from
May 1999 was 133 ft above sea level. This cone of
depression alters local ground-water flow directions
from the regional direction, with ground water flowing

towards Hope from all directions. No other cones of
depression were evident in the Nacatoch aquifer. A
comparison with the 1996 potentiometric surface maps
for the Nacatoch aquifer shows no substantial changes
over large areas (Schrader, 1998).

Long-Term Water-Level Changes

Nine hydrographs from wells completed in the
Nacatoch aquifer display long-term (minimum of 20
years) water-level altitudes (fig. 5). Four wells (sites A-
D) are located in the northeastern subarea (fig. 3).
Water levels in each of these wells generally declined
over the period of record an average of 0.5 to 1.4 foot
per year (ft/yr). Water withdrawal rates from the Naca-
toch aquifer for Greene and Clay Counties increased
from 0.25 Mgal/d in 1965 to 2.09 Mgal/d in 1995, with
a maximum of 2.21 Mgal/d in 1990, an increase of
approximately 736 percent from the 1965 withdrawal
rates (table 2). The decrease in water levels may be
associated with the increased withdrawal from the
Nacatoch aquifer in Greene and Clay Counties.

Five wells with historical water-level measure-
ments (sites E-I; fig. 5), are located in the southwestern
subarea (fig. 4). 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.

Table 2. Estimated withdrawal rates by county from the Nacatoch aquifer
[Units are million gallons per day. Data from Holland, 1999; Holland, 1993; Holland, 1987; Holland and Ludwig, 1981; Halberg, 1977;

Halberg, 1972; Halberg and Stephens, 1966]

Estimated withdrawal rate

County 1965 1970 1975 1980 1985 1990 1995
Clark 0.44 0.55 0.64 1.73 0.91 0.29 0.34
Clay 0.25 0.51 0.63 1.55 1.13 1.98 1.72
Greene 0.00 0.06 0.08 0.16 0.09 0.23 0.37
Hempstead 1.12 1.72 1.44 1.98 0.15 0.20 0.32
Howard 0.00 0.14 0.22 0.24 0.00 0.00 0.00
Little River 0.20 0.04 0.04 0.06 0.00 0.00 0.00
Miller 0.14 0.03 0.04 0.06 0.00 0.00 0.00
Nevada 0.21 0.45 0.55 0.68 Ll 0.44 0.36
Total 2.36 3.50 3.64 6.46 3.39 3.14 3.11

Nacatoch Sand 9


Site E, CLARK COUNTY, 08S19W09ACC1

1/1/00

f {| —_} | es ee

1/1/95

oe _ 4 | lo —— 4. = —|—
+ g
4 ae a ~ ls |
a —+— -4 wo
g
+ }—- +, i=}
2
to +—+-HI-- —+—+— =

= | + 4 =a

240

13A31 W4S SAOaV 1334 NI ‘TIA37 HALYM

120

W160 «1/1/65 =1/1/70 1/1/75

11/55

Site F, CLARK COUNTY, 09S20W16DDC1

Seo eeeeeeee

TAA31 WAS SAO8V 1334 NI

fo} 2
0 ve]

“T3A37 HALVM

110

W1/60 «1/1/65 1/1/70 1/1/75 1/1/80 1/1/85 1/1/90 1/1/95 1/1/00
Figure 5. Water-level altitudes for selected wells completed in the Nacatoch aquifer—Continued.

1/1/55

12 _ Status of Water Levels in Aquifers in the Nacatoch Sand of Southwestern and Northeastern Arkansas and the Toklo Formation

of Southwestern Arkansas, 1999