U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 005-99

July 1999

Arkansas

Geologic Mapping

The U.S. Geological Survey (USGS)

is mapping the geology of the Ozark

Plateaus of northern Arkansas near

the Buffalo National River to provide

information to the National Park

Service (NPS). The highest concern is

understanding geologic factors that

control paths of ground-water flow in

the park area. This information is

intended to help identify areas that

are likely to introduce sediments,

nutrients, and contaminants into the

Buffalo River.

Initial studies focused on an area of

known interbasin transfer of ground

water. In this area, water from an

agricultural, north-draining, basin

flows southward in the subsurface

and enters the Buffalo River Basin at

large springs. New geologic mapping

illustrates that the stratigraphy of rock

formations and the faults that cut

them influence this interbasin flow.

The most springs in the mapped area

are found at the base of the cherty

limestone of the Boone Formation

(fig. 1). Also, newly discovered faults

that intersect near the large springs

are thought to control the location of

discharging waters.

The USGS also is supporting geologic mapping in other parts of the

State. The Arkansas Geological

Commission (AGC) is mapping parts

of southwestern Arkansas, and the

University of Arkansas and AGC are

mapping parts of northern Arkansas.

Earthquake Loss Reduction

Researchers from the USGS, the

University of Maryland, the Arkansas

Archeological Survey, and the

University of Memphis have been

studying the record of prehistoric

earthquakes at archeological sites in

the New Madrid seismic zone. Native

American artifacts, charcoal, and

other organic materials can be used to

date the eruption of sands to the

ground surface during earthquakes.

Many sites throughout the region are

being examined to develop a chronology of large ancient earthquakes and

to estimate the probabilities of future

earthquakes, a critical aspect of

seismic hazard evaluation.

The USGS is supporting a cooperative earthquake monitoring network

consisting of conventional and

broadband stations that can record a

broader range of earthquake sizes,

within and surrounding the seismic

zone (fig. 2). The University of

Memphis and Saint Louis University

have primary responsibility for

network development and operation.

This network records ground motions

for use in scientific studies and for

rapid notification of the public about

significant earthquakes.

The USGS also is supporting preparation of soil liquefaction classification

maps in the seismic zone. A map of

an area that includes parts of northeastern Arkansas recently was

completed by the AGC and several

other State geology agencies.

Figure 2. Stations of the Cooperative

New Madrid Seismic Network. Dots

in the background are 1974–98

earthquake epicenters.

91° 90° 89° 88°

35°

36°

37°

38°

39°

Memphis

St. Louis

Mississippi

Arkansas 

Kentucky

Tennessee

Missouri

Illinois

CONVENTIONAL STATIONS

BROADBAND STATIONS

EARTHQUAKE EPICENTERS (1974–98)

Figure 1. Relation of spring frequency

and stratigraphy.

DISTANCE OF SPRINGS ABOVE OR BELOW

BASE OF MISSISSIPPIAN AGE ROCK, IN FEET
science for a changing world

Water Use

Water-use data collected by the

USGS, in cooperation with the

Arkansas Soil and Water Conservation Commission, indicate that more

water is used for irrigation than for

any other purpose in Arkansas. Water

withdrawals for irrigation in Arkansas

in 1995 were estimated to be 5,938

million gallons per day. Of this

amount, 83 percent was ground water.

Irrigation water use has increased by

61 percent since 1980 (fig. 3).

Although the average annual application rate of water decreased about 40

percent between 1980–95, the amount

of irrigated land increased. Public

supplies in Arkansas served about 2

million people, or 80 percent of the

population, in 1995. The population

served by public-supply facilities in

Arkansas has increased 17 percent

since 1980. Meanwhile, total publicsupply water use in Arkansas increased by 46 percent.

prepare a source water-assessment

program (SWAP) for all public

drinking-water supplies. The assessment aims to determine the potential

susceptibility to contamination of the

State’s drinking-water supplies. The

Arkansas Department of Health

(ADH) is the lead State agency to

develop the SWAP. The USGS is

conducting a 4-year project in cooperation with ADH to provide the

tools necessary to complete the

SWAP. The USGS will lead the effort

and coordinate the assessment work

of the Arkansas Water Resources

Research Center, the University of

Arkansas Department of Geology,

and the Center for Advanced Spatial

Technologies.

Ground-Water Flow Modeling in

Critical Ground-Water Areas

The Sparta and Mississippi River

Valley alluvial aquifers are major

water sources for municipal, industrial, and agricultural uses. Recently,

the demand for water in some areas

has significantly exceeded recharge to

the aquifers, and water users and

managers have begun to question the

ability of the aquifers to supply water

for the long term. Based on conditions in these aquifers, the Arkansas

Soil and Water Conservation Commission (ASWCC) established two

Critical Ground-Water Areas (fig. 4)

in 1996 and 1998. This designation

mandates maintaining aquifer conditions within specific, water-level

based limits.

The USGS and ASWCC developed a

regional-scale, computerized groundwater flow model in the mid-1980’s

for testing water-use strategies that

could affect the Sparta aquifer.

Modeling shows that the aquifer

cannot supply water for more than 30

years at the current increasing demand. However, model results show

that conservation measures and use of

alternative sources of water could

result in considerable recovery of

water levels in the aquifer.

The USGS, in cooperation with the

U.S. Army Corps of Engineers, is

using a similar model of the alluvial

aquifer to evaluate the regional effects

of aquifer and alternative water

source development on water-level

declines. The effects of projected

ground-water withdrawals are being

simulated through the year 2049. The

primary objective is to determine

what portion of projected total water

demand can be met by the alluvial

aquifer while maintaining a certain

minimum saturated thickness in the

of aquifer material.

Clean Water and Watershed

Restoration Initiative—Buffalo

National River

The USGS and the NPS have developed a partnership to identify waterquality needs in park resourcemanagement plans. Beginning in

1999, the USGS will collaborate on

three water-quality assessment

projects on the Buffalo National

River (fig. 5). A planned 3-year study

on Bear Creek, a tributary to the

Buffalo River, will collect streamflow

and water-quality information. BedMILLION GALLONS PER DAY 6000

5000

4000

3000

2000

1000

0 1980 1985 1990 1995

IRRIGATION

PUBLIC SUPPLY

YEAR

Figure 3. Irrigation and public-supply

water use in Arkansas, 1980–1995.

Source Water Assessment

Program

The Safe Drinking Water Act Amendments of 1996 require each State to

Figure 4. Critical Ground-Water Areas.

CRITICAL GROUND-WATER AREAS

AREA UNDERLAIN BY SPARTA OR

 MISSISSIPPI RIVER VALLEY

 ALLUVIAL AQUIFERS

 

El Dorado

Pine Bluff
Arkansas

sediment samples will be collected

from a tributary of the Buffalo River

to determine the extent and occurrence of organic compounds previously detected. To assist in development of a Water Resources Management Plan for the Buffalo National

River, the USGS will perform statistical analyses of existing water-quality

and streamflow data.

National Water-Quality

Assessment Program

Ozark Plateaus

Between 1992–95, ground- and

surface-water-quality samples were

collected and ecological assessments

were performed to describe the

regional water-quality conditions of

the Ozark Plateaus National WaterQuality Assessment (NAWQA) study

unit in Arkansas, Kansas, Missouri,

and Oklahoma (fig. 6). Increases in

confined-animal populations and

human activities pose threats to the

quality of water in the sensitive karst

environment of the Ozark Plateaus.

Nutrients, bacteria, pesticides, trace

elements, and fish communities in

Ozark Plateaus water have been

affected by agricultural, urban, or

mining activities.

Mississippi Embayment

The Mississippi Embayment

NAWQA study (fig. 6) has been

collecting water-quality data from

two streams and several aquifers in

Arkansas. Concentrations of all

sampled constituents were found to

be well within Federal drinking-water

standards. Water-quality data from

wells open to the Mississippi River

Valley alluvial aquifer are being

investigated in 1999.

Southern Forested Wetlands

Forested wetlands constitute the

majority of wetlands in the southern

United States. As part of the multistate Southern Forested Wetland

Initiative, the USGS has wetland

forest study sites in Arkansas and is

working with managers at several

National Wildlife Refuges. The

USGS provides broad expertise in

monitoring the success of forested

wetland restoration, improving

wildlife habitat-management techniques, and studying the genetic

diversity of bottomland hardwoods.

Scientists also are studying bird

populations whose reduced numbers

have paralleled the tremendous loss

of southern forested wetlands.

Wild Turkey Population Decline in

the Ouachita Mountains

As part of the Arkansas Cooperative

Fish and Wildlife Research Unit in

Fayetteville, the USGS has worked

with the Arkansas Game and Fish

Commission and the National Wild

Turkey Federation to determine the

causes of decline in a wild turkey

population in the Ouachita Mountains. Researchers estimated the

reproductive success of turkey hens

by radiotagging and tracking individuals from 1993 to 1996. The

studies found that low nesting success, low nesting attempts, and small

clutch size were typical of this

population. Predator density may

interact with weather and hen condition to influence success and may

alter nest site selection. Disease did

not appear to be a substantial population-limiting factor. The findings and

relations identified in this research

are intended to assist agencies in

developing appropriate management

strategies.

Figure 5. The Buffalo National River. (Photograph courtesy of A.C. Haralson, Arkansas

Department of Parks and Tourism.)

Figure 6. NAWQA study units in

Arkansas.

 Ozark Plateaus

Mississippi

Embayment
Printed on recycled paper

USGS office locations USGS State Representative

401 Hardin Road

Little Rock AR 72211-3258

(501) 228-3600

FAX (501) 228-3601

USGS Home Page

http://www.usgs.gov

Reports and products

1-888-ASK-USGS

The USGS has 49

employees in Arkansas

Little Rock

Fort Smith

Fayetteville

Figure 7. A biologist examining a dead

bald eagle.

Bald Eagles and Coots Suffer

Mysterious Deaths

At least 56 bald eagles and an unknown number of American coots

have died in south-central Arkansas.

The USGS is working with the

Arkansas Game and Fish Commission

and other Federal, State, and private

laboratories to identify the cause of

these mysterious deaths (fig. 7).

USGS scientists have identified an

unusual microscopic lesion in the

white matter of the eagle and coot

brains. The cause of the lesions

remains unknown, but scientists

suspect that the lesions are related to a

toxic agent. The USGS is continuing

field investigations and diagnostic

efforts to identify the source of the

problem.

Topographic Map Revision

The USGS has developed a strategy

to help identify the 7.5-minute

topographic maps that are in demand

and that need to be revised (fig. 8).

This plan uses monthly map sales as

one criterion for determining demand,

and then prioritizes the map in the

revision process. Also, the AGC

selects maps to be revised under a

cooperative program with the USGS.

Figure 8. Topographic map revision plan, February 3, 1999.

94° 92° 90°

34°

33°

35°

36°

MAPS REQUESTED FOR

REVISION BY ARKANSAS

GEOLOGICAL COMMISSION

CANDIDATES FOR REVISION

DUE TO MONTHLY SALES