U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Prepared in cooperation with

GREENE COUNTY, MISSOURI, THE U.S. ARMY CORPS OF ENGINEERS, AND

THE MISSOURI DEPARTMENT OF NATURAL RESOURCES

SCIENTIFIC INVESTIGATIONS MAP 3003

Richards, J.M., and Mugel, D.N., 2008,

Potentiometric surface of the Ozark aquifer near Springfield, Missouri, 2006–07

Potentiometric Surface of the Ozark Aquifer near Springfield, Missouri, 2006–07

By

Joseph M. Richards and Douglas N. Mugel

2008

Introduction

A study of the water resources of the Springfield, Missouri, area 

in the 1970s determined that a cone of depression, formed by groundwater pumping, had developed in the Ozark aquifer beneath the city 

(Emmett and others, 1978). Continued ground-water usage in the 

1970s and 1980s caused concern that ground-water resources would 

not be sufficient to meet the future needs of Springfield, Missouri, 

during periods of drought. As a result, a ground-water flow model of 

the Springfield area was developed by the U. S. Geological Survey 

(USGS) to assess the future role of ground water as a water source 

for the area (Imes, 1989). Results of the USGS model led to a decision by the City Utilities of Springfield to primarily rely on surface 

water from Stockton Lake as a source of city drinking water. Municipal and industrial ground-water usage continues in Springfield, but 

at lower rates than previously experienced (Jim Vandike, Missouri 

Department of Natural Resources, written commun., 2007).

Rapid growth in the area has caused commercial, industrial, 

and domestic water use to increase. Population growth has been 

especially rapid in Nixa, Ozark, and Republic, and water use in the 

vicinity of these cities has grown an estimated 39 percent since 1990 

(Dintelmann and others, 2006). Unlike Springfield, ground water is 

the primary source of water for these cities. The increased stress on 

the Ozark aquifer (fig. 1), the primary aquifer in the study area, has 

Figure 1. Correlation of geohydrologic units and stratigraphic units in 

the Springfield, Missouri, area (modified from Imes, 1989).

raised new concerns about possible further water-level declines in the 

areas of increased ground-water use. Although there continues to be 

new development in the Ozark aquifer, since 1987 no new watersupply wells that produce water from the Springfield Plateau aquifer 

(fig. 1) have been allowed to be constructed in most of Greene and 

northern Christian counties (Jim Vandike, Missouri Department of 

Natural Resources, written commun., 2007). There is concern that if 

the potentiometric surface of the Ozark aquifer continues to decline, 

increased leakage of contaminants into the Ozark aquifer from 

the overlying Springfield Plateau aquifer (fig. 1) could occur (Jim 

Vandike, Missouri Department of Natural Resources, written commun., 2007). To address this concern, the USGS, in cooperation with 

Greene County, Missouri, the U.S. Army Corps of Engineers, and the 

Missouri Department of Natural Resources, constructed a map of the 

potentiometric surface of the Ozark aquifer for 2006–2007. The map 

can be compared to previously constructed potentiometric-surface 

maps by Emmett and others (1978) and Imes (1989) to evaluate 

changes in ground-water flow directions, but the comparison is 

beyond the scope of this report.

Hydrogeology of the Study Area

The study area encompasses approximately 2,870 square miles 

and is centered approximately on the city of Springfield, Missouri. 

The maximum land surface elevation (1,740 feet above the National 

Geodetic Vertical Datum of 1929 (NGVD 29)) occurs in the east 

central part of the study area and the lowest land surface elevation (805 

feet) occurs in the northwest part of the study area. The Ozark aquifer 

is confined in about two-thirds of the study area by the Ozark confining 

unit, and is unconfined elsewhere. A secondary aquifer, the Springfield 

Plateau aquifer, occurs above the Ozark confining unit; however, it typically yields sufficient water only for domestic and stock use. Currently 

(2007), water use from the Springfield Plateau aquifer is minor (Jim 

Vandike, Missouri Department of Natural Resources, written commun., 2007). The Springfield Plateau aquifer is confined locally by the 

Western Interior Plains confining system. There is a general downward 

hydraulic gradient from the Springfield Plateau aquifer to the Ozark 

aquifer (Imes, 1989). The Ozark aquifer and the Springfield Plateau 

aquifer exhibit karst features such as springs, caves, sinkholes, losing 

streams, and solution enlarged fractures. These features are important 

hydrologically because they can move water (and contaminants) into 

and through the ground-water system quickly, and can move ground 

water between surface-water drainage basins.

Methods

An updated potentiometric-surface map was constructed using 

119 water-level measurements collected from 115 wells. Data are 

available in the USGS National Water Information System (http://

water.data.usgs.gov/nwis). The USGS made 88 measurements during 

the spring and summer of 2006, and made 17 additional measurements 

in the summer of 2007. Public water-supply managers reported 3 measurements from the spring and summer of 2006, and 11 measurements 

from the spring and summer of 2007. The potentiometric-surface map 

was drawn using ground-water level measurements made at existing wells that either were not pumping or were shut down for a brief 

period (usually about 15 minutes) to allow the water level in the well 

to recover. Water levels were measured to the nearest 0.01 foot with 

an electric tape, to the nearest 0.5 foot with an acoustic meter, or to the 

nearest 5 feet by taking an air-line reading. The largest source of error 

was from determining the land-surface altitudes from USGS 1:24,000 

scale topographic maps, which are accurate to one-half of the contour 

interval (plus or minus 10 feet). Well locations were determined using 

hand-held Global Positioning System (GPS) units. Water-level measurements in wells that were open to the Springfield Plateau aquifer 

and the Ozark aquifer did not represent the potentiometric surface in 

the Ozark aquifer, but were used as supplemental control points to aid 

in contouring. In areas where the Ozark aquifer is exposed at the land 

surface, streambed elevations and some springs also were used to aid in 

contour delineation. The potentiometric surface was constructed using 

a 100- foot contour interval. 

Potentiometric Surface

Potentiometric surface contours of the Ozark aquifer can be 

used to infer direction of ground-water flow. The horizontal component of ground-water flow is perpendicular to the potentiometric 

contour lines. Ground water flows away from ground-water highs 

and discharges to rivers or springs, or is captured by pumping wells. 

Ground-water recharge occurs to the Ozark aquifer from precipitation 

that infiltrates directly into the aquifer where it is exposed at the land 

surface or from flow from the overlying Ozark confining unit. Areas 

of ground-water usage are evident as cones of depression or as potentiometric contours that have shifted from pre-development positions 

as defined by Imes (1989). Based on the potentiometric contours, 

except for the northwest corner, nearly all of Greene County falls in 

the ground-water capture area for the ground-water cone of depression centered on the city of Springfield. 

References Cited

Dintelmann, D., Gutierrez, M., and Gouzie, D., 2006, Groundwater 

potentiometric decline in the Springfield, Missouri area: Environmental Geology, v. 50, no. 4, p. 541–549.

Emmett, L.F., Skelton, John, Luckey, R.R., and Miller, D.E., 1978, 

Water resources and geology of the Springfield area, Missouri: 

Missouri Division of Geology and Land Survey, Water Resources 

Report 34, 150 p.

Imes, J.L., 1989, Analysis of the effect of pumping on ground-water 

flow in the Springfield Plateau and Ozark aquifers near Springfield, Missouri: U.S. Geological Survey Water-Resources Investigations Report 89–4079, 63 p.

Missouri Department of Natural Resources, 2007, Missouri Environmental Geology Atlas: Rolla, Division of Geology and Land 

Survey, CD-ROM.

Western 

Interior Plains 

confining 

system

Springfield 

Plateau 

aquifer

Ozark 

confining 

unit

Ozark aquifer

Pennsylvanian 

channel-sand 

deposits

Hydraulic properties are 

unknown. Presumably, most 

of these localized, thin 

deposits are unsaturated.

Sand and 

clay

St. Louis Limestone

Salem Formation

Warsaw Formation

Keokuk Limestone

Burlington Limestone

Elsey Formation

Reeds Spring

 Formation

Pierson Limestone

Northview Shale

Compton Limestone

Bachelor Formation

Chattanooga Shale

Smithville Dolomite

Cotter Dolomite

Jefferson City

 Dolomite

Roubidoux Formation

Gasconade Dolomite

Eminence Dolomite

Potosi Dolomite

Limestone 

and chert

Shale, silt, 

and 

limestone

Dolostone 

and 

sandstone

Aquifer with karst zone in 

upper part. Yield to wells 

usually is less than 20 gallons 

per minute. Adequate for 

domestic and stock use only. 

Contamination potential large 

because of extensive network 

of karst features and surficial

position.

Confining unit with confining 

material primarily in the 

Northview Shale.

Productive aquifer yielding 

about 1,000 gallons per 

minute to wells open to the 

entire sequence of rock units. 

Upper part of aquifer 

generally is less productive. 

Most productive rock units 

are the Roubidoux Formation, 

Gasconade Dolomite, and the 

Potosi Dolomite.

Lithology Water-bearing properties Geohydrologic

unit

Stratigraphic

unit

MISSOURI

Study area

Western Interior Plains confining system

Springfield Plateau aquifer

Ozark confining unit

Ozark aquifer

Approximate direction of ground-water flow

Potentiometric contour—Shows altitude at which 

 water level would have stood in tightly cased well. 

 Hachures indicate depression of potentiometric surface. 

 Dashed line indicates where approximately located.

 Contour interval 100 feet. Vertical datum is NGVD 29

Ground-water level data control point—Number is the 

 altitude of the water level, in feet

Ground-water level data supplemental control point—

 Well open to Springfield Plateau and Ozark Aquifers. 

 Number is the altitude of the measured water level, in feet. 

 Altitude of Ozark Aquifer water level is less than measured 

 value of control point 

EXPLANATION

848

<990

900

39

14

13

13

14

44

44

60

65

65

60

160

1100

1000

1200

1100

900

900

1400

1000

900

1100

800

800

1100

1300

1200

1000

1000

1200

1300

1100

900

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1067

718 1102

729

960

1134

1191

1262

1160

1204 <1131

1044

1111

1003 1282

960

963 966 1273

1240

1211

950

<990

1171 1070

938

968

1273 950

946

1372

954 1331

930

974 1264

1100

970

966

1011

<1015 934 744

1422

832 1407

1022

1037 <1119 918 1307

907

1021 1301 956 998

997 1001 1416

1212

1214 943

<1148 959 <1064

1026 1357

952 <1167 1046

1204 925

1107

1135

1125

940

986

1094 972 <1281 1110 1075

1284 1269 1079 1308 1274

1276 <1112 959

1091

1099

1069

1026

1064 992

958

969

<1382 1025

1120

1279

1281

1083

1074

1058

1062 979 980 1030

1070

1114 899

956

965

1340

GREENE

WEBSTER

CHRISTIAN

DADE POLK

LAWRENCE

STONE

DOUGLAS

BARRY

DALLAS

LACLEDE

Springfield

Nixa

Ozark

Willard

Aurora

Republic

Marshfield

Brookline

Highlandville

Fair

Grove

Seymour

Strafford

Crane

Conway

Battlefield

Sparta

Verona

Marionville

Ash Grove

Billings

Dadeville

Diggins

Rogersville

Clever

Fordland

Spokane

Pleasant

Hope

Hurley

Niangua

Everton

Fremont 

Hills

Walnut Grove

Morrisville

Halltown

BattlefieldSac River

Fault

Graydon Springs

Fault

Chesapeake

Fault

South 

 Sac 

 Creek

River

Stockton

Lake

Fellows

Lake

Lake Springfield

McDaniel

Lake

Pomme de Terre River

Niangua River

James River

Pierson Creek

Creek

Creek

Wilsons

James River

Sac River

Turnback

Creek

Bull Creek

Swan

Finley

Creek

Beaver Creek

James

Little

River

93°30' 93°00'

37°30'

37°00'

0 10 20 MILES

0 10 20 KILOMETERS

Geohydrologic units modified from Missouri Department

of Natural Resources digital data, 2007, 1:500,000

Base from U.S. Geological Survey digital data, 1991, 2006, 1:100,000; 

U.S. Census Bureau digital data, 2000, 1:100,000;

Universal Transverse Mercator projection, North American Datum (NAD) 1983