Abstract 

Regional ground-water flow at the 

Fort Leonard Wood Military Reservation 

(FLWMR) generally is east and west 

away from a regional ground-water divide 

towards the Big Piney River and Roubidoux Creek. Ground-water flow in the 

northern FLWMR is strongly affected by 

solution-enlarged fractures and bedding 

planes in the Roubidoux Formation and 

Gasconade Dolomite. Several large 

springs located on the FLWMR (Sandstone Spring) and off the FLWMR 

(Shanghai Spring, Roubidoux Spring, and 

Miller Spring) receive water from precipitation recharge and stream flow loss on 

the FLWMR. 

Introduction 

A basewide regional geologic and 

hydrologic assessment of the FLWMR, 

south-central Missouri, was begun in 

1994 by the U.S. Geological Survey 

(USGS) in cooperation with the FLWMR 

Directorate of Public Works, Environmental Division. The assessment area 

included the 64,000-acre FLWMR and 

surrounding areas bounded to the east by 

the Big Piney River, to the west by Roubidoux Creek, to the north by Interstate 44, 

and to the south by the southern boundary 

of the FLWMR (fig. 1). The purpose of 

the 1-year study was to describe and map 

geologic structures that can affect groundwater flow and to conduct ground-waterlevel measurements in area wells and dyetrace investigations to determine regional 

ground-water flow directions and spring 

recharge areas in and near the FLWMR. 

Geologic Framework 

Three rock formations are exposed 

at the FLWMR. From youngest to oldest, 

these formations are the Jefferson City 

Dolomite, Roubidoux Formation, and 

Gasconade Dolomite. The Jefferson City 

Dolomite is exposed in the southern part 

of the FLWMR along a central upland 

ridge between the Big Piney River and 

Roubidoux Creek. The underlying Roubidoux Formation is exposed in upland 

areas and hillsides on the western, eastern, and northern parts of the FLWMR. 

The lithology of the Roubidoux Formation ranges from a sandstone upper zone 

to a dolostone lower zone. The underlying 

Gasconade Dolomite primarily is exposed 

along the Big Piney River and Roubidoux 

Creek valleys where it forms prominent 

bluffs. Beneath the Gasconade Dolomite 

but not exposed in the study area are the 

Eminence Dolomite, Potosi Dolomite, 

Derby-Doe Run Dolomites, Davis Formation, Bonneterre Formation, Lamotte 

Sandstone, and Precambrian basement 

rocks. 

Ground-Water Movement 

Controlled by Fractures 

and Karst Features 

The geologic mapping also included 

a concentrated effort to identify fractures 

(a break in the bedrock caused by stress 

relief, including cracks, joints, and faults), 

bedding planes (a rock layer surface that 

tends to split, break, or separate from 

overlying or underlying layers), and other 

rock features that can affect ground-water 

flow. Selected physical properties of 

observed fractures and bedding planes 

were described. These properties included 

length, width, and orientation of the rock 

opening, and evidence that fracture or 

bedding-plane openings were being 

reduced (cementation) or enlarged (dissolution) by ground-water flow. 

Limestones and dolostones are carbonate rocks capable of being dissolved 

by ground water, a process called dissolution. Karst is a geologic terrane caused by 

dissolution of carbonate rock. Karst terrane typically is characterized by the presence of sinkholes, caves, streams that lose 
water, and springs. These features are 

common in the central and northeastern 

part of the FLWMR and can greatly 

increase the rate of ground-water flow 

through carbonate rock. No evidence of 

solution activity was observed in areas 

where the Jefferson City Dolomite is 

exposed. Most caves and large springs at 

the FLWMR are contained in the upper 

part of the Gasconade Dolomite. 

Observations of hundreds of fractures in the study area revealed that about 

98 percent of all fractures have openings 

less than 0.5 inch, and less than 10 percent of the fractures extended through the 

entire thickness of the formation 

(through-going) in which they occur. Of 

all observed fractures, only about 4.5 percent in the Jefferson City Dolomite, about 

1.5 percent in the Roubidoux Formation, 

and about 20 percent in the Gasconade 

Dolomite showed evidence of solution 

activity. Bedding planes in the lower carbonate-rich part of the Roubidoux Formation and upper Gasconade Dolomite 

showed evidence of extensive rock dissolution such as solution cavities and bedding-plane controlled caves. These 

bedding-plane features and the lack of 

substantial solution activity in fractures 

indicate that most ground water is transported from recharge areas to large 

springs through solution-enlarged bedding planes rather than through fractures. 

The magnitude of the bedding-plane 

solution activity in the lower Roubidoux 

Formation is apparent from the large 

structural differences between the top of 

the Gasconade Dolomite and the Roubidoux Formation. Bedding planes in the 

upper Gasconade Dolomite are nearly 

horizontal, but bedding planes in the 

sandstone beds of the upper part of the 

overlying Roubidoux Formation consistently show a pattern of narrow steepsided troughs and ridges. This difference 

probably is caused by extensive dissolution of the dolomitic lower part of the 

Roubidoux Formation and subsequent 

collapse of the overlying sandstone-rich 

beds. 

Many of the sinkholes in the northcentral part of the FLWMR are located 

along a 1-mile-wide linear trend oriented 

northeast to southwest (fig. 2). The axis of 

part of the thick Ozark aquifer, are productive water-bearing formations at 

FLWMR. The uppermost Jefferson City 

Dolomite normally is unsaturated; however, locally it can be partly saturated. 

Wells completed in the Roubidoux Formation-Gasconade Dolomite rock 

sequence commonly yield several tens to 

several hundreds of gallons of water per 

minute. Wells completed in the Potosi 

Dolomite can yield from several hundreds 

to as much as 1,000 gallons per minute. 

Recharge to the Ozark aquifer primarily is by percolation of precipitation 

through overburden and bedrock. 

Ground-water flow in non-karst areas is 

controlled by regional topography. General ground-water-flow directions were 

determined by mapping and contouring 

water-level altitude measurements made 

in domestic, public-supply, and monitoring wells. Ground-water flow directions 

typically are perpendicular and downgradient to the contours. However, a complex 

combination of flow through solutionenlarged bedding planes causes local 

this band of sinkholes is parallel to a 1.5-

mile-long near linear reach of Roubidoux 

Creek. This reach of the creek is within a 

longer reach of Roubidoux Creek that is 

characterized by a sequence of near rightangle shifts in the stream channel and 

complete flow loss. The axis intersects 

Hurd Hollow Stream at the point of flow 

loss in that creek. The occurrence of 

abrupt changes in stream channel directions, linear stream segments, flow loss in 

two streams, and a linear band of sinkholes oriented along a common axis 

strongly indicates an area of substantial 

hydrologic control by fractures. Two narrower bands of sinkholes are oriented 

northwest to southeast. The axes of these 

bands coincide with near linear reaches of 

Roubidoux Creek in an area characterized 

by abrupt stream-channel changes. 

Ground-Water Yield to Wells 

and Flow Patterns 

The rock sequence from the Roubidoux Formation to the Potosi Dolomite, 
anomalies in flow directions at the 

FLWMR. Water-level measurements were 

made twice during the study, once during 

seasonal high-base flow and once during 

seasonal low-base flow conditions. 

Ground-Water Levels—High-Base 

Flow 

Sixty high-base flow water levels 

were measured from November 2 to 

December 2, 1994. Ground-water levels 

in the southern one-half of the mapped 

area were higher along the major ridges 

and lower in the major river valleys (fig. 

3). Ground water flows from the higher 

altitudes of the upland ridges (recharge 

areas) downgradient to the lower altitude 

regional streams (discharge areas). 

Regional ground-water levels generally 

are 100 to 200 feet beneath the smaller 

upland streams. The regional groundwater divide between the Big Piney River 

and Roubidoux Creek is offset slightly to 

the west of the regional topographic 

divide, indicating that bedrock is more 

permeable east of the topographic divide. 

In the central part of FLWMR, the 

regional ground-water divide between the 

Big Piney River and Roubidoux Creek is 

as much as 2 miles west of the regional 

topographic divide (fig. 3). This large lateral separation between the ground-water 

and topographic divides indicates a much 

larger bedrock permeability east of the 

topographic divide. Much of the groundwater flow east of the ground-water 

divide is northward toward Shanghai 

Spring rather than directly eastward to 

Big Piney River. This northward redirection of ground-water flow is caused by the 

well-developed karst terrane as evidenced by the large concentration of sinkholes in the central and northeastern parts 

of the FLWMR. 

Ground-Water Levels—Low-Base 

Flow 

Low-base flow water-level measurements were made from August 28 to 

August 31, 1995, in the same general set 

of wells as the high-base flow measurements. Low-base flow ground-water levels were similar to the high-base flow 

measurements with the notable difference that low-base flow water levels were 

about 35 feet lower within and near the 

northern part of the FLWMR and about 

10 feet lower in the Roubidoux Creek valley. 

Vertical Ground-Water Flow 

Based on water-level measurements 

made in three well pairs located on the 

FLWMR, vertical hydraulic gradients 

generally are thought to be small (probably less than about 10 feet per 100 foot 

decline in altitude) and downward from 

the Gasconade Dolomite to the Potosi 

Dolomite. Where rock dissolution is substantial in the Roubidoux Formation and 

Gasconade Dolomite, water is rapidly 

transported through conduits to discharge 

points (springs) several hundred feet 

lower than the upland recharge area. Vertical hydraulic gradients may be upward 

from the Potosi Dolomite in these areas 

because hydraulic heads in the Roubidoux 

Formation and Gasconade Dolomite are 

substantially lowered by rapid ground92°07'30" 92° water transport to discharge points. 

Roubidoux

Creek

Big

Piney

River

Gasconade

River

Roubidoux

Spring

Shanghai

Spring

Sandstone

Spring

Falling

SpringCreasy

Spring

Bartlett

Mill

Spring

Smith

Branch

Hurd

Hollow Stream

Dry

Creek

Miller

Spring

92°15'

1100

1100

1000

900

800

750

EXPLANATION

RECHARGE AREAS OF

MAJOR SPRINGS Dye-Trace Investigations of Fracture FORT LEONARD WOOD

MILITARY and Conduit Flow RESERVATION

BOUNDARY

750 WATER-LEVEL CONTOUR- Dye-tracing techniques were used at Shows altitude of water

table. Contour interval the FLWMR to supplement water-level is variable. Datum is

sea level measurements and provide evidence of 

hydraulic connections between ground- STREAM-Shaded reach 37° water recharge areas, such as sinkholes 45'

37°

37'

30"

is dry except during flood stage

GROUND-WATER DIVIDE

TOPOGRAPHIC DIVIDE

MEASURED GROUNDWATER LEVEL

and losing streams, and ground-water discharge areas, such as springs, seeps, and 

perennial streams. Dye-tracing investigations are a valuable method for determining ground-water flow rates and 

directions in complex karst terrane and 

for defining spring recharge areas. 

Ten dye-trace tests with successful 

recovery of dye were conducted by the 

USGS at the FLWMR during the study. 

Several historical dye-trace tests also have 

been conducted at the FLWMR. Dye 

injection locations were dictated by the 

availability of large openings through the 

overburden to the water table. These 

include openings in the bottom of sinkholes, stream reaches where substantial 

0 2.5 5 MILES

0 2.5 5 KILOMETERS

Figure3. Altitude of shallow ground-water levels in and near the Fort Leonard Wood

Military Reservation during high-base flow conditions (November 2-December 2, 1994). flow is lost to the subsurface over a short 
distance, and an abandoned monitoring 

well. 

The dye-tracing procedure included 

placing a fluorescent dye (fluorescein, 

Rhodamine WT, or eosine) in the injection opening and, when necessary and 

practical, injecting several hundreds of 

gallons of water into the injection opening 

to flush the dye into the subsurface. Activated charcoal packets were placed in 

water at potential recovery sites to adsorb 

dissolved dye. Adsorbed dye was 

removed from the charcoal by soaking the 

packets in a chemical solution. The solution was then analyzed by a scanning 

spectrofluorophotometer for the presence 

of dye. 

Spring Recharge Areas 

The probable recharge areas of four 

springs on and near the FLWMR were 

determined using dye-trace data and 

ground-water-level measurements (figs. 3, 

4). The combined recharge areas of Falling, Creasy, and Bartlett Mill Springs 

northwest of the FLWMR are based on 

dye-tracing investigations conducted by 

the Missouri Department of Natural 

Resources, Division of Geology and Land 

Survey (on file at the office in Rolla, Missouri). Spring recharge area boundaries at 

the FLWMR were estimated using injection points of successful dye-traces, and 

ground-water flow lines and divides 

determined from water-level maps. The 

probable recharge area of Shanghai 

Spring lies west and southwest of the 

spring and encompasses most of the cantonment area of the FLWMR. The western recharge boundary is the regional 

ground-water divide. The probable 

recharge area for Sandstone Spring 

extends west of the spring and shares 

common boundaries with the recharge 

areas of Shanghai Spring and Miller 

Spring. The probable recharge area of 

Miller Spring extends west of the spring 

to the regional ground-water divide and is 

assumed to share a common boundary 

with Shanghai Spring and Sandstone 

Spring [referred to as the pumping station 

spring in Imes and others (1996)]. No 

recharge area has been defined for Roubidoux Spring. However, dye-trace tests and 

spring discharge measurements show that 

Roubidoux Spring receives surface runoff from upstream of injection points 

shown in figure 4 on Roubidoux Creek 

and Hurd Hollow Stream. Discharge measurements at Roubidoux Spring indicate 

that about one-third of the spring flow 

cannot be attributed to surface water lost 

from Roubidoux Creek. 

—Michael J. Kleeschulte and 

Jeffrey L. Imes 

References 

Imes, J.L., Schumacher, J.G., and Kleeschulte, M.J., 1996, Geohydrologic 

and water-quality assessment of the 

Fort Leonard Wood Military Reservation, Missouri, 1994–95: U.S. 

Geological Survey Water-Resources 

Investigations Report 

96–4270, 134 p. 

Harrison, R.W., Orndorff, R.C., and 

Weems, Robert, 1996, Geology of 

the Fort Leonard Wood Military 

Reservation and adjacent areas of 

south-eastern Missouri, with contributions on Quaternary terraces by 

Paul E. Albertson, Dennis Meinert, 

and Grant Butler: U.S. Geological 

Survey Open-File Report 96–60, 

225 p., 10 pl. 

For More Information 

For more information, please contact: 

District Chief 

U.S. Geological Survey


1400 Independence Road


Mail Stop 100


Rolla, Missouri 65401


(573) 308-3664


Additional information on other U.S. 

Geological Survey programs in Missouri 

can be obtained by accessing the Home 

Page at “http://wwwdmorll.er.usgs.gov” 

on the World Wide Web. 

May 1997 Fact Sheet FS–101–97