Geohydrologic Framework, Ground-Water Hydrology
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Geohydrologic Framework, Ground-Water Hydrology, and Water Use in the Gasconade River Basin upstream from Jerome, Missouri, including the Fort Leonard Wood Military Reservation by Douglas N. Mugel and Jeffrey L. Imes Abstract as deep as 300 feet below the land surface beneath upland areas where karst features are prevalent. The Ozark aquifer is the principal source of Although the Jefferson City Dolomite and the ground water in the Gasconade River Basin Roubidoux Formation are the uppermost bedrock upstream from Jerome, Missouri (herein referred formations in the upland areas of the FLWMR, the to as the upper Gasconade River Basin), including water table generally is deep enough to occur in the Fort Leonard Wood Military Reservation the underlying Gasconade Dolomite throughout (FLWMR). The Ozark aquifer is composed of, in most of the FLWMR. Discharge from springs [311 order of increasing age, the Cotter Dolomite, Jef 3 ferson City Dolomite, Roubidoux Formation, Gas ft /s (cubic feet per second)] represented 56 per conade Dolomite, Eminence Dolomite, and Potosi cent of the August 1999 discharge of the Gascon 3 Dolomite. Sedimentary strata are nearly horizon ade River at Jerome, Missouri (552 ft /s). tal, except along folds and collapse zones where From 1993 through 1997, annual pumpage dips can be steep. The basin is cut by numerous from all public water-supply wells in the upper faults, most of which trend generally northwest- Gasconade River Basin ranged from 1,820 Mgal southeast. The Jefferson City Dolomite and the [million gallons; an average daily rate of 4.99 Cotter Dolomite generally yield little water to Mgal/d (million gallons per day)] in 1993 to 2,030 wells. Wells completed in the Roubidoux Forma Mgal (an average daily rate of 5.56 Mgal/d) in tion and Gasconade Dolomite commonly yield 1997. Including an estimated 4 Mgal/d from from several tens to several hundred gallons per domestic wells, the average daily pumping rate for minute of water. The Eminence Dolomite may all wells is estimated to range from 8.99 Mgal/d in form a weak hydrologic barrier to vertical ground 1993 to 9.56 Mgal/d in 1997. During the same water flow between the overlying Gasconade Dolomite and the underlying Potosi Dolomite. The period, annual pumpage from the Big Piney River, Potosi Dolomite is the most permeable formation which supplies most of the water used at the in the Ozark aquifer. Wells completed in the Potosi FLWMR, ranged from 1,136 Mgal (an average of Dolomite may yield from several hundred to 1,000 3.11 Mgal/d) in 1997 to 1,334 Mgal (an average of gallons per minute of water. 3.65 Mgal/d) in 1995, and as a percentage of total Water-table contours indicate several areas water use in the upper Gasconade River Basin, of high permeability karst terrain in the upper Gas ranged from about 24.5 percent in 1997 to about conade River Basin. Ground-water levels may be 28.8 percent in 1993. Abstract 1 INTRODUCTION The FLWMR receives most of its water supply from a surface-water intake in the Big Piney River (fig. The Gasconade River Basin upstream from Jer 2) along the eastern boundary of the military reserva ome, Missouri, is the study area for this report, and tion. A large part of the water in the Big Piney River hereinafter is referred to as the upper Gasconade River comes from springs that discharge into the river. Basin (fig. 1). It encompasses 2,836 mi2 (square miles) Ground-water level data collected during this study can of predominately rural countryside in parts of eight help determine sources of water to the Big Piney River, counties in south-central Missouri. It is drained by the and areas of spring recharge within the Big Piney River Gasconade River and its tributaries, including the Little Basin upstream from the surface-water intake. Piney Creek, Big Piney River, Roubidoux Creek, and Osage Fork (fig. 1). The 64,000-acre Fort Leonard Purpose and Scope Wood Military Reservation (FLWMR) is a large federal facility predominantly in Pulaski County in the north- The purpose of this report is to describe the geo central part of the basin. hydrologic framework, ground-water hydrology, and The FLWMR (fig. 2) has been a major combat- water use in the upper Gasconade River Basin (study troop training area since 1940. The U.S. Army base area; fig. 1). The three major components of this report contains a variety of weapons training facilities, includ reflect the major tasks of the study: (1) to describe and ing small-arms firing ranges, grenade ranges, artillery map the geohydrologic units at the FLWMR and upper ranges, an Air National Guard cannon and strafing Gasconade River Basin, particularly the structure of range, and areas for armored vehicle training. The several geologic formations; (2) to measure and map ground-water levels in the FLWMR and upper Gascon FLWMR presently (2003) is in a period of growth in ade River Basin; and (3) to compile water-use data, par personnel and training facilities. A chemical warfare ticularly pumpage data for public water-supply wells in training school recently was transferred to the the upper Gasconade River Basin. Ground-water levels FLWMR. Construction activities at the FLWMR have measured in spring 1998; stream and spring discharge increased substantially and are expected to continue. measurements made in September 1995, September Past, present, and future operations at the FLWMR 1998, and August 1999; and water-use data compiled involve the use, storage, and disposal of chemicals and for 1993–98 are presented in this report. petroleum products. These chemicals and petroleum The study area is much larger than the FLWMR products are potential ground-water contaminants. area and includes areas south of the FLWMR that There is concern that these potential contami potentially supply water to the FLWMR (fig. 1). Well- nants could migrate into the FLWMR public water-sup- log and water-use data were compiled and ground ply wells or domestic and public water-supply wells water levels were measured in the study area and in a 6 located adjacent to and downgradient from the mi (mile) wide band surrounding the study area. Data FLWMR. The U.S. Geological Survey (USGS), in were collected in the surrounding area to provide addi cooperation with the Directorate of Public Works, tional control to geologic and hydrologic contours near Environmental Division (DPW-ED), FLWMR, began a the study boundary and to define regional hydrologic study in 1998 of the geohydrologic framework, boundaries. ground-water hydrology, and water use in the upper Gasconade River Basin. The results of this study will Description of Study Area improve the understanding of the contributing areas of recharge to water-supply wells at and in the vicinity of Most of the study area (fig. 1) is located within the FLWMR, and thereby help protect the quality of the Salem Plateau of the Ozarks Plateaus physio water supplied by the water-supply wells. Data pre graphic province (Fenneman, 1938). The Salem Pla sented in this report can be used in future studies of teau is a large area of uplifted Cambrian- and contributing areas of recharge to wells and in other Ordovician-age sedimentary strata in southern Mis ground-water assessments of the upper Gasconade souri and northern Arkansas. It consists of an upland River Basin. Contributing areas of recharge refers to plain along a major southwesterly trending topographic the source area (recharge area) of ground water divide, and more rugged topography north and south of pumped from wells. the divide where stream erosion has been more exten- 2 Geohydrologic Framework, Ground-Water Hydrology, and Water Use in the Gasconade River Basin Introduction 3 4 Geohydrologic Framework, Ground-Water Hydrology, and Water Use in the Gasconade River Basin sive. The extreme southwestern part of the study area is ered with oak and hickory trees. Private land primarily in the Springfield Plateau of the Ozark Plateaus physi is in fescue pasture to support livestock grazing. The ographic province (Fenneman, 1938), which is under towns of Waynesville and St. Robert and the areas lain by uplifted Mississippian-age sedimentary strata. around them are the most populated areas near the The southern part of the study area is characterized by FLWMR. gently rolling upland hills covered with forest and pas ture. The northern and central parts of the study area are heavily forested areas where stream incision by the Previous Investigations northerly to northeasterly flowing Gasconade River The USGS developed a regional ground-water and its tributaries (fig. 1) has resulted in narrow, steep- flow model for the Ozark Plateaus Aquifer System walled stream valleys separating erosional remnants of (Imes and Emmett, 1994) that covered parts of Mis the upland plain. Most of the FLWMR is located on a souri, Arkansas, Oklahoma, and Kansas, and included broad upland ridge between the northerly flowing Big the study area. Regional structure-contour, isopach, Piney River to the east and the northerly flowing Rou potentiometric, and water-quality maps of geohydro bidoux Creek to the west (fig. 2). The upland ridge is logic units were prepared in support of the model. The further dissected by tributaries to these streams. three-dimensional finite difference model was used to The study area has a humid, temperate climate simulate pre-development regional ground-water flow. with warm, humid summers and cool, wet winters. The Because of the large size of the model area and com long-term monthly average temperature from a weather puter resource limitations at the time the model was station at the Forney Army Airport at the FLWMR developed (1981 to 1986), model cells were 14 miles o ranges from 31.8 F (degrees Fahrenheit) in January to square; therefore, the model grid is too coarse to be a o 76.8 F in July (National Oceanic and Atmospheric useful tool to assess the ground-water flow at the Administration, 2000).