POTENTIOMETRIC SURFACE AND WATER QUALITY IN THE PRINCIPAL AQUIFER, MISSISSIPPIAN PLATEAUS REGION, KENTUCKY By P.O. Plebuch and Robert J. Faust, U.S. Geological Survey Margaret A. Townsend, Kentucky Geological Survey U.S. Geological Survey Water-Resources Investigations Report 84-4102 Prepared in cooperation with the KENTUCKY GEOLOGICAL SURVEY UNIVERSITY OF KENTUCKY Donald C. Haney, Director and State Geologist Louisville, Kentucky 1985 UNITED STATES DEPARTNENT OF THE INTERIOR WILLIAM P. CLARK, Secretary GEOLOGICAL SURVEY Dallas L. Peck, Director For additional information Copies of this report write to: can be purchased from: District Chief Open-File Services Section U.S. Geological Survey Western Distribution Branch Water Resources Division U.S. Geological Survey Room 572 Federal Building Box 25425 Federal Center 600 Federal Place Lakewood, CO 80225 Louisville, KY 40202 Telephone: (303) 234-5888 CONTENTS Page Abstract............................................................... 1 Introduction........................................................... 2 Purpose and scope.................................................. 2 Location and description of area................................... 3 General geologic framework of the principal aquifer.................... 3 Water in the principal aquifer......................................... 6 Occurrence......................................................... 6 Hydrogeology....................................................... 9 Residual mantle or residuum.................................... 9 Lower Chesterian Limestones.................................... 9 Ste. Genevieve Limestone....................................... 10 St. Louis Limestone............................................ 10 Salem Limestone................................................ 11 Warsaw (Harrodsburg) Limestone................................. 11 Fort Payne Formation........................................... 12 Recharge........................................................... 12 Potentiometrie surface, movement, and depth to water............... 14 Discharge.......................................................... 15 Water quality...................................................... 16 Methods........................................................ 16 Water chemistry in the principal aquifer....................... 18 Trace elements............................................. 26 Statistical analysis of data................................... 26 Contamination.................................................. 32 Vulnerability.............................................. 32 Sources.................................................... 32 Biological................................................. 33 Summary................................................................ 34 Selected References.................................................... 35 III ILLUSTRATIONS (Plate in pocket at back of report) Plate 1. Generalized geology and configuration of the potentiometric surface in the principal aquifer, Mississippian Plateaus region, Kentucky Page Figure 1. Maps showing generalized geology, physiographic regions, and counties in Kentucky................................. 4 2. Chart showing stratigraphic column and formations of the principal aquifer in the Mississippian Plateaus region.................................................. 3 3. Index map showing geologic quadrangles in the Mississippian Plateaus region............................ 7 4. Generalized geologic sections in the Mississippian Plateaus region.......................................... & 5. Map showing mean-annual precipitation of Kentucky for the period 1948-77................................... 13 6. Hydrograph of Western State Hospital well near Hopkinsville, Christian County........................... 17 7-10. Trilinear diagram for: 7. Water from the Ste. Genevieve Limestone.............. 21 8. Water from the St. Louis Limestone................... 22 9. Water from the Salem and Warsaw Limestones........... 23 10. Water from the Fort Payne Formation.................. 24 11. Chart showing frequency analysis of specific conductivity values...................................... 27 12. Chart showing frequency analysis of sulfate values......... 28 TABLES Table 1. Statistical data for selected constituents in water from wells and springs.......................................... 19 2. Water-quality standards for selected properties of water and inorganic constituents dissolved in water.............. 25 3. Concentrations of trace elements in water from wells and springs................................................... 38 4. Summary of results for analysis of variance.................. 30 5. Summary of results of Student f s t-test analysis.............. 31 IV CONVERSION FACTORS For use of readers who prefer to use metric units, conversion factors for terms used in this report are listed below: Multip_ly_ By_ To jDbtain foot (ft) 0.3048 meter (m) gallon per minute (gal/min) 0.0630 liter per second (L/s) inch (in.) 25.40 millimeter (mm) inch per year (in/yr) 25.40 millimeter per year (mm/yr) mile (mi) 1.609 kilometer (km) micromho per centimeter at 1.000 microsiemens per centimeter 25° Celsius (umho/cm at 25°C) at 25° Celsius (uS/cm at 25°C) Temperature in degrees Fahrenheit (°F) can be converted to degrees Celsius (°C) as follows: °C = (°F-32)/1.8 National Geodetic Vertical Datum of 1929 (NGVD of 1929): A geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called mean sea level, is referred to as sea level in this report. POTENTIOMETRIC SURFACE AND WATER QUALITY IN THE PRINCIPAL AQUIFER, MISSISSIPPIAN PLATEAUS REGION, KENTUCKY by R. 0. Plebuch, Robert J. Faust and Margaret A. Townsend ABSTRACT The Mississippian Plateaus region is the outcrop area of rocks of Mississippian age which extends as a broad arcuate band around the Western Coal Field in west-central Kentucky. Much of the area is characterized by plains of low relief containing numerous sinkholes, subsurface drainage, and a low density of surface streams. The principal aquifer consists of 1,000 to 2,000 feet of limestones extending downward stratigraphically from the base of the Chesterian Series to the black shales at the top of the Devonian rocks. Well yields range from several gallons per minute to as much as 500 gallons per minute in some karst areas where secondary openings are well developed. The potentiometric map indicates that ground-water movement generally conforms to the surface drainage pattern. The actual direction of movement varies from river basin to river basin. Most water from the principal aquifer is a calcium magnesium bicarbonate type and is generally good relative to current drinking water standards. The lower St. Louis Limestone, in places, yields a calcium magnesium sulfate water that is corrosive and has a strong hydrogen sulfide odor. The karst areas of the principal aquifer are vulnerable to contamination because of the well-developed subsurface drainage. Urban areas, industries, and agriculture are sources of contaminants that can be easily flushed into the ground-water system. INTRODUCTION This is the final report in a series done in cooperation with the Kentucky Geological Survey to describe the configuration of the potentio- metric surface and the general ground-water quality in part of the Mississippian Plateaus region of Kentucky. It deals with the principal limestone aquifer for the entire region whereas previous reports dealt only with selected segments of the region. This regional study was initiated in 1975. It includes not only data collected from 1975 to 1982, but also data from earlier studies. Earlier data are considered valid as ground-water levels seem to have remained relatively stable on a regional basis, except for normal seasonal variations, for at least a quarter of a century. Little surface water is available in much of the Plateaus region, except along major streams and from man-made lakes and reservoirs. Except for the larger municipal areas and areas served by water districts, most people depend on ground water as a source of supply. Because pollutants can enter the principal limestone aquifer easily and move rapidly down gradient for long distances, data on the potentiometric surface, the direction of water movement, and basic water quality are essential for the proper utilization and protection of the ground-water system. Purpose and Scope The primary purpose of this report is to provide a potentiometric map of the principal aquifer which represents the level of the static head in the aquifer as defined by the height to which water will rise in tightly cased wells. This map can be used to determine the general direction of ground-water movement, to aid in determining possible paths of pollutant movement, and to help in selecting drilling sites. The altitude of the potentiometric surface also can be used, in conjunction with land-surface altitudes, to determine minimum drilling depths to water. The secondary purpose of the report is to describe the general water quality in the principal aquifer. This information will aid in determining the suitability of the water for various uses and will provide baseline data for monitoring changes in chemical quality that may result from man's activities. Location and Description of Area The Mississippian Plateaus region comprises one of the five physio­ graphic regions of Kentucky (fig. 1). It is the outcrop area