KWRRI Research Reports


The hydrogeology of about 12% of the 5600 km2 Inner Bluegrass Karst Region of central Kentucky was investigated by water tracing and other techniques. Using fluorescent dyes adsorbed on fabric and charcoal detectors, 96 traces (average length 2.7 km, maximum length 15 km) resulted in the identification of 38 groundwater basins (with areas up to 15 km2). Within the basins, subsurface flow is in a dendritic conduit system at depths up to 30 m below the surface, while in the interbasin areas which separate them flow is generally less than 5 m deep. Each groundwater basin discharges at a spring whose median discharge is approximately 20 l/s·km2 of basin area. The largest spring (Royal Spring) in the study area has a median discharge greater than 300 l/s (Meinzer second magnitude).

The Ordovician Lexington Limestone which underlies the region is thin bedded with shale partings and argillaceous units. Within groundwater basins, sinkhole drains and other conduits have breached the interbedded shales and descend nearly vertically to a level determined by equilibrium flow in the larger conduits. The general location and flow directions in groundwater basins is probably determined by a potentiometric gradient prior to conduit development, and some basins are localized by a favorably oriented regional joint set or other structural element. Otherwise, lithologic and structural factors have little influence in the occurrence and flow of subsurface water in the region.

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Funding Information

The work upon which this report is based was supported in part by funds provided by the Office of Water Research and Technology, United States Department of the Interior, Washington, D.C., as authorized by the Water Research and Development Act of 1978. Public Law 95-467.

Although major funding was provided by the Office of Water Research and Technology, additional support for the work described in this report was furnished by the McFarlan Fund of the Department of Geology, University of Kentucky, Dames and Moore, the Georgetown Municipal Water and Sewer Service, the Research Committee of the University of Kentucky, the Institute for Mining and Minerals Research of the University of Kentucky, and the National Speleological Society.