PRELIMINARY DELINEATION OF THE HYDROLOGY OF THE HORN HOLLOW KARST SYSTEM, CARTER CAVES STATE RESORT PARK, NORTHEASTERN KENTUCKY

The Horn Hollow Karst system (HHK), located in Carter Caves State Resort Park in northeastern Kentucky, is comprised of the surface and subterranean drainage system associated with the Horn Hollow Creek valley which is tributary to Cave Branch, Tygart's River, and ultimately, about 40 km to the north, the Ohio River.

Hydrological studies in June 2005 and 2006 provide a preliminary delination of the approximate extent and general flow pathways within HHK. Hydrologic delineation is based on a combination of tracer studies (fluorescein and bromide) and geochemical analysis. Geochemical sampling was conducted during baseflow and stormflow conditions at between 7 and 20 locations (depending on the specific sampling event) where water sinks or re-emerges throughout the system. The pH and saturation index of waters show a general decreasing trend between the upper reaches of the system and the outlet at H₂O spring. The same trend occurs through individual reaches where water sinks and subsequently re-emerges downstream. Geochemical analyses were performed both in the field using a portable spectrophotometer and subsequently in the lab using ICP and IC to analyze cations and anions. Analyses of the geochemical data of various waters sampled throughout the system indicate three distinct waters within the system: soil, subterranean, and surface waters. As these waters join the system at various points they contribute to the longitudinal evolution of the water throughout HHK.

Based on geochemistry and tracer tests, we have determined that water is gathered into the system at various swallets and pits generally located near the contact of sandstones and shales in the Pennington Formation and underlying Upper Member Limestone unit of the Newman Limestone Formation. Water from various sources in the upper portion of HHK mix in unexplored subterranean pathways between Boundary Cave and Bowel Cave Spring. The ultimate discharge location for water draining through HHK is the spring at the mouth of H₂O Cave just before the confluence with Cave Branch. A nearby spring at Laurel Cave appears to drain soil water that presumably originates very locally. However, Laurel Cave is clearly (based on passage and entrance relationships) the overflow pathway for the H₂O Cave pathway during extremely large, and presumably rare, discharge events.