KARST CARBONATE WATERSHED DELINEATION OF BOBCAT CAVE: HYDROLOGIC, GEOCHEMICAL, AND GEOPHYSICAL METHODS FOR DETERMINING GROUNDWATER FLOW PATHS

The Bobcat Cave watershed is part of a large Mississippian-limestone aquifer system that serves as a vital water supply in northern Alabama. The cave is also home to the endangered Alabama Cave Shrimp (Palaemonias alabamae). The watershed is situated in the “Industrial Zone” of Redstone Arsenal, a military installation adjacent to Huntsville in Madison County, Alabama, causing concern for potential groundwater contamination. Watershed delineation is crucial for the development of a scientifically defensible water resource research and management plan and protection of the P. alabamae.

This research incorporates an assessment of various parameters including: 1) water level and water quality (temperature, pH, oxidation reduction potential, conductivity, dissolved oxygen, 2) field dye tracer tests, and 3) geochemical (major ions and trace elements) and stable isotope data of water samples (¹⁸O/¹⁶O, ²H/¹H, ¹³C/¹²C) to investigate the hydrologic regime and structure of the karstic Bobcat Cave catchment basin.

Approximately 20 dye traces from multiple studies in and around Bobcat Cave have generated inconclusive results in attempts to determine groundwater flow paths. In order to prevent duplication of previous work, we have selected dye tracer injection points located to the east and north of the Bobcat Cave where no prior study has been conducted. Electrical resistivity surveys were conducted to help identify potential injection points associated with sinkholes. Results of hydrologic and geochemical analysis will be used to interpret water sources, recharge areas, groundwater mixing, and geochemistry of the Bobcat Cave catchment basin.