Dye Tracing to Delineate Drainage Basins and Determine Groundwater Sensitivity, Mammoth Cave, Kentucky; with Special Reference to Potential Groundwater Contamination from Spills Along Interstate I-65

摘要

The Mammoth Cave System of south central Kentucky encompasses more than 560 km of surveyed cave passages. The largest groundwater basin (244 km2) found within this cave system emerges from the Turnhole Bend Spring on the Green River. During high flow conditions, water from this groundwater basin will spill over into the Echo River section of the cave. Previous research, including cave mapping and dye tracing (Quinlan and Ray, 1989; Currens and Ray, 1998; Coons, 1994), has delineated the boundaries of spring groundwater basins for numerous springs along the Green and Barren Rivers. These data showed that 60% of the water that flows through the Turnhole Bend Aquifer comes from beyond the boundaries and protection of Mammoth Cave National Park. This area outside the park is crossed by several major transportation routes, including Interstate 1-65, U.S. Highway 31 -W, and CSX Railroad. Because the Turnhole Bend Aquifer is crossed by these major transportation routes, the aquifer is vulnerable to contamination from accidental spills of hazardous materials. Dye tracing methods were utilized to better delineate the boundaries and sub-basins of the Turnhole Bend Groundwater Basin along Interstate Highway 1-65. The approximate boundaries developed by previous research by others were first used to located areas that had not been previously dye traced. Fluorescent dyes were used as tracers and were detected by both qualitative (yes/no) methods and by quantitative (discrete water sampling) methods. Data from quantitative dye traces performed during this research provided additional information on the behavior of water flow into and through the maturely karstified limestones found in the south central Kentucky karst. Dye traces performed during the wet season, late winter and spring, have shown that average flood pulse groundwater flow velocities often exceed 1 km/hr. These high flow rates are contrasted by flow rates in the order of 0.5 km/day during the summer when evapotranspiration is high and rainfall is less frequent. Data from the quantitative dye traces also indicate a significant difference in the residence times of the dye between the wet and dry seasons. Dye that was injected during the wet season had a relatively short residence time in the cave streams of approximately 2 to 3 days. Dry season quantitative dye traces are very different with residence times of over 12 days being recorded. This information is vital in determining the consequences of a sudden release of hazardous materials within the drainage basin of Mammoth Cave and demonstrates that emergency planning is crucial.