Landuse and Water Quality at the Abraham Lincoln Birthplace National Historical Site

Groves, Chris; Glennon, Alan; Anthony, Darlene; Shaw, Kathryn

Sinking Spring is a small perennial karst window at the Abraham Lincoln Birthplace National Historical Site near Hodgenville, Kentucky. Water emerges from the base of a small limestone bluff, falls about 2 meters as a waterfall, and disappears back into the subsurface at the base of the falls. This dependable water supply attracted Thomas and Nancy Lincoln to settle here in 1808, where their son Abraham was born the following year. The spring still serves as a key focal point for interpretive activities at the park. Results of a field study into the hydrogeology and landuse in the vicinity of Sinking Spring indicates that the spring has a recharge area of about 0.5 km^2, and that overall, current water quality threats are minimal. Because of the limestone karst hydrology of the area, the extent of the recharge areas does not simply correspond with surface topography. Fluorescent dye tracing and consideration of the area unit baseflow were used to estimate recharge area. A part of the Sinking Spring's recharge area does extend beyond the boundaries of the park, with evidence of impact from agricultural activities. At current levels, these impacts pose little serious threat to water quality at the spring. Study of the artificial, 1920's era drainage system indicates that it does little to significantly ameliorate flooding problems, which occur due to limitations in the rate with which water can drain through Lower Sinking Spring Cave during heavy rains. Potentially hazardous conditions occur with the buildup of carbon dioxide gas within this drainage system. While only two areas were found to contain hazardous CO2 levels during the study, it would be prudent to secure all grates and other entrances to the system. This carbon dioxide gas appears to pose no threat to park visitors in normal visitation areas at this time.