QUANTIFYING SHALLOW GROUNDWATER RECHARGE FROM EPHEMERAL RIDGETOP WETLANDS, DANIEL BOONE NATIONAL FOREST, KENTUCKY

Ephemeral wetlands on Appalachian ridgetops in the Daniel Boone National Forest, Kentucky are hydrologically connected to shallow groundwater. These ephemeral wetlands collect rainwater and provide focused groundwater recharge. The quantity of water provided by this groundwater surface water interaction may provide ecosystem support to vegetation during drought and recharge springs found near the base of ridges. It was the objective of this research to quantify the volumes of water exchanged between wetland and groundwater in five ridge top wetlands (3 natural and 2 constructed). Digital elevation models (DEM) of the wetlands were created from interpolated point cloud data which was gathered in the field by means of optical transit and accurate GPS. These data were used to calculate a depth-area relationship for the open water portion of each wetland basin in order to determine infiltration area. Depth-area relationships were coupled with water level and hydraulic conductivity measurements in order to calculate discharge via Darcy’s Law. Results show that groundwater recharge occurs both annually and seasonally. Seasonal rates of groundwater recharge during storms may be the same order of magnitude as annual rates, though the seasonal groundwater is consumed by evapotranspiration at a much higher rate. Constructed wetlands had small amounts of groundwater recharge due to low hydraulic conductivity. Further, it was discovered that wetland area and watershed slope controlled the rate at which the groundwater was recharged. The largest wetland had smallest slope but greatest area, while the smaller wetlands had greater slope and higher gradient, but smaller area.