INFERRING GROUNDWATER FLOW AND RECHARGE FROM STORM RESPONSES IN THE CUMBERLAND PLATEAU SINKHOLE PLAIN OF SOUTHEASTERN KENTUCKY

Epigenic karst aquifers overlain by extensive agriculture and farming are highly vulnerable to surface contaminants from point and non-point sources. Currently, the karstic landscapes of the Southeastern Kentucky platform are impacted by a rapid proliferation of confined animal feeding operations. Recharge mechanisms in this region include direct infiltration through the sinkhole-conduit system and diffuse recharge through soil and epikarst. The analyses of karst aquifer responses to storm events provide qualitative information regarding aquifer recharge flow paths and groundwater residence time, and the knowledge of spatial and temporal variations in recharge and flow is crucial to the understanding of the fate of surface contaminants. Time series correlation analyses on long-term physicochemical data recorded at the outlet of Grayson Gunnar Cave, an epigenic karst system located along the Cumberland escarpment in Southeastern Kentucky, revealed the existence of two separate conduit branches responding a few hours apart from each other. The fastest responding branch accounts for the majority (90%) of the spring discharge. Data highlight the control of climate and groundwater storage saturation in the recharge processes. During the winter, cumulative rainfall, increased soil moisture and conduit saturation, and relatively low evapotranspiration all contribute to the flushing of previously stored groundwater by the incoming storm water. During the summer, the combined effect of low groundwater reserve, low soil moisture, and high evapotranspiration accelerates storm water recharge into the karst aquifer and flow toward the spring.