Vulnerability of Karst Aquifers to Agricultural Contaminants: A Case Study in the Pennyroyal Plateau of Kentucky.

Karst landscapes are common in many agricultural regions in the US. Well-developed karst landscapes are characterized by shallow soils, sinkholes, sinking streams, underground conduits, and springs. In these landscapes surface runoff is minimal and most recharge enters the subsurface relatively quickly and without significant filtering of the water. Once in the subsurface, recharge water can enter large conduits where it can travel quickly over great distances with minimal filtering prior to reaching surface waters or becoming part of the aquifer system. In this way, these landscapes have similarities to tile-drained fields in that water moves through the soil quickly and is directed to surface or groundwaters with minimal filtering potential and reaction time in soils. As a result, these landscapes are susceptible to contamination from agrochemicals, including P, applied on the surface. Here, we present research conducted at a well-instrumented field site in south-central Kentucky designed to monitor surface-subsurface hydrology to better understand the processes controlling flow in karst landscapes. Specifically, our focus is on the role of the epikarst – the soil-rock interface that provides a storage component – on the flow of water and movement of agrochemicals. We also present results from tracer injections into a sinking stream to evaluate the potential of attenuation of P in underground karst streams.