ANALYSIS OF HYDROLOGIC AND GEOCHEMICAL TIME SERIES DATA AT JAMES CAVE, VIRGINIA: IMPLICATIONS FOR EPIKARST INFLUENCE ON RECHARGE IN APPALACHIAN KARST AQUIFERS

The epikarst, which consists of highly weathered rock in the upper vadose zone of exposed epigenic karst systems, is part of the critical zone that controls the hydrologic and geochemical characteristics of recharge to an underlying karst aquifer. For this study, we utilized time series hydrologic and geochemical data collected at James Cave, Virginia, to examine the influence of epikarst on the quantity and quality of recharge in doline dominated karst. Results indicate a strong seasonality of both the hydrology and geochemistry of recharge. These results have implications for management of karst aquifers in temperate doline karst aquifers. First, although recharge generally reaches a maximum in late winter-early spring, the start of the recharge season varied over the six year monitoring record, with some years starting as early as December and other years starting as late as March. Second, the seasonally variable residence time for water in the epikarst influences rock-water interaction, and hence, the geochemical characteristics of recharge. Overall, these results point to the complex influence of epikarst on karst recharge, which necessitates collection of long-term and high-resolution datasets.