STATISTICAL ANALYSIS OF GEOCHEMICAL DATA TO CHARACTERIZE THE ROLE OF THE EPIKARST IN CONTROLLING THE QUANTITY AND QUALITY OF RECHARGE TO A TELOGENETIC KARST AQUIFER

Karst aquifers are highly productive groundwater systems but are also vulnerable to contamination. As such, it is imperative to examine how water infiltrates through the epikarst (the uppermost portion of a karst system comprised of topsoil and weathered bedrock) and how contaminants are potentially transported from the surface to the underlying aquifer. This research utilizes principal component analysis (PCA) in conjunction with end member mixing analysis (EMMA) to examine geochemical and hydrologic data from epikarst drips, precipitation, cave stream, and soil water within a telogenetic karst system in the Appalachian Valley and Ridge of southwestern Virginia. Using PCA, chemical signatures of the hydrologic system end waters (dilute precipitation, soil water, and calculated epikarst water) were determined and their partitioning was examined with EMMA and compared with several hydrologically dependent variables including epikarst thickness, drip rate, season, and antecedent conditions. Results from the PCA support previous work concerning the evolution of water, with respect to major ions, through the epikarst—for example, the concentration of strontium and calcium increase along the flow path from precipitation to soil water to epikarst drips to the cave stream. Preliminary results from the EMMA indicate distinct differences in the end member water contributions at different epikarst drip sites. Overall, this study sheds light on a notable spatial and temporal variability with respect to epikarst drip water geochemistry and therefore the influence of the epikarst on recharge quality and quantity in this karst aquifer system.