Recharge processes within the Cacapon Mountain Aquifer, Ridge and Valley Province, West Virginia

During the 2006-2007 water year, apparent recharge rates for three streams draining the Cacapon Mountain Aquifer, in the Valley and Ridge Province of northern West Virginia, were estimated using hydrograph separation techniques. The techniques use stream baseflow, dominated by groundwater discharge, as a surrogate for groundwater recharge. Two of the streams draining the aquifer were strike-normal (Rock Gap Run and Breakneck Run) and one was strike-parallel (Sir Johns Run). The strike-normal streams had significantly lower apparent recharge rates (Rock Gap Run: 2.52 in/yr; Breakneck Run: 6.57 in/yr) than the strike-parallel stream (Sir Johns Run: 13.31 in/yr). The large variations in recharge rate are interpreted to be due to water lost to the Helderberg Limestone, a local conduit-forming unit, in the two former drainages. In this particular geologic setting, apparent recharge rates of strike-parallel and strike-normal streams draining the same aquifer may differ substantially. Estimating recharge rates from stream flow data may give inaccurate numbers if the stream flows over highly transmissive conduit forming limestone or extensive fractures.