COMPARING HYDROGEOLOGIC IMPACTS FROM URBAN AND AGRICULTURAL LAND USE PRACTICES AT KARST SPRINGS, CUMBERLAND VALLEY, PENNSYLVANIA

Groundwater quality, geochemistry, capture area size and storm response were related to urban and agricultural land cover types at five karst springs in the Cumberland Valley of south-central Pennsylvania. Based on 1 year of monthly samples, mean nitrate for springs located in agricultural watersheds was 4 mg/L greater than springs located in more urbanized watersheds and mean chloride at the urban springs was 51 mg/L greater than the agricultural springs. Positive correlations between percent agricultural land cover and mean nitrate and percent urban land cover and chloride were identified. Storm response in spring water conductivity was rapid (hour-scale) at the two urban springs, but significant storm responses were not observed at the agricultural springs. Comparison of storm response between the urban springs indicated that more urban land cover does not necessarily equate to faster storm response. Mean saturation index of calcite was oversaturated (0.23) for the agricultural springs, undersaturated (-0.17) for the urban springs, and strongly related to capture area size and thus land cover type. The correlations between the anthropogenic ions and land cover type provided a nonpoint source of these ions. An increase in chloride after a period of snowmelt further implies that urban springs can be prone to seasonal contaminant fluxes that are event driven and controlled by the urban landscape. Capture area size, storm response and geochemistry indicated that the urban springs had shallower and shorter flow paths compared to the agricultural springs. Results of this study highlight the diversity in impacts related to land cover at the selected karst springs and indicates that impacts include both water quantity and water quality degradation in karst systems.