This data set provides information for evaluation of streamflow loss as mechanism of transport of potential contaminants when assessing sensitivity of ground-water to contamination in Lawrence County, SD. This data set is a result of a larger work (WRIR 00-4103 cited above), which includes a paper plate titled: "Map showing drainage areas upstream from potential streamflow-loss zones and locations of selected streamflow-gaging stations in Lawrence County, SD." Streamflow loss is an important source of recharge to the Minnekahta, Minnelusa, and Madison aquifers. Water recharged from streamflow loss compared to direct infiltration of precipitation is more likely to enter rapid flowpaths through the unsaturated zone and aquifer media because of solution openings. This data set includes arcs that represent the stream reaches that cross the outcrops of the Minnekahta Limestone, Minnelusa Formation, and Madison Limestone that have potential to recharge the aquifers from streamflow loss. The source data includes digital data that characterizes the geology of the Black Hills area, which has been compiled at 1:100,000 scale and published in 1999 as part of the Black Hills Hydrology Study. USGS digital line graphs were used to describe the hydrography. The loss-zone data set has been archived at the USGS Water Resources National Spatial Data Information Node.