During 2008-10, the U.S. Geological Survey, in coop-eration with the City of Austin, the City of Dripping Springs, the Barton Springs/Edwards Aquifer Conservation District, the Lower Colorado River Authority, Hays County, and Travis County, collected and analyzed water samples from five streams (Barton, Williamson, Slaughter, Bear, and Onion Creeks), two groundwater wells (Marbridge well YD-58-50-704] and Buda well LR-58-58-403]), and the main orifice of Barton Springs in Austin, Texas, with the objective of char-acterizing concentrations and isotopic compositions of nitrate and concentrations of wastewater compounds in the Barton Springs zone.