This data release documents water-quality data collected from April 2010 through December 2016 by the U.S. Geological Survey in cooperation with the San Antonio Water System from across the San Antonio segment of the Edwards aquifer with particular emphasis on nutrients and pesticides. Additional data regarding inorganic compounds and selected stable isotopes were obtained to provide a geochemical framework for characterizing source inputs and observed chemical changes during periods of hydrologic transition. Water-quality data were collected from surface-water and groundwater sites representing rural and urban land cover types. Data were obtained from unconfined wells in the recharge zone to characterize the rapid changes in water-level altitudes and water quality that occur during groundwater recharge. Water-quality data were also obtained from confined groundwater wells and springs to represent the deeper confined water in the aquifer system.