Water-quality data from a study by the U.S. Geological Survey on the Southern Ute Indian Reservation in southwestern Colorado are presented in two tables. The data were collected during 1973-76 from 338 ground-water and surface-water samples. All samples were analyzed for major catons and anions, and selenium and arsenic. Data in the tables are keyed by numbers to maps showing the locations of sampling sites. Many of the samples contained arsenic, chloride, dissolved solids, fluoride, iron, magnesium, manganese, nitrate, nitrite-plus-nitrate as nitrogen, selenium, and sulfate in concentrations exceeding recommended or mandatory standards for drinking water established by the Colorado Department of Health and U.S. Public Health Service. (Woodard-USGS)