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Groundwater-quality data in the Coachella Valley Domestic Supply Aquifer Study Unit, 2020: Results from the California GAMA Priority Basin Project

May 16, 2022

The U.S. Geological Survey collected groundwater samples from 38 wells used for domestic and small system drinking water supply in the Coachella Valley of California in 2020. The wells were sampled for the Coachella Valley Basin (CODA) Domestic Aquifer Study Unit of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project’s assessment of the quality of groundwater resources used for domestic and small system drinking water supplies. Coachella Valley is located in the Desert hydrogeologic province (Johnson and Belitz, 2003) and is structurally divided into four subbasins by the San Andreas fault: the Indio subbasin, the Mission Creek subbasin, the Desert Hot Springs subbasin, and the San Gorgonio Pass subbasin (California Department of Water Resources, 2016). These basins have CA basin designations 7-21.01, 7-21.02, 7-21.03, and 7-21.04 respectively. The study area was divided into 30 equal-area grid cells with at least one well sampled in 26 of the 30 cells. The 10 understanding wells were selected to provide more data in areas where wells were more abundant and to provide more water quality data for wells in the State Small Water System program. In three cases, Sampled wells within 1 mile of an unsampled cell were used to represent unsampled grid cells. Groundwater samples from all 38 wells were analyzed for field water-quality parameters and microbial indicators, volatile organic compounds, pesticides and pesticide degradates, major ions and trace elements, chromium (VI), perchlorate, nutrients, carbon-14 in dissolved inorganic carbon, stable isotopic ratios of water, tritium, per- and polyfluoroalkyl substances (PFAS), sulfur hexafluoride, and noble gases. Groundwater levels were measured in 31 of the 38 wells. All results are presented in this data release, except results sulfur hexafluoride and noble gases.