The U.S. Geological Survey collected groundwater samples from 71 domestic wells and 4 springs in Nevada, Yuba, Sierra, and Placer Counties, California in 2015-2016. The sites were sampled for the Yuba and Bear Watersheds Shallow 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 drinking water supply. Domestic wells commonly are screened at shallower depths than are public-supply wells. The Yuba and Bear Watersheds Shallow Aquifer Study Unit includes the hard rock aquifer systems of the eastern Sierra Nevada in the Upper Yuba and Upper Bear watersheds (HUC8 18020125 and 18020126). The study unit was divided into equal area grid cells and one domestic well was sampled in each cell. Groundwater samples were analyzed for field water-quality parameters, volatile organic compounds, pesticides and pesticide degradates, nutrients, major ions and trace elements, hexavalent chromium, perchlorate, gross alpha and gross beta particle activities, noble gases, tritium, carbon-14 in dissolved inorganic carbon, stable isotopic ratios of water and dissolved nitrate, and microbial indicators.