Quality of groundwater used for domestic supply in the northern San Joaquin Valley, California

First posted July 28, 2021 For additional information, contact: GAMA Project ChiefCalifornia Water Science CenterU.S. Geological Survey6000 J Street, Placer HallSacramento, CA 95819Telephone number: (916) 278-3000GAMA Program Unit ChiefState Resources Control BoardDivision of QualityPO Box 2231, Sacramento, 95812Telephone 341-5855 Groundwater provides more than 40 percent California’s drinking water. To protect this vital resource, the State California created Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin (PBP) a comprehensive assessment State’s groundwater quality increased public access to groundwater-quality information. Private domestic small-system drinking-water wells in Northern San Joaquin Valley (NSJV) were target for assessment. These tend pump water from shallower parts alluvial aquifers compared deeper, long-screened public-supply region.