Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Private domestic and small system drinking water wells in the Redding–Red Bluff study unit primarily draw from shallow aquifers which are the target for this assessment.