Yolo County, California: drinking water report. Yolo County west of Sacramento has about 221,000 residents, including Davis (home to UC Davis) and Woodland.
Yolo County west of Sacramento has about 221,000 residents, including Davis (home to UC Davis) and Woodland. Water sources include groundwater, Sacramento River diversions, and treated surface water from the Woodland-Davis Clean Water Agency. The county's agricultural economy – tomatoes, rice, almonds, and wine grapes – is among the most diverse in California.
Yolo County completed a major infrastructure shift in 2023 when the Woodland-Davis Clean Water Agency began delivering treated Sacramento River water to both cities, reducing dependence on groundwater that had been contaminated with chromium-6 and other naturally occurring metals. According to the State Water Board's 2024 data, the new surface water supply meets all standards, though groundwater wells still in use in some areas show chromium-6 at levels above the former state notification level.
The former McClellan Air Force Base in neighboring Sacramento County has a PFAS contamination plume that affects the regional groundwater system. A 2024 State Water Board investigation found low-level PFAS in Yolo County monitoring wells near the Sacramento River, likely from upstream military and industrial sources rather than local activity.
Yolo County residents who recently transitioned from groundwater to Sacramento River water may notice taste differences – the surface water has a different mineral profile than the deep wells. Both sources are treated to meet all standards, but the transition is still settling in.
Check your water for current data. For chromium-6 in areas still on groundwater, reverse osmosis is the effective treatment. For the treated surface water supply, a carbon filter addresses taste and disinfection byproducts. Our water filter guide covers both scenarios. Pull your detailed report for your area, and visit our California page for statewide data.