Riverside County, California: drinking water report. Riverside County stretches from the dense suburbs of the Inland Empire to the desert communities of
Riverside County stretches from the dense suburbs of the Inland Empire to the desert communities of the Coachella Valley, covering a population of about 2.5 million across wildly different geographies. Water sources range from local groundwater basins to imported State Water Project and Colorado River supplies. Dozens of water agencies operate independently – Western Municipal Water District, Eastern Municipal Water District, the City of Riverside, and Coachella Valley Water District among the largest – each with distinct source water and treatment approaches.
The Inland Empire has a well-documented history of groundwater contamination. March Air Reserve Base, a former active-duty facility in the Moreno Valley area, is a confirmed source of PFAS contamination from AFFF use. The California State Water Resources Control Board's monitoring data shows PFAS detections across 22 public water systems in Riverside County, with concentrations varying significantly by proximity to the base and other industrial sources.
Perchlorate contamination from historical rocket motor manufacturing also persists in parts of the county. According to the California Department of Toxic Substances Control, several groundwater cleanup sites in Riverside County are still in active remediation decades after the contamination was first identified.
The sheer diversity of water providers in Riverside County means your neighbor's water quality could be entirely different from yours if you are served by different agencies. Desert communities face different challenges – high mineral content and arsenic in some wells – compared to western county suburbs dealing with industrial legacy contamination.
Check your water to see data specific to your provider and ZIP code. For PFAS near March ARB, reverse osmosis is the strongest option. Our water filter guide details which systems are certified for specific contaminants. Pull your detailed report for trends. See our California page for the broader picture.
Drinking water is one exposure route. These federal datasets also cover Riverside County, CA.
The EPA places Riverside County, CA in Zone 2 - a moderate-risk category, with a predicted average indoor radon level between 2 and 4 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
31% of homes in Riverside County, CA were built before 1980, and 4% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Riverside County, CA averages 9.3 µg/m³, above the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide