Pima County, Arizona: drinking water report. Pima County – Tucson and surrounding communities – serves about 1.05 million residents in the Sonoran Desert.
Pima County – Tucson and surrounding communities – serves about 1.05 million residents in the Sonoran Desert. Tucson Water draws from the Central Arizona Project canal (Colorado River water), local groundwater, and reclaimed water. The city transitioned from near-total groundwater dependence to a CAP-blended supply in the early 2000s, a shift that initially caused widespread customer complaints about taste and pipe corrosion due to the dramatically different water chemistry.
Tucson's transition to CAP water was rocky, but the current blended supply has stabilized. The Tucson Water system now recharges CAP water into the aquifer through spreading basins, allowing natural filtration before pumping it back to the surface – a process called aquifer storage and recovery (ASR). This approach provides additional treatment beyond conventional plant processes.
UCMR5 data shows PFAS detections in some Pima County water systems. Davis-Monthan Air Force Base, an active installation in Tucson, is a documented PFAS source. According to the Arizona Department of Environmental Quality, monitoring wells near the base have shown PFAS concentrations above state screening levels. The Department of Defense is conducting remediation, but cleanup timelines remain uncertain.
Pima County's blended supply means quality varies by well and by season. Areas near Davis-Monthan AFB face the highest documented PFAS risk.
Check your water to see data specific to your area. For PFAS, reverse osmosis or activated carbon are effective household options. Our water filter guide covers which systems work for Tucson's specific water chemistry. Pull your detailed report for trend data, and see our Arizona page for statewide context.
Drinking water is one exposure route. These federal datasets also cover Pima County, AZ.
The EPA places Pima County, AZ 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.
40% of homes in Pima County, AZ were built before 1980, and 5% 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 Pima County, AZ averages 6 µg/m³, within 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