Ontario
Ontario, CA water profile — supply sources, drought status, wastewater reuse, and the key water issues facing the city.
ontario municipal utilities company
surface water (rivers/reservoirs) · local government · PWSID CA3610034
Below EPA's 15 ppb lead action level at last testing.
Source: EPA Safe Drinking Water Information System (SDWIS) · 2026 Q1
With about 171,214 residents, Ontario ranks as the 29th-largest city in California and a mid-sized city. Water in Ontario is sourced chiefly from Sierra snowpack, Colorado River, State Water Project, and groundwater, the backbone of California's supply.
The defining water pressure here mirrors the state's: drought. Orange County runs the world's largest groundwater replenishment system, and the state adopted direct potable reuse rules in 2023 — but the Central Valley's groundwater overdraft remains severe.
Statewide, California recycles about 23% of its wastewater with established reuse programs. Locally, Ontario faces abnormally dry to moderate drought conditions.
The California state profile covers the regional supply outlook; the issues below detail what's driving Ontario's water future.
San Bernardino County water quality
Source: EPA SDWIS · 2026 Q1
At a glance
- Population ~171,214 (29th-largest in California)
- Primary sources: Sierra snowpack, Colorado River, State Water Project, and groundwater
- Drought: abnormally dry to moderate conditions
- State reuse rate: ~23% of wastewater
Statewide drought history
% of California in severe+ drought (Moderate (D1) now).
Source: U.S. Drought Monitor
Common questions
Is tap water safe in Ontario?
Ontario's largest water system, ONTARIO MUNICIPAL UTILITIES COMPANY, serves about 185,010 people. EPA records show 0 health-based violation(s) since 2016 and a most-recent 90th-percentile lead level of 0.6 ppb (EPA action level is 15 ppb). Always check your own provider's annual Consumer Confidence Report.
Where does Ontario get its water?
ONTARIO MUNICIPAL UTILITIES COMPANY draws primarily from surface water (rivers/reservoirs), part of California's supply from Sierra snowpack, Colorado River, State Water Project.
Related water issues
Drought
Much of the American West is in a multi-decade dry period that researchers describe as the most severe in over a millennium, reshaping how communities plan for water.
ExploreColorado River
The river that supplies 40 million people has lost roughly a fifth of its flow since 2000, forcing a renegotiation of how seven states share the water.
ExploreGroundwater Depletion
Aquifers from the Central Valley to the Ogallala are being pumped faster than they recharge, causing land subsidence and threatening long-term supply.
ExplorePotable Reuse
Advanced purification turns treated wastewater into water that meets or exceeds drinking-water standards — increasingly essential in water-stressed regions.
Explore