Corona Water Hardness & Quality Report (2026)

The City of Corona Utilities Department operates a mixed water supply system serving Riverside County, California. The utility draws 42.3% from local groundwater wells, 55.8% from Lake Mathews (Colorado River source via the Metropolitan Water District of Southern California), and 1.9% from the State Water Project's California Aqueduct. Water is treated at two surface water treatment facilities — Sierra Del Oro and Lester — and at the Temescal Desalter, a reverse osmosis facility dedicated to groundwater treatment.

Corona's water supply reflects the Santa Ana River watershed geology, which flows through mineral-rich sedimentary layers containing limestone, dolomite, and gypsum. Deeper municipal aquifer wells (400+ feet) have contacted Cretaceous and Tertiary sedimentary formations for decades, concentrating dissolved minerals and producing a hard water supply. The Colorado River source adds further dissolved minerals through the treatment process at Lake Mathews.

At 171 ppm (10 grains per gallon), Corona's water is classified as hard and causes noticeable scale buildup on fixtures, reducing appliance lifespan and increasing energy costs. Water heaters, dishwashers, and washing machines are particularly affected; soap lathering is reduced and skin may feel dry. A water softener is recommended, especially for high-usage households or those with sensitive appliances. The Temescal Desalter removes nitrates, per-fluorinated compounds, 1,2,3-Trichloropropane (TCP), and perchlorates via reverse osmosis; surface water undergoes coagulation, multimedia filtration, and disinfection with sodium hypochlorite. The official Consumer Confidence Report indicates no health violations despite detection of contaminants including chromium-6, arsenic, and trihalomethanes.