Oxnard Water Hardness & Quality Report (2026)

Oxnard, California receives its municipal water supply through the City of Oxnard Water Division, sourcing from three primary origins: imported water from the State Water Project (SWP) delivered via the Calleguas Municipal Water District and United Water Conservation District infrastructure; groundwater from the Oxnard Plain Groundwater Basin — the primary alluvial aquifer beneath the Ventura coastal plain; and surface water from Lake Bard, a local storage facility. The mix of imported Sierra Nevada water, local groundwater, and surface storage allows the city to balance supply reliability with quality. Water hardness in Oxnard, Ventura County measures 87 mg/L — classified as moderately soft.

Oxnard's moderate hardness reflects the mixed character of its supply sources. State Water Project imports from the Sacramento Delta are moderately mineralised after blending with Sacramento and San Joaquin River water. The Oxnard Plain Groundwater Basin occupies a coastal alluvial plain underlain by Quaternary marine and fluvial sediments — sand and gravel layers deposited by the Santa Clara River and coastal processes — which contribute moderate dissolved calcium. The relatively young, silica-dominated alluvial matrix limits calcium dissolution compared with limestone-rich inland aquifers, producing a supply in the moderately soft range.

With hardness at 87 mg/L, Oxnard residents experience only modest scale formation. Faucet aerators and showerheads may require descaling every few months to maintain flow, and kettle interiors develop a light mineral ring over time. Glassware from dishwashers shows occasional light spotting without rinse-aid, but the low-to-moderate hardness makes this manageable. Hot water systems experience modest scale build-up over their operational life — an occasional inspection is worthwhile but not urgent. The city's proximity to the Pacific moderates mineral loading, and overall water quality in Oxnard is generally considered reliable.