Corcoran Water Hardness & Quality Report (2026)

Corcoran, California, in Kings County in the central San Joaquin Valley — home to the California State Prison-Corcoran, formerly the site of Tulare Lake (once the largest freshwater lake west of the Mississippi, now drained for agriculture) — receives its municipal water from the City of Corcoran Water Division, which draws from the Kings River alluvial aquifer through groundwater wells or from the Friant-Kern Canal surface water delivery (part of the California State Water Project Central Valley Project). Kings County's water supply depends on the San Joaquin Valley alluvial aquifer system.

The moderately hard 127 mg/L hardness and TDS of 343.8 mg/L reflect the Kings River alluvial basin's groundwater and surface water character. The Kings River drains the southern Sierra Nevada — predominantly Cretaceous granitic batholiths (Sierra Nevada intrusive complex) and Precambrian metamorphic roof pendant rocks (soft water sources) — and deposits alluvial gravel, sand, and silt across the Tulare Basin floor. As Sierra Nevada-origin water percolates through the Quaternary alluvial fan deposits of the Tulare Basin, it accumulates calcium, magnesium, and dissolved solids from the calcareous alluvial sediments and residual evaporite minerals in the ancient lake bed soils, producing a moderately hard finished supply.

At 127 mg/L, Corcoran's water is moderately hard — consistent with the San Joaquin Valley alluvial basin supply profile. Scale builds in kettles and appliances over months, the dishwasher benefits from rinse aid, and faucet aerators need periodic cleaning. Quarterly descaling of heating appliances is the standard schedule. The PFAS level of 5.6 ppt warrants a certified drinking water filter — Kings County's Central Valley agricultural practices, the Corcoran state prison complex's industrial water use, and the San Joaquin Valley's extensive history of military and agricultural PFAS sources contribute to the regional PFAS background.