Colton Water Hardness & Quality Report (2026)

Colton, California, in San Bernardino County in the Inland Empire at the Santa Ana River's Colton Narrows — a major Inland Empire industrial and logistics hub (Union Pacific Colton Intermodal Terminal, the largest rail intermodal facility west of the Mississippi) with a large Latino and working-class community — draws its municipal water supply from the Bunker Hill–San Bernardino Groundwater Basin and State Water Project (SWP) imports via the City of Colton Water Department. Water hardness in Colton measures 82 mg/L — classified as moderately soft.

Colton's moderate softness reflects the Bunker Hill Basin's SWP import dilution and the Santa Ana River alluvial recharge at the Colton Narrows. The Bunker Hill Basin at the Colton Narrows (where the Santa Ana River exits the San Bernardino Valley through the Colton fault zone — a major structural constriction of the valley) receives: State Water Project Bay-Delta imports through basin spreading grounds; local Santa Ana River recharge from the San Bernardino Mountains (calcium-poor granitic batholith recharge); and minimal calcareous valley floor alluvium. Colton's position at the valley outlet — where the freshest, most recently recharged groundwater is pumped — produces the relatively soft 82 mg/L.

With hardness at 82 mg/L, Colton residents enjoy moderately soft water for an Inland Empire community. City of Colton Water Department consistently delivers water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.