Pasco Water Hardness & Quality Report (2026)

Pasco, Washington, the Franklin County seat in the Tri-Cities area of southeast Washington state (Pasco–Kennewick–Richland) at the confluence of the Columbia and Snake Rivers — a rapidly growing agricultural and nuclear energy hub (adjacent to the Hanford Site) — draws its municipal water supply from the Columbia River via the City of Pasco Public Works Water Division, treating Columbia River water at the Pasco Water Treatment Plant. The Columbia River at Pasco carries runoff from the vast Pacific Northwest Columbia River Basin. Water hardness in Pasco measures 47.5 mg/L — classified as moderately soft.

Pasco's soft supply reflects the Columbia River's dilute chemistry through the Columbia Plateau. The Columbia River at Pasco drains the Columbia Plateau — the immense Miocene Columbia River Basalt Group lava plateau covering eastern Washington, Oregon, and Idaho. Basalt — a calcium-poor, iron-magnesium dominated volcanic rock — dissolves very slowly and contributes minimal dissolved calcium to surface drainage. The Cascades volcanic arc watersheds (Okanogan, Methow, Entiat, Wenatchee, Yakima Rivers) draining into the upper Columbia contribute similarly soft water from volcanic terrain. The Columbia River's enormous volume and dilute chemistry from basalt-dominated catchments produces the soft supply at Pasco consistent with neighboring Kennewick (similar hardness) in the Tri-Cities.

With hardness at 47.5 mg/L, Pasco residents enjoy very soft water with minimal scale challenges. City of Pasco Public Works Water Division consistently delivers water meeting all Washington DOH and EPA Safe Drinking Water Act requirements.