Pueblo Water Hardness & Quality Report (2026)

Pueblo, Colorado, a major Arkansas River city in Pueblo County, draws its municipal water supply from the City of Pueblo Board of Water Works, sourcing from the Arkansas River via Pueblo Reservoir (Lake Pueblo) — a major Bureau of Reclamation reservoir on the Arkansas River west of Pueblo in Pueblo County — and from Fountain Creek (an Arkansas River tributary) at upstream intake structures. Pueblo Reservoir stores both Arkansas River water and water from the Transmountain Fryingpan–Arkansas Project (western slope water from the Fryingpan River, Roaring Fork watershed) delivered through the Charles H. Boustead Tunnel across the Continental Divide. Water hardness measures 140 mg/L — classified as moderately hard.

Pueblo's moderate hardness reflects the blended character of Arkansas River and transmountain water in Pueblo Reservoir. The Arkansas River headwaters drain the Sawatch Range (Precambrian Pikes Peak Granite, Collegiate Peaks granodiorite — soft Sierra-like crystalline terrain) and the upper Arkansas valley formations. However, the mid-Arkansas below Salida crosses the Wet Mountains granite and Permian Sangre de Cristo Formation calcareous terrain, and Fountain Creek drains the Colorado Springs front-range zone where the Denver Basin Cretaceous marine formations contribute moderate calcium. The Fryingpan transmountain water adds soft western slope Roaring Fork Colorado River water to the blend.

At 140 mg/L, Pueblo residents encounter moderate scale accumulation in household use. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is practical maintenance. Dishwashers produce cleaner glassware with rinse-aid. City of Pueblo Board of Water Works consistently delivers water meeting all Colorado CDPHE and EPA Safe Drinking Water Act requirements.