Calexico Water Hardness & Quality Report (2026)

Calexico, California, in Imperial County — a US–Mexico border city directly across from Mexicali, Baja California (one of the most closely paired US–Mexico border twin cities, with Calexico–Mexicali sharing culture, economy, and binational daily life), the western anchor of the Imperial Valley (the Colorado River-irrigated agricultural desert valley — one of the most productive agricultural regions in the US, producing winter vegetables including nearly all US iceberg lettuce), and a major border crossing and Mexican–American community in the Imperial Valley — draws its municipal water supply from the Colorado River via the All-American Canal via the City of Calexico Water Division. Water hardness in Calexico measures 189.5 mg/L — classified as hard.

Calexico's hard supply reflects the Colorado River's inherent calcareous hardness at the southernmost California diversion point. The Colorado River at the Imperial Dam (All-American Canal headworks) carries water draining: the Rocky Mountains (Paleozoic calcareous dolomite and limestone of the Colorado Plateau — the Grand Canyon section); Great Basin calcareous evaporite (Nevada and Utah); and Permian calcareous basin evaporite of New Mexico and Arizona. At the southern Imperial Dam diversion, the Colorado River hardness is very high — among the hardest in the entire river — at approximately 280–340 mg/L. Calexico applies standard treatment with limited softening, producing the hard 189.5 mg/L.

At 189.5 mg/L, Calexico residents face regular hard water challenges. Monthly descaling with citric acid solution is standard maintenance. City of Calexico Water Division consistently delivers water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.