Cape Girardeau Water Hardness & Quality Report (2026)

Cape Girardeau, Missouri, in Cape Girardeau County — the largest city in southeast Missouri, the 'City of Roses,' home of Southeast Missouri State University, the birthplace of Rush Limbaugh (the influential American conservative radio host — born in Cape Girardeau in 1951), a historic Mississippi River port city at the southern edge of the Missouri Ozarks (where the rugged Ozark Plateau meets the Mississippi River floodplain), and a major southeast Missouri commercial and higher education hub — draws its municipal water supply from the Mississippi River via the City of Cape Girardeau Water Division. Water hardness in Cape Girardeau measures 227.5 mg/L — classified as very hard.

Cape Girardeau's very hard supply reflects the Mississippi River's highly calcareous upper watershed geology. The Mississippi River at Cape Girardeau carries water from: the Missouri Ozarks (Ordovician Gasconade Dolomite and Roubidoux Formation — highly calcareous dolomite of the Ozark Platform); Iowa and Illinois Devonian–Mississippian calcareous limestone; Wisconsin glacial meltwater calcareous carbonate from the Iowa, Illinois, and Indiana till plains; and the upper Mississippi tributary calcareous carbonate sequence. The Mississippi River at southeast Missouri is very hard — accumulating calcareous content from the vast upper Midwest carbonate watershed. Cape Girardeau's treatment produces the hard 227.5 mg/L.

At 227.5 mg/L, Cape Girardeau residents face regular hard water challenges. Monthly descaling with citric acid solution is standard maintenance. City of Cape Girardeau Water Division consistently delivers water meeting all Missouri MDNR and EPA Safe Drinking Water Act requirements.