Manhattan Water Hardness & Quality Report (2026)

Manhattan, Kansas, the Riley County seat on the Kansas River and Blue River — home of Kansas State University, 'The Little Apple,' and the Aggieville entertainment district — draws its municipal water supply from Tuttle Creek Reservoir (on the Blue River, a Kansas River tributary) via the City of Manhattan Public Works Water Division, treating Blue River watershed water for the Manhattan area. Water hardness in Manhattan measures 127 mg/L — classified as moderately hard.

Manhattan's moderate hardness reflects the Blue River–Tuttle Creek watershed's Flint Hills calcareous geology. The Blue River above Tuttle Creek Reservoir drains: the Permian Flint Hills Chase Group (Permian Wreford and Matfield Limestone — the characteristic Flint Hills limestone formations of the Chase Group that form the Tallgrass Prairie escarpment — calcareous limestone and shale); the Permian Council Grove Group (calcareous cyclothemic limestone and shale — typical of the Kansas Permian platform); and the Cretaceous Dakota Formation (calcareous sandstone of the high plains). The Permian Flint Hills limestone dissolves at a moderate rate in the Blue River watershed, producing the moderate 127 mg/L at Manhattan — softer than the more arid Kansas communities with concentrated calcareous groundwater but reflecting the region's Permian carbonate geology.

At 127 mg/L, Manhattan residents encounter moderate scale accumulation. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is practical maintenance. City of Manhattan Public Works Water Division consistently delivers water meeting all Kansas KDH&E and EPA Safe Drinking Water Act requirements.