Ann Arbor Water Hardness & Quality Report (2026)

Ann Arbor, Michigan — home to the University of Michigan — draws its municipal water supply from the Huron River via the City of Ann Arbor Water Treatment Services, operating the Water Treatment Plant drawing from Barton Pond — an impoundment on the Huron River created by the Barton Dam in Ann Arbor — along with the Geddes Pond and Superior Road intake structures along the Huron River in Washtenaw County. The Huron River drains southeastern Michigan from Oakland and Livingston Counties to Lake Erie at Lake Erie State Park. Water hardness in Ann Arbor measures 232 mg/L — classified as very hard.

Ann Arbor's very hard supply reflects the Michigan Basin carbonate geology of the Huron River watershed. The Huron River drains the southeastern Michigan Lower Peninsula — underlain by the Silurian Niagara Group dolomite (the formation underlying Niagara Falls), the Devonian Hamilton Group limestone and shale, and the Devonian Monroe Formation dolomite — ancient marine carbonate sequences deposited when the Michigan Basin was a warm inland sea. These highly soluble carbonate formations, combined with Pleistocene glacial till and outwash derived from pulverised Michigan Basin carbonate bedrock, contribute very high dissolved calcium and magnesium to Huron River runoff. The result is one of the hardest municipal supplies among Michigan's major university cities.

At 232 mg/L, Ann Arbor residents face significant hard water challenges. Scale deposits form rapidly on faucet aerators, showerheads, shower glass, and tile — bi-weekly to monthly cleaning with citric acid descaler is standard home maintenance. Dishwashers require rinse-aid to produce acceptable glassware results, and water heaters accumulate significant scale that requires annual professional inspection. City of Ann Arbor Water Treatment Services consistently delivers water meeting all Michigan EGLE and EPA Safe Drinking Water Act requirements.