Impaired Lakes in Minnesota

Reading the Minnesota impairment landscape

70% of Minnesota's tracked lakes — 1,630 of 2,333 — appear on the EPA Clean Water Act §303(d) impaired-waters list. At that share, impairment is the default state rather than an exception: the majority of lakes are flagged for at least one pollutant exceeding water-quality standards. Trip-planning for clean water in Minnesota typically requires checking impairment status as a first filter, not as an edge case.

Mercury leads the impairment causes in Minnesota — a contaminant category that is most relevant for fish consumption rather than for swimming or boating. Mercury and PCB impairments typically come from atmospheric deposition or legacy industrial discharge; they bioaccumulate up the food chain, so larger and longer-lived fish carry the highest tissue concentrations. Check the state's fish-consumption advisory before keeping a catch from these waters.

Impaired-waters listings come from the state environmental agency's §303(d) submission to EPA, refreshed on a roughly 2-year cycle. A listed lake stays on the list until either a TMDL is established and the cleanup completes, or subsequent monitoring shows the pollutant concentrations no longer exceed water-quality standards. The list below reflects the most recent available Minnesota submission to the EPA Assessment, Total Maximum Daily Load Tracking and Implementation System (ATTAINS) dataset.