Michigan Lake Water Quality

Michigan lists 3,392 lakes across 83 counties, 581 of them with a recent water-quality reading. Most of that sampling flows through monitoring run by the Michigan Department of Environment, Great Lakes, and Energy (EGLE), which feeds state, federal, and volunteer measurements into the EPA Water Quality Portal. The remainder are here because they are real named lakes, not because anyone has sampled them recently. A large share of the state's measured lakes carry low phosphorus and chlorophyll-a readings, which reflects the depth and natural nutrient poverty of glacial lakes in the region.

By surface area the largest lake here is Houghton Lake, at about 20,070 acres, and 232 of the lakes in this index cover more than 500 acres. Size is worth knowing before you go: a large deep basin buffers nutrient inputs by sheer volume, while a shallow one warms quickly and can turn over its whole water column in a single summer storm. Mesotrophic is the dominant trophic class among the measured lakes, a workable middle ground between the pristine oligotrophic deep lakes and the algal-pressured eutrophic shallow ones. The county with the lowest nutrient and algae readings on average is Dickinson. The gap between counties is large enough that a single figure for Michigan lake water quality hides real local variation.