Macoupin County Lake Quality

There are 17 monitored lakes in Macoupin County. The mix is varied enough that the county-level average tells you the broad strokes, not the choose-this-cabin specifics. 3 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. The county average is F — the most-stressed bracket in our rubric. Most monitored lakes here show persistent nutrient loading and algal pressure.

The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Palmyra-Modesto Lake (D); the most-stressed is Otter Lake (F).