Rock Island County Lake Quality

Rock Island County has 3 monitored lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. 1 of those lake carry recent nutrient and algae readings. The county-level summary describes that subset, not every water body listed. The county's readings sit in the middle of the Illinois range, with one or two lakes pulling the average up or down depending on year.

Many of the county's lakes are deep glacial basins, over 50 feet at their deepest point, which gives them thermal stratification and a buffer against summer warming. George Lake has the lowest nutrient and algae readings in the county.