Clinton County Lake Quality
Illinois, 1 lakes, average grade F (Very Poor)
Clinton County has 1 graded 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. 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 Carlyle Lake (F); the most-stressed is Carlyle Lake (F).
Quick Answers for Clinton County
Planning a trip? Check special fishing regulations for Carlyle Lake — or check the official Illinois fishing regulations.
All Lakes in Clinton County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Carlyle Lake | F | 1.8 ft | 200.5 µg/L |
Other Counties in Illinois
See how Clinton County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 15 states.
Where to stay near Clinton County
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Source: EPA National Aquatic Resource Surveys, 2026.