Carroll County Lake Quality
Illinois, 1 lakes, average grade B (Good)
Carroll 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. With an average grade of B, Carroll County sits comfortably above the Illinois median.
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 Timber Lake (B); the most-stressed is Timber Lake (B).
Quick Answers for Carroll County
Planning a trip? Check special fishing regulations for Timber Lake — or check the official Illinois fishing regulations.
All Lakes in Carroll County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Timber Lake | B | 11.5 ft | - |
Other Counties in Illinois
See how Carroll 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 Carroll County
Top-rated places to stay near Carroll County
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Source: EPA National Aquatic Resource Surveys, 2026.