Winnebago County Lake Quality
Illinois, 1 lakes, average grade A (Excellent)
Winnebago 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's average grade is A — among the cleanest in Illinois. 1 lakes pull an A on their own, and almost none fall into the D or F brackets.
Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Baumann Park Lake (A) is the cleanest in the county.
Quick Answers for Winnebago County
Planning a trip? Check special fishing regulations for Baumann Park Lake — or check the official Illinois fishing regulations.
All Lakes in Winnebago County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Baumann Park Lake | A | 10.2 ft | 11.5 µg/L |
Other Counties in Illinois
See how Winnebago 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 Winnebago County
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Source: EPA National Aquatic Resource Surveys, 2026.