Grundy County Lake Quality
Wisconsin, 1 lakes, average grade F (Very Poor)
Grundy 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 Crowder S.P. Lake (F); the most-stressed is Crowder S.P. Lake (F).
Quick Answers for Grundy County
Planning a trip? Check special fishing regulations for Crowder S.P. Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Grundy County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Crowder S.P. Lake | F | 1 ft | - | 110 µg/L |
Source: EPA National Aquatic Resource Surveys, 2026.