Decatur County Lake Quality
Wisconsin, 3 lakes, average grade C (Fair)
Only 3 lakes in Decatur County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county. Decatur County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.
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 Nine Eagles Lake (A); the most-stressed is Little River Lake (F).
Quick Answers for Decatur County
Planning a trip? Check special fishing regulations for Nine Eagles Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Decatur County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Nine Eagles Lake | A | 11 ft | - | - |
| 2 | Slipbluff Lake | B | 9 ft | - | - |
| 3 | Little River Lake | F | 2.3 ft | - | - |
Source: EPA National Aquatic Resource Surveys, 2026.