Hillsdale County Lake Quality
Wisconsin, 7 lakes, average grade D (Poor)
Only 7 lakes in Hillsdale 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. On average, Hillsdale County lakes grade D, with phosphorus loading and reduced clarity showing up across most of the dataset.
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 Crystal Lake (B); the most-stressed is Perch Lake (F).
Quick Answers for Hillsdale County
Planning a trip? Check special fishing regulations for Crystal Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Hillsdale County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Crystal Lake | B | 9.5 ft | - | - |
| 2 | Paw Paw Lake | C | 8 ft | - | - |
| 3 | Crystal Lake | C | 9.5 ft | - | - |
| 4 | Paw Paw Lake | C | 8 ft | - | - |
| 5 | Lake Diane South Basin; Amboy Township | D | 2.5 ft | - | - |
| 6 | Perch Lake | F | 3.3 ft | - | - |
| 7 | Perch Lake | F | 3.3 ft | - | - |
Source: EPA National Aquatic Resource Surveys, 2026.