St. Charles County Lake Quality
Wisconsin, 11 lakes, average grade D (Poor)
Only 11 lakes in St. Charles 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, St. Charles 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 Lake 37 (B); the most-stressed is Lake St. Louis Nr. Hwy 40 (F).
Quick Answers for St. Charles County
Planning a trip? Check special fishing regulations for Lake 37, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in St. Charles County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Lake 37 | B | 4 ft | - | 16 µg/L |
| 2 | L. Ste. Louise Lake | D | 2.6 ft | - | 40.8 µg/L |
| 3 | Callaway Fork Lake | D | 3.3 ft | - | 39.5 µg/L |
| 4 | L. Ste. Louise Lake | D | 3.2 ft | - | 33.5 µg/L |
| 5 | Callaway Fork Lake | D | 2.1 ft | - | 78.5 µg/L |
| 6 | Lake 36 | D | 2.5 ft | - | 31 µg/L |
| 7 | Lake St. Louis | D | 2.7 ft | - | 50 µg/L |
| 8 | Lake 35 | D | 2.7 ft | - | - |
| 9 | Lake St. Louis by Dam | F | 2.3 ft | - | 74.8 µg/L |
| 10 | Lake St. Louis Nr. Hwy 40 | F | 1 ft | - | 125.8 µg/L |
| 11 | Kruse Lake | F | 2.6 ft | - | - |
Source: EPA National Aquatic Resource Surveys, 2026.