Madison County Lake Quality
Wisconsin, 8 lakes, average grade A (Excellent)
Madison County has 8 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. On average, Madison County lakes grade an A. That puts it near the top of the New York county ranking.
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 Bradley Brook Reservoir (A); the most-stressed is Earlville Lake (C).
Quick Answers for Madison County
Planning a trip? Check special fishing regulations for Bradley Brook Reservoir, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Madison County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Bradley Brook Reservoir | A | 20.7 ft | - | - |
| 2 | Deruyter Reservoir | A | 17.6 ft | - | - |
| 3 | Lake Moraine | A | 20.3 ft | - | - |
| 4 | Eaton Reservoir | A | 18.2 ft | - | - |
| 5 | Tuscarora Lake | A | 20.5 ft | - | - |
| 6 | Cazenovia Lake | A | 16.7 ft | - | - |
| 7 | Hatch Lake | B | 13.4 ft | - | - |
| 8 | Earlville Lake | C | 7.8 ft | - | - |
Source: EPA National Aquatic Resource Surveys, 2026.