Seneca County Lake Quality
Wisconsin, 1 lakes, average grade A (Excellent)
Seneca 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. On average, Seneca County lakes grade an A. That puts it near the top of the New York county ranking.
Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Seneca Lake Platform (A) is the cleanest in the county.
Quick Answers for Seneca County
Planning a trip? Check special fishing regulations for Seneca Lake Platform, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Seneca County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Seneca Lake Platform | A | 11.5 ft | - | 6 µg/L |
Source: EPA National Aquatic Resource Surveys, 2026.