Sullivan County Lake Quality
Wisconsin, 2 lakes, average grade B (Good)
Sullivan County has 2 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. With an average grade of B, Sullivan County sits comfortably above the Indiana median.
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. Wwl-06 Lake (A) is the cleanest in the county.
Quick Answers for Sullivan County
Planning a trip? Check special fishing regulations for Wwl-06 Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Sullivan County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Wwl-06 Lake | A | 10.3 ft | - | - |
| 2 | Wbu-15 Lake | C | 5.7 ft | - | - |
Source: EPA National Aquatic Resource Surveys, 2026.