Ontonagon County Lake Quality
Wisconsin, 6 lakes, average grade A (Excellent)
Only 6 lakes in Ontonagon 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. The county's average grade is A — among the cleanest in Michigan. 5 lakes pull an A on their own, and almost none fall into the D or F brackets.
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. Su16 Lake (A) is the cleanest in the county.
Quick Answers for Ontonagon County
Planning a trip? Check special fishing regulations for Su16 Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Ontonagon County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Su16 Lake | A | - | - | - |
| 2 | Su17m Lake | A | 39.4 ft | - | - |
| 3 | Csmi 2021 Station Med-57a Lake | A | - | - | - |
| 4 | Csmi 2021 Station Med Lake | A | - | - | - |
| 5 | Csmi 2021 Station Med Lake | A | - | - | - |
| 6 | Lake Gogebic; North Deep Basin; Bergland Township | C | 6.5 ft | - | - |
Source: EPA National Aquatic Resource Surveys, 2026.