Fond du Lac County Lake Quality
Wisconsin, 10 lakes, average grade C (Fair)
Only 10 lakes in Fond du Lac 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 average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.
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. Forest Lake (A) is the cleanest in the county.
Quick Answers for Fond du Lac County
Planning a trip? Check special fishing regulations for Forest Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
DNR Reports (1)
Wisconsin DNR Fisheries Survey resources for lakes in Fond du Lac County. browse all reports →
- 2023Lakeside Park (Lake Winnebago) spring shocking survey, 2023Spring Shocking Survey · WI DNR · 2023 (PDF)
All Lakes in Fond du Lac County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Forest Lake | A | 14 ft | 32 ft | 14.2 µg/L |
| 2 | Kettle Moraine Lake | A | 11 ft | 30 ft | 16.2 µg/L |
| 3 | De Neveu Lake | A | 11 ft | 67 ft | 18.1 µg/L |
| 4 | Long Lake | B | 9.1 ft | 47 ft | 19.3 µg/L |
| 5 | Auburn Lake | B | 7.6 ft | 29 ft | 24.4 µg/L |
| 6 | Wolf Lake | C | 5 ft | 47 ft | 35 µg/L |
| 7 | Mauthe Lake | C | 6 ft | 23 ft | 54 µg/L |
| 8 | Bernice Lake | D | 6.5 ft | 11 ft | 74.9 µg/L |
| 9 | Dickman Lake | F | 3 ft | 12 ft | - |
| 10 | Giltners Lake | F | - | 13 ft | 159.5 µg/L |
Source: EPA National Aquatic Resource Surveys, 2026.