Knox County Lake Quality
Wisconsin, 1 lakes, average grade D (Poor)
Knox 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. The county-wide average grade is D — water quality issues are persistent across most of the monitored basins. 0 lakes fall into the F bracket outright.
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 Henry Sever Lake (D); the most-stressed is Henry Sever Lake (D).
Quick Answers for Knox County
Planning a trip? Check special fishing regulations for Henry Sever Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Knox County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Henry Sever Lake | D | 2.1 ft | - | 58 µg/L |
Source: EPA National Aquatic Resource Surveys, 2026.