Johnson County Lake Quality
Wisconsin, 2 lakes, average grade D (Poor)
Johnson 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. The county-wide average grade is D — water quality issues are persistent across most of the monitored basins. 1 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 Lamb Lake (C); the most-stressed is Wed-07 Lake (F).
Quick Answers for Johnson County
Planning a trip? Check special fishing regulations for Lamb Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Johnson County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Lamb Lake | C | 7.2 ft | - | - |
| 2 | Wed-07 Lake | F | 3.3 ft | - | - |
Source: EPA National Aquatic Resource Surveys, 2026.