Clay County Lake Quality
Wisconsin, 9 lakes, average grade D (Poor)
Clay County has 9 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. 3 lakes fall into the F bracket outright.
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. Watkins Mill Lake (D) is the cleanest in the county.
Quick Answers for Clay County
Planning a trip? Check special fishing regulations for Watkins Mill Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Clay County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Watkins Mill Lake | D | 3.2 ft | - | 41 µg/L |
| 2 | Smithville Lake | D | 2.6 ft | - | 34 µg/L |
| 3 | Smithville Lake by Dam | D | 3.3 ft | - | 37 µg/L |
| 4 | Smithville Lake | D | 2 ft | - | 48.8 µg/L |
| 5 | Hamilton Heights Park Lake | D | - | - | - |
| 6 | Lakewood Greenway Lake | D | - | - | - |
| 7 | Chaumiere Lake | F | 1.4 ft | - | 130 µg/L |
| 8 | Chaumiere Park Lake | F | - | - | 159.5 µg/L |
| 9 | Englewood Park Lake | F | - | - | - |
Source: EPA National Aquatic Resource Surveys, 2026.