Lewis County Lake Quality
Wisconsin, 3 lakes, average grade A (Excellent)
Lewis County has 3 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's average grade is A — among the cleanest in New York. 2 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. Lake Bonaparte (A) is the cleanest in the county.
Quick Answers for Lewis County
Planning a trip? Check special fishing regulations for Lake Bonaparte, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Lewis County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Lake Bonaparte | A | 15.8 ft | - | - |
| 2 | Barnes Lake | A | - | - | 15 µg/L |
| 3 | Brantingham Lake | B | 10.7 ft | - | - |
Source: EPA National Aquatic Resource Surveys, 2026.