Boulder Lake vs Plum Lake
Water quality, depth, fish species, and recreation comparison.
Boulder Lake and Plum Lake both received the same overall water quality grade of B (Good). Both are in Vilas County, Wisconsin.
Both Boulder Lake and Plum Lake sit in Wisconsin. A same-state comparison strips out the state-level water-quality regime as a variable: any grade differences here are about the lakes themselves, not the agencies grading them. The grades are close: Boulder Lake (B) and Plum Lake (B) are within one letter of each other on the LakeGrade rubric. The per-parameter sub-grades below will show where the small differences actually live.
With grades this close, the choice between the two lakes turns on non-water-quality factors: depth, fish species, public access, distance from home. The per-lake pages below cover all of those.
Boulder Lake
Murky, only visible to about 5.6 ft.
Plum Lake
Good clarity, visible to about 14.2 ft.
Side-by-Side Metrics
| Metric | Boulder Lake | Plum Lake |
|---|---|---|
| Overall Grade | B (Good) | B (Good) |
| Water Clarity | 5.6 ft | 14.2 ft |
| Phosphorus | 21.6 µg/L | 13 µg/L |
| Chlorophyll-a (Algae) | No data | No data |
| Maximum Depth | 23 ft | 57 ft |
| Surface Area | 516 acres | 1,057 acres |
| Public Access | Yes | Yes |
| Fish Species | 6 | 6 |
| Trophic State | eutrophic | oligotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Both lakes earn the same Grade B. The tiebreakers come down to clarity (Boulder Lake: 5.6 ft, Plum Lake: 14.2 ft) and what you want from the lake. Boulder Lake matches its peer on species count.
Source: EPA National Aquatic Resource Surveys, 2026.