Boulder Lake vs Flambeau Lake
Water quality, depth, fish species, and recreation comparison.
Boulder Lake and Flambeau Lake both received the same overall water quality grade of B (Good). Both are in Vilas County, Wisconsin.
Boulder Lake and Flambeau Lake are both in Wisconsin — a same-state head-to-head where the comparison comes down to lake-specific differences in depth, watershed, and monitoring history rather than the broader state-level water-quality regime. These two are within a letter of each other on the rubric — Boulder Lake (B) versus Flambeau Lake (B). The deciding factors for a recreational visitor are likely physical (depth, access, fish species) rather than water-quality differences.
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.
Flambeau Lake
No clarity data.
Side-by-Side Metrics
| Metric | Boulder Lake | Flambeau Lake |
|---|---|---|
| Overall Grade | B (Good) | B (Good) |
| Water Clarity | 5.6 ft | No data |
| Phosphorus | 21.6 µg/L | 9 µg/L |
| Chlorophyll-a (Algae) | No data | No data |
| Maximum Depth | 23 ft | 78 ft |
| Surface Area | 516 acres | 1,166 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 what you want from the lake. Boulder Lake matches its peer on species count.
Source: EPA National Aquatic Resource Surveys, 2026.