Boulder Lake vs Forest Lake
Water quality, depth, fish species, and recreation comparison.
Boulder Lake and Forest Lake both received the same overall water quality grade of B (Good). Both are in Vilas County, Wisconsin.
Both Boulder Lake and Forest 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. These two are within a letter of each other on the rubric — Boulder Lake (B) versus Forest 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.
Forest Lake
Crystal clear, you can see 22.2 ft down.
Side-by-Side Metrics
| Metric | Boulder Lake | Forest Lake |
|---|---|---|
| Overall Grade | B (Good) | B (Good) |
| Water Clarity | 5.6 ft | 22.2 ft |
| Phosphorus | 21.6 µg/L | 12.8 µg/L |
| Chlorophyll-a (Algae) | No data | No data |
| Maximum Depth | 23 ft | 60 ft |
| Surface Area | 516 acres | 468 acres |
| Public Access | Yes | Yes |
| Fish Species | 6 | 5 |
| 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, Forest Lake: 22.2 ft) and what you want from the lake. Boulder Lake supports more documented fish species.
Source: EPA National Aquatic Resource Surveys, 2026.