Big Portage Lake vs Boulder Lake
Water quality, depth, fish species, and recreation comparison.
Big Portage Lake and Boulder Lake read the same on nutrients and algae. Both are in Vilas County, Wisconsin.
Big Portage Lake and Boulder 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. The readings are close: Big Portage Lake and Boulder Lake sit within a narrow band of each other on phosphorus, chlorophyll-a and clarity. The per-parameter table below shows where the small differences actually live.
With readings 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.
Big Portage Lake
Crystal clear, you can see 18.5 ft down.
Boulder Lake
Murky, only visible to about 5.6 ft.
Side-by-Side Metrics
| Metric | Big Portage Lake | Boulder Lake |
|---|---|---|
| Water Clarity | 18.5 ft Better | 5.6 ft |
| Phosphorus | 12 µg/L Better | 21.6 µg/L |
| Chlorophyll-a (Algae) | No data | No data |
| Maximum Depth | 40 ft Better | 23 ft |
| Surface Area | 586 acres | 516 acres |
| Public Access | Yes | Yes |
| Fish Species | 4 | 6 Better |
| Trophic State | oligotrophic | eutrophic |
A green ✓ marks the better value for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better). Surface area and trophic state carry no tick — a bigger lake is not a better lake.
Swap a lake
Compare Big Portage Lake or Boulder Lake against a different lake.
Verdict
Both lakes earn the same Grade B. The tiebreakers come down to clarity (Big Portage Lake: 18.5 ft, Boulder Lake: 5.6 ft) and what you want from the lake. Big Portage Lake has fewer fish species than Boulder Lake.
Source: EPA National Aquatic Resource Surveys, 2026.