Big Portage (W Bay Lake vs Birch Lake
Water quality, depth, fish species, and recreation comparison.
Big Portage (W Bay Lake and Birch Lake read the same on nutrients and algae. Both are in Cass County, Minnesota.
Both Big Portage (W Bay Lake and Birch Lake sit in Minnesota. A same-state comparison strips out the state-level water-quality regime as a variable: any differences in the readings here are about the lakes themselves, not the agencies sampling them. The readings are close: Big Portage (W Bay Lake and Birch 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 (W Bay Lake
Moderate clarity, visible to about 8.5 ft.
Birch Lake
Good clarity, visible to about 14 ft.
Side-by-Side Metrics
| Metric | Big Portage (W Bay Lake | Birch Lake |
|---|---|---|
| Water Clarity | 8.5 ft | 14 ft Better |
| Phosphorus | 18.5 µg/L | 12 µg/L Better |
| Chlorophyll-a (Algae) | 5.6 µg/L | 4 µg/L Better |
| Maximum Depth | 23 ft | 45 ft Better |
| Surface Area | 902 acres | 1,267 acres |
| Public Access | Yes | Yes |
| Fish Species | 13 | 14 Better |
| Trophic State | mesotrophic | mesotrophic |
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 (W Bay Lake or Birch Lake against a different lake.
Verdict
Both lakes earn the same Grade A. The tiebreakers come down to clarity (Big Portage (W Bay Lake: 8.5 ft, Birch Lake: 14 ft) and what you want from the lake. Big Portage (W Bay Lake has fewer fish species than Birch Lake.
Source: EPA National Aquatic Resource Surveys, 2026.