Big Portage (W Bay Lake vs Birch Lake
Water quality, depth, fish species, and recreation comparison.
Birch Lake reads lower on nutrients and algae than Big Portage (W Bay Lake. 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.
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Verdict
Big Portage (W Bay Lake and Birch Lake read the same on nutrients and algae overall. 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.
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Where to stay near Big Portage (W Bay Lake and Birch Lake
Compare cabins, hotels, and vacation rentals around Big Portage (W Bay Lake and Birch Lake. Both lakes are pinned on the map, so you can see which stays sit nearer the one you pick. Switch to Satellite to see how close each is to the water.
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Source: EPA National Aquatic Resource Surveys, 2026.