Bear Island Lake vs Birch Lake
Water quality, depth, fish species, and recreation comparison.
Bear Island Lake reads lower on nutrients and algae than Birch Lake. Both are in St. Louis County, Minnesota.
Bear Island Lake and Birch Lake are both in Minnesota — 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 meaningfully apart: Bear Island Lake carries clearly lower phosphorus and chlorophyll-a readings than Birch Lake. A spread that wide reflects real underlying differences, in watershed inputs, depth profiles, or monitoring rigor.
For a recreational visitor, the wider gap in the readings is decisive: Bear Island Lake has the lower nutrient and algae numbers. For a researcher, the gap is the interesting part: what is different about the two watersheds, and which of those differences is mutable?
Bear Island Lake
Moderate clarity, visible to about 7 ft.
Birch Lake
Murky, only visible to about 3.9 ft.
Side-by-Side Metrics
| Metric | Bear Island Lake | Birch Lake |
|---|---|---|
| Water Clarity | 7 ft Better | 3.9 ft |
| Phosphorus | 15 µg/L Better | 21.5 µg/L |
| Chlorophyll-a (Algae) | 6.4 µg/L Better | 7.5 µg/L |
| Maximum Depth | 62 ft Better | 25 ft |
| Surface Area | 2,362 acres | 7,074 acres |
| Public Access | Yes | Yes |
| Fish Species | 13 Better | 10 |
| Trophic State | mesotrophic | 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.
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Compare Bear Island Lake or Birch Lake against a different lake.
Verdict
Bear Island Lake reads lower on nutrients and algae than Birch Lake. Water clarity: 7 ft vs 3.9 ft. For fishing diversity, Bear Island Lake also leads with 13 species.
Source: EPA National Aquatic Resource Surveys, 2026.