Bear Island Lake vs Birch Lake
Water quality, depth, fish species, and recreation comparison.
Bear Island Lake has a higher water quality grade (A, Excellent) than Birch Lake (C, Fair). 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 grades are meaningfully apart: Bear Island Lake grades a A while Birch Lake grades a C. That two-letter spread reflects real underlying differences — different watershed inputs, different depth profiles, or different monitoring rigor.
For a recreational visitor, the wider grade gap is decisive — Bear Island Lake is the better water-quality choice. 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 |
|---|---|---|
| Overall Grade | A (Excellent) | C (Fair) |
| Water Clarity | 7 ft | 3.9 ft |
| Phosphorus | 15 µg/L | 21.5 µg/L |
| Chlorophyll-a (Algae) | 6.4 µg/L | 7.5 µg/L |
| Maximum Depth | 62 ft | 25 ft |
| Surface Area | 2,362 acres | 7,074 acres |
| Public Access | Yes | Yes |
| Fish Species | 13 | 10 |
| Trophic State | mesotrophic | eutrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Bear Island Lake wins on overall water quality with a Grade A versus Birch Lake's Grade C. 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.