Birch Lake vs Johnson Lake
Water quality, depth, fish species, and recreation comparison.
Birch Lake has a higher water quality grade (C, Fair) than Johnson Lake (F, Very Poor). Both are in St. Louis County, Minnesota.
Birch Lake and Johnson 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. Birch Lake (C) is materially cleaner than Johnson Lake (F). A gap that wide is unlikely to close in a single year of remediation work; it reflects multi-decade differences in the lakes themselves.
For a recreational visitor, the wider grade gap is decisive — Birch 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?
Birch Lake
Murky, only visible to about 3.9 ft.
Johnson Lake
Very murky, less than 3 ft of visibility.
Side-by-Side Metrics
| Metric | Birch Lake | Johnson Lake |
|---|---|---|
| Overall Grade | C (Fair) | F (Very Poor) |
| Water Clarity | 3.9 ft | 3 ft |
| Phosphorus | 21 µg/L | No data |
| Chlorophyll-a (Algae) | No data | No data |
| Maximum Depth | 25 ft | 18 ft |
| Surface Area | 7.1K acres | 455.98 acres |
| Public Access | Yes | Yes |
| Fish Species | 1 | 1 |
| Trophic State | eutrophic | eutrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Birch Lake wins on overall water quality with a Grade C versus Johnson Lake's Grade F. Water clarity: 3.9 ft vs 3 ft. For fishing diversity, Birch Lake also leads with 1 species.