Birch Lake vs Johnson Lake
Water quality, depth, fish species, and recreation comparison.
Birch Lake and Johnson Lake both received the same overall water quality grade of C (Fair). 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. These two are within a letter of each other on the rubric — Birch Lake (C) versus Johnson Lake (C). The deciding factors for a recreational visitor are likely physical (depth, access, fish species) rather than water-quality differences.
With grades 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.
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) | C (Fair) |
| Water Clarity | 3.9 ft Better | 3 ft |
| Phosphorus | 21.5 µg/L Better | 33 µg/L |
| Chlorophyll-a (Algae) | 7.5 µg/L Better | 9.8 µg/L |
| Maximum Depth | 25 ft Better | 18 ft |
| Surface Area | 7,074 acres | 456 acres |
| Public Access | Yes | Yes |
| Fish Species | 10 | 11 Better |
| Trophic State | eutrophic | 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.
Swap a lake
Compare Birch Lake or Johnson Lake against a different lake.
Verdict
Both lakes earn the same Grade C. The tiebreakers come down to clarity (Birch Lake: 3.9 ft, Johnson Lake: 3 ft) and what you want from the lake. Birch Lake has fewer fish species than Johnson Lake.
Source: EPA National Aquatic Resource Surveys, 2026.