Big Deep Lake vs Birch Lake
Water quality, depth, fish species, and recreation comparison.
Big Deep Lake and Birch Lake read the same on nutrients and algae. Both are in Cass County, Minnesota.
Both Big Deep 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. These two sit close on the readings, Big Deep Lake versus Birch Lake. The deciding factors for a recreational visitor are likely physical (depth, access, fish species) rather than water-quality differences.
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 Deep Lake
Crystal clear, you can see 19.4 ft down.
Birch Lake
Good clarity, visible to about 14 ft.
Side-by-Side Metrics
| Metric | Big Deep Lake | Birch Lake |
|---|---|---|
| Water Clarity | 19.4 ft Better | 14 ft |
| Phosphorus | 7 µg/L Better | 12 µg/L |
| Chlorophyll-a (Algae) | 1.9 µg/L Better | 4 µg/L |
| Maximum Depth | 107 ft Better | 45 ft |
| Surface Area | 536 acres | 1,267 acres |
| Public Access | No | Yes |
| Fish Species | 13 | 14 Better |
| Trophic State | oligotrophic | 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.
Swap a lake
Compare Big Deep Lake or Birch Lake against a different lake.
Verdict
Both lakes earn the same Grade A. The tiebreakers come down to clarity (Big Deep Lake: 19.4 ft, Birch Lake: 14 ft) and what you want from the lake. Big Deep Lake has fewer fish species than Birch Lake.
Source: EPA National Aquatic Resource Surveys, 2026.