Big Deep Lake vs Long Lake
Water quality, depth, fish species, and recreation comparison.
Big Deep Lake and Long Lake both received the same overall water quality grade of A (Excellent). Both are in Cass County, Minnesota.
Big Deep Lake and Long 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 — Big Deep Lake (A) versus Long Lake (A). 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.
Big Deep Lake
Crystal clear, you can see 17.1 ft down.
Long Lake
Crystal clear, you can see 21.5 ft down.
Side-by-Side Metrics
| Metric | Big Deep Lake | Long Lake |
|---|---|---|
| Overall Grade | A (Excellent) | A (Excellent) |
| Water Clarity | 17.1 ft | 21.5 ft |
| Phosphorus | 6.5 µg/L | 9 µg/L |
| Chlorophyll-a (Algae) | No data | No data |
| Maximum Depth | 107 ft | 115 ft |
| Surface Area | 535.75 acres | 1.0K acres |
| Public Access | No | Yes |
| Fish Species | 1 | 1 |
| Trophic State | oligotrophic | oligotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Both lakes earn the same Grade A. The tiebreakers come down to clarity (Big Deep Lake: 17.1 ft, Long Lake: 21.5 ft) and what you want from the lake. Big Deep Lake matches its peer on species count.