Big Carnelian Lake vs Pool of Lake St. Croix
Water quality, depth, fish species, and recreation comparison.
Big Carnelian Lake has a higher water quality grade (A, Excellent) than Pool of Lake St. Croix (C, Fair). Both are in Washington County, Minnesota.
Big Carnelian Lake and Pool of Lake St. Croix 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: Big Carnelian Lake grades a A while Pool of Lake St. Croix 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 — Big Carnelian 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?
Big Carnelian Lake
Crystal clear, you can see 15 ft down.
Pool of Lake St. Croix
Murky, only visible to about 4.3 ft.
Side-by-Side Metrics
| Metric | Big Carnelian Lake | Pool of Lake St. Croix |
|---|---|---|
| Overall Grade | A (Excellent) | C (Fair) |
| Water Clarity | 15 ft | 4.3 ft |
| Phosphorus | No data | 39.2 µg/L |
| Chlorophyll-a (Algae) | No data | No data |
| Maximum Depth | 66 ft | 78 ft |
| Surface Area | 457.03 acres | 8.4K acres |
| Public Access | Yes | No |
| Fish Species | 12 | 36 |
| Trophic State | oligotrophic | eutrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Big Carnelian Lake wins on overall water quality with a Grade A versus Pool of Lake St. Croix's Grade C. Water clarity: 15 ft vs 4.3 ft. For more fish-species variety, Pool of Lake St. Croix edges ahead with 36 documented species.