Big Carnelian Lake vs Lake St. Croix
Water quality, depth, fish species, and recreation comparison.
Big Carnelian Lake has a higher water quality grade (A, Excellent) than Lake St. Croix (B, Good). Both are in Washington County, Minnesota.
Both Big Carnelian Lake and Lake St. Croix sit in Minnesota. A same-state comparison strips out the state-level water-quality regime as a variable: any grade differences here are about the lakes themselves, not the agencies grading them. The grades are close: Big Carnelian Lake (A) and Lake St. Croix (B) are within one letter of each other on the LakeGrade rubric. The per-parameter sub-grades below will show where the small differences actually live.
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 Carnelian Lake
Crystal clear, you can see 15 ft down.
Lake St. Croix
Murky, only visible to about 5.2 ft.
Side-by-Side Metrics
| Metric | Big Carnelian Lake | Lake St. Croix |
|---|---|---|
| Overall Grade | A (Excellent) | B (Good) |
| Water Clarity | 15 ft | 5.2 ft |
| Phosphorus | No data | 18 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 | mesotrophic |
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 Lake St. Croix's Grade B. Water clarity: 15 ft vs 5.2 ft. For more fish-species variety, Lake St. Croix edges ahead with 36 documented species.