Big Carnelian Lake vs Long Lake
Water quality, depth, fish species, and recreation comparison.
Big Carnelian Lake has a higher water quality grade (A, Excellent) than Long Lake (D, Poor). Both are in Washington County, Minnesota.
Both Big Carnelian Lake and Long Lake 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. Big Carnelian Lake (A) is materially cleaner than Long Lake (D). A gap that wide is unlikely to close in a single year of remediation work; it reflects multi-decade differences in the lakes themselves.
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.
Long Lake
Very murky, less than 2.8 ft of visibility.
Side-by-Side Metrics
| Metric | Big Carnelian Lake | Long Lake |
|---|---|---|
| Overall Grade | A (Excellent) | D (Poor) |
| Water Clarity | 15 ft | 2.8 ft |
| Phosphorus | No data | 47.5 µg/L |
| Chlorophyll-a (Algae) | No data | 26 µg/L |
| Maximum Depth | 66 ft | 60 ft |
| Surface Area | 457.03 acres | 1.8K acres |
| Public Access | Yes | Yes |
| Fish Species | 12 | 12 |
| 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 Long Lake's Grade D. Water clarity: 15 ft vs 2.8 ft. For fishing diversity, Big Carnelian Lake also leads with 12 species.