Big Lake vs W Two Rivers Reservoir
Water quality, depth, fish species, and recreation comparison.
Big Lake has a higher water quality grade (A, Excellent) than W Two Rivers Reservoir (C, Fair). Both are in St. Louis County, Minnesota.
Both Big Lake and W Two Rivers Reservoir 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 meaningfully apart: Big Lake grades a A while W Two Rivers Reservoir 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 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 Lake
Moderate clarity, visible to about 8.2 ft.
W Two Rivers Reservoir
Murky, only visible to about 6.4 ft.
Side-by-Side Metrics
| Metric | Big Lake | W Two Rivers Reservoir |
|---|---|---|
| Overall Grade | A (Excellent) | C (Fair) |
| Water Clarity | 8.2 ft | 6.4 ft |
| Phosphorus | 14 µg/L | 29 µg/L |
| Chlorophyll-a (Algae) | 4.9 µg/L | 5.5 µg/L |
| Maximum Depth | 22 ft | 27 ft |
| Surface Area | 1,904 acres | 967 acres |
| Public Access | Yes | Yes |
| Fish Species | 8 | 0 |
| Trophic State | mesotrophic | eutrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Big Lake wins on overall water quality with a Grade A versus W Two Rivers Reservoir's Grade C. Water clarity: 8.2 ft vs 6.4 ft. For fishing diversity, Big Lake also leads with 8 species.
Source: EPA National Aquatic Resource Surveys, 2026.