Marion Lake vs Preston Lake
Water quality, depth, fish species, and recreation comparison.
Marion Lake and Preston Lake both received the same overall water quality grade of F (Very Poor). Both are in Minnesota.
Both Marion Lake and Preston 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. These two are within a letter of each other on the rubric — Marion Lake (F) versus Preston Lake (F). 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.
Marion Lake
No clarity data.
Preston Lake
Murky, only visible to about 5 ft.
Side-by-Side Metrics
| Metric | Marion Lake | Preston Lake |
|---|---|---|
| Overall Grade | F (Very Poor) | F (Very Poor) |
| Water Clarity | No data | 5 ft |
| Phosphorus | 71 µg/L | 222 µg/L |
| Chlorophyll-a (Algae) | 73 µg/L | 39.2 µg/L |
| Maximum Depth | 15.2 ft | 11 ft |
| Surface Area | 520 acres | 655 acres |
| Public Access | Yes | Yes |
| Fish Species | 13 | 13 |
| Trophic State | eutrophic | eutrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Both lakes earn the same Grade F. The tiebreakers come down to what you want from the lake. Marion Lake matches its peer on species count.
Source: EPA National Aquatic Resource Surveys, 2026.