Mary Lake vs Ruth Lake
Water quality, depth, fish species, and recreation comparison.
Ruth Lake reads lower on nutrients and algae than Mary Lake. Both are in Crow Wing County, Minnesota.
Both Mary Lake and Ruth Lake sit in Minnesota. A same-state comparison strips out the state-level water-quality regime as a variable: any differences in the readings here are about the lakes themselves, not the agencies sampling them. Ruth Lake reads materially cleaner than Mary Lake on nutrients and algae. 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 gap in the readings is decisive: Ruth Lake has the lower nutrient and algae numbers. For a researcher, the gap is the interesting part: what is different about the two watersheds, and which of those differences is mutable?
Mary Lake
Murky, only visible to about 4.9 ft.
Ruth Lake
Crystal clear, you can see 16 ft down.
Side-by-Side Metrics
| Metric | Mary Lake | Ruth Lake |
|---|---|---|
| Water Clarity | 4.9 ft | 16 ft Better |
| Phosphorus | 20.5 µg/L | 11 µg/L Better |
| Chlorophyll-a (Algae) | 8.8 µg/L | 2.7 µg/L Better |
| Maximum Depth | 34 ft | 39 ft Better |
| Surface Area | 413 acres | 599 acres |
| Public Access | No | Yes |
| Fish Species | 13 Better | 12 |
| Trophic State | eutrophic | oligotrophic |
A green ✓ marks the better value for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better). Surface area and trophic state carry no tick — a bigger lake is not a better lake.
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Verdict
Ruth Lake reads lower on nutrients and algae than Mary Lake. Water clarity: 16 ft vs 4.9 ft. For more fish-species variety, Mary Lake edges ahead with 13 documented species.
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Source: EPA National Aquatic Resource Surveys, 2026.