Portage Lake vs Six Mile Lake
Water quality, depth, fish species, and recreation comparison.
Six Mile Lake reads lower on nutrients and algae than Portage Lake. Both are in Cass County, Minnesota.
Both Portage Lake and Six Mile 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. The readings are meaningfully apart: Six Mile Lake carries clearly lower phosphorus and chlorophyll-a readings than Portage Lake. A spread that wide reflects real underlying differences, in watershed inputs, depth profiles, or monitoring rigor.
For a recreational visitor, the wider gap in the readings is decisive: Six Mile 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?
Portage Lake
Moderate clarity, visible to about 7.5 ft.
Six Mile Lake
Good clarity, visible to about 11.5 ft.
Side-by-Side Metrics
| Metric | Portage Lake | Six Mile Lake |
|---|---|---|
| Water Clarity | 7.5 ft | 11.5 ft Better |
| Phosphorus | 22 µg/L | 14.5 µg/L Better |
| Chlorophyll-a (Algae) | 7.1 µg/L | 6.7 µg/L Better |
| Maximum Depth | 55 ft | 68 ft Better |
| Surface Area | 1,539 acres | 1,323 acres |
| Public Access | Yes | Yes |
| Fish Species | 15 | 16 Better |
| Trophic State | mesotrophic | mesotrophic |
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
Six Mile Lake reads lower on nutrients and algae than Portage Lake. Water clarity: 11.5 ft vs 7.5 ft. For fishing diversity, Six Mile Lake also leads with 16 species.
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Source: EPA National Aquatic Resource Surveys, 2026.