Gratiot Lake vs Siskiwit Lake
Water quality, depth, fish species, and recreation comparison.
Siskiwit Lake reads lower on nutrients and algae than Gratiot Lake. Both are in Keweenaw County, Michigan.
Gratiot Lake and Siskiwit Lake are both in Michigan — a same-state head-to-head where the comparison comes down to lake-specific differences in depth, watershed, and monitoring history rather than the broader state-level water-quality regime. The readings are close: Gratiot Lake and Siskiwit Lake sit within a narrow band of each other on phosphorus, chlorophyll-a and clarity. The per-parameter table below shows where the small differences actually live.
With readings 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.
Gratiot Lake
Crystal clear, you can see 17 ft down.
Siskiwit Lake
Crystal clear, you can see 20.5 ft down.
Side-by-Side Metrics
| Metric | Gratiot Lake | Siskiwit Lake |
|---|---|---|
| Water Clarity | 17 ft | 20.5 ft Better |
| Phosphorus | 9 µg/L | 4.4 µg/L Better |
| Chlorophyll-a (Algae) | No data | No data |
| Maximum Depth | 70 ft | - |
| Surface Area | 1,453 acres | 4,008 acres |
| Public Access | Unknown | Unknown |
| Fish Species | 1 | 2 Better |
| Trophic State | oligotrophic | 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
Gratiot Lake and Siskiwit Lake read the same on nutrients and algae overall. The tiebreakers come down to clarity (Gratiot Lake: 17 ft, Siskiwit Lake: 20.5 ft) and what you want from the lake. Gratiot Lake has fewer fish species than Siskiwit Lake.
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Where to stay near Gratiot Lake and Siskiwit Lake
Compare cabins, hotels, and vacation rentals around Gratiot Lake and Siskiwit Lake. Both lakes are pinned on the map, so you can see which stays sit nearer the one you pick. Switch to Satellite to see how close each is to the water.
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Source: EPA National Aquatic Resource Surveys, 2026.