Siskiwit Lake is a mesotrophic lake in Keweenaw County, Michigan. Water quality is graded A based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. The lake supports 2 documented fish species including Lake herring and Lake whitefish. Compared to the 18 other monitored lakes in Keweenaw County, Siskiwit Lake ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, Michigan DNR, last sampled 2024-07-26. Grade methodology: LakeGrade methodology.
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 19.3 ft down. Phosphorus level: 24.5 µg/L. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 19.3 ft | A |
| Phosphorus | 24.5 µg/L | B |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Siskiwit Lake
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Fish Species
Click a species to see every graded lake where it is documented.
Fishing Siskiwit Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.067 m/yr | 5 |
| Phosphorus | ↓ Declining | +8.9 µg/L/yr | 2 |
Water Temperature
Siskiwit Lake averages about 52°F at the surface in summer, usually warmest in Aug (about 55°F) and coldest in Jun (about 49°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 1,747 field readings (2010–2024) via the EPA Water Quality Portal. See the full Siskiwit Lake water temperature breakdown →
Location
County Ranking
Ranked #9 of 19 lakes in Keweenaw County
Nearby Lakes in Keweenaw County
Explore Siskiwit Lake across LakeGrade
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Fish species and best lakes in Keweenaw County
Species activity outlook by water temperature and season
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Moderate nutrients, good water quality
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Other Grade A Lakes in Michigan
Iron County · Clarity: 20 ft
Iron County · Clarity: 20 ft
Gogebic County · Clarity: 15.7 ft
Gogebic County · Clarity: 18 ft
Gogebic County · Clarity: 18 ft
Iron County · Clarity: 15.5 ft
Mesotrophic Lakes in Michigan
More records, surveys & data sources
EPA Impairment Status
Siskiwit Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MI040203000001-02 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2024-07-26
Monitoring stations: 1