Feldtmann Lake is a mesotrophic lake in Keweenaw County, Michigan. Water quality is graded B based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. The lake supports 3 documented fish species including Northern pike, White sucker, and Yellow perch. Compared to the 18 other monitored lakes in Keweenaw County, Feldtmann Lake ranks #12 for water quality.
Source: EPA Water Quality Portal sampling records, Michigan DNR, last sampled 2024-08-19. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Moderate clarity, visible to about 7.3 ft. Phosphorus level: 14.2 µg/L. Trophic State Index: 45.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 7.3 ft | C |
| Phosphorus | 14.2 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 45 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Feldtmann Lake
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Fish Species
Click a species to see every graded lake where it is documented.
Fishing Feldtmann Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.039 m/yr | 5 |
| Phosphorus | ↓ Declining | +2.2 µg/L/yr | 5 |
Water Temperature
Feldtmann Lake averages about 69°F at the surface in summer, usually warmest in Jul (about 71°F) and coldest in May (about 49°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 424 field readings (2010–2024) via the EPA Water Quality Portal. See the full Feldtmann Lake water temperature breakdown →
Location
County Ranking
Ranked #12 of 19 lakes in Keweenaw County
Cleaner Lakes Within 30 Miles
Feldtmann Lake holds Grade B. 2 nearby lakes hold higher grades.
- ASiskiwit LakeKeweenaw County · 20.5 mi · Higher grade (B → A)
- ALake HarveyKeweenaw County · 22.2 mi · Higher grade (B → A)
Nearby Lakes in Keweenaw County
Explore Feldtmann Lake across LakeGrade
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Moderate nutrients, good water quality
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Other Grade B Lakes in Michigan
Gogebic County · Clarity: 10.3 ft
Gogebic County · Clarity: 12 ft
Gogebic County · Clarity: 11.5 ft
Gogebic County · Clarity: 11.5 ft
Gogebic County · Clarity: 12 ft
Gogebic County · Clarity: 9.5 ft
Mesotrophic Lakes in Michigan
More records, surveys & data sources
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2024-08-19
Monitoring stations: 1