Lake Gratiot is a cold, clear oligotrophic lake in Keweenaw County, Michigan. Water quality is graded A based on 1 sampling years through 2022. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 18 other monitored lakes in Keweenaw County, Lake Gratiot ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Michigan DNR, last sampled 2022-09-13. 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 17.8 ft down. Trophic State Index: 36.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 17.8 ft | A |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 36 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Lake Gratiot
Compare lakeside cabins, hotels, and vacation rentals near Lake Gratiot in Keweenaw County, Michigan — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Lake Gratiot
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Fishing Lake Gratiot
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +4.495 m/yr | 3 |
Recreation & Access
Location & Depth Map
Free interactive depth-contour map of Lake Gratiot, reaching a maximum surveyed depth of 70 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Michigan DNR.
County Ranking
Ranked #1 of 19 lakes in Keweenaw County
Nearby Lakes in Keweenaw County
Explore Lake Gratiot 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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Low nutrients, clear water, excellent for swimming
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Other Grade A Lakes in Michigan
Iron County · Clarity: 18 ft
Iron County · Clarity: 17 ft
Marquette County · Clarity: 15.3 ft
Iron County · Clarity: 21 ft
Iron County · Clarity: 19.5 ft
Iron County · Clarity: 18 ft
Oligotrophic 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
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2022-09-13
Monitoring stations: 1