Thumb Lake is a cold, clear oligotrophic lake in Charlevoix County, Michigan. Water quality is graded A based on 1 sampling years through 2022. The lake supports 3 documented fish species including Blacknose shiner, Rock bass, and Smallmouth bass. Public access is available with 1 public boat landing. Compared to the 18 other monitored lakes in Charlevoix County, Thumb Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Michigan DNR, last sampled 2022-08-26. 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 17 ft down. Trophic State Index: 36.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 17 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 Thumb Lake
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Fish Species
Click a species to see every graded lake where it is documented.
Fishing Thumb Lake
Recreation & Access
Location & Depth Map
Free interactive depth-contour map of Thumb Lake, reaching a maximum surveyed depth of 152 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Michigan DNR.
County Ranking
Ranked #3 of 19 lakes in Charlevoix County
Nearby Lakes in Charlevoix County
Explore Thumb Lake across LakeGrade
Fish species and top-graded lakes across Michigan
Fish species and best lakes in Charlevoix County
Species activity outlook by water temperature and season
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Where to stay at Michigan's top lakes, each with its grade
Low nutrients, clear water, excellent for swimming
Michigan's cleanest and most-polluted lakes, ranked
More Michigan Lake Rankings
Other Grade A Lakes in Michigan
Oligotrophic Lakes in Michigan
More records, surveys & data sources
EPA Impairment Status
Thumb Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MI040700040103-04 · 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
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2022-08-26
Monitoring stations: 1