Thumb Lake
Thumb Lake in Charlevoix County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 17 ft visibility. Maximum depth: 152 ft. Surface area: 507.5 acres.
- Clarity
- 17 ft
- Max depth
- 152 ft
- Area
- 508 acres
- Public access
- Yes
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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.
Why Thumb Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Thumb Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by EGLE and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Thumb Lake is a 508-acre lake in Charlevoix County, Michigan with a maximum depth of 152 feet. The lake supports 3 documented fish species including Blacknose shiner, Rock bass, and Smallmouth bass. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2022-08-26. Grade methodology: LakeQuality methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Thumb Lake
These readings exist but are not enough for an A–F grade — see why.
Crystal clear, you can see 17 ft down. Trophic State Index: 36.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 17 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 36 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Thumb Lake
Compare lakeside cabins, hotels, and vacation rentals near Thumb Lake in Charlevoix 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 Thumb Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 152 ft |
| Surface Area | 508 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Thumb LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Thumb Lake
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
Graded lakes near Thumb Lake
Thumb Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Charlevoix County
Frequently asked questions about Thumb Lake
Where is Thumb Lake?
- Thumb Lake is a lake in Charlevoix County, Michigan. LakeQuality has not rated this lake (UNRATED) — there is not enough recent sampling to assign a letter.
What is the water quality grade for Thumb Lake?
- Thumb Lake in Charlevoix County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 17 ft visibility. Maximum depth: 152 ft. Surface area: 507.5 acres.
Is Thumb Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Thumb Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
How deep is Thumb Lake?
- Thumb Lake has a maximum depth of 152 feet. The lake covers 507.5 acres.
What fish are in Thumb Lake?
- Fish species found in Thumb Lake include Blacknose shiner, Rock bass, Smallmouth bass. Thumb Lake is located in Charlevoix County, Michigan.
Are there boat ramps on Thumb Lake?
- Thumb Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Thumb Lake. Public access is listed as yes.
Explore Thumb Lake across LakeQuality
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Where this data comes from
13 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- North American Lake Management Society
NALMS13 samples · 2022
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory