Lake Gratiot
Keweenaw County, Michigan1,453 acresView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- 70 ft max depth
- Public access
- Limited data
Lake Gratiot in Keweenaw County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 16.5 ft visibility. Maximum depth: 70 ft. Surface area: 1453.1 acres.
- Clarity
- 16.5 ft
- Max depth
- 70 ft
- Area
- 1,453 acres
- Trend
- → Stable
- Public access
- Yes
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Watch Lake Gratiot’s letter
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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.
Why Lake Gratiot has no grade
Lake Gratiot has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Lake Gratiot is Not Rated — not an F. Its 16.5-foot median from 72 readings collected 2016–2022 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. 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.
Lake Gratiot is a 1,453-acre lake in Keweenaw County, Michigan with a maximum depth of 70 feet. Water clarity is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2022-09-13. Grade methodology: LakeQuality methodology.
What Lake Gratiot is good for
From access and monitoring records, not editorial picks.
- Clear water16.5 ft of visibility
- Boat launch1 documented ramp
- Deep water70 ft surveyed max depth
- Big water1,453 acres
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Lake Gratiot
These readings exist but are not enough for an A–F grade — see why.
Crystal clear, you can see 16.5 ft down. TSI 37.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 70 ft |
| Surface Area | 1,453 acres |
| Public Access | Yes |
Recreation & Access
- Gratiot LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Lake Gratiot
Water Quality Trend: → Stable
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.868 m/yr | 7 |
| Phosphorus | ↓ Declining | +0.54 µg/L/yr | 7 |
Graded lakes near Lake Gratiot
Lake Gratiot has no grade, but these lakes within a short drive do.
Nearby Lakes in Keweenaw County
Frequently asked questions about Lake Gratiot
Where is Lake Gratiot?
- Lake Gratiot is a lake in Keweenaw County, Michigan. LakeQuality has not rated this lake (UNRATED) — 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.
What is the water quality grade for Lake Gratiot?
- Lake Gratiot in Keweenaw County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 16.5 ft visibility. Maximum depth: 70 ft. Surface area: 1453.1 acres.
Is Lake Gratiot safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
How deep is Lake Gratiot?
- Lake Gratiot has a maximum depth of 70 feet. The lake covers 1453.1 acres.
Are there boat ramps on Lake Gratiot?
- Lake Gratiot has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Gratiot Lake. Public access is listed as yes.
Explore Lake Gratiot across LakeQuality
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Where this data comes from
72 measurements from 1 monitoring station, 2016–2022. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- North American Lake Management Society
NALMS72 samples · 2016–2022
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
Named boat-access points from the USGS National Boat Ramps inventory