Mary Lake
Dickinson County, Michigan230 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.
- Impaired · Mercury
- 80 ft max depth
- Limited data
Mary Lake in Dickinson County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 14.5 ft visibility. Maximum depth: 80 ft. Surface area: 230 acres.
- Clarity
- 14.5 ft
- Max depth
- 80 ft
- Area
- 230 acres
- Trend
- ↓ Declining
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Watch Mary Lake’s letter
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Free interactive depth-contour map of Mary Lake, reaching a maximum surveyed depth of 80 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Michigan DNR.
Why Mary Lake has no grade
Mary Lake 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, Mary Lake is Not Rated — not an F. Its 14.5-foot median from 64 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.
Mary Lake is a 230-acre lake in Dickinson County, Michigan with a maximum depth of 80 feet. Overall water quality is declining over recent sampling years. The lake supports 1 documented fish species including Lake herring.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2022-09-05. Grade methodology: LakeQuality methodology.
What Mary Lake is good for
From access and monitoring records, not editorial picks.
- Clear water14.5 ft of visibility
- Deep water80 ft surveyed max depth
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Mary Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Water quality measurements for Mary Lake
These readings exist but are not enough for an A–F grade — see why.
Good clarity, visible to about 14.5 ft. TSI 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 14.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 80 ft |
| Surface Area | 230 acres |
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Mary Lake
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.02 m/yr | 6 |
| Phosphorus | ↓ Declining | +0.96 µg/L/yr | 4 |
Reservoir Info (USACE NID)
Mary Lake is a man-made reservoir impounded by the Mary Lake Dam, built primarily for other on the Hamilton Creek; concrete-type dam, 7 ft tall and 237 ft long.
- Surface area
- 230 ac
- Normal storage
- 350 ac-ft
- Max storage
- 764 ac-ft
- Drainage area
- 15.1 sq mi
- Hazard class
- Low
- Owner
- Waucedah Township
Source: USACE National Inventory of Dams, NID ID MI01247 · Operator website
EPA Impairment Status
Mary Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MI040301080407-01 · Official waterbody report · Matched by proximity (2.58 km)
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Mary Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Norway WwtpNorway · 4.5 mi away · NPDES MI0020214Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Graded lakes near Mary Lake
Mary Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Dickinson County
Frequently asked questions about Mary Lake
Where is Mary Lake?
- Mary Lake is a lake in Dickinson 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 Mary Lake?
- Mary Lake in Dickinson County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 14.5 ft visibility. Maximum depth: 80 ft. Surface area: 230 acres.
Is Mary Lake safe to swim in?
- The letter is not a swimming clearance. Mary Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
How deep is Mary Lake?
- Mary Lake has a maximum depth of 80 feet. The lake covers 230 acres.
What fish are in Mary Lake?
- Fish species found in Mary Lake include Lake herring. Mary Lake is located in Dickinson County, Michigan.
Explore Mary Lake across LakeQuality
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7.3 mi away
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Where this data comes from
64 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
NALMS64 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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)