Mary Lake is a 230-acre cold, clear oligotrophic lake in Dickinson County, Michigan. Water quality is graded B based on 1 sampling years through 2022. Overall water quality is improving over recent sampling years. The lake supports 1 documented fish species including Lake herring. Public access is available with 1 public boat landing. Compared to the 5 other monitored lakes in Dickinson County, Mary Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Michigan DNR, last sampled 2022-09-05. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Good clarity, visible to about 13.8 ft. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 13.8 ft | B |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 230 acres |
| Public Access | Yes |
Where to stay near Mary Lake
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Fish Species
Click a species to see every graded lake where it is documented.
Fishing Mary Lake
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.88 m/yr | 2 |
Recreation & Access
Location & Depth Map
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.
County Ranking
Ranked #5 of 6 lakes in Dickinson County
Nearby Lakes in Dickinson County
Explore Mary Lake across LakeGrade
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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 B Lakes in Michigan
Marquette County · Clarity: 11.8 ft
Iron County · Clarity: 12.5 ft
Iron County · Clarity: 13 ft
Marquette County · Clarity: 12 ft
Marquette County · Clarity: 14.3 ft
Iron County · Clarity: 11 ft
Oligotrophic Lakes in Michigan
More records, surveys & data sources
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.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2022-09-05
Monitoring stations: 1