Mary Lake
Dickinson County, Michigan230 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- Impaired · Mercury
- #3 of 9 in the county
- Public access
- Limited data
Mary Lake in Dickinson County, Michigan has a water quality grade of A (Excellent). Water clarity: 14.5 ft visibility. Phosphorus: 8 µg/L. Chlorophyll-a (algae): 1.8 µg/L. Surface area: 230 acres.
- Clarity
- 14.5 ft
- Area
- 230 acres
- Type
- Oligotrophic
- Phosphorus
- 8 µg/L
- Chlorophyll-a
- 1.8 µg/L
- Trend
- ↓ Declining
- Public access
- Yes
Stays via Stay22
Stays near Mary Lake
Compare lakeside cabins, hotels, and vacation rentals near Mary Lake in Dickinson 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 Mary Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Michigan’s top lakes →
Watch Mary Lake’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Mary Lake is a 230-acre cold, clear oligotrophic lake in Dickinson County, Michigan. Water quality is graded A based on 2 sampling years through 2022. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 8 other monitored lakes in Dickinson County, Mary Lake ranks #3 for water quality.
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
- Boat launch1 documented ramp
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The A is nutrients and algae, 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 Grade: A (Excellent)
Good clarity, visible to about 14.5 ft. Phosphorus 8 µg/L. Chlorophyll-a 1.8 µg/L. TSI 36. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 14.5 ft | Not graded |
| Phosphorus | 8 µg/L | Good |
| Chlorophyll-a (Algae) | 1.8 µg/L | Good |
| Trophic State Index (TSI) | 36 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 230 acres |
| Public Access | Yes |
No bathymetric survey has been published for Mary Lake, so its depth is not documented here.
Recreation & Access
- Lake Mary ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
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 · Matched by proximity (0.24 km)
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 (2.48 km)
County Ranking
Ranked #3 of 9 lakes in Dickinson County
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 grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Mary Lake?
- Mary Lake in Dickinson County, Michigan has a water quality grade of A (Excellent). Water clarity: 14.5 ft visibility. Phosphorus: 8 µg/L. Chlorophyll-a (algae): 1.8 µg/L. Surface area: 230 acres.
Is Mary Lake safe to swim in?
- The A is nutrients and algae, 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.
Are there boat ramps on Mary Lake?
- Mary Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Lake Mary Park. Public access is listed as yes.
Explore Mary Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
7.3 mi away
Fish species and top-graded lakes across Michigan
Fish species and best lakes in Dickinson County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Upper Peninsula area
Where to stay at Michigan's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
Michigan's cleanest and most-polluted lakes, ranked
More Michigan Lake Rankings
Other Grade A Lakes in Michigan
Oligotrophic Lakes in Michigan
Where this data comes from
76 measurements from 1 monitoring station, 2016–2022. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- Michigan EGLE - MiCorps
21MICH_MICORPS76 samples · 2016–2022
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
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
Named boat-access points from the USGS National Boat Ramps inventory