Margrethe Lake
Crawford County, Michigan1,920 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- Impaired · Mercury
- #1 of 3 in the county
- 65 ft max depth
- Public access
- Limited data
Margrethe Lake in Crawford County, Michigan has a water quality grade of A (Excellent). Water clarity: 16 ft visibility. Phosphorus: 8 µg/L. Chlorophyll-a (algae): 1 µg/L. Maximum depth: 65 ft. Surface area: 1919.7 acres.
- Clarity
- 16 ft
- Max depth
- 65 ft
- Area
- 1,920 acres
- Type
- Oligotrophic
- Trend
- → Stable
- Public access
- Yes
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Free interactive depth-contour map of Margrethe Lake, reaching a maximum surveyed depth of 65 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Michigan DNR.
Margrethe Lake is a 1,920-acre cold, clear oligotrophic lake in Crawford County, Michigan with a maximum depth of 65 feet. Water quality is graded A based on 2 sampling years through 2023. Water clarity is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 2 other monitored lakes in Crawford County, Margrethe Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2023-09-08. Grade methodology: LakeQuality methodology.
What Margrethe Lake is good for
From access and monitoring records, not editorial picks.
- Clear water16 ft of visibility
- Boat launch1 documented ramp
- Deep water65 ft surveyed max depth
- Big water1,920 acres
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. Margrethe Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pFAS. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Crystal clear, you can see 16 ft down. Phosphorus 8 µg/L. Chlorophyll-a 1 µg/L. TSI 34. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16 ft | Not graded |
| Phosphorus | 8 µg/L | Good |
| Chlorophyll-a (Algae) | 1 µg/L | Good |
| Trophic State Index (TSI) | 34 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 65 ft |
| Surface Area | 1,920 acres |
| Public Access | Yes |
Recreation & Access
- Lake Margrethe (South)Public
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Margrethe Lake
Water Quality Trend: → Stable
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.982 m/yr | 6 |
| Phosphorus | ↓ Declining | +0.35 µg/L/yr | 5 |
| Chlorophyll-a | → Stable | 0 µg/L/yr | 3 |
EPA Impairment Status
Margrethe 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 MI040601030104-04 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Margrethe Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Harrietta-Grayling Fish HatchGrayling · 4.5 mi away · NPDES MI0059209Recent 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.
County Ranking
Ranked #1 of 3 lakes in Crawford County
Nearby Lakes in Crawford County
Frequently asked questions about Margrethe Lake
Where is Margrethe Lake?
- Margrethe Lake is a lake in Crawford County, Michigan. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Margrethe Lake?
- Margrethe Lake in Crawford County, Michigan has a water quality grade of A (Excellent). Water clarity: 16 ft visibility. Phosphorus: 8 µg/L. Chlorophyll-a (algae): 1 µg/L. Maximum depth: 65 ft. Surface area: 1919.7 acres.
Is Margrethe Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Margrethe Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pFAS. Check local advisories before you swim.
How deep is Margrethe Lake?
- Margrethe Lake has a maximum depth of 65 feet. The lake covers 1919.7 acres.
Are there boat ramps on Margrethe Lake?
- Margrethe Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Lake Margrethe (South). Public access is listed as yes.
Explore Margrethe Lake across LakeQuality
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Low nutrients, clear water. The letter is not a swimming clearance.
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Where this data comes from
84 measurements from 1 monitoring station, 2016–2023. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- Michigan EGLE - MiCorps
21MICH_MICORPS84 samples · 2016–2023
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Named boat-access points from the USGS National Boat Ramps inventory