Mary Lake
Mary Lake in Lincoln County, Wisconsin is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 21 ft visibility. Maximum depth: 42 ft. Surface area: 25 acres.
- Clarity
- 21 ft
- Max depth
- 42 ft
- Area
- 25 acres
- Trend
- ↑ Improving
Next lake in Lincoln County
Why Mary Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Mary Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by WI DNR and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Mary Lake is a 25-acre lake in Lincoln County, Wisconsin with a maximum depth of 42 feet. Overall water quality is improving over recent sampling years. The lake supports 1 documented fish species including Largemouth Bass.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2023-07-24. Grade methodology: LakeGrade methodology.
Watch Mary Lake water quality
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Mary Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Crystal clear, you can see 21 ft down. Trophic State Index: 33.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 21 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 33 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Mary Lake
Compare lakeside cabins, hotels, and vacation rentals near Mary Lake in Lincoln County, Wisconsin — 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
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 42 ft |
| Surface Area | 25 acres |
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Mary Lake
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. 1 station on file (most recent sample 2023).
Fish Species (DNR-rated)
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Mary Lake covering fish populations, stocking, water quality, and management. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- 2025Pine Lake spring summary report, 2025Fisheries Survey · WI DNR · 2025 (PDF)
Water Quality Trend: ↑ Improving
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.929 m/yr | 6 |
| Phosphorus | ↑ Improving | -1.58 µg/L/yr | 7 |
EPA Impairment Status
Mary Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit WI10026794 · Official waterbody report · Matched by proximity (1.57 km)
Graded lakes near Mary Lake
Mary Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Lincoln County
Frequently asked questions about Mary Lake
What is the water quality grade for Mary Lake?
- Mary Lake in Lincoln County, Wisconsin is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 21 ft visibility. Maximum depth: 42 ft. Surface area: 25 acres.
Is Mary Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Mary Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
How deep is Mary Lake?
- Mary Lake has a maximum depth of 42 feet. The lake covers 25 acres.
What fish are in Mary Lake?
- Fish species found in Mary Lake include Largemouth Bass. Mary Lake is located in Lincoln County, Wisconsin.
Explore Mary Lake across LakeGrade
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Where this data comes from
2 measurements from 1 monitoring station, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX2 samples · 2023
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
Fish and recreation data from Wisconsin DNR Lakes