Mary Lake
Wright County, Minnesota190 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Mary Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Impaired biota (cause unknown)
- 46 ft max depth
- Public access
Mary Lake in Wright County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 8.9 ft visibility. Phosphorus: 21 µg/L. Chlorophyll-a (algae): 8.3 µg/L. Maximum depth: 46 ft. Surface area: 189.97 acres.
Minnesota DNR's Targeted Survey on July 22, 2024 caught 3.00 walleye per gill net at Mary Lake. DNR survey details →
Mary Lake is a 190-acre mesotrophic lake in Wright County, Minnesota with a maximum depth of 46 feet (18-foot average). Overall water quality is declining over recent sampling years. The lake supports 13 documented fish species including black crappie, bluegill, and brown bullhead. Public access is available. Compared to the 50 other monitored lakes in Wright County, Mary Lake ranks #19 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-17. Methodology: how these readings are compared.
What Mary Lake is good for
From access and monitoring records, not editorial picks.
- Fishing13 species recorded
- Ice seasonIce-out around Apr 9
- Deep water46 ft surveyed max depth
Swimming conditions
Readings onlyModerate algae
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Mary Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury. Check local advisories before you swim.
Whether Mary Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Mary Lake
These are the measurements Minnesota PCA publishes for Mary Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 8.9 ft. Phosphorus 21 µg/L. Chlorophyll-a 8.3 µg/L. TSI 48.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 8.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 21µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 8.3µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 48 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Mary Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Mary Lake typically sits around 60°F at the surface in October. Summer average is about 62°F. Usually warmest in Sep (about 64°F) and coldest in May (about 53°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (53°F) to its warmest (64°F).
Typical surface water temperature by month, from 145 field readings (2011–2023) via the EPA Water Quality Portal. See the full Mary Lake water temperature breakdown →
Minnesota DNR's Targeted Survey on July 22, 2024 caught 3.00 walleye per gill net at Mary Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mary Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
9 surveys on file from MN DNR Fisheries. Most recent: 2024-07-22 (Targeted Survey).
9 surveys on file · most recent 2024-07-22 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 47.53 | 3–8 in 2024-07-22 | 0.15 lb |
| Green Sunfish | 12.36 | 3–5 in 2024-07-22 | 0.11 lb |
| Yellow Bullhead | 10.19 | 8–11 in 2024-07-22 | 0.84 lb |
| Largemouth Bass | 9.92 | 6–26 in 2024-07-22 | 0.68 lb |
| Yellow Perch | 7.07 | 1–7 in 2024-07-22 | 0.12 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Bluegill
Green Sunfish
Yellow Bullhead
Largemouth Bass
From the 2024-07-22 survey
A targeted survey of nearshore fish species in Mary Lake was conducted beginning on July 22nd, 2024, by Index of Biological Integrity (IBI) Program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine, where possible.…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Mary Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — MaryFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — MaryFish Stocking History · MN DNR LakeFinder
Lake Details
Max depth
46 ft
Average depth
17.8 ft
Surface area
190 acres
Shoreline
2.3 mi
Littoral zone
45%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
1 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,004 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Mary Lake
Compare lakeside cabins, hotels, and vacation rentals near Mary Lake in Wright County, Minnesota — 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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Fish Species
Click a species to see every lake where it is documented.
Fishing Mary Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Improving-0.51 µg/L/yr6 years
Chlorophyll-a
Worsening+0.41 µg/L/yr6 years
Ice season
Typical ice-out
Apr 9
Earliest Mar 3, 1990 · Latest May 2, 2018
Typical ice-in
Dec 1
Earliest Nov 15, 1991 · Latest Dec 20, 2001
Most recent ice-out
Apr 19
2023
170 observations · Minnesota PCA ice records
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
Designated uses not supporting: Aquatic life, Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN86-0193-00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Mary Lake under Clean Water Act (NPDES) discharge permits.
- Tioga Dairy LlcWaverly · 3.6 mi away · NPDES MN0064041
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.
Nearby Lakes in Wright County
Frequently asked questions about Mary Lake
Where is Mary Lake?
- Mary Lake is a lake in Wright County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Mary Lake?
- Mary Lake in Wright County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 8.9 ft visibility. Phosphorus: 21 µg/L. Chlorophyll-a (algae): 8.3 µg/L. Maximum depth: 46 ft. Surface area: 189.97 acres.
Is Mary Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Mary Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury. Check local advisories before you swim.
What is the water temperature of Mary Lake?
- Mary Lake typically sits around 60°F at the surface in October, from 145 EPA Water Quality Portal field readings (2011–2023). That is a typical value for the month, not a live reading.
How deep is Mary Lake?
- Mary Lake has a maximum depth of 46 feet and an average depth of 17.8 feet. The lake covers 189.97 acres.
What fish are in Mary Lake?
- Fish species found in Mary Lake include black crappie, bluegill, brown bullhead, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. Mary Lake is located in Wright County, Minnesota.
What did the DNR fisheries survey find at Mary Lake?
- Minnesota DNR's Targeted Survey on July 22, 2024 caught 3.00 walleye per gill net at Mary Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mary Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does Mary Lake thaw?
- Mary Lake typically has ice-out around Apr 9. Ice typically forms around Dec 1. The open water season is approximately 236 days.
Can I fish at Mary Lake?
- Public access to Mary Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Mary Lake across LakeQuality
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Where this data comes from
161 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA161 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate