Little Mary Lake
Wright County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Little Mary Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- Eurasian watermilfoil
- 35 ft max depth
- Public access
- Limited data
Little Mary Lake in Wright County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 1.5 ft visibility. Phosphorus: 160 µg/L. Chlorophyll-a (algae): 85.4 µg/L.
Little Mary Lake is a highly nutrient-loaded hypereutrophic lake in Wright County, Minnesota with an estimated average depth of about 35 feet. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 50 other monitored lakes in Wright County, Little Mary Lake ranks #46 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-10-12. Methodology: how these readings are compared.
What Little Mary Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
Readings onlyRecreation use not supported
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. Little Mary Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Little 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 Little Mary Lake
These are the measurements Minnesota PCA publishes for Little Mary Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 1.5 ft of visibility. Phosphorus 160 µg/L. Chlorophyll-a 85.4 µg/L. TSI 74.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 160µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 85.4µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 74 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Little Mary Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Little Mary Lake typically sits around 57°F at the surface in October. Summer average is about 72°F. Usually warmest in Jul (about 74°F) and coldest in Oct (about 57°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (57°F) to its warmest (74°F).
Typical surface water temperature by month, from 181 field readings (2022–2022) via the EPA Water Quality Portal. See the full Little Mary Lake water temperature breakdown →
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Little Mary Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Aquatic Plant Report — Little Mary (North Bay) (2020)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — Little Mary (North Bay)Public Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
~35 ft est.
Public access
Yes
Listed by Minnesota PCA
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Little Mary Lake.
Lake Size & Watershed
Watershed (drainage) area
41 sq mi
HydroLAKES / HydroSHEDS
Surface area
106 acres
HydroLAKES / HydroSHEDS
Shoreline
2.5 mi
HydroLAKES / HydroSHEDS
Elevation
958 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Lake Maria State ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Little Mary Lake
Compare lakeside cabins, hotels, and vacation rentals near Little 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Little Mary Lake are listed below.
Top-rated places to stay near Little Mary Lake
Prices for Oct 9–11, 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 Minnesota’s top lakes →
Follow Little Mary Lake’s readings
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Fishing Little Mary Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
EPA Impairment Status
Little 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: Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN86-0139-02 · Official waterbody report
Nearby Lakes in Wright County
Frequently asked questions about Little Mary Lake
Where is Little Mary Lake?
- Little 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 Little Mary Lake?
- Little Mary Lake in Wright County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 1.5 ft visibility. Phosphorus: 160 µg/L. Chlorophyll-a (algae): 85.4 µg/L.
Is Little Mary Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Little Mary Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Little Mary Lake?
- Little Mary Lake typically sits around 57°F at the surface in October, from 181 EPA Water Quality Portal field readings (2022–2022). That is a typical value for the month, not a live reading.
How deep is Little Mary Lake?
- No published bathymetric survey covers Little Mary Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 35 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on Little Mary Lake?
- Little Mary Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Lake Maria State Park. Public access is listed as yes.
Can I fish at Little Mary Lake?
- Little Mary Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. 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 Little Mary Lake across LakeQuality
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Where this data comes from
79 measurements from 2 monitoring stations, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA79 samples · 2022
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (2)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory