Little Mary Lake
Little Mary Lake in Wright County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1.5 ft visibility. Phosphorus: 160 µg/L. Chlorophyll-a (algae): 85.4 µg/L.
- Clarity
- 1.5 ft
- Typical in August
- 72°F
- Mean depth
- ~11 ft est.
- Type
- Hypereutrophic
- Public access
- Yes
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Little Mary Lake →
Next lake in Wright County
Little Mary Lake is a highly nutrient-loaded hypereutrophic lake in Wright County, Minnesota with an estimated average depth of about 11 feet. Water quality is graded F based on 2 sampling years through 2022. 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. Grade methodology: LakeGrade methodology.
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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.
Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.5 ft of visibility. Phosphorus level: 160 µg/L. Chlorophyll-a: 85.4 µg/L. Trophic State Index: 74.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.5 ft | Not graded |
| Phosphorus | 160 µg/L | Poor |
| Chlorophyll-a (Algae) | 85.4 µg/L | Poor |
| Trophic State Index (TSI) | 74 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay 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 grade measures nutrients and algae, not lodging — cabins and rentals around Little Mary Lake are listed below.
Top-rated places to stay near Little Mary Lake
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 →
Water Temperature
Little Mary Lake typically sits around 72°F at the surface in August. 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.
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 →
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~11 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Minnesota has not published bathymetry for Little Mary Lake.
Lake Size & Watershed
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
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.
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
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN86-0139-01 · Official waterbody report · Matched by proximity (0.38 km)
County Ranking
Ranked #46 of 51 lakes in Wright County
Nearby Lakes With Higher Grades
Little Mary Lake holds Grade F. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Wright County
Frequently asked questions about Little Mary Lake
What is the water quality grade for Little Mary Lake?
- Little Mary Lake in Wright County, Minnesota has a water quality grade of F (Algae-prone). 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?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Little Mary Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 85.4 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Little Mary Lake?
- Little Mary Lake typically sits around 72°F at the surface in August, 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 11 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.
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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)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory