Prairie Lake
St. Louis County, Minnesota794 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Prairie Lake. Here is what has been measured.
- Impaired · Mercury
- 47 ft max depth
- Public access
- Limited data
Prairie Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 5 ft visibility. Maximum depth: 47 ft. Surface area: 794.33 acres.
Minnesota DNR's Targeted Survey on August 13, 2025 caught 0.07 walleye per fyke net at Prairie Lake. Length samples in the latest survey that recorded them ran 7–24 inches. DNR survey details →
Prairie Lake is a 794-acre lake in St. Louis County, Minnesota with a maximum depth of 47 feet. The lake supports 15 documented fish species including black crappie, bluegill, and bowfin (dogfish). Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-04. Methodology: how these readings are compared.
Prairie Lake covers about 790 acres in St. Louis County. It has one public boat landing. The median ice-out date is April 21, which is when the open-water season begins. If you are planning to stay, you can search lake houses and cabins around Prairie Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Prairie Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing15 species recorded
- Ice seasonIce-out around Apr 21
- Deep water47 ft surveyed max depth
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Prairie Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Whether Prairie 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 Prairie Lake
These are the measurements Minnesota PCA publishes for Prairie Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 5 ft. TSI 54.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 54 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Prairie Lake
Answers come straight from the public measurements and survey records on this page.
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Prairie Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was low (7,870 cells/mL) on May 16, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Targeted Survey on August 13, 2025 caught 0.07 walleye per fyke net at Prairie Lake. Length samples in the latest survey that recorded them ran 7–24 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Prairie Lake’s water-quality measurements separately, and the water-quality trend over 4 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2025-08-13 (Targeted Survey).
8 surveys on file · most recent 2025-08-13 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Yellow Perch | 16.03 | 4–9 in 2023-08-21 | 0.16 lb |
| Golden Shiner | 12.44 | ||
| Walleye | 6.33 | 7–24 in 2023-08-21 | 1.18 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.
Yellow Perch
Walleye
From the 2025-08-13 survey
A targeted survey of nearshore fish species in Prairie Lake was conducted on August 13th-20th, 2025, by Lake Biological Monitoring and Assessment (LBMA) program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing, mini-fyke nets, and seining with a 50-foot or…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Prairie Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — PrairieFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Prairie (1873)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — PrairieFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — PrairiePublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
47 ft
Surface area
794 acres
Shoreline
8.2 mi
Littoral zone
34%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
36 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,266 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Prairie LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Prairie Lake
Compare lakeside cabins, hotels, and vacation rentals near Prairie Lake in St. Louis 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 Prairie 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 Prairie Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Prairie Lake
Water Quality Trend: Stable
Based on 4 years of monitoring (2020–2025).
Water clarity
Stable4 years
Ice season
Typical ice-out
Apr 21
Earliest Apr 12, 2015 · Latest Apr 30, 2008
Typical ice-in
Nov 29
Earliest Nov 19, 2018 · Latest Nov 29, 2007
Most recent ice-out
Apr 12
2015
6 observations · Minnesota PCA ice records
EPA Impairment Status
Prairie 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: Fish consumption.
Source: EPA ATTAINS assessment unit MN69-0848-00 · Official waterbody report
Nearby Lakes in St. Louis County
Frequently asked questions about Prairie Lake
Where is Prairie Lake?
- Prairie Lake is a lake in St. Louis County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Prairie Lake?
- Prairie Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 5 ft visibility. Maximum depth: 47 ft. Surface area: 794.33 acres.
Is Prairie Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Prairie Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
How deep is Prairie Lake?
- Prairie Lake has a maximum depth of 47 feet. The lake covers 794.33 acres.
What fish are in Prairie Lake?
- Fish species found in Prairie Lake include black crappie, bluegill, bowfin (dogfish), brown bullhead, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, shorthead redhorse, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Prairie Lake is located in St. Louis County, Minnesota.
What did the DNR fisheries survey find at Prairie Lake?
- Minnesota DNR's Targeted Survey on August 13, 2025 caught 0.07 walleye per fyke net at Prairie Lake. Length samples in the latest survey that recorded them ran 7–24 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Prairie Lake’s water-quality measurements separately, and the water-quality trend over 4 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
When does Prairie Lake thaw?
- Prairie Lake typically has ice-out around Apr 21. Ice typically forms around Nov 29. The open water season is approximately 222 days.
Does Prairie Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Prairie Lake (clouds, ice, or an off-season gap). The most recent reading was low (7,870 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Prairie Lake?
- Prairie Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Prairie Lake. Public access is listed as yes.
Can I fish at Prairie Lake?
- Prairie 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.
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Where this data comes from
38 measurements from 3 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA38 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (3)
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
Ice data from Minnesota DNR Climate