Big Lake
St. Louis County, Minnesota1,904 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Big Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- 22 ft max depth
- Public access
- Limited data
Big Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 8.2 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 4.9 µg/L. Maximum depth: 22 ft. Surface area: 1903.97 acres.
Free interactive depth-contour map of Big Lake, reaching a maximum surveyed depth of 20 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Big Lake is a 1,904-acre mesotrophic lake in St. Louis County, Minnesota with a maximum depth of 22 feet (9-foot average). The lake supports 8 documented fish species including black crappie, burbot, and northern pike. Public access is available with 1 public boat landing. Compared to the 67 other monitored lakes in St. Louis County, Big Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-08-25. Methodology: how these readings are compared.
What Big Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing8 species recorded
- Big water1,904 acres
Swimming conditions
Readings onlyLimited data
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. Big Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Big 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 Big Lake
These are the measurements Minnesota PCA publishes for Big 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 8.2 ft. Phosphorus 14 µg/L. Chlorophyll-a 4.9 µg/L. TSI 45.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 8.2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 14µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 4.9µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 45 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Big 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 Big Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was moderate (34,041 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 ↗
Lake Details
Max depth
22 ft
Average depth
9 ft
Surface area
1,904 acres
Shoreline
25.9 mi
Littoral zone
80%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
11 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,404 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Big 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 Big Lake
Compare lakeside cabins, hotels, and vacation rentals near Big 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 Big 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 Big Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fish Species
Click a species to see every lake where it is documented.
Fishing Big Lake
EPA Impairment Status
Big Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN69-0190-00 · Official waterbody report
Nearby Lakes in St. Louis County
Frequently asked questions about Big Lake
Where is Big Lake?
- Big 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 Big Lake?
- Big Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 8.2 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 4.9 µg/L. Maximum depth: 22 ft. Surface area: 1903.97 acres.
Is Big Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Big Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
How deep is Big Lake?
- Big Lake has a maximum depth of 22 feet and an average depth of 9 feet. The lake covers 1903.97 acres.
What fish are in Big Lake?
- Fish species found in Big Lake include black crappie, burbot, northern pike, rock bass, smallmouth bass, walleye, white sucker, yellow perch. Big Lake is located in St. Louis County, Minnesota.
Does Big Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Big Lake (clouds, ice, or an off-season gap). The most recent reading was moderate (34,041 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Big Lake?
- Big Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Big Lake. Public access is listed as yes.
Can I fish at Big Lake?
- Big 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 Big Lake across LakeQuality
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in St. Louis County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Lake Vermilion Area area
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Lake Superior Basin (MN+WI), ranked by water quality
Lakes in the Rainy Lake Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
State Parks Near Big Lake
Other Lakes in Minnesota
Mesotrophic Lakes in Minnesota
Compare Big Lake With Nearby Lakes
Where this data comes from
14 measurements from 1 monitoring station, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA14 samples · 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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory