Big Lake
Big Lake in St. Louis County, Minnesota has a water quality grade of A (Excellent). 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.
- Clarity
- 8.2 ft
- Max depth
- 22 ft
- Area
- 1,904 acres
- Type
- Mesotrophic
- Public access
- Yes
Next lake in St. Louis County
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). Water quality is graded A based on 2 sampling years through 2025. 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. 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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Moderate clarity, visible to about 8.2 ft. Phosphorus level: 14 µg/L. Chlorophyll-a: 4.9 µg/L. Trophic State Index: 45.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.2 ft | Not graded |
| Phosphorus | 14 µg/L | Good |
| Chlorophyll-a (Algae) | 4.9 µg/L | Good |
| Trophic State Index (TSI) | 45 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay 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
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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
| Characteristic | Value |
|---|---|
| Maximum Depth | 22 ft |
| Average Depth | 9 ft |
| Surface Area | 1,904 acres |
| Shoreline Length | 25.9 mi |
| Littoral Zone | 80% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Big LakePublic
Fish Species
Click a species to see every graded 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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN69-0190-00 · Official waterbody report
County Ranking
Ranked #1 of 68 lakes in St. Louis County
Nearby Lakes in St. Louis County
Frequently asked questions about Big Lake
What is the water quality grade for Big Lake?
- Big Lake in St. Louis County, Minnesota has a water quality grade of A (Excellent). 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?
- Excellent for swimming, crystal clear water with minimal algae. Big Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 4.9 µg/L. Always check local health department advisories before swimming.
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.
Explore Big Lake across LakeGrade
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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)
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