Big Lake
Mahnomen County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Big Lake. Here is what has been measured.
- 47 ft max depth
- Limited data
Big Lake in Mahnomen County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2.1 ft visibility. Phosphorus: 33 µg/L. Chlorophyll-a (algae): 32.3 µg/L.
Big Lake is a lake in Mahnomen County, Minnesota with an estimated average depth of about 47 feet. Limited fish-species data available. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-09-27. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. 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.
Very murky, less than 2.1 ft of visibility. Phosphorus 33 µg/L. Chlorophyll-a 32.3 µg/L. TSI 62.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 33µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 32.3µg/L | Measured, not scored 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. | 62 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Big Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~47 ft est.
Public access
No
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 Big Lake.
Lake Size & Watershed
Watershed (drainage) area
1 sq mi
HydroLAKES / HydroSHEDS
Surface area
121 acres
HydroLAKES / HydroSHEDS
Shoreline
2.2 mi
HydroLAKES / HydroSHEDS
Elevation
1,483 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.
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Fishing Big Lake
Nearby Lakes in Mahnomen County
Frequently asked questions about Big Lake
Where is Big Lake?
- Big Lake is a lake in Mahnomen 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 Mahnomen County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2.1 ft visibility. Phosphorus: 33 µg/L. Chlorophyll-a (algae): 32.3 µg/L.
Is Big Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Big Lake?
- No published bathymetric survey covers Big Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 47 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Can I fish at Big Lake?
- Public access to Big Lake is listed as no on the lake record, so confirm before you make the trip. 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
4 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA4 samples · 2022
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 2120 B ~ Color in Water by Visual Comparison
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder