Big Lake
Big Lake in Mahnomen County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 2.1 ft visibility. Phosphorus: 33 µg/L. Chlorophyll-a (algae): 32.3 µg/L.
- Clarity
- 2.1 ft
- Mean depth
- ~13 ft est.
- Public access
- No
Next lake in Mahnomen County
Why Big Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Big Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity, phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Big Lake is a lake in Mahnomen County, Minnesota with an estimated average depth of about 13 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Big Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Very murky, less than 2.1 ft of visibility. Phosphorus level: 33 µg/L. Chlorophyll-a: 32.3 µg/L. Trophic State Index: 62.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.1 ft | Not graded |
| Phosphorus | 33 µg/L | Not graded |
| Chlorophyll-a (Algae) | 32.3 µg/L | Not graded |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Big Lake
Compare lakeside cabins, hotels, and vacation rentals near Big Lake in Mahnomen 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.
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Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~13 ft est. |
| Public Access | No |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Minnesota has not published bathymetry for Big 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.
Fishing Big Lake
Graded lakes near Big Lake
Big Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Mahnomen County
Frequently asked questions about Big Lake
What is the water quality grade for Big Lake?
- Big Lake in Mahnomen County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 2.1 ft visibility. Phosphorus: 33 µg/L. Chlorophyll-a (algae): 32.3 µg/L.
Is Big Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Big Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Algae concentration (chlorophyll-a) is 32.3 µg/L. Always check local health department advisories before swimming.
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 13 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Big Lake across LakeGrade
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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)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder