Green Lake
Beltrami County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Green Lake. Here is what has been measured.
- Oligotrophic
- 32 ft max depth
Green Lake in Beltrami County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 18.5 ft visibility. Phosphorus: 7 µg/L. Chlorophyll-a (algae): 1.6 µg/L.
Green Lake is a cold, clear oligotrophic lake in Beltrami County, Minnesota with an estimated average depth of about 32 feet. Overall water quality is improving over recent sampling years. Compared to the 84 other monitored lakes in Beltrami County, Green Lake ranks #13 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-25. Methodology: how these readings are compared.
What Green Lake is good for
From access and monitoring records, not editorial picks.
- Clear water18.5 ft of visibility
Swimming conditions
Readings onlyLow algae
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. Check local advisories before you swim.
Whether Green 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 Green Lake
These are the measurements Minnesota PCA publishes for Green Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 18.5 ft down. Phosphorus 7 µg/L. Chlorophyll-a 1.6 µg/L. TSI 34.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 18.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 7µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 1.6µg/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. | 34 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Green Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Green Lake typically sits around 55°F at the surface in October. Summer average is about 72°F. Usually warmest in Jul (about 77°F) and coldest in Jan (about 34°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (34°F) to its warmest (77°F).
Typical surface water temperature by month, from 85 field readings (2010–2025) via the EPA Water Quality Portal. See the full Green Lake water temperature breakdown →
Lake Details
Max depth
~32 ft est.
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Green Lake.
Lake Size & Watershed
Watershed (drainage) area
1 sq mi
HydroLAKES / HydroSHEDS
Surface area
62 acres
HydroLAKES / HydroSHEDS
Shoreline
1.2 mi
HydroLAKES / HydroSHEDS
Elevation
1,220 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.
Stays via Stay22
Stays near Green Lake
Compare lakeside cabins, hotels, and vacation rentals near Green Lake in Beltrami 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 Green Lake
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Fishing Green Lake
Water Quality Trend: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Improving6 years
Phosphorus
Improving-0.49 µg/L/yr6 years
Chlorophyll-a
Improving-0.16 µg/L/yr6 years
Nearby Lakes in Beltrami County
Frequently asked questions about Green Lake
Where is Green Lake?
- Green Lake is a lake in Beltrami County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Green Lake?
- Green Lake in Beltrami County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 18.5 ft visibility. Phosphorus: 7 µg/L. Chlorophyll-a (algae): 1.6 µg/L.
Is Green Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Green Lake?
- Green Lake typically sits around 55°F at the surface in October, from 85 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Green Lake?
- No published bathymetric survey covers Green Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 32 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Green Lake across LakeQuality
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Where this data comes from
96 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Red Lake DNR
REDLAKE_WQX96 samples · 2020–2025
Analytical methods
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity by Nephelometry
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