Big Lake is a lake in Stillwater County, Montana. Its water-quality measurements are published by Montana DEQ and shown on this page as reported.

Big Lake

Stillwater County, Montana2,583 acresView map Directions

No nutrient or algae sampling on record from Montana DEQ for this lake.

Area

2,583 acres

Surface area

Impaired · Salinity / chlorides

See the measurements Directions Where to stay

Big Lake in Stillwater County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Surface area: 2583 acres.

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Big Lake is a 2,583-acre lake in Stillwater County, Montana.

Source: EPA Water Quality Portal sampling records, Montana DEQ. Methodology: how these readings are compared.

What Big Lake is good for

From access and monitoring records, not editorial picks.

Big water2,583 acres

Swimming conditions

No reading

Not rated

Nutrient and algae readings are not a swimming clearance. Big Lake is listed impaired under Clean Water Act §303(d) (IR 5) for salinity / chlorides. Check local advisories before you swim.

Whether Big Lake is safe to swim in today is a call for the Montana Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.

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Water quality measurements for Big Lake

These are the measurements Montana DEQ 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.

No clarity data. TSI undefined.

Ask about Big Lake

Answers come straight from the public measurements and survey records on this page.

Lake Details

Surface area

2,583 acres

No bathymetric survey has been published for Big Lake, so its depth is not documented here.

Stays via Stay22

Stays near Big Lake

Compare lakeside cabins, hotels, and vacation rentals near Big Lake in Stillwater County, Montana — 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 16–18, 4 adults. Change dates on the map below.

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Follow Big Lake’s readings

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Fishing Big Lake

→ Big Lake fishing regulations (limits, seasons, special rules)

EPA Impairment Status

Big Lake is officially listed as impaired under Clean Water Act §303(d) in the 2021 EPA reporting cycle (IR category 5).

Causes of impairment

Salinity / chlorides

Designated uses not supporting: Drinking water, Aquatic life, Other.

Source: EPA ATTAINS assessment unit MT43F003_010 · Official waterbody report

Nearby Lakes in Stillwater County

Hunter Lake2.9 miView →Halfbreed Lake6.5 miView →Hailstone Lake11.1 miView →Dallmann Lake10.9 miView →Emerald Lake—View →Mystic Lake—View →

Frequently asked questions about Big Lake

Where is Big Lake?: Big Lake is a lake in Stillwater County, Montana. Its water-quality measurements are published by Montana DEQ and shown on this page as reported.
What is the water quality of Big Lake?: Big Lake in Stillwater County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Surface area: 2583 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 5) for salinity / chlorides. Check local advisories before you swim.