Upper Stillwater Lake
Flathead County, MontanaView mapDirections
Montana DEQ publishes the water-quality measurements for Upper Stillwater Lake. Here is what has been measured.
- Limited data
Upper Stillwater Lake in Flathead County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Water clarity: 21.9 ft visibility.
Upper Stillwater Lake is a lake in Flathead County, Montana. Overall water quality is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2023-08-27. Methodology: how these readings are compared.
For a place on the water, look through cabin and lake-house rentals near Upper Stillwater Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Upper Stillwater Lake is good for
From access and monitoring records, not editorial picks.
- Clear water21.9 ft of visibility
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Upper Stillwater 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.
Water quality measurements for Upper Stillwater Lake
These are the measurements Montana DEQ publishes for Upper Stillwater 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 21.9 ft down. TSI 33.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 21.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading 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. | 33 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Upper Stillwater Lake
Answers come straight from the public measurements and survey records on this page.
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Stays near Upper Stillwater Lake
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Top-rated places to stay near Upper Stillwater Lake
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Fishing Upper Stillwater Lake
Water quality readings over time
2 seasons of samples on record (2020–2023). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Nearby Lakes in Flathead County
Frequently asked questions about Upper Stillwater Lake
Where is Upper Stillwater Lake?
- Upper Stillwater Lake is a lake in Flathead County, Montana. Its water-quality measurements are published by Montana DEQ and shown on this page as reported.
What is the water quality of Upper Stillwater Lake?
- Upper Stillwater Lake in Flathead County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Water clarity: 21.9 ft visibility.
Is Upper Stillwater Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Explore Upper Stillwater Lake across LakeQuality
Planning a trip around Glacier?
Upper Stillwater Lake is about 39 miles from Glacier National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Glacier →More lakes in Montana
Other Lakes in Montana
Oligotrophic Lakes in Montana
Where this data comes from
6 measurements from 1 monitoring station, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North American Lake Management Society
NALMS6 samples · 2020–2023
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.