East Bay Lake
Lake County, MontanaView mapDirections
Montana DEQ publishes the water-quality measurements for East Bay Lake. Here is what has been measured.
- Oligotrophic
East Bay Lake in Lake County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Phosphorus: 3 µg/L.
East Bay Lake is a cold, clear oligotrophic lake in Lake County, Montana. Overall water quality is declining over recent sampling years. Compared to the 17 other monitored lakes in Lake County, East Bay Lake ranks #8 for water quality.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2026-06-30. Methodology: how these readings are compared.
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 East Bay 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 East Bay Lake
These are the measurements Montana DEQ publishes for East Bay 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. Phosphorus 3 µg/L. TSI 20.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 3µg/L | Good GoodFairPoor |
| 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. | 20 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
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Answers come straight from the public measurements and survey records on this page.
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Stays near East Bay Lake
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Fishing East Bay Lake
Water quality readings over time
3 seasons of samples on record (2023–2025). Calling a direction takes at least 4 years of the same measurement.
Phosphorus
Worsening+1.5 µg/L/yr3 years
Nearby Lakes in Lake County
Frequently asked questions about East Bay Lake
Where is East Bay Lake?
- East Bay Lake is a lake in Lake County, Montana. Its water-quality measurements are published by Montana DEQ and shown on this page as reported.
What is the water quality of East Bay Lake?
- East Bay Lake in Lake County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Phosphorus: 3 µg/L.
Is East Bay Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
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Oligotrophic Lakes in Montana
Where this data comes from
52 measurements from 1 monitoring station, 2023–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Confederated Salish and Kootenai Tribes
CSKTRIBE52 samples · 2023–2026
Analytical methods
- Phosphorus by Colorimetry
- 4500 N C ~ Persufate Method for Total Nitrogen
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.