Tetrault Lake
Lincoln County, MontanaView mapDirections
Montana DEQ publishes the water-quality measurements for Tetrault Lake. Here is what has been measured.
- Limited data
Tetrault Lake in Lincoln County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Water clarity: 21.8 ft visibility.
Tetrault Lake is a lake in Lincoln County, Montana. Overall water quality is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2023-09-01. Methodology: how these readings are compared.
What Tetrault Lake is good for
From access and monitoring records, not editorial picks.
- Clear water21.8 ft of visibility
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Tetrault 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 Tetrault Lake
These are the measurements Montana DEQ publishes for Tetrault 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 21.8 ft down. TSI 33.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 21.8ft | 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 Tetrault Lake
Answers come straight from the public measurements and survey records on this page.
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Stays near Tetrault Lake
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Fishing Tetrault Lake
Water Quality Trend: Worsening
Based on 12 years of monitoring (2012–2023).
Water clarity
Stable3 years
Phosphorus
Worsening+0.92 µg/L/yr11 years
Chlorophyll-a
Worsening+0.06 µg/L/yr12 years
Nearby Lakes in Lincoln County
Frequently asked questions about Tetrault Lake
Where is Tetrault Lake?
- Tetrault Lake is a lake in Lincoln County, Montana. Its water-quality measurements are published by Montana DEQ and shown on this page as reported.
What is the water quality of Tetrault Lake?
- Tetrault Lake in Lincoln County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Water clarity: 21.8 ft visibility.
Is Tetrault Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
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Where this data comes from
17 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
NALMS17 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.