Swan Lake North End
Lake County, MontanaView mapDirections
Montana DEQ publishes the water-quality measurements for Swan Lake North End. Here is what has been measured.
- Oligotrophic
- Impaired · Nutrients (phosphorus, nitrogen)
Swan Lake North End in Lake County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Phosphorus: 3.1 µg/L. Chlorophyll-a (algae): 1.1 µg/L.
Swan Lake North End 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, Swan Lake North End ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2023-08-02. 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. Swan Lake North End is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen), oxygen depletion (low DO), sediment / turbidity. Check local advisories before you swim.
Whether Swan Lake North End 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 Swan Lake North End
These are the measurements Montana DEQ publishes for Swan Lake North End, 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 3.1 µg/L. Chlorophyll-a 1.1 µg/L. TSI 26.
| 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 | 3.1µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 1.1µg/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. | 26 | 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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Fishing Swan Lake North End
Water Quality Trend: Worsening
Based on 11 years of monitoring (2012–2023).
Phosphorus
Stable-0.03 µg/L/yr11 years
Chlorophyll-a
Worsening+0.04 µg/L/yr11 years
EPA Impairment Status
Swan Lake North End is officially listed as impaired under Clean Water Act §303(d) in the 2021 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MT76K002_010 · Official waterbody report
Nearby Lakes in Lake County
Frequently asked questions about Swan Lake North End
Where is Swan Lake North End?
- Swan Lake North End 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 Swan Lake North End?
- Swan Lake North End in Lake County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Phosphorus: 3.1 µg/L. Chlorophyll-a (algae): 1.1 µg/L.
Is Swan Lake North End safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Swan Lake North End is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen), oxygen depletion (low DO), sediment / turbidity. Check local advisories before you swim.
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Where this data comes from
53 measurements from 1 monitoring station, 2012–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Montana Watershed
MTWTRSHD_WQX53 samples · 2012–2023
Analytical methods
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 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.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database