Flathead Lake is a mesotrophic lake in Lake County, Montana. Water quality is graded B based on 1 sampling years through 2012. Compared to the 26 other monitored lakes in Lake County, Flathead Lake ranks #25 for water quality.
Source: EPA Water Quality Portal sampling records, Montana DNR, last sampled 2012-07-11. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Good clarity, visible to about 11.8 ft. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11.8 ft | B |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Flathead Lake
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Fishing Flathead Lake
Location
County Ranking
Ranked #25 of 27 lakes in Lake County
Cleaner Lakes Within 30 Miles
Flathead Lake holds Grade B. 5 nearby lakes hold higher grades.
Nearby Lakes in Lake County
Explore Flathead Lake across LakeGrade
More Montana Lake Rankings
Other Grade B Lakes in Montana
Mesotrophic Lakes in Montana
More records, surveys & data sources
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2012-07-11
Monitoring stations: 1