Flathead County, Montana · Water Quality Report Card
Lake of the Woods
Lake of the Woods in Flathead County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 5 µg/L. Chlorophyll-a (algae): 0.1 µg/L.
- Mean depth
- ~17 ft est.
- Type
- Oligotrophic
Lake of the Woods is a cold, clear oligotrophic lake in Flathead County, Montana with an estimated average depth of about 17 feet.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2012-08-29. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not rated for swimming — there is not enough monitoring data to judge this lake
Water Quality Grade: Not rated
No clarity data. Phosphorus level: 5 µg/L. Chlorophyll-a: 0.1 µg/L. Trophic State Index: 18.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | 5 µg/L | |
| Chlorophyll-a (Algae) | 0.1 µg/L | |
| Trophic State Index (TSI) | 18 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~17 ft est. |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Montana has not published bathymetry for Lake of the Woods.
Where to stay near Lake of the Woods
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Fishing Lake of the Woods
Location
Nearby Lakes in Flathead County
Explore Lake of the Woods across LakeGrade
Planning a trip around Glacier?
Lake of the Woods 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 Montana Lake Rankings
Other Lakes in Montana
Oligotrophic Lakes in Montana
More records, surveys & data sources
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Where this data comes from
2 measurements from 1 monitoring station, 2012. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Montana Watershed
MTWTRSHD_WQX2 samples · 2012
Analytical methods
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
Grade thresholds come from the U.S. EPA National Lakes Assessment 2022 Technical Support Document (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated.
Data Sources
Water quality data from the EPA Water Quality Portal
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Most recent sample: 2012-08-29
Monitoring stations: 1