Willow Flat Reservoir
Willow Flat Reservoir in Valley County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 26 acres.
- Area
- 26 acres
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Why Willow Flat Reservoir has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Willow Flat Reservoir, no water-quality sampling on record for this lake.
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by Montana DEQ and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Willow Flat Reservoir is a 26-acre lake in Valley County, Montana.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled recent years. Grade methodology: LakeQuality methodology.
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Swimming Safety
Not ratedElevated nutrients
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Willow Flat Reservoir
These readings exist but are not enough for an A–F grade — see why.
No clarity data. Trophic State Index: undefined.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) |
Where to stay near Willow Flat Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Willow Flat Reservoir in Valley County, Montana — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Willow Flat Reservoir
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 26 acres |
No bathymetric survey has been published for Willow Flat Reservoir, so its depth is not documented here.
Fishing Willow Flat Reservoir
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Frequently asked questions about Willow Flat Reservoir
Where is Willow Flat Reservoir?
- Willow Flat Reservoir is a lake in Valley County, Montana. LakeQuality has not rated this lake (UNRATED) — no water-quality sampling on record for this lake.
What is the water quality grade for Willow Flat Reservoir?
- Willow Flat Reservoir in Valley County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 26 acres.
Is Willow Flat Reservoir safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Willow Flat Reservoir is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
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Where this data comes from
Measurements for Willow Flat Reservoir come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.