Saint Marys Lake
Saint Marys Lake in Lake County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 272 acres.
- Area
- 272 acres
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Why Saint Marys Lake 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 Saint Marys Lake, 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.
Saint Marys Lake is a 272-acre lake in Lake 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 Saint Marys Lake
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 Saint Marys Lake
Compare lakeside cabins, hotels, and vacation rentals near Saint Marys Lake in Lake 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 Saint Marys Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 272 acres |
No bathymetric survey has been published for Saint Marys Lake, so its depth is not documented here.
Fishing Saint Marys Lake
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Frequently asked questions about Saint Marys Lake
Where is Saint Marys Lake?
- Saint Marys Lake is a lake in Lake 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 Saint Marys Lake?
- Saint Marys Lake in Lake County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 272 acres.
Is Saint Marys Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Saint Marys Lake 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 Saint Marys Lake come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.