Castle Rock Lake
Rosebud County, Montana153 acresView mapDirections
Not enough samples to grade — no water-quality sampling on record for this lake. No letter yet. Here is what we do have.
Castle Rock Lake in Rosebud County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 153 acres.
- Area
- 153 acres
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Stays near Castle Rock Lake
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Watch Castle Rock Lake’s letter
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Why Castle Rock 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 Castle Rock 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.
Castle Rock Lake is a 153-acre lake in Rosebud County, Montana.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled recent years. Grade methodology: LakeQuality methodology.
Swimming Safety
Not ratedElevated nutrients
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Castle Rock Lake
These readings exist but are not enough for an A–F grade — see why.
No clarity data. TSI 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) |
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 153 acres |
No bathymetric survey has been published for Castle Rock Lake, so its depth is not documented here.
Fishing Castle Rock Lake
Nearby Lakes in Rosebud County
Frequently asked questions about Castle Rock Lake
Where is Castle Rock Lake?
- Castle Rock Lake is a lake in Rosebud 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 Castle Rock Lake?
- Castle Rock Lake in Rosebud County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 153 acres.
Is Castle Rock Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
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Where this data comes from
Measurements for Castle Rock Lake come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.