
Rosebud County Lake Quality
Montana, 15 lakes — no lake here has enough monitoring data for a grade
There are 15 monitored lakes in Rosebud County. The mix is varied enough that the county-level average tells you the broad strokes, not the choose-this-cabin specifics. No lake in Rosebud County has enough sampling behind it for an A–F grade yet. The 15 monitored lakes below carry whatever clarity, phosphorus, and chlorophyll-a measurements exist.
Most of the county's monitored lakes are shallow, under 50 feet, which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed.
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Top-rated places to stay near Rosebud County
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Quick Answers for Rosebud County
Planning a trip? Check special fishing regulations for Castle Rock Lake — or check the official Montana fishing regulations.
All Lakes in Rosebud County
15 lakes · 0 graded, 15 not rated0 graded lakes · 15 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| NRCastle Rock LakeRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRStellar LakeRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBoies ReservoirRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBarley ReservoirRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBarley ReservoirsRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBrown Coulee ReservoirRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRKerns ReservoirRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBlacktail ReservoirRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBlacktail ReservoirRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRZempel LakeRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRZempel LakeRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRDonleys ReservoirRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRThebes LakeRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBlack Sea ReservoirRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBlack Sea ReservoirRosebud | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded |
NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
Lake Match
Which lake suits how you actually use one?
Six questions — swimming, fishing, quiet, cabins, drive time — and a shortlist of graded lakes that fit, with the water quality behind each one.
Other Counties in Montana
See how Rosebud County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..
Source: EPA National Aquatic Resource Surveys, 2026.