Crook County Lake Quality
Wyoming, 9 lakes, average grade B (Good)
Crook County has 9 monitored lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. 1 of those lake carry an A–F grade. The county-level summary describes that subset, not every water body listed. With an average grade of B, Crook County sits comfortably above the Wyoming median.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Keyhole Reservoir (B); the most-stressed is Keyhole Reservoir (B).
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Quick Answers for Crook County
Planning a trip? Check special fishing regulations for Keyhole Reservoir — or check the official Wyoming fishing regulations.
All Lakes in Crook County
9 lakes · 1 graded, 8 not rated1 graded lake · 8 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | BKeyhole ReservoirCrook | B | 7.7 ft | 20 µg/L | No recent samples | No recent samples | ✓ Public |
| NRSundance Fairgrounds PondCrook | NR | 4.1 ft | 10 µg/L | No recent samples | No recent samples | Not recorded | |
| NRBush ReservoirCrook | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBattle Creek ReservoirCrook | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRKilpatrick ReservoirCrook | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NROak Creek ReservoirCrook | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRRocky Ford ReservoirCrook | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRHagerman ReservoirCrook | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRArrowhead ReservoirCrook | 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 Wyoming
See how Crook 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.