Washington County Lake Quality
Utah, 8 lakes, average grade B (Good)
Washington County has 8 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. 5 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. With an average grade of B, Washington County sits comfortably above the Utah 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 Gunlock Reservoir (A); the most-stressed is Baker Dam Reservoir (D).
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Quick Answers for Washington County
Planning a trip? Check special fishing regulations for Gunlock Reservoir — or check the official Utah fishing regulations.
All Lakes in Washington County
8 lakes · 5 graded, 3 not rated5 graded lakes · 3 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | AGunlock ReservoirWashington | A | 4.6 ft | 21 µg/L | 2.9 µg/L | No recent samples | ✓ Public |
| 2 | AQuail Creek ReservoirWashington | A | 14.6 ft | 6.1 µg/L | 0.9 µg/L | No recent samples | Not recorded |
| 3 | CUpper Enterprise ReservoirWashington | C | 5.2 ft | 35 µg/L | 6.4 µg/L | No recent samples | Not recorded |
| 4 | CKolob ReservoirWashington | C | 10.5 ft | 14.3 µg/L | 2.1 µg/L | No recent samples | Not recorded |
| 5 | DBaker Dam ReservoirWashington | D | 3.6 ft | 78 µg/L | 29.5 µg/L | No recent samples | Not recorded |
| NRIvins ReservoirWashington | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRAsh Creek ReservoirWashington | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBlue Springs ReservoirWashington | 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 Utah
See how Washington 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.