Washington County Lake Quality
Colorado, 2 lakes — no lake here has enough monitoring data for a grade
Washington County holds 2 monitored lakes. With a sample that small the county-level summary describes those specific waters, not necessarily every water body in the county. No lake in Washington County has enough sampling behind it for an A–F grade yet. The 2 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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Quick Answers for Washington County
Planning a trip? Check special fishing regulations for Prewitt Reservoir — or check the official Colorado fishing regulations.
All Lakes in Washington County
2 lakes · 0 graded, 2 not rated0 graded lakes · 2 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| NRPrewitt ReservoirWashington | NR | 1.8 ft | 87 µg/L | 31.5 µg/L | No recent samples | ✓ Public | |
| NRDeering LakeWashington | 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
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Other Counties in Colorado
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 and Québec), and 38 other country hubs..
Source: EPA National Aquatic Resource Surveys, 2026.