Loudoun County Lake Quality
Virginia, 5 lakes, average grade A (Excellent)
Loudoun County has 5 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. 2 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. On average, Loudoun County lakes grade an A. That puts it near the top of the Virginia county ranking.
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 Goose Creek Reservoir (A); the most-stressed is Goose Creek Reservoir (A).
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Quick Answers for Loudoun County
Planning a trip? Check special fishing regulations for Goose Creek Reservoir — or check the official Virginia fishing regulations.
All Lakes in Loudoun County
5 lakes · 2 graded, 3 not rated2 graded lakes · 3 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | AGoose Creek ReservoirLoudoun | A | 2.1 ft | 65 µg/L | 2.1 µg/L | No recent samples | Not recorded |
| 2 | ABeaverdam Creek ReservoirLoudoun | A | 5.4 ft | 10 µg/L | 4 µg/L | No recent samples | Not recorded |
| NRSleeter LakeLoudoun | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NROliver LakeLoudoun | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRDulles Airport PondLoudoun | 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.
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Other Counties in Virginia
See how Loudoun 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.