Union County Lake Quality
North Carolina, 6 lakes, average grade F (Algae-prone)
Union County has 6 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. 3 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. The county average is F — the most-stressed bracket in our rubric. Most monitored lakes here show persistent nutrient loading and algal pressure.
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 Lake Lee (F); the most-stressed is Lake Lee (F).
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Quick Answers for Union County
Planning a trip? Check special fishing regulations for Lake Lee — or check the official North Carolina fishing regulations.
All Lakes in Union County
6 lakes · 3 graded, 3 not rated3 graded lakes · 3 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | FLake LeeUnion | F | No recent samples | 210 µg/L | 90.5 µg/L | No recent samples | Not recorded |
| 2 | FLake MonroeUnion | F | No recent samples | 110 µg/L | 62 µg/L | No recent samples | Not recorded |
| 3 | FLake TwittyUnion | F | No recent samples | 80 µg/L | 49 µg/L | No recent samples | Not recorded |
| NRLake LeeUnion | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRAero Plantation Lake Number TwoUnion | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLake TwittyUnion | 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 North Carolina
See how Union 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.