Weld County Lake Quality
Colorado, 6 lakes, average grade F (Very Poor)
Only 6 lakes in Weld County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county. 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 Windsor Lake (F); the most-stressed is Windsor Lake (F).
Quick Answers for Weld County
Planning a trip? Check special fishing regulations for Windsor Lake — or check the official Colorado fishing regulations.
All Lakes in Weld County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Windsor Lake | F | 2 ft | - |
| 2 | Prospect Lake | F | - | 250 µg/L |
| 3 | Union Reservoir | F | 3.2 ft | - |
| 4 | Milton Reservoir | F | 2.6 ft | - |
Other Counties in Colorado
See how Weld County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 12 states.
Where to stay near Weld County
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Source: EPA National Aquatic Resource Surveys, 2026.