Grand County Lake Quality
Colorado, 6 lakes, average grade B (Good)
Only 6 lakes in Grand 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. With an average grade of B, Grand County sits comfortably above the {{stateName}} 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 Lake Granby (A); the most-stressed is Willow Creek Reservoir (C).
Quick Answers for Grand County
Planning a trip? Check special fishing regulations for Lake Granby — or check the official Colorado fishing regulations.
All Lakes in Grand County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Lake Granby | A | 12.7 ft | 17 µg/L |
| 2 | Wolford Mountain Reservoir | B | 8.3 ft | 10 µg/L |
| 3 | Grand Lake | B | 8.9 ft | 14 µg/L |
| 4 | Windy Gap Reservoir | B | - | 52.5 µg/L |
| 5 | Shadow Mountain Lake | B | 7.8 ft | 20 µg/L |
| 6 | Willow Creek Reservoir | C | 3.9 ft | 87.5 µg/L |
Other Counties in Colorado
See how Grand 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 Grand County
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Source: EPA National Aquatic Resource Surveys, 2026.