Green Mountain Reservoir is a mesotrophic lake in Summit County, Colorado. Water quality is graded B based on 1 sampling years through 2025. Compared to the 2 other monitored lakes in Summit County, Green Mountain Reservoir ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Colorado DNR, last sampled 2025-09-11. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Good clarity, visible to about 11.5 ft. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11.5 ft | B |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
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Fishing Green Mountain Reservoir
Location
County Ranking
Ranked #3 of 3 lakes in Summit County
Cleaner Lakes Within 30 Miles
Green Mountain Reservoir holds Grade B. One nearby lake has a higher grade.
Nearby Lakes in Summit County
Explore Green Mountain Reservoir across LakeGrade
More Colorado Lake Rankings
Other Grade B Lakes in Colorado
Mesotrophic Lakes in Colorado
More records, surveys & data sources
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-09-11
Monitoring stations: 1