Upper Stillwater Reservoir is a mesotrophic lake in Duchesne County, Utah. Water quality is graded B based on 2 sampling years through 2024. Compared to the 22 other monitored lakes in Duchesne County, Upper Stillwater Reservoir ranks #10 for water quality.
Source: EPA Water Quality Portal sampling records, Utah DNR, last sampled 2024-07-29. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Moderate clarity, visible to about 8.7 ft. Chlorophyll-a: 2.8 µg/L. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.7 ft | C |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 2.8 µg/L | A |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Upper Stillwater Reservoir
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Fishing Upper Stillwater Reservoir
Location
County Ranking
Ranked #10 of 23 lakes in Duchesne County
Nearby Lakes in Duchesne County
Explore Upper Stillwater Reservoir across LakeGrade
More Utah Lake Rankings
Other Grade B Lakes in Utah
Summit County · Clarity: 8.9 ft
Summit County · Clarity: 7.5 ft
Summit County · Clarity: 5 ft
Wasatch County · Clarity: 10.6 ft
Summit County · Clarity: 10.6 ft
Wasatch County · Clarity: 8.2 ft
Mesotrophic Lakes in Utah
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: 2024-07-29
Monitoring stations: 1