What is the water quality grade for Prineville Reservoir?

Prineville Reservoir in Crook County, Oregon received a water quality grade of B (Good). Chlorophyll-a (algae): 7.5 µg/L.

Is Prineville Reservoir safe to swim in?

Good for swimming, clear water with low algae levels. Prineville Reservoir has an overall water quality grade of B. Algae concentration (chlorophyll-a) is 7.5 µg/L. Always check local health department advisories before swimming.

Crook County, Oregon

Prineville Reservoir

Grade BGood water quality

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Limited DataEutrophic

Prineville Reservoir is a productive, nutrient-rich eutrophic lake in Crook County, Oregon. Water quality is graded B based on 1 sampling years through 2025. Compared to the 2 other monitored lakes in Crook County, Prineville Reservoir ranks #1 for water quality.

Source: EPA Water Quality Portal sampling records, Oregon DNR, last sampled 2025-09-23. Grade methodology: LakeGrade methodology.

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Swimming Safety

Good for swimming, clear water with low algae levels

Water Quality Grade: B, Good

No clarity data. Chlorophyll-a: 7.5 µg/L. Trophic State Index: 50.

Metric	Value	Grade
Water Clarity (Secchi Depth)	No data
Phosphorus	No data
Chlorophyll-a (Algae)	7.5 µg/L	B
Trophic State Index (TSI)	50	Eutrophic

High nutrients, frequent algae, reduced clarity

Where to stay near Prineville Reservoir

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