What is the water quality grade for John Flannagan Reservoir?

John Flannagan Reservoir in Dickenson County, Virginia received a water quality grade of A (Excellent). Water clarity: 13.1 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 1.5 µg/L.

Is John Flannagan Reservoir safe to swim in?

Excellent for swimming, crystal clear water with minimal algae. John Flannagan Reservoir has an overall water quality grade of A. Algae concentration (chlorophyll-a) is 1.5 µg/L. Always check local health department advisories before swimming.

Dickenson County, Virginia

John Flannagan Reservoir

Grade AExcellent · 13.1 ft clarity

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Oligotrophic

John Flannagan Reservoir is a cold, clear oligotrophic lake in Dickenson County, Virginia. Water quality is graded A based on 2 sampling years through 2026. Compared to the 3 other monitored lakes in Dickenson County, John Flannagan Reservoir ranks #3 for water quality.

Source: EPA Water Quality Portal sampling records, Virginia DNR, last sampled 2026-06-24. Grade methodology: LakeGrade methodology.

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Swimming Safety

Excellent for swimming, crystal clear water with minimal algae

Water Quality Grade: A, Excellent

Good clarity, visible to about 13.1 ft. Phosphorus level: 10 µg/L. Chlorophyll-a: 1.5 µg/L. Trophic State Index: 37.

Metric	Value	Grade
Water Clarity (Secchi Depth)	13.1 ft	B
Phosphorus	10 µg/L	A
Chlorophyll-a (Algae)	1.5 µg/L	A
Trophic State Index (TSI)	37	Oligotrophic

Low nutrients, clear water, excellent for swimming

Where to stay near John Flannagan Reservoir

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