What is the water quality grade for Sam Rayburn Reservoir?

Sam Rayburn Reservoir in San Augustine County, Texas received a water quality grade of C (Fair). Water clarity: 3.9 ft visibility. Phosphorus: 27.5 µg/L. Chlorophyll-a (algae): 18.6 µg/L.

Is Sam Rayburn Reservoir safe to swim in?

Swim with caution, moderate algae may be present. Sam Rayburn Reservoir has an overall water quality grade of C. Algae concentration (chlorophyll-a) is 18.6 µg/L. Always check local health department advisories before swimming.

San Augustine County, Texas · 31.23°N

Sam Rayburn Reservoir

Grade CFair · 3.9 ft clarity

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Eutrophic

Sam Rayburn Reservoir is a productive, nutrient-rich eutrophic lake in San Augustine County, Texas. Water quality is graded C based on 2 sampling years through 2025. Compared to the 2 other monitored lakes in San Augustine County, Sam Rayburn Reservoir ranks #1 for water quality.

Source: EPA Water Quality Portal sampling records, Texas DNR, last sampled 2025-12-10. Grade methodology: LakeGrade methodology.

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Swimming Safety

Swim with caution, moderate algae may be present

Water Quality Grade: C, Fair

Murky, only visible to about 3.9 ft. Phosphorus level: 27.5 µg/L. Chlorophyll-a: 18.6 µg/L. Trophic State Index: 56.

Metric	Value	Grade
Water Clarity (Secchi Depth)	3.9 ft	D
Phosphorus	27.5 µg/L	C
Chlorophyll-a (Algae)	18.6 µg/L	C
Trophic State Index (TSI)	56	Eutrophic

High nutrients, frequent algae, reduced clarity

Where to stay near Sam Rayburn Reservoir

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