What is the water quality grade for Pat Mayse Reservoir?

Pat Mayse Reservoir in Lamar County, Texas received a water quality grade of C (Fair). Water clarity: 3.9 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 21.8 µg/L.

Is Pat Mayse Reservoir safe to swim in?

Swim with caution, moderate algae may be present. Pat Mayse Reservoir has an overall water quality grade of C. Algae concentration (chlorophyll-a) is 21.8 µg/L. Always check local health department advisories before swimming.

Lamar County, Texas

Pat Mayse Reservoir

Grade CFair · 3.9 ft clarity

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Eutrophic

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

Source: EPA Water Quality Portal sampling records, Texas DNR, last sampled 2025-09-10. 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: 30 µg/L. Chlorophyll-a: 21.8 µg/L. Trophic State Index: 57.

Metric	Value	Grade
Water Clarity (Secchi Depth)	3.9 ft	D
Phosphorus	30 µg/L	C
Chlorophyll-a (Algae)	21.8 µg/L	D
Trophic State Index (TSI)	57	Eutrophic

High nutrients, frequent algae, reduced clarity

Where to stay near Pat Mayse Reservoir

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