What is the water quality grade for Grapevine Lake Northwest?

Grapevine Lake Northwest in Denton County, Texas received a water quality grade of C (Fair). Water clarity: 2.4 ft visibility. Phosphorus: 40 µg/L. Chlorophyll-a (algae): 27.6 µg/L.

Is Grapevine Lake Northwest safe to swim in?

Swim with caution, moderate algae may be present. Grapevine Lake Northwest has an overall water quality grade of C. Algae concentration (chlorophyll-a) is 27.6 µg/L. Always check local health department advisories before swimming.

Denton County, Texas

Grapevine Lake Northwest

Grade CFair · 2.4 ft clarity

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Eutrophic

Grapevine Lake Northwest is a productive, nutrient-rich eutrophic lake in Denton County, Texas. Water quality is graded C based on 2 sampling years through 2025. Compared to the 5 other monitored lakes in Denton County, Grapevine Lake Northwest ranks #3 for water quality.

Source: EPA Water Quality Portal sampling records, Texas DNR, last sampled 2025-12-16. Grade methodology: LakeGrade methodology.

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Swimming Safety

Swim with caution, moderate algae may be present

Water Quality Grade: C, Fair

Very murky, less than 2.4 ft of visibility. Phosphorus level: 40 µg/L. Chlorophyll-a: 27.6 µg/L. Trophic State Index: 62.

Metric	Value	Grade
Water Clarity (Secchi Depth)	2.4 ft	F
Phosphorus	40 µg/L	C
Chlorophyll-a (Algae)	27.6 µg/L	D
Trophic State Index (TSI)	62	Eutrophic

High nutrients, frequent algae, reduced clarity

Where to stay near Grapevine Lake Northwest

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