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LakeQuality
Late afternoon sun over Slim Lake, scattering a bright path across wind-textured water
D

Harris County Lake Quality

Texas, 22 lakes, average grade D (Nutrient-rich)

Harris County's 22 monitored lakes fall in the moderate-density bracket for Texas. The county-level average smooths over real differences — a single agricultural watershed near the southwest corner can pull the average down even if the rest of the county runs clean. 3 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. On average, Harris County lakes grade D, with phosphorus loading and reduced clarity showing up across most of the dataset.

The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Lynchburg Reservoir (C); the most-stressed is Lake Houston S Union Pacific Rr Bridge (F).

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All Lakes in Harris County

22 lakes · 3 graded, 19 not rated3 graded lakes · 19 not rated, hidden

#LakeGradeClarityPhosphorusAlgaeTrophicAccess
1CLynchburg ReservoirHarrisC1.1 ft98.5 µg/L5.9 µg/LNo recent samples✓ Public
2DLake HoustonHarrisD0.6 ft780 µg/L26.2 µg/LNo recent samplesNot recorded
3FLake Houston S Union Pacific Rr BridgeHarrisF1.3 ft210.5 µg/L36.7 µg/LNo recent samplesNot recorded
NRL Houston W of Lake ShadowsHarrisNR1.5 ft180 µg/L56.1 µg/LNo recent samplesNot recorded
NRCedar Bayou LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRHighlands ReservoirHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRMuleshoe LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samples✓ Public
NRLake SandyHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samples✓ Public
NRSheldon ReservoirHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRBuckhorn LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRMarshall LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRMud LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samples✓ Public
NRLake NassauHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRTaylor LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRTucker LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRHegar LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRMallard LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRWarren Estate ReservoirHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRDennison LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRSouthard LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRJaphet LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRHegar Brothers LakeHarrisNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded

NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.

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See how Harris County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..

Source: EPA National Aquatic Resource Surveys, 2026.