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LakeQuality

Data Report · Updated July 2026

The State of Oklahoma’s Lakes 2026

Of 83 monitored lakes in Oklahoma, 6% earn a water-quality grade of A or B and 66.3% score D or F (average grade D). Nla Lake is the cleanest;

83
Monitored lakes graded
D
Average grade
6%
Grade A or B
0%
On impaired list

Oklahoma grade distribution

C
D
F
A: 1 (1.2%)B: 4 (4.8%)C: 23 (27.7%)D: 31 (37.3%)F: 24 (28.9%)

Cleanest lakes in Oklahoma

Highest combined water-quality score, 2026.

  1. 1.BNla Lake — Grady County8.9 ft clarity · 18 µg/L P · 3 µg/L chl-a
  2. 2.BNla Lake — Logan County2.8 ft clarity · 42 µg/L P · 6 µg/L chl-a
  3. 3.BNla Lake — Osage County4.8 ft clarity · 31 µg/L P · 7 µg/L chl-a
  4. 4.BNla Lake — Comanche County5.7 ft clarity · 27 µg/L P · 4 µg/L chl-a
  5. 5.CLake Texoma — Grayson County4.2 ft clarity · 34 µg/L P · 13 µg/L chl-a
  6. 6.CNla Lake — Osage County3.3 ft clarity · 26 µg/L P · 14 µg/L chl-a
  7. 7.CNla Lake — Okmulgee County0.4 ft clarity · 30 µg/L P · 12 µg/L chl-a
  8. 8.CNla Lake — Stephens County6.1 ft clarity · 42 µg/L P · 11 µg/L chl-a
  9. 9.CWes Watkins Reservoir — Pottawatomie County1.8 ft clarity · 32 µg/L P · 18 µg/L chl-a
  10. 10.CThunderbird Lake Hog Creek — Cleveland County33 µg/L P · 18 µg/L chl-a

Most-polluted lakes

Lowest combined water-quality score among monitored lakes.

  1. 1.FNla Lake — Canadian County0.7 ft clarity · 245281 µg/L P · 109 µg/L chl-a
  2. 2.FNla Lake — Caddo County1.5 ft clarity · 128000 µg/L P · 159 µg/L chl-a
  3. 3.FNla Lake — Noble County0.4 ft clarity · 2150000 µg/L P · 148 µg/L chl-a
  4. 4.FNla Lake — Sequoyah County1.1 ft clarity · 94121 µg/L P · 50 µg/L chl-a
  5. 5.FNla Lake — Washita County0.7 ft clarity · 250 µg/L P · 118 µg/L chl-a
  6. 6.FNla Lake — Hughes County1.2 ft clarity · 327000 µg/L P · 95 µg/L chl-a
  7. 7.FNla Lake — Stephens County0.6 ft clarity · 209000 µg/L P · 91 µg/L chl-a
  8. 8.FNla Lake — Pawnee County1.0 ft clarity · 142000 µg/L P · 65 µg/L chl-a
  9. 9.FNla Lake — Canadian County1.1 ft clarity · 104 µg/L P · 92 µg/L chl-a
  10. 10.FNla Lake — Atoka County0.7 ft clarity · 205 µg/L P · 48 µg/L chl-a

Worst algae hotspots

Highest measured chlorophyll-a (algae) concentration.

  1. 1.FGrand Lake — Delaware County384000 µg/L chlorophyll-a
  2. 2.FLake Texoma — Johnston County233 µg/L chlorophyll-a
  3. 3.FNla Lake — Caddo County159 µg/L chlorophyll-a
  4. 4.FNla Lake — Noble County148 µg/L chlorophyll-a
  5. 5.FNla Lake — Washita County118 µg/L chlorophyll-a
  6. 6.FNla Lake — Canadian County109 µg/L chlorophyll-a
  7. 7.FNla Lake — McCurtain County105 µg/L chlorophyll-a
  8. 8.FNla Lake — Hughes County95 µg/L chlorophyll-a
  9. 9.FNla Lake — Canadian County92 µg/L chlorophyll-a
  10. 10.FNla Lake — Stephens County91 µg/L chlorophyll-a

Explore Oklahoma lakes

Lake Fishing Forecast

Species activity outlook by water temperature and season

Grades combine Secchi clarity, total phosphorus, and chlorophyll-a from the EPA Water Quality Portal and state agencies. See the full methodology, the national State of America’s Lakes report, or all Oklahoma lakes.

Cite this report: LakeQuality, “The State of Oklahoma’s Lakes 2026,” lakequality.org/report/ok.