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LakeQuality
Pink and orange afterglow over the treeline on Slim Lake after sunset

Updated August 2026

The State of Oklahoma's Lakes 2026

Of 152 lakes in Oklahoma, 0% earn a water-quality grade of A or B and 91.7% score D or F (average grade D). Lake Texoma is the cleanest; 87 lakes (57.2%) are on an official impaired-waters list.

Data Report

152
Monitored lakes graded
D
Average grade
0%
Grade A or B
57.2%
On impaired list

Oklahoma grade distribution

C
D
A: 0 (0.0%)B: 0 (0.0%)C: 2 (8.3%)D: 22 (91.7%)F: 0 (0.0%)

Cleanest lakes in Oklahoma

Highest combined water-quality score, 2026.

  1. 1.CLake Texoma — Grayson County4.2 ft clarity · 36 µg/L P · 13 µg/L chl-a
  2. 2.DGrand Lake — Delaware County1.6 ft clarity · 720 µg/L P
  3. 3.DWes Watkins Reservoir — Pottawatomie County1.8 ft clarity · 32 µg/L P · 18 µg/L chl-a
  4. 4.DLake Nahni Waiya Tuskahomma — Pushmataha County250 µg/L P
  5. 5.DLake Sardis Clayton — Pushmataha County260 µg/L P
  6. 6.DLake Hugo Hugo — Choctaw County430 µg/L P

Most-polluted lakes

Lowest combined water-quality score among monitored lakes.

  1. 1.DGrand Lake — Delaware County1.6 ft clarity · 720 µg/L P
  2. 2.DWes Watkins Reservoir — Pottawatomie County1.8 ft clarity · 32 µg/L P · 18 µg/L chl-a
  3. 3.DLake Nahni Waiya Tuskahomma — Pushmataha County250 µg/L P
  4. 4.DLake Sardis Clayton — Pushmataha County260 µg/L P
  5. 5.DLake Hugo Hugo — Choctaw County430 µg/L P
  6. 6.CLake Texoma — Grayson County4.2 ft clarity · 36 µg/L P · 13 µg/L chl-a

Worst algae hotspots

Highest measured chlorophyll-a (algae) concentration.

  1. 1.NRLake Texoma — Johnston County233 µg/L chlorophyll-a
  2. 2.DLake Thunderbird — Cleveland County29 µg/L chlorophyll-a
  3. 3.NRThunderbird Lake Nature Center — Pottawatomie County29 µg/L chlorophyll-a
  4. 4.DCoon Creek Lake — Kay County24 µg/L chlorophyll-a
  5. 5.DLake Texoma — Marshall County23 µg/L chlorophyll-a
  6. 6.DThunderbird Lake Fisherman'S — Cleveland County21 µg/L chlorophyll-a

Trending lakes

Improving

  1. 1.DGrand Lake — Delaware County
  2. 2.DLake Konawa — Seminole County
  3. 3.DEucha Lake — Delaware County
  4. 4.DSportsman Lake — Seminole County
  5. 5.DWewoka Lake — Seminole County
  6. 6.DSandy Beach Lake — Osage County
  7. 7.DOsage Cove Lake — Osage County
  8. 8.DThunderbird Lake Hog Creek — Cleveland County

Declining

  1. 1.DGreenleaf Lake — Muskogee County
  2. 2.DSpavinaw Lake — Mayes County
  3. 3.DLake Sardis Clayton — Pushmataha County
  4. 4.NRFairfax Lake — Osage County
  5. 5.NROologah Lake — Rogers County
  6. 6.NRSardis Lake — Pushmataha County
  7. 7.NRFoss Reservoir — Custer County
  8. 8.NRLangston Lake — Logan County

Impaired waters in Oklahoma

87 lakes appear on the EPA/state 303(d) impaired-waters list (81 formally listed, 20 with a cleanup plan/TMDL).

Mercury · 49Turbidity · 48Algal growth · 34Oxygen depletion (low DO) · 24pH / acidity · 11Nutrients (phosphorus, nitrogen) · 5Metals (other than mercury) · 5Pathogens (E. coli, fecal) · 3

Explore Oklahoma lakes

Lake Fishing Forecast

Species activity outlook by water temperature and season

Oklahoma Lake Trips

Where to stay at Oklahoma's top lakes, each with its grade

Grades combine total phosphorus, total nitrogen, chlorophyll-a, and turbidity 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”.