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LakeQuality

Data Report · Updated July 2026

The State of Utah’s Lakes 2026

Of 216 monitored lakes in Utah, 65.7% earn a water-quality grade of A or B and 20.8% score D or F (average grade B). Flaming Gorge Reservoir Antelope Flat is the cleanest;

216
Monitored lakes graded
B
Average grade
65.7%
Grade A or B
0%
On impaired list

Utah grade distribution

A
B
C
D
F
A: 77 (35.6%)B: 65 (30.1%)C: 29 (13.4%)D: 24 (11.1%)F: 21 (9.7%)

Cleanest lakes in Utah

Highest combined water-quality score, 2026.

  1. 1.AFlaming Gorge Reservoir Antelope Flat — Daggett County25.3 ft clarity · 1 µg/L chl-a
  2. 2.AFlaming Gorge Lake — Daggett County29.5 ft clarity · 1 µg/L chl-a
  3. 3.AFlaming Gorge Reservoir — Daggett County31.8 ft clarity · 1 µg/L chl-a
  4. 4.ANla Lake — Summit County18.2 ft clarity · 4 µg/L chl-a
  5. 5.ANla Lake — Summit County17.2 ft clarity · 1 µg/L chl-a
  6. 6.ANla Lake — Duchesne County15.9 ft clarity · 2 µg/L chl-a
  7. 7.ANla Lake — Salt Lake County20.4 ft clarity · 2 µg/L chl-a
  8. 8.ANla Lake — Sevier County33.1 ft clarity · 2 µg/L chl-a
  9. 9.AFlaming Gorge-Green River Lake — Daggett County18.9 ft clarity · 1 µg/L chl-a
  10. 10.AStrawberry Lake — Wasatch County20.0 ft clarity · 2 µg/L chl-a

Most-polluted lakes

Lowest combined water-quality score among monitored lakes.

  1. 1.FNla Lake — Cache County0.5 ft clarity · 76 µg/L chl-a
  2. 2.FNla Lake — Uintah County0.7 ft clarity · 186 µg/L chl-a
  3. 3.FNla Lake — Sevier County0.5 ft clarity · 50 µg/L chl-a
  4. 4.FNla Lake — Salt Lake County0.7 ft clarity · 31 µg/L chl-a
  5. 5.FNla Lake — Weber County0.1 ft clarity · 90 µg/L chl-a
  6. 6.FUtah Lake — Utah County0.5 ft clarity · 159 µg/L chl-a
  7. 7.FUtah Lake — Utah County0.7 ft clarity · 96 µg/L chl-a
  8. 8.FUtah Lake Goshen Bay Southwest End — Utah County0.7 ft clarity · 50 µg/L chl-a
  9. 9.FUtah Lake Outside Entrance To Provo Bay — Utah County0.7 ft clarity · 41 µg/L chl-a
  10. 10.FMantua Reservoir — Box Elder County3.0 ft clarity · 40 µg/L chl-a

Worst algae hotspots

Highest measured chlorophyll-a (algae) concentration.

  1. 1.FNla Lake — Uintah County186 µg/L chlorophyll-a
  2. 2.FUtah Lake — Utah County159 µg/L chlorophyll-a
  3. 3.FUtah Lake — Utah County145 µg/L chlorophyll-a
  4. 4.FUtah Lake — Utah County96 µg/L chlorophyll-a
  5. 5.FNla Lake — Weber County90 µg/L chlorophyll-a
  6. 6.FFarmington Bay Lake — Davis County90 µg/L chlorophyll-a
  7. 7.DNewcastle Reservoir — Iron County89 µg/L chlorophyll-a
  8. 8.FNla Lake — Cache County76 µg/L chlorophyll-a
  9. 9.DKoosharem Reservoir — Sevier County58 µg/L chlorophyll-a
  10. 10.FUtah Lake — Utah County55 µg/L chlorophyll-a

Explore Utah 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 Utah lakes.

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