Skip to main content
LakeQuality
Pink and orange afterglow over the treeline on Slim Lake after sunset

Updated August 2026

The State of Wyoming's Lakes 2026

Of 164 lakes in Wyoming, 78.1% sit in EPA's favourable condition classes for nutrients and algae and 15.6% in its poorer ones. Boysen Reservoir Transitional Embayment is the cleanest; 6 lakes (3.7%) are on an official impaired-waters list.

Data Report

164
Monitored lakes sampled
B
Average readings
78.1%
low nutrient and algae readings
3.7%
On impaired list

Wyoming nutrient and algae readings

Cleanest lakes in Wyoming

Cleanest combined nutrient and algae readings, 2026.

  1. 1.Boysen Reservoir Transitional Embayment — Fremont County11.0 ft clarity · 10 µg/L P
  2. 2.Brooks Lake — Fremont County6.3 ft clarity · 50 µg/L P

Highest measured algae

Highest measured chlorophyll-a (algae) concentration.

No qualifying lakes with sufficient data.

Trending lakes

Improving

  1. 1.Alcova Reservoir Transitional Pelagic — Natrona County
  2. 2.Glendo Reservoir Riverine Pelagic — Platte County
  3. 3.Seminoe Reservoir Lacustrine Pelagic — Carbon County
  4. 4.Alcova Reservoir Riverine Pelagic — Natrona County
  5. 5.Crystal Reservoir — Laramie County
  6. 6.Granite Springs Reservoir — Laramie County
  7. 7.Lake Desmet Lpd — Johnson County
  8. 8.Rob Roy Reservoir — Albany County

Declining

  1. 1.Hawk Springs Reservoir — Goshen County
  2. 2.Festo Lake — Platte County
  3. 3.Brooks Lake — Fremont County
  4. 4.Unnamed Reservoir — Big Horn County
  5. 5.Seminoe Reservoir Riverine Pelagic — Carbon County
  6. 6.Glendo Reservoir Lacustrine Pelagic — Platte County
  7. 7.Seminoe Reservoir Transitional Pelagic — Carbon County
  8. 8.Lake Hattie — Albany County

Impaired waters in Wyoming

6 lakes appear on the EPA/state 303(d) impaired-waters list (5 formally listed, 1 with a cleanup plan/TMDL).

Nutrients (phosphorus, nitrogen) · 5pH / acidity · 5Sediment / turbidity · 1

Explore Wyoming lakes

Lake Fishing Forecast

Species activity outlook by water temperature and season

Wyoming Lake Trips

Where to stay at Wyoming's top lakes, each with its readings

Readings 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 Wyoming lakes.

Cite this report: LakeQuality, “The State of Wyoming's Lakes 2026”.