New Harmful Cyanobacterial Bloom (HCB) Recreational Use Advisories

Wyoming Department of Environmental Quality  | view as a webpage

Wyoming Department of Environmental Quality

New Harmful Cyanobacterial Bloom (HCB) Recreational Use Advisories

A harmful cyanobacterial bloom (HCB) recreational use Bloom Advisory has been issued for Bighorn Reservoir and McKenzie Lake. The Wyoming Department of Health (WDH) works cooperatively with the Wyoming Department of Environmental Quality to issue recreational use advisories when cyanobacterial cell densities or cyanotoxin concentrations pose a risk to people engaging in swimming or similar water contact activities in areas where cyanobacterial blooms occur. HCBs may also pose a health risk to animals. The WDH is working directly with resource management agencies to ensure signs are posted at these waterbodies. Additional details regarding advisories and other HCB resources can be found at

Bloom advisories are issued when a HCB is present and cyanotoxins may be present. Toxin advisories are issued when cyanotoxins exceed recreational thresholds. Waterbodies under an advisory are not closed since HCBs may only be present in certain areas and conditions can change frequently. Advisories will remain in place until blooms have fully dissipated and cyanotoxin concentrations are below recreational use thresholds identified in Wyoming's HCB Action Plan. 

If you encounter a potential HCB, the Wyoming Department of Health and the Wyoming Livestock Board recommend the following:

  • Avoid contact with water in the vicinity of the bloom, especially in areas where cyanobacteria are dense and form scums.
  • Do not ingest water from the bloom. Boiling, filtration and/or other treatments will not remove toxins.
  • Rinse fish with clean water and eat only the fillet portion.
  • Avoid water spray from the bloom.
  • Do not allow pets or livestock to drink water near the bloom, eat bloom material, or lick fur after contact.
  • If people, pets, or livestock come into contact with a bloom, rinse off with clean water as soon as possible and contact a doctor or veterinarian.

Questions about health effects and recreational use advisories can be directed to Courtney Tillman, Surveillance Epidemiologist, Wyoming Department of Health, at or (307) 777-5522. Questions regarding cyanobacteria sampling can be directed to Kelsee Hurshman, Natural Resource Analyst, Wyoming Department of Environmental Quality, at or (307) 777-2073.

Current HCB Recreational Use Advisories*

Waterbody Name      Observation or Sampling Location(s)    Advisory Type   Date Issued
Alcova Reservoir Dam Bloom 08/25/2023
Beck Lake East Ramp Bloom 08/03/2023
Bighorn Reservoir Cottonwood Creek Ramp Bloom 08/29/2023
Boysen Reservoir Brannon Ramp Toxin 08/24/2023
Brooks Lake South Ramp Bloom 08/03/2023
Buffalo Bill Reservoir Bartlett Beach Bloom 08/18/2023
Festo Lake East Shore Bloom 07/13/2023
Flaming Gorge Reservoir Firehole Beach Bloom 07/19/2023
Gillette Fishing Lake East Dam, North Shore Bloom 08/18/2023
Glendo Reservoir Custer Cove, Cottonwood Campground Bloom 08/09/2023
Goshen Hole Reservoir Northwest Campground Bloom 07/29/2023
West Granite Springs Reservoir West Causeway Bloom 08/09/2023
High Savery Reservoir Dam Bloom 07/12/2023
Kemmerer City Reservoir East Access Bloom 08/18/2023
Lake Viva Naughton East Shore Bloom 07/19/2023
Leazenby Lake South Access Toxin 08/02/2023
McKenzie Lake East Cove Bloom 08/29/2023
Miller Lake Northeast Shore Bloom  08/01/2023
Ocean Lake Long Point Toxin 08/24/2023
Pathfinder Reservoir Bishops Point Toxin 08/10/2023
Rainbow Lake (Shoshone Forest) Entire Lake Bloom 08/24/2023
Saratoga Lake West-Central Shore Toxin 08/10/2023
Seminoe Reservoir Sunshine Beach Toxin 08/10/2023
Sloans Lake South Beach Bloom 08/14/2023
Sodergreen Lake Southeast Access Bloom 08/09/2023
Toltec Reservoir West Shore Bloom 08/25/2023
Twin Buttes Lake South-Central Ramp Bloom 08/09/2023
Upper Brooks Lake Northwest Cove Bloom 08/24/2023
Wind River Upper Wind River Campground Bloom 08/25/2023
Wheatland Reservoir Number 3 Northwest Causeway Toxin 08/03/2023
Woodruff Narrows Reservoir North Ramp Bloom 08/04/2023

*There may be additional waterbodies with HCBs that WDH and WDEQ are not aware of. Please report potential blooms to WDEQ and HCB-related illnesses to WDH.