The Wyoming Department of Health has issued a recreational use advisory for Seminoe Reservoir in Carbon County due to a harmful cyanobacterial bloom (HCB). HCBs are also referred to as harmful algal blooms (HABs) since cyanobacteria are commonly known as blue-green algae. The Department of Health issues advisories to inform the public that there may be health risks for people and animals in areas where HCBs occur. Lakes and reservoirs under a recreational use advisory are not closed since HCBs may only be present in certain areas of the waterbody and conditions can change frequently. The advisory will remain in place until the bloom has fully dissipated and cyanotoxin concentrations are below threshold values, or until the primary recreation season ends on September 30th, whichever comes first.

On July 9, 2020, satellite imagery from the Cyanobacteria Assessment Network (CyAN) identified elevated densities of cyanobacteria covering a large portion of Seminoe Reservoir. The Wyoming Department of Environmental Quality visited the reservoir on July 15, 2020, and collected water samples at the Boat Club Picnic Area. Cyanobacteria densities exceeded the 20,000 cells/mL recreational use threshold identified in Wyoming’s HCB Action Plan. Cyanotoxin results are pending. The status of advisories in Wyoming as well as other HCB resources can be found at WyoHCBs.org.

The Wyoming Department of Health is working directly with Seminoe State Park to post advisory signs at the reservoir.

The Wyoming Department of Health and 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 Dr. Karl Musgrave, State Environmental Health Epidemiologist / State Public Health Veterinarian, Wyoming Department of Health, at This email address is being protected from spambots. You need JavaScript enabled to view it. or (307) 777-5825.

Questions regarding cyanobacteria sampling can be directed to Michael Thomas, Natural Resource Analyst, Wyoming Department of Environmental Quality, at This email address is being protected from spambots. You need JavaScript enabled to view it. or (307) 777-2073, or Lindsay Patterson, Surface Water Quality Standards Coordinator, Wyoming Department of Environmental Quality, at This email address is being protected from spambots. You need JavaScript enabled to view it. or (307) 777-7079.