Blue-green algae bloom in Lower North Crow Reservoir

BOPU 8-13-20

The Wyoming Department of Environmental Quality (DEQ) has issued a warning about the rising dangers of a blue-green algae bloom in the City of Cheyenne Board of Public Utilities’ (Board) Lower North Crow Reservoir which is located at the John and Annie Woodhouse Recreation and Wildlife Habitat Area 27 miles northwest of Cheyenne. The Lower North Crow Reservoir’s water is used for irrigation purposes and is not used for the City’s drinking water supply.

Blue-green algae can form harmful blooms in slow-moving water during late summer months when water temperatures are warmer. These blooms are considered harmful because they produce toxins and other irritants which can pose a risk to humans, pets, livestock and wildlife.

“Since this reservoir is not part of Cheyenne’s drinking water supply, the City’s tap water continues to be safe,” stated the Board’s Director, Brad Brooks. “However recreational use of the Lower North Crow Reservoir should be limited.”

The Board is assisting DEQ by asking residents to follow these recommendations:

  • Avoid contact with water in the vicinity of the bloom, especially in areas where cyanobacteria are dense and form scum.
  • 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.

For more information about blue-green algae, please visit