Algae bloom prompts CPW caution for Deweese Reservoir

blue-green algae bloom at DeWeese Reservoir prompted Colorado Parks and Wildlife to caution people to avoid contact and keep their pets out of the water. Fish taken from the water are safe to eat if properly cleaned and thoroughly cooked.


People and their pets are encouraged to avoid contact with water in DeWeese Reservoir State Wildlife Area near Westcliffe due to a blue-green algae bloom that could be harmful if touched or ingested.

Colorado Parks and Wildlife officials said they are concerned about increased levels of toxicity found Wednesday in tests of the water after elevated levels of algae continued to be observed in a turquoise-colored film and in testing of the reservoir. 

CPW Area Wildlife Manager Mike Trujillo advised in a press release to be “algae aware” and avoid recreating in waters with visible algae blooms. Follow instructions on all CPW cautionary signs posted at the reservoir about blue-green algae.

“All skin-to-water contact should be avoided for humans and pets,” Trujillo said. “We encourage no contact with the water for humans or their pets. Contact with the water could cause minor skin rashes and make pets ill. So avoidance is the best policy.”

Algae blooms are common when temperatures rise, but they usually occur later in the summer, Trujillo said. CPW will monitor the reservoir closely to see if toxic levels increase or decrease and will adjust the status from caution, danger or clear accordingly.

Fishing is still allowed, but anglers are cautioned to avoid the water. It’s important to take care handling and cleaning any fish caught in DeWeese. Toxins accumulate in the liver and guts of fish, so any fish taken must be properly cleaned and thoroughly cooked before eating. 

Trujillo said algae are an important part of aquatic food webs, but some types of blue-green algae are capable of producing toxins that may cause negative health impacts for humans and pets at elevated concentrations. Currently there is no method to remove toxins from lakes.

The public can help reduce the occurrence of blue-green algae blooms by preventing nutrients (nitrogen and phosphorus) from entering waterways through responsible use of lawn fertilizers, picking up pet waste and avoiding using de-icers that contain urea.