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CPW News Release
CPW News Release
Toxic algae bloom on DeWeese Reservoir prompts CPW to limit water recreation to fishing only with no water contact

Joey Livingston
Statewide Public Information Officer
303-345-4658 /

CPW limits water contact activities to fishing only on DeWeese Reservoir

Danger signs are being posted at DeWeese Reservoir State Wildlife Area announcing the lake is closed due to an outbreak of toxic blue-green algae. Photo courtesy of Colorado Parks and Wildlife
CPW limits water contact activities to fishing only on DeWeese Reservoir

WESTCLIFFE, Colo. – A growing bloom of toxic blue-green algae at DeWeese Reservoir State Wildlife Area prompted Colorado Parks and Wildlife to warn the public to avoid contact with the water.

“Algae has become a seasonal problem at DeWeese, forcing CPW in recent summers to close the water to all activity except fishing to prevent the risk of exposure to humans and their pets,” said CPW District Wildlife Manager Justin Krall. “The algae can be harmful to people and pets if touched. It can give sensitive people a bad rash, for example. And it’s possibly fatal if ingested.”

Signs are being posted at the reservoir by CPW warning visitors to avoid the water and explaining the danger of the algae blooms.

The signs warn people to keep kids and pets out of the water at risk of death from the toxic algae. The signs warn people not to drink the water and no water recreation including swimming, skiing, paddle-boarding and wading.

If anyone or their pet comes into contact with the algae, the signs urge them to shower immediately with fresh, clean water.

The warning was prompted after testing found dangerous levels of toxicity in the water and elevated levels of algae were observed in a turquoise-colored film on the reservoir. 

“You can still fish during an algae bloom,” Krall said. “But there should be no skin-to-water contact.

“It’s also important to take care when handling and cleaning any fish caught in DeWeese. Toxins accumulate in the liver and guts of fish. So it’s important any fish taken is properly cleaned and thoroughly cooked before eating it.” 

Algae blooms are common when temperatures rise, usually in late summer, he said. CPW has been monitoring the reservoir closely, taking weekly water samples to check for elevated toxicity.

DeWeese Reservoir SWA is a 300-acre property near Westcliffe with good fishing. Other forms of recreation still allowed at the SWA include: picnicking, hiking, wildlife viewing and camping.  

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 Colorado Department of Public Health and Environment (CDPHE) recommends the following:
  • Keep kids out
  • No pets in water
  • Do not drink water
  • Avoid contact with algae
  • If exposed, shower immediately
More information on blue-green algae is available on CDPHE’s website.

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 deicers that contain urea. 
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CPW is an enterprise agency, relying primarily on license sales, state parks fees and registration fees to support its operations, including: 42 state parks and more than 350 wildlife areas covering approximately 900,000 acres, management of fishing and hunting, wildlife watching, camping, motorized and non-motorized trails, boating and outdoor education. CPW's work contributes approximately $6 billion in total economic impact annually throughout Colorado.
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