The National Park Service has sampled, analyzed, and determined the presence of cyanotoxins in the Iola Basin section of Blue Mesa Reservoir in concentrations that exceed safe exposure levels. Certain types of algae blooms can produce toxins called cyanotoxins, which can be harmful to humans and animals.

The National Park Service has closed areas in the Iola Basin to full body contact. Use caution and avoid unnecessary exposure to reservoir water if fishing, boating, or recreating. Other areas of Blue Mesa Reservoir may also contain these toxins, please use caution. Avoid areas with suspected algal mats.

Boating and fishing remain open throughout Blue Mesa. Clean harvested fish in treated water. As always, remember to clean, drain, and dry all boats and fishing gear.

Do not let dogs or other animals drink water from any portion of the Iola Basin. Until further notice, the park recommends that dogs not swim in or drink reservoir waters.

Contact medical care (doctor or veterinarian) if, after exposure to the water, individuals or pets exhibit nausea, vomiting, digestive distress, breathing problems, seizure, or unexplained illness.

Harmful algae, also known as blue-green algae, is common and natural to our waters and found throughout Colorado. The algae can multiply rapidly to form blooms and scums, particularly in areas of shallow, warm water.

Water quality staff are sampling and monitoring the situation. Visit for more information.

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