In early July TriCounty Health posted signs at Matt Warner Reservoir limiting recreation due to a Harmful Algal Bloom. While swimming and recreation was restricted, fishing was still considered safe. This week that changed and new signs have been posted closing the waters entirely due to the toxic algae, meaning the lake is now closed to the public. A joint press release was issued on Wednesday from the Department of Environmental Quality, TriCounty Health, and the Division of Natural Resources explaining that a recent water sample at Matt Warner showed 109 million cells per milliliter of cyanobacteria – which is over 11 times the EPA’s threshold for closure. “Harmful algal blooms happen frequently at Matt Warner Reservoir. Throughout the season, the bacteria grow,  bloom and die. As the cells die, toxins are released that are harmful to human and animal health,” explains Environmental Health Scientist Eric Larsen. “There is nothing we can do to mitigate or prevent the toxins. The best thing we can do is stay out of the water until the bacteria and toxins dissipate on their own.” DWR Director Mike Fowlks issued an emergency amendment to the 2019 Utah Fishing Guidebook to ensure the word spreads. “The risk to humans and animals is too great. All contact with the water and any fish in the water should be avoided until the algal bloom subsides and toxicity levels decrease,” says Fowlks. “Typically, it is still safe to fish during algal blooms, but these levels caused safety concerns for any kind of contact with the water.” Hunting and camping in the Diamond Mountain Wildlife Management Area is still allowed but campers and hunters with dogs should avoid the area so there is no chance of exposure to their pet. There have been multiple national stories this week of pets killed after exposure to harmful algal blooms. For more information, visit


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