Gem State Roundup

Health advisory issued for eastern Idaho’s Henrys Lake for harmful algal bloom

By: - September 26, 2023 2:42 pm
cyanobacterial bloom in water

If the water in Idaho’s rivers and lakes smells bad, looks foamy or thick (like paint was spilled into the water), appears scummy, blue-green, or brownish-red in color, stay out, health officials advise. (Courtesy of the Centers for Disease Control and Prevention)

A health advisory has been issued for Henrys Lake, and the Idaho Department of Health and Welfare is urging caution for those recreating in or near its water.

Recent samples from the lake showed high amounts of cyanobacteria, which can produce cyanotoxins that are harmful to people, pets and livestock.

Summer heat can cause dangerous conditions, harmful algal blooms in Idaho’s rivers and lakes

The health advisory, which is issued by the health department in conjunction with the Idaho Department of Environmental Quality, is similar to others around the state, including advisories for the Brownlee Reservoir, Cedar Creek Reservoir near the south boat ramp, Fernan Lake and Hells Canyon from the Big Bar campground to the dam. A previous health advisory for the Island Park Reservoir has been lifted. To view a map of the advisories around the state, go to

Health officials urge the public recreating near or in Henrys Lake to take the following precautions:

  • Avoid swimming, wading, or other contact with the water. Take extra care to ensure children do not drink or get the water on them.
  • Ensure pets and livestock do not drink or go into the water. If they have contact with the water, clean their skin, hide, or fur with clean water right away.
  • Do not drink or cook with the water. Boiling or filtering the water does not remove the toxins and can increase the risk of becoming sick.
  • Wash hands thoroughly in clean water after handling fish or objects from the water.
  • If you choose to eat fish from the water, clean and wash fish thoroughly in uncontaminated water. Filet the fish, and remove all fat, skin and internal organs before cooking. Cyanotoxins can build up in fish, and the risk to people is unknown.
  • Watch for symptoms. If you touch or swim in the water or breathe in water droplets, you might experience a rash, hives, red eyes, wheezing, coughing, or shortness of breath. If you swallow the water, you might have stomach pain, diarrhea or vomiting. You might have a headache, muscle weakness or dizziness. If your liver is damaged, your skin might turn yellow, and you will have dark urine. If you think you might be sick from cyanotoxin, consult your health care provider or call the poison center at 1-800-222-1222. In addition, notify [email protected].
  • Monitor media reports and DHW’s website for health advisories.


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Christina Lords
Christina Lords

Christina Lords is the editor-in-chief of the Idaho Capital Sun and has been a professional journalist covering local and state government since graduating from the University of Idaho in 2009. A Pocatello native, Lords is a fifth-generation Idahoan who served as a reporter at the Moscow-Pullman Daily News and the Post Register in Idaho Falls and served as assistant editor for the Idaho Press in Nampa. She also led the Idaho Statesman in Boise for two years before turning to nonprofit journalism.