Two Idaho Lakes Under Health Advisory Due to Toxic Algae

Jul 29, 2021

Hayden Lake is under an algal bloom warning.
Credit Pandhandle Health District.

The hot temperatures this summer have promoted algae growth at some area lakes, and Idaho officials are warning people to try to avoid contact with contaminated lake water, which can be a health threat.

The algae appears as discolored water, streaks or globs of scum, or thick green matts along the shore.

Katherine Hoyer of the Panhandle health District says advisories have been issued for the northern part of Hayden lake, as well as Fernan Lake near Coeur d Alene. They want to keep people, especially young children, from accidentally ingesting the algae which can be toxic.

“You could have a rash, hives, diarrhea, upset stomach, vomiting, you could be coughing or wheezing. If you have more severe symptoms, that means it could be affecting your liver or nervous system, depending on the level of toxin that's there in the water.”

Hoyer says pets should also be kept out of the water because they can experience the same symptoms.

The algae blooms often arrive when the weather warms up, and this year's heat is promoting growth at several area lakes.

Kristin Lowell of the Idaho Department of Environmental quality says this summer's high temperatures have also played a role in promoting algae growth:

“The northern part of Hayden lake is shallow, as is Fernan lake. This year is even more shallow, we've seen a drop in the lake levels because of the extreme heat.”

When the temperatures start to cool in the fall, the blooms are likely to decrease at Hayden lake, but usually won't go away at Fernan until winter arrives.

Presence of phosphorous in the water also promotes algae growth. That can come from different sources including over-fertilized lawns nearby, as well as the plants in the lake that die, like invasive millfoil, that decompose and add to the phosphorus level.

“Lawns on the shoreline, fertilizing and over irrigating. It can be up in the watershed, streams that feed Hayden lake, if there are phosphorus sources upstream in the water shed that can be part of it. And the internal cycling as the plants are dying and being decomposed and that internal phosphorus source.” 

DEQ is asking anyone who sees algae blooms at other area lakes to notify their offices.