As of August 13, 2021, at least 12 separate water bodies across Idaho have experienced outbreaks of toxic algae. That means that the water is so dangerous that you shouldn’t allow it to come into contact with your body, your pet, or your livestock.

Outbreaks are ongoing across the state, with warnings issued today for Lake Cascade (Valley County) and Mann Lake (Nez Perce County). Previously-issued warnings remain in effect for Salmon Falls Creek (Twin Falls County), Fernan Lake (Kootenai County), Lake Lowell (Canyon County), and reservoirs along the Snake River including Brownlee and Hells Canyon (Washington and Adams Counties) along the Idaho/Oregon border. Each of these lakes and rivers are popular recreation and swimming areas, and the outbreaks pose very real health threats.

The warnings are issued by local health districts, in coordination with the Idaho Department of Environmental Quality.

Are algae outbreaks on the rise, what causes them?

Heat waves, drought, and excessive pollution are contributing to what could be the worst year ever for toxic algae in Idaho. In particular nitrogen and phosphorous pollution contribute to the growth of cyanobacteria which can release harmful toxins when populations explode. In Idaho, these pollutants flow primarily from wastewater treatment plants, agricultural and dairy operations, along with runoff from storm drains, septic tanks, and fertilized lawns.

What are the health effects of toxic algae?

Harmful toxin-producing cyanobacteria can also lead to fish and bird kills and pose serious health threats to livestock, pets, wildlife, and humans. Last week, four dogs died in Eastern Washington after swimming in rivers contaminated with toxic algae. In humans, exposure to the toxins can cause neurological problems like paralysis and seizures.

While drinking water sources in Idaho haven’t seen outbreaks yet, outbreaks in other states have led to millions without access to clean water.

How can I recognize an algae outbreak and what should I do?

Algae outbreaks can vary in appearance, and may look like mats, foam, spilled paint, or surface scum, and sometimes can have a foul odor. Outbreaks can appear blue-green in color, or sometimes a reddish-brown color (if it looks off-color, just avoid it). Outbreaks can be discovered in one area of a water body, but can also move to different areas and water depths, and can change in severity with changing flows, temperatures, and winds.

According to DEQ, some of the most common indicators of toxic algae include:

  • The water has foam, scum, algal mats, or paint-like streaks on the surface,
  • The water looks discolored, and/or
  • The water smells unusually bad.

You can’t tell if an outbreak is harmful just by looking at it, so use caution and stay away from the water.

Symptoms of exposure

Symptoms of exposure to toxic algae include rashes, hives, diarrhea, vomiting, coughing, and/or wheezing. More severe symptoms affecting the liver and nervous system may result from ingesting water. If you think you may have symptoms caused by an outbreak of algae, talk to your healthcare provider and tell them you might have recently come into contact with cyanobacteria or its toxins. If your pet begins to show signs of toxic exposure after playing in a reservoir or lake, connect with your vet immediately for treatment.

If your pet comes into contact with water you suspect to be contaminated, wash your pet with clean water and shampoo. If it shows symptoms such as vomiting, staggering, drooling, or convulsions, contact your vet immediately.

Are these outbreaks ‘natural’?

While the cyanobacteria that lead to outbreaks are naturally occurring in our environment, the rapid growth of this bacteria, leading to the release of toxins and public health threats, is not a natural occurrence. Without excessive pollution from nitrogen and phosphorous, these outbreaks simply did not occur. And gobal warming is making harmful freshwater toxic algae more frequent and more intense. Further, climate scientists determined that the heat wave that we experienced earlier this summer would have been impossible without climate change.

So, extensive outbreaks of toxic algae are about as normal as a 116 degree June day in Portland, OR…

What are we doing about it?

ICL is working across the state to protect water quality and prevent toxic algae before it becomes a problem. We’re working at the local, regional, state and national levels. We’re working to reduce pollutants from sources including wastewater treatment plants, agricultural and dairy operations, and to reduce the pollutants that flow into some of our treasured lakes like Coeur d’Alene, Pend Oreille, Payette and many, many others. And, we’re working to make Idaho carbon neutral, to address the root causes of climate change. Join with us! 

For more info

Check out the DEQ website for up-to-date info on current advisories and potential outbreaks.

Report suspicious-looking water to DEQ by phone, email, with the BloomWatch app, or online.