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Water Quality


NOTICE: Blue Green Algae Alert!

Potentially harmful levels of naturally occurring blue green algae have been detected in portions of the Snake River in Hells Canyon and Brownlee Reservoir. These are temporary situations, but water users, including pets and livestock, should avoid contact with water in the affected areas.

Details of current algae-related health advisories are available on the Idaho Department of Environmental Quality website.


Bacteria and algae are vitally important to freshwater ecosystems. Cyanobacteria are a type of bacteria commonly referred to as blue green algae. When cyanobacteria begin to grow rapidly a bloom can result. This is a natural occurrence, but these algal blooms can create a potential hazard for humans and animals. Water users should take note of whether visible blooms are present in areas where they or their pets or livestock may come into contact with the water.

Blue green algae blooms can be unsightly and vary in appearance. These blooms can appear as visible green, blue-green, or reddish brown foam, scum, or mats that float on or near the water surface, especially near the shoreline.

Blooms may appear at different times of day. They may be associated with foul odors either during the bloom or after the algae begins to die.

Most algae neither reach nuisance levels nor become harmful to human and animal health. A harmful algal bloom (HAB), however, can occur when certain types of algae are present in high concentrations or produce toxic substances that can harm people, pets, and livestock.

HABs are most often caused by cyanobacteria. Humans who drink, swim, or enjoy other recreational activities in water that contains high concentrations of cyanobacteria or cyanobacterial toxins may experience diarrhea and vomiting, skin irritation, allergic responses, or liver damage. The toxins tend to accumulate in the internal organs of fish, so eating fish not properly cleaned could pose health risks. Animals, including pets, livestock, and wildlife, are also at risk of illness or possible death.

Find more information on the following websites:

Water Quality at Idaho Power

Snowfall in the Tetons, a farmer's method of manure removal, and a water user's process for returning wastewater to the river all impact the level of water quality throughout the Snake River. Pollutants are abundant in our water system and they impact everything from aquatic habitats to water temperature.

At Idaho Power, we believe our role is to serve not just our customers' need for power but to do it in a way that serves the environment in which we live. That's why water quality is at the top of our list. While our dam operations affect water temperatures, our research has shown that there are a multitude of other forces above our dams that are contributing to the Snake River’s temperature issues.

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