Updated at 9:00 a.m. on October 7, 2024: DEQ issued an Air Quality Advisory for one Idaho county, Lemhi County, where all burning is prohibited. Take steps to protect your health and check DEQ’s open burning map for future burn decisions.
Official Government Website

Cyanobacteria Harmful Algal Blooms

DEQ and the Idaho Department of Health and Welfare (DHW) each play a role in identifying, responding to, and monitoring cyanobacteria harmful algal blooms (HABs).

The health advisory map is available on DHW’s Recreational Water Health Advisories web page.

Our staff are responsible for responding to HAB reports from the public, sampling Idaho waterbodies, and analyzing water quality data. We provide sample results to DHW and the public health district in the area where the HAB is reported, and they decide if it warrants a health advisory.

Due to the extensive number of waterbodies in the state, it is not possible for DEQ to monitor them all, at all times. HAB tests can also take up to a week to get back, and HABs can develop or dissipate quickly, particularly in hot weather. For more information about what a HAB looks like, see our Cyanobacteria Harmful Algal Bloom Information StoryMap. If the water looks bad, stay out, and report to our team using the methods below.

Water Quality Test Results

As water quality sample results become available, you will see them in the table below. 

County

Waterbody

Sample Date

*Threshold Level

Health Advisory

Kootenai

Hayden Lake (North Arm)

9/26/2024

Below


Twin Falls

Salmon Falls Creek Reservoir

8/28/2024

Below


Twin Falls

Cedar Creek Reservoir

9/19/2024

Above

Link to health advisory

Washington

Brownlee Reservoir (Wolf Creek)

7/31/2024

Above

Link to health advisory

Blaine

Fish Creek Reservoir

6/24/2024

Below

Washington

Mann Creek Reservoir

7/31/2024

Below

Washington

Eagle Bar, Hells Canyon

7/31/2024

Above

Link to health advisory

Washington

Snake River, at Cottonwood Creek (River Mile 294)

7/31/2024

Above

Link to health advisory

Elmore

C.J. Strike Reservoir (Airforce Marina)

9/3/2024

Below

Kootenai

Fernan Lake

8/2/2024

Above

Link to health advisory

Kootenai

Avondale Lake

8/2/2024

Above

Link to health advisory

Fremont

Island Park Reservoir

8/15/2024

Below

Clearwater

Elk Creek Reservoir

8/15/2024

Below

Valley

Cascade (Van Wyck) Reservoir

10/2/2024

Below

Nez Perce

Soldiers Meadow Reservoir

9/27/2024

Below

Fremont

Henrys Lake (West Side)

9/10/2024

Above

Link to health advisory

Kootenai

Cave Lake

9/3/2024

Below

Canyon

Lake Lowell (Upper Boat Ramp)

9/25/2024

Below

Bonneville

Ririe Reservoir (Ririe Boat Ramp)

9/18/2024

Below

Power

American Falls Reservoir (West Side)

9/18/2024

Above

Link to health advisory

Gooding

Thorn Creek Reservoir (South End)

9/27/2024

Above

Link to health advisory

Valley

Kelly Whitewater Park

10/2/2024

Below

Adams

Hells Canyon at Big Bar

9/26/2024

Below

Latah

Spring Valley Reservoir

10/1/2024

Above

Link to health advisory

*For more details on threshold values, please click on “DEQ’s Role and More Bloom Information” below.

Report a Potential Harmful Algal Bloom

Report a potential harmful algal bloom: 

Health Concerns

Idaho’s health agencies offer citizens education and advice on cyanobacteria exposures. Contact the Idaho Department of Health and Welfare or your local public health district for health concerns and cyanobacteria information.

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