Official Government Website

Cyanobacteria Harmful Algal Blooms

This page provides information related to current recreation water quality health advisories involving cyanobacteria harmful algal blooms (HABs) and E. coli bacteria. The map is updated with the most current information as health advisories are issued and lifted throughout the season. 

Recreation Water Bloom Advisories and Warnings

The map below provides additional information for active health advisories. Click on the marker in the map for updates. 

Cyanobacteria Bloom and Advisory Updates

Although Idaho’s bloom season should be winding down, cyanobacteria are still active in many areas. We encourage the public to avoid fishing or hunting where the water is green. Download the USGS field guide for identifying cyanobacteria.

Please remember to wash hands with fresh water or use a wipe after handling fish, lures, and waterfowl. Hand sanitizer does not protect against cyanotoxins. Cyanobacteria can cause serious health issues and even death in dogs. 

The table below provides updates for each water body with an active bloom, active advisory, and a lifted health advisory. 

Status Update County Waterbody Advisory Issued Advisory Lifted
Lifted Kootenai Black Lake 10-07-2021 11-01-2021
Active Bloom Bonner Boyer Slough 2021 August 20
Lifted Washington Brownlee Reservoir 08-06-2021 10-08-2021
Lifted Valley Cascade Reservoir 08-13-2021 10-08-2021
Lifted Kootenai Cave Lake 10-07-2021 11-01-2021
Lifted Bonner Chuck Slough 08-04-2021 11-01-2021
Lifted Clearwater Dworshak 09-23-2021 11-08-2021
Lifted Clearwater Elk Creek Reservoir 08-04-2021 11-08-2021
Lifted Kootenai Fernan Lake 07-28-2021 11-01-2021
Active Bloom Kootenai Hauser Lake 10-07-2021 11-01-2021
Active Bloom Kootenai Hayden Lake - near McCleans Bay (where it is shallow with an abundance of aquatic vegetation; including McCleans Bay). 07-27-2021 11-01-2021
Lifted Adams Hells Canyon Reservoir 08-06-2021 10-08-2021
Lifted Fremont Henry's Lake 09-10-2021 10-29-2021
Lifted Latah Hordemann Pond - Closed Until Further Notice 07-26-2021 11-08-2021
Active Advisory Canyon Lake Lowell 08-06-2021
Active Advisory Twin Falls County Magic Reservoir 08-09-2021
Lifted Nez Perce Mann Lake 08-13-2021 11-08-2021
Lifted Bonner Priest Lake Outlet: From Outlet Bay Road (48.4934, -116.8907) to the dam 08-27-2021 09-10-2021
Lifted Bonner Sagle Slough and Comeback Bay 08-04-2021 11-01-2021
Active Advisory Twin Salmon Falls Creek Reservoir 08-09-2021
Active Bloom Bonner Solomon Lake 09-12-2021 11-01-2021
Lifted Kootenai Spirit Lake 08-23-2021 11-01-2021
Lifted Latah Spring Valley Reservoir 07-26-2021 11-08-2021
Active Advisory Fremont Upper Island Park Reservoir shoreline 09-10-2021

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Water Quality Standards Analyst

Brian Reese
Brian.Reese@deq.idaho.gov
(208) 373-0570

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