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
The Idaho Department of Health and Welfare has lifted health advisories for water bodies affected by cyanobacterial harmful algal blooms for the 2025 season. The Idaho Department of Environmental Quality monitors and samples when risk to recreationists is high. Conditions that support toxic blooms significantly diminish with cooler temperatures, but the public should remain cautious as blooms can remain active in cooler months.
As water quality sample results become available, you will see them in the table below. Visit “DEQ’s Role and More Bloom Information” for more details on threshold values.
County | Waterbody | Sample Date | *Threshold Level | Health Advisory |
|---|---|---|---|---|
| — | — | — | — | — |
*Two samples below threshold taken one week apart are required to lift a health advisory.
Report a Potential Harmful Algal Bloom
Report a potential harmful algal bloom:
- Online form
- By phone: (866) 671-5385
- By email: algae@deq.idaho.gov
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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