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).
Idaho’s Cyanobacteria Recreational Waters Response Plan outlines how harmful algal blooms (HABs) are identified, monitored, and communicated to the public. As part of the updated plan, Idaho’s response framework includes two additional risk levels—Health Watch and Health Alert—to provide timely public information while toxin test results are pending. Waterbodies with a Health Watch, Health Alert, or Health Advisory will be displayed on the DHW Recreational Water Health Advisories Map and the CyanoHAB Risk Data Table below. Scroll down for more information.
Our staff are responsible for responding to HAB reports from the public, sampling Idaho waterbodies, and analyzing water quality data. We provide sample results and other relevant information to DHW and the local public health district. Using that information, DHW determines whether public health notifications are warranted.
Due to the large number of waterbodies across Idaho, DEQ cannot continuously monitor every waterbody at all times. HABs can develop quickly, particularly in hot weather. If the water looks bad, stay out, and report to our team using the methods below.
For more information about what a HAB looks like, see our Cyanobacteria Harmful Algal Bloom Information StoryMap.
CyanoHAB Risk Data Table
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.
When water quality data results in a change to a waterbody’s risk level, the information will be available in the table below. Reference the CyanoHAB Risk Rating and Communication Table for more details.
| Risk Level | Waterbody | County | Data Type | Collection Date | More Information |
|---|---|---|---|---|---|
| Watch | Winchester Lake | Lewis | Field Observations | 06/11/2026 | This cyanoHAB watch indicates evidence of a toxic bloom. Cyanotoxin levels are low but can change rapidly. |
| Watch | Mann Lake | Nez Perce | Field Observations | 06/11/2026 | This cyanoHAB watch indicates evidence of a toxic bloom. Cyanotoxin levels are low but can change rapidly. |
| Watch | Little Wood River Reservoir | Blaine | Field Observations | 06/17/2026 | This cyanoHAB watch indicates evidence of a potentially toxic bloom without confirmed presence of toxigenic cells or cyanotoxins. |
| Watch | Lake Lowell | Canyon | Field Observations | 06/16/2026 | This cyanoHAB watch indicates evidence of a potentially toxic bloom without confirmed presence of toxigenic cells or cyanotoxins. |
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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