In the Klamath Basin blue-green algae blooms typically occur between June and October when temperatures rise and water conditions are favorable for algal growth. Blue-green algae monitoring typically occurs May - November. If river conditions exceed public health standards for toxic algae the area is posted with a health advisory sign.

BGA Tracker 20230918

View the Klamath BGA Tracker Interactive Map


For more information, please check California's HAB Incident Reports Map.


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Updated Posting Status

Yurok Warning 2 9/18/23- The Klamath River between Weitchpec and Turwar has been posted at the Warning level based on microcystin results which exceed Yurok tribal standards.  

Yurok Caution9/18/23- The Klamath River between Turwar and the estuary has been posted at the Caution level due to the detection of microcystin in this reach. 

CA CautionActionTrigger Yellow29/11/23- The Klamath River between Iron Gate Dam and Weitchpec has been posted at the Caution level due to the presence of microcystins. This extends the 8/18/23 Caution posting between Iron Gate Dam and I-5 further downriver. 

CA CautionActionTrigger Yellow2 8/18/23- The Klamath River between Iron Gate Dam and I-5 has been posted at the Caution level due to the presence of microcystins. 

CA CautionActionTrigger Yellow2 8/1/23- Iron Gate Reservoir has been posted at the Caution level due to the presence of microcystins.

OR Advisory Red2 7/25/23- A recreational use advisory has been expanded for all of Upper Klamath Lake and Agency Lake based on samples collected at the Henzel Boat Launch. 

CA DangerTier2 Red2 7/21/23- Copco Reservoir has been posted at the Danger level due to the presence of microcystins. 

OR Advisory Red2 6/30/23- recreational use advisory has been posted for the southern portion of Upper Klamath Lake due to the presence of microcystins in Howards Bay and Moore Park.

Below Threshold 6/30/23- All other reaches of the Klamath River are below public health thresholds for cyanotoxins.   


About the Tracker

The BGA Tracker Map was built to inform the public and research community regarding river conditions. The Tracker utilizes current information to track  and map the blue-green algae blooms throughout the Klamath Basin. The Blue-Green Algae Tracker identifies blue-green algae public health threats  (i.e. exceeds health thresholds identified in the appropriate guidance) by river reaches bounded by public health monitoring locations.

River reaches which exceed applicable criteria for public health are indicated by different colors on the map that vary depending on the number of tiers within each jurisdiction's advisory thresholds. Advisory colors within the map are:                 



Yurok Tribe   Yurok Caution 1 Yurok Warning 2 Yurok Danger 3


Blue-green Algae Official Notifications

Other Information