California
Toxic algae in Humboldt County lakes
24 lakes and waterways in Humboldt County have harmful algal bloom reports in California's official data. The most recent entry is for Eel River: There are no bloom reports for Eel River in the last 30 days of California's data. The most recent was a bloom report on 7 September 2026. Eel River, Mad River and South Fork Eel River and 3 more have had blooms in three or more years.
Lakes with bloom history
Newest report first. Each lake has its own page with the full history and what the results mean.
- Eel River Bloom reported
- Mad River Awareness sign
- South Fork Eel River Awareness sign
- Van Duzen River Awareness sign
- Humboldt Bay Bloom reported
- Stone Lagoon Bloom reported
- Big Lagoon Bloom reported
- Klamath River Bloom reported
- Big Lagoon Hydrologic Area Bloom reported
- North Fork Mad River Hydrologic Area Caution
Other waterbodies with a report
These have one or two reports in a single year, which isn't enough history for a page of their own yet.
- Blue Creek 2022
- Canoe Creek 2021
- Cheenitch Creek 2022
- Freshwater Lagoon 2024
- Grouse Creek Hydrologic Subarea 2020
- Horse Mountain Creek 2026
- Little Lost Man Creek 2022
- Lost Man Creek 2021
- Mattole River 2024
- Other River 2019
- Redwood Creek 2023
- Sholes Creek 2026
- Squaw Creek 2022
- Tepee Creek 2026
Source: California State Water Resources Control Board, official data, checked 24 October 2026. For today's conditions see the California HABs Portal map. No report doesn't mean a lake is safe: most water is only tested occasionally.