California
Toxic algae in Tehama County lakes
7 lakes and waterways in Tehama County have harmful algal bloom reports in California's official data. The most recent entry is for Carter Creek: A bloom was reported at Carter Creek on 1 October 2026 at Carter Creek ~1.2mi above Deer Cr. (509CTC033). Black Butte Reservoir has 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.
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.
- Battle Creek 2026
- Lake California 2022
- Plum Creek 2021
- Sacramento River 2022
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.