California
Toxic algae in Modoc County lakes
9 lakes and waterways in Modoc County have harmful algal bloom reports in California's official data. The most recent entry is for Emerson Creek: There are no bloom reports for Emerson Creek in the last 30 days of California's data. The most recent was a bloom report on 19 August 2026 at ~0.7mi below Hwy 81 (641EMR001).
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.
- Big Sage Reservoir 2023
- Donovan Reservoir 2023
- Fitzhugh Creek 2021
- Mill Creek 2026
- Owl Creek 2026
- Turner Creek 2024
- Twelvemile Creek 2026
- West Valley Reservoir 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.