California
Toxic algae in Nevada County lakes
24 lakes and waterways in Nevada County have harmful algal bloom reports in California's official data. The most recent entry is for Prosser Reservoir: A bloom was reported at Prosser Reservoir on 7 October 2026 at near boat launch. Martis Creek Reservoir, Little Truckee River and Prosser Creek 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.
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.
- Crabtree Creek 2026
- Flora Lake 2022
- Lake Angela 2022
- Lake Of The Pines 2026
- Lake Wildwood 2024
- Lake Zyac 2026
- Little Dry Creek 2023
- Middle Fork American River 2025
- Other Lake Or Reservoir 2020
- Pond On Marin Pl 2026
- Prosser Creek Reservoir 2023
- Sagehen Creek 2026
- Scotts Flat Lake 2022
- South Fork Yuba River 2023
- South Yuba River 2026
- Trout Creek 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.