Is the lake safe?

California

Toxic algae in Orange County lakes

16 lakes and waterways in Orange County have harmful algal bloom reports in California's official data. The most recent entry is for San Juan Creek: There are no bloom reports for San Juan Creek in the last 30 days of California's data. The most recent was an algal mat alert sign on 19 August 2026 at Near horse trail. San Diego Creek 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.

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.