Oregon
Toxic algae in Multnomah County lakes
4 lakes and waterways in Multnomah County have harmful algal bloom reports in Oregon's official data. The most recent entry is for Wapato Marsh: Oregon issued a health advisory for Wapato Marsh in 2025, listed on 2 December 2025. Willamette River and Blue Lake 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.
Source: Oregon Health Authority (OHA), official data, checked 24 October 2026. For today's conditions see the OHA current advisories page. No report doesn't mean a lake is safe: most water is only tested occasionally.