Created
Sep 3, 2023 2:49 AM
Tags
portland
TLDR: Cyanobacteria (harmful algae) blooms in the Willamette River are caused by stagnant water in Ross Island Lagoon, a former gravel pit. The affected areas are downstream of the lagoon, which is located about midway between the Sellwood Bridge and the Ross Island Bridge. ☠️ They are especially toxic to dogs, but also harmful to humans ☠️.
Safe to swim: Sellwood Riverfront Park and Elk Rock Island are significantly upstream of Ross Island Lagoon, and health advisories for harmful algae blooms have not been issued for these areas.
Get info: Check OHA’s current advisories for current information and to learn how to identify algae blooms.
This page is currently a draft! If you note any errors, email me.
Notes
The Willamette River is tidal and sometimes flows in reverse direction up to Willamette Falls. However, harmful algae bloom advisories have not historically been issued upstream of Ross Island Lagoon, as the river still primarily flows towards the Columbia River.
Sources
Year | Maximum Extent | Advisory Dates | Advisory Links |
2023 | Ross Island to Cathedral Park | July 28 - ? | |
2022 | Willamette Cove to Cathedral Park | August 17 - September 16 | |
2021 |
Thanks to John Niekrasz for suggestions.