SCIENCE SAYS IT’S SAFE

It is safe to swim and recreate in the Willamette most times of the year.

State and local agencies, including the Oregon Department of Environmental Quality (DEQ) and Portland’s Bureau of Environmental Services, regularly monitor water quality — and data going back to 2012 show that bacteria levels are almost always within healthy limits. It wasn't always this way. In November 2011, Portland completed a 20-year combined sewer overflow (CSO) control program that greatly reduced untreated waste to the Willamette River. Before CSO control, combined sewers overflowed to the river an average of 50 times a year. Exposure to bacteria is the greatest health concern for people swimming or enjoying other sports on the river.

GOOD RULES OF THUMB

While it is generally considered safe to swim in the Willamette River, the river has a large watershed and pollutants can reach the water from many potential sources. Stay out of the water if it looks bright green, scummy or thick like blue green paint. This could be the sign of blue-green algae, which can produce toxins that are harmful to humans and pets. Also, bacteria can wash into the river following heavy rains, so avoid swimming at those times (Oregon DEQ).

HARMFUL CYANOBACTERIA BLOOMS IN THE WILLAMETTE

A harmful cyanobacteria bloom (HCB), or harmful algae bloom, is a rapid overgrowth of cyanobacteria, a photosynthetic, single-celled bacteria that naturally occurs in fresh water and saltwater all over the world. HCBs tend to form in warm, calm, nutrient-rich water--conditions that are becoming more common with climate change. You should not swim in the river if an HCB is present; toxins from HCBs affect people, pets, and wildlife. If toxin levels are too high, Oregon Health Authority will issue health advisories for affected areas. However, HCBs are easy to spot if you know what to look for. Signs include: large snowflake-like specks and/or brightly colored patches of water that are pea-green, blue-green, or brownish red.

The Ross Island Lagoon is a particular hotspot for these blooms, and HAP is working to address the problem by restoring circulation to the island. Learn more about our work to mitigate the Ross Island Lagoon HCB here. For more information and Willamette River advisories click here.

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