Water Quality


It’s a fact. The Willamette River in downtown Portland is safe for recreation, except in the now rare instances when Combined Sewer Overflow (CSO) conditions are present. If you think otherwise, you are simply a science denier. Sorry.

Here’s what state officials and health experts say:

From the State of Oregon website: Yes, it’s safe to swim in the Willamette most times of the year. DEQ and the city of Portland regularly monitor bacteria levels in the river. Data collected since 2012 show that bacteria are almost always at healthy levels in Portland. 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.

Read from the DEQ website here.

Oregon DEQ states: When CSO conditions are not present, “the Willamette River is safe for swimming and other recreational uses.”
Oregon Health Authority states: The levels of chemical contamination in the Willamette River water are too low to be considered harmful to the health of the public, even for sensitive groups like children and pregnant and nursing women.
Portland’s Bureau of Environmental Services tests water quality in the Willamette River at several locations during the summer. From its website: Thanks to ratepayers’ investment in the $1.4 billion Big Pipe project – the largest public works project in Portland history that was completed in 2011 – almost all combined sewer overflows (CSOs) to the Willamette River have been eliminated. With that drop in sewage exposure comes a drop in E. coli bacteria – an indicator of fecal matter and the single biggest health concern for swimming and other direct-contact recreation, according to the state Department of Environmental Quality.
Find water testing result for the Willamette River here.
The USGS provides up-to-date info and graphs on a variety of river conditions such as river temperature, discharge, turbidity and more. For those who want to dive deeper into water quality!
For those who want to dive deeper into water quality!



  • A HAB is a Harmful Algae Bloom that is not actually algae at all. HABs are created by cyanobacteria, a photosynthetic, single-celled bacteria that naturally occur in fresh water and saltwater all over the world.
  • HABs usually appear as thick, brightly colored scum – pea-green, blue-green, or brownish red.


  • When testing shows acceptable cyanotoxin levels from a bloom, people can swim and recreate in the water. If toxin levels are too high, Oregon Health Authority will issue health advisories for affected areas.
  • As necessary, DEQ gathers data at Ross Island Lagoon and other areas on the Lower Willamette.
  • Climate change is creating conditions that favor cyanobacteria and the development of HABs. Reduced snowpack, lower/warmer water levels, and less nutrient distribution equals more blooms.


  • Avoid swallowing water in any natural waterway. If you do swallow water where you see a HAB, watch for symptoms similar to food poisoning, or tingling in fingers, toes, or around the lips.
  • All cyanobacteria can cause skin rashes, but cyanotoxins do not pass through the skin. Exposure occurs through swallowing affected water.


  • In the Lower Willamette River (LWR), HABs typically form in warm, still water with minimal flow and high nutrient (nitrogen and phosphorous) concentrations. Cyanobacteria can multiply into large colonies called “blooms” that can produce cyanotoxins.
  • Ross Island Lagoon is essentially a pond within the Lower Willamette River with a favorable environment for cyanobacteria to multiply into a bloom. There are also other areas on the river where blooms can form.


  • Cyanotoxins from a HAB can harm and even kill dogs. Don’t let your pet drink or swim in water with a HAB. If it happens, wash your pet with clean water and consult a vet.
  • For more information, go to www.healthoregon.org/hab

Grant funds provided from East Multnomah Soil and Water Conservation District helped support this page.

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