Cyanobacteria and the Tualatin River - What to Know

June 12th, 2024

As summer approaches and more people enjoy the Tualatin River, it's important to stay informed about water safety, especially concerning harmful algal blooms (HABs). HAB’s can occur during summer and fall due to low water flow, high temperatures, and nutrient availability. Fortunately, Clean Water Services (CWS) summer cold water releases into the river reduce levels of all nuisance algae, including cyanobacteria, from what we used to see in the distant past, but some do remain present in the river.

CWS partners with USGS for gauges in the river at several locations that provide an indirect measure of blue green algae through phycocyanin, a light harvesting, pigment binding protein isolated from algae, Though not a direct metric, it’s a good relative indicator. The gauges may provide an indication of relative abundance, but do not necessarily indicate that cyanotoxins are present.

People and pets should avoid the river if the water appears foamy, scummy, bright green, or thick like blue-green paint. These conditions can produce toxins harmful to humans and pets. Dogs are particularly sensitive and should be kept away from affected waters.

The Oregon Health Authority recommends these precautions to reduce exposure to pollutants:

●        Avoid swimming after heavy rainfall.

●        Remind children not to ingest river water.

●        Do not drink untreated water from any waterbody.

●        Shower after swimming.

●        Wash your hands before eating.

●        Avoid swimming in cloudy water.

For the latest information on harmful algal blooms, consult the Oregon Health Authority: Current Cyanobacteria Advisories. Clean Water Services and the USGS also monitor water quality near popular recreation areas on the Tualatin River during the summer. For real-time data, visit USGS Water Quality Information.

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