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Cyanobacteria Season

As temperatures heat up during spring and summer, be on the watch for cyanobacteria blooms when recreating in Oregon lakes, rivers and reservoirs.

When a cyanobacteria bloom is detected and lab results show that cyanotoxins are present at levels over OHA recreational use values, OHA issues an advisory. Advisories provide information about blooms and cyanotoxins so that people can make appropriate recreational decisions to avoid affected water and potential illness.

We send recreational use health advisories via press release, the media, email, social media, via hotline messaging and this website. Sign up to receive email alerts.


Exposure to cyanobacteria and cyanotoxins can be serious and result in a range of symptoms including skin rash, diarrhea, cramps, vomiting, numbness, dizziness and fainting. Children, people with weakened immune systems and pets are most vulnerable to illness.

Pets are at risk, too

Due to their size and level of activity, dogs are very susceptible to the affects of cyanotoxins. In the past, we’ve had reports of dog deaths from drinking water affected by cyanotoxins. OHA and Douglas County Health Department conducted specific outreach efforts along the South Umpqua River and mainstem Umpqua River following widespread publicity of dog deaths in the area. The concern triggered by this event has increased awareness among pet owners who are taking additional action to protect their pets. 

When to avoid water contact

Because only a fraction of Oregon’s fresh waters are visually monitored and sampled, the public can’t count on being notified about all cyanobacteria blooms or the toxins they may be producing. Information is provided on this website to help you to identify blooms to stay safe and healthy when recreating in Oregon. If the water smells bad or looks foamy, scummy, thick like paint and pea-green, blue-green or brownish-red in color, it’s best to stay out.