As spring and summer bring warmer temperatures, keep and eye out for cyanobacteria harmful algae blooms (cyanoHABs) in Oregon's lakes, rivers, and reservoirs.
Not all recreational waterbodies in Oregon are monitored for cyanoHABs due to limited funding. For those that are monitored, when lab tests confirm cyanotoxins at levels above OHA safety limits, or conditions indicate potential of a health risk for recreators, OHA issues recreational health advisories or precautions to indicate level of concern. Advisories and precautions help people make safe choices and avoid certain activities at affected water to prevent illness.
We share advisories through press releases, media, email, social media, hotline messages, and our webmap. Sign up for email alterts to stay informed.No press releases are issued for precautions, but precautions are noted on our webmap and on hotline messages.
An advisory means that conditions are not safe for recreational activities like swimming where water can be ingested or boating activities where water is splashing in your face, and not safe for drinking or cooking. During a recreational advisory, conditions are not safe for pets.
A precaution means that conditions *may not* safe for recreational activities like swimming where water can be ingested or boating activities where water is splashing in your face, and may not be safe for drinking and cooking. During a recreational precaution, conditions *may not* be safe for pets.
Advisories and precautions are NOT waterbody closures. OHA encourages people to visit waterbodies with advisories or precautions and enjoy activities such as camping, hiking, biking, picnicking, bird watching, canoeing, and kayacking. Boating is safe as long as speeds do not create excesive water spray.
Fish caught from areas where cyanobacteria blooms are present may pose unknown health risks, so OHA recommends not eating fish from those areas. Those who decide to eat the fish should remove fat, skin and organs before cooking or freezing. Toxins are more likely to collect in these tissues. Fillets should also be rinsed with clean water.
Pets Are at Risk, Too
Dogs are especially vulnerable to cyanotoxins because of their size and activity level. Sadly, there have been reports of dog deaths from drinking affected waters. After several dog deaths along the South Umpqua and mainstem Upmqua Rivers, OHA launched an outreach effort to raise awareness. This event helped pet owners take extra stesps to keep their pets safe.
When to Avoid Water Contact
Most of Oregon's fresh waters aren't regularly monitored, so you may not always get warnings about CyanoHABs and their toxins. Use the information on OHA's webmap to recognize blooms and stay safe while enjoying Oregon's waters. Avoid water that smells bad or looks foamy, scummy, thick like paint, or is pea-green, blue-green, or brownish red. When in doubt, stay out!
DEQ CyanoHAB Recreational Monitoring Sites
The map below shows waterbodies where the Oregon Department of Environmental Quality (DEQ) performs seasonal cyanoHAB monitoring. DEQ samples each site 3-4 times throughout the cyanoHAB season, typically May - September. Waterbodies are tested for cyanotoxins, including microcystin, cylindrospermopsin, anatoxin-a, and saxitoxin. 
2026 DEQ CyanoHAB Monitoring Sites.pdf to view a list of monitoring sites and the seasonal sampling schedule.