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Toxic Algae Advisories

Toxic Algae Advisories

Cyanobacteria blooms may look like mats floating in the water or stuck on the bottom or the shore. Be on the lookout for waters that look suspicious—foamy, scummy, thick like paint, pea-green, blue-green or brownish red, or bright green cells suspended in the water column. 

Not all Oregon waterways are monitored for cyanobacteria. This resource can help you tell the difference between normal algae and toxic algae, but when in doubt, stay out!

Health advisories for toxic algae levels have been issued for the following bodies of water in Oregon.

Active advisories

Pets should avoid contact with the affected water. Drinking water directly from areas affected by a bloom is especially dangerous. Toxins cannot be removed by boiling, filtering or treating water with camping-style filters.

  • North Santiam River from the confluence with the South Santiam River up to the mouth of the Little North Fork Santiam River in Mehama in Marion/Linn Counties 7.16.24
  • North Santiam River from Mehama upstream to, and including, Big Cliff Reservoir and Detroit Reservoir in Marion/Linn Counties (precautionary advisory)  7.16.24
  • McKay Reservoir in Umatilla County 7.3.24
  • Cold Springs Reservoir in Umatilla County (precautionary advisory) 6.13.24

Lifted advisories

Official OHA advisories are lifted when values fall below those that cause human illness. Although the levels detected in these places are below the recreational use values for people, they may continue to be above OHA’s guideline values for dogs. Owners should be aware of the potential exposure to their pets while at these areas, especially shallow, marshy areas where cyanobacteria blooms can form. Cyanobacteria can be present on green algae, growing from the sediment or on rocks. Illness in pets can still occur at lower toxin values, so please continue to exercise caution with pets at these areas:

  • None at this time

Permanent advisory

  • South Umpqua River: The advisory covers the South Umpqua River from Canyonville downstream to the confluence with the mainstem Umpqua River, and the mainstem Umpqua River downstream past Elkton to Sawyers Rapids. Pools in the bedrock along the rivers edge are known to develop cyanobacteria (blue-green algae) blooms that can be harmful to pets and people if accidental ingestion occurs.

Children and pets are particularly susceptible to this toxin

Exposure to toxins can produce symptoms of numbness, tingling and dizziness that can lead to difficulty breathing or heart problems and require immediate medical attention. Symptoms of skin irritation, weakness, diarrhea, nausea, cramps and fainting should also receive medical attention if they persist or worsen. Children and pets are particularly susceptible.


Swallowing or inhaling water droplets should be avoided, as well as skin contact with water by humans or animals. Drinking water from these bodies of water is especially dangerous. Oregon Public Health officials advise campers and other visitors that toxins cannot be removed by boiling, filtering or treating the water with camping-style filters.

Oregon Public Health recommends that people who choose to eat fish from waters where algae blooms are present should remove all fat, skin and organs before cooking since toxins are more likely to collect in these tissues.

A hazard for dogs

Dogs have become very sick and even died after swimming in and swallowing water affected by toxic algae. If you find thick, brightly colored foam or scum at a lake, pond or river, don’t let your pet drink or swim in the water. Avoid contact with the water, as toxins can be absorbed through the skin.

Symptoms in dogs

Exposure to toxic blue-green algae can result in:

  • Weakness or collapse
  • Nausea, vomiting
  • Excessive drooling
  • Abdominal pain
  • Diarrhea
  • Difficulty breathing
  • Shaking, trembling
  • Tremors, rigidity, paralysis

If your dog goes into the water:

  • Don’t let your pet lick its fur.
  • Wash your pet with clean water as soon as possible.
  • If your dog has symptoms such as drooling, weakness, vomiting, staggering and convulsions after being in water, seek immediate veterinary care. Acute, life-threatening symptoms from cyanobacterial toxins often develop rapidly. Death can occur within minutes to hours after exposure.

For more information, contact the Harmful Algae Bloom Surveillance program at (971) 673-0400.

Updated: July 17, 2024