CyanoHAB Monitoring Season

Cyanobacteria Harmful Algae Bloom Monitoring in Oregon

As spring and summer bring warmer temperatures, cyanobacteria harmful algae blooms (cyanoHABs) can show up in Oregon's lakes, rivers, and reservoirs. This page has information about how blooms are monitored and reported.

DEQ CyanoHAB Recreational Monitoring Sites

The Oregon Department of Environmental Quality (DEQ) is in charge of seasonal cyanoHAB monitoring. DEQ samples specific sites 3-4 times throughout the cyanoHAB season, usually May to September. Waterbodies are tested for different cyanotoxins, including microcystin, cylindrospermopsin, anatoxin-a, and saxitoxin.

Check out the map below or view the list of DEQ 2026 Cyanotoxin Sampling Sites_Routes and Sites.pdf to see which areas are monitored and when they are sampled. It's important to know that many recreational waterbodies in Oregon are not monitored for cyanoHABs due to limited funding.

OHA's Role

A pond with an active bloom. The water looks like light green paint has been spilled on it.

When lab tests confirm cyanotoxins at levels above OHA safety limits, or conditions show there could be a health risk for people and pets, OHA issues recreational health advisories or precautions.

Advisories and precautions help people make safe choices and avoid certain activities to prevent illness. They are not waterbody closures.

OHA encourages people to visit waterbodies with advisories or precautions to enjoy activities like camping, hiking, biking, picnicking, bird watching, canoeing, and kayaking. Boating is safe as long as speeds do not create a large amount of water spray, and boaters avoid activities that could result in accidentally swallowing water (like waterskiing, wakeboarding, and inner-tubing).

What is an advisory?

An advisory means that conditions are not safe for:

Certain activities, like swimming, where water can be ingested (swallowed).
Using the water for drinking or cooking.
Taking pets to swim in or play in the water. Blooms can be deadly for pets.

OHA shares advisories through press releases, media, email, social media, hotline messages, and our webmap. Sign up for email alerts to stay informed.

What is a precaution?

A precaution means that conditions may not be safe for the activities listed above. No press releases are issued for precautions, but precautions are listed on our webmap and on hotline messages.

A bloom in a marshy area. The surface of the water is covered in green scum.

When in Doubt, Stay Out!

Because most of Oregon's fresh waters aren't regularly monitored, you may not always get warnings about cyanoHABs and their toxins. Learning how to recognize blooms helps you stay safe while enjoying Oregon's waters. Avoid water that:

Smells bad or looks foamy, scummy, or thick like paint
Is pea-green, blue-green, or brownish red

When in doubt, stay out!