Residents and visitors planning summer trips to Lake Billy Chinook should be aware of an ongoing health advisory. The Oregon Health Authority (OHA) issued a recreational use health advisory for the Jefferson County reservoir due to the presence of cyanotoxins — toxins produced by harmful algae — above Recreational Use Values (RUVs).

The advisory was first issued in mid-June and remains in effect. Officials warn that people should avoid swimming, wading, or any activity where they might swallow water or breathe in spray from affected areas of the lake.

What the Advisory Means

Cyanotoxins are produced by cyanobacteria, commonly known as blue-green algae, during warm-weather blooms. The toxins cannot be removed by boiling or filtering. Exposure can cause a range of symptoms:

  • Stomach cramps, nausea, diarrhea, and vomiting
  • Numbness, tingling, and dizziness in more serious cases
  • Skin irritation or rash from direct contact
  • In severe cases, trouble breathing requiring medical attention

Children and pets face higher risk due to their size and tendency to swallow water during play. Dogs in particular can become critically ill within minutes to hours of exposure by drinking the water, licking their fur, or eating algae crusts along the shoreline. Symptoms in dogs include difficulty walking and seizures — pet owners should keep animals away from the water.

Safe Activities Still Available

Despite the advisory, OHA still encourages people to visit and enjoy the reservoir responsibly. Safe activities include:

  • Fishing (fish from affected waters may be eaten if rinsed and the gut removed — do not eat the organs)
  • Camping, hiking, biking, and picnicking
  • Canoeing and kayaking, with care to avoid splashing water
  • Boating at low speeds to reduce spray exposure

People with private water systems that draw directly from the lake should use an alternative drinking water source. Standard camping filters and boiling will not remove cyanotoxins.

When Will It Be Lifted?

OHA monitors Lake Billy Chinook regularly throughout the summer. Advisories are lifted when cyanotoxin levels return below RUVs. Historically, blooms at the reservoir have recurred in hot, dry summers — conditions that match the 2026 forecast.

For the latest advisory status, visit OHA’s harmful algae bloom page at oregon.gov or call the Jefferson County Health Department. Visitors are advised to check the status before any trip to the lake this summer.