Winchester Lake

WINCHESTER – Public Health – Idaho North Central District in cooperation with the Nez Perce Tribe are issuing a public health advisory today (Friday, Sept. 27) for Winchester Lake. Residents are urged to use caution when recreating in or near the water.

Recent samples taken by the Nez Perce Tribe Water Resources Division show elevated levels of toxins, produced by cyanobacteria or blue-green algae, which can be harmful to people, pets, and livestock. Those with existing liver or kidney damage are most at risk.

Cyanobacteria or blue-green algae are a natural part of Idaho’s water bodies. When temperatures rise, their populations can bloom and toxic chemical compounds, or cyanotoxins, can be released into the water. Harmful Algal Blooms (HABs) can vary in appearance, and may look like mats, foam, spilled paint, or surface scum, and have a foul odor. While blooms can be discovered in one area of recreational water, they can move around to different areas, water depths and can change in severity.

When recreating near or in any surface water with a health advisory in effect, take the following precautions:

  • Avoid swimming, wading, or other activities. Take extra precautions to ensure children, pets, and livestock are not exposed to the water.
  • Do not drink or cook with water containing a bloom. Boiling and filtering the water can increase the risk.
  • Wash your hands thoroughly after handling fish caught in water experiencing a bloom. Cyanotoxins can accumulate in fish and the risk to people is being researched. Any fish caught should be cleaned and washed thoroughly in uncontaminated water and any internal organs disposed of before consumption. If people choose to eat fish from this area, filet the fish and remove all of the fat, skin, and organs before cooking.
  • Clean with potable water as soon as possible if water contacts skin or pet fur.

Symptoms of cyanotoxin exposure include rashes, hives, diarrhea, vomiting, coughing, and/or wheezing. More severe symptoms affecting the liver and nervous system may result from ingesting water. If symptoms persist, consult your healthcare provider.

For information on cyanobacteria blooms and a map of recreational water quality health advisories in Idaho, visit

Many harmful algal blooms are identified through public reporting. If you suspect a bloom on a recreational water body in Idaho, report it to DEQ at .

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