Health advisory issued for CJ Strike Reservoir in Owyhee/Elmore Counties; Cascade Reservoir in Valley County being monitored

Photo of CJ Strike Reservoir Harmful Algal Bloom Credit: Idaho DEQ
Photo of CJ Strike Reservoir Harmful Algal Bloom Credit: Idaho DEQ

Public Health Advisory

September 18, 2020

Health advisory issued for CJ Strike Reservoir in Owyhee/Elmore Counties; Cascade Reservoir in Valley County being monitored

Central District Health (CDH), Southwest District Health (SWDH), and the Idaho Department of Environmental Quality (DEQ) have issued a health advisory for CJ Strike Reservoir due to the presence of a Harmful Algal Bloom (HAB). CJ Strike has access points in both Owyhee and Elmore Counties.

Recent water samples taken by DEQ indicate that concentrations of toxin-producing cyanobacteria are present in the CJ Strike Reservoir. These cyanobacteria can be harmful to humans and animals, and those with liver or kidney damage are at an increased risk of illness.

Surface water experts have also recently sampled Cascade Reservoir in Valley County for a potential HAB. While test results came back as below the threshold for issuing a health advisory, the reservoir is seeing increased levels of microcystin (a type of cyanotoxin) that warrant users to take precautions. DEQ will continue to monitor Cascade Reservoir.

Cyanobacteria 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. Blooms 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. HABs are most common in the summer months through the fall.

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

  • 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

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. Wash your pet with clean water and shampoo if it has been around a harmful algal bloom. If it shows symptoms such as vomiting, staggering, drooling or convulsions, contact your vet immediately.

More Information / How to Report a Potential Harmful Algal Bloom

The public will be advised when water testing indicates a HAB is no longer likely to be a concern at CJ Strike Reservoir.

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

CJ Strike Reservoir has access points in both Elmore and Owyhee counties. CDH’s jurisdiction includes Elmore County; SWDH’s jurisdiction includes Owyhee County. Valley County’s Cascade Reservoir is located exclusively within CDH’s jurisdiction. For additional photos for download and use, please visit the following link:


Central District Health Media Contact

Christine Myron                208.871.1712     

Southwest District Health Media Contact

Katrina Williams                208.455.5317