PRICE — The Southeast Utah Health Department closed Scofield Reservoir to swimming after an outbreak of cyanobacteria, or blue-green algae.
People can still fish from the shore or from boats, but should thoroughly clean fish and wash their hands afterward.
The harmful algal bloom has cell counts of toxins that are considerably higher than initially thought, officials said. The combination of hot temperatures and a stagnant weather pattern could make conditions worse over time.
Routine sampling by water quality scientists with the Utah Department of Environmental Quality last week revealed the presence of cyanobacteria, which can contain toxins that impact the liver or respiratory system.
Toxin test strip results Thursday from two areas of the reservoir showed negative results, but officials found cyanobacteria in "a few isolated pockets at the upstream inlet of Madsen Bay" and through microscopic examination of water samples.
People who visit the reservoir are encouraged to keep pets and livestock away, avoid areas with scum when boating and not drink the water.
City drinking water and canal water, the health department stressed, has not been impacted.
The Utah County Health Department closed Lincoln Marina and Beach at Utah Lake June 29 because of the high level of toxins.
Warnings remain in effect for the waters at Provo Bay, Sandy Beach and Utah State Lake Park.
Algal blooms are the result of the buildup of nutrients like nitrogen and phosphorus — which are naturally occurring but also result from human activities that include urban runoff, agricultural operations and wastewater treatment discharges.
The state Division of Water Quality is involved in a multi-pronged $1 million study through funding granted by the Utah State Water Quality Board.
Brigham Young University, too, is routinely sampling the water through a citizen scientist network aimed at capturing nutrient levels in waterways before they reach Utah Lake.
More information on blooms is available at the state's website.