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East Bay Regional Park District officials closed Livermore’s Lake Del Valle for swimming after park staff detected a bloom of blue-green algae Monday afternoon near the boat launch, and preliminary testing found the water’s toxicity exceeded the 20 parts per billion limit. SFGate.com says:

While filtration and treatment processes used after obtaining the water from the reservoir keep it safe to drink, the liquid’s toxicity exceeded the safety threshold set by the park district, said Carolyn Jones, a park district spokeswoman.

“People will still be drinking it, but it does call into question what is the acceptable threshold for drinking water,” Jones said, adding “there is no imminent threat to people’s health.”

Exposure to blue-green algae can cause skin irritation, diarrhea, vomiting and headaches. In high levels, it can cause death, according to the California Department of Public Health.

“In the 80-year history of the park district, they’ve had zero toxic blooms, and then in the past two or three years, they’ve had a bunch,” she said. “The thinking is that it’s somehow related to drought conditions.”

Other lakes in the district are also faced with toxic blooms, including Quarry Lakes in Fremont and Lake Chabot in Castro Valley. Blooms at Lake Temescal in Oakland and Lake Anza in Berkeley have cleared Jones said, but the lakes are closed for the season and will reopen in April 2016.

The entire park remains open for visitors. The lake is visited by boaters, windsurfers, and swimmers. People should keep their dogs away from the water, since algal toxins can be fatal for canines.

-Bill at