Lake Temescal in Oakland For Third Consecutive Summer Closed Because of Toxic Algae Bloom

For the third summer in a row, Oakland's Lake Temescal will be closed to swimmers indefinitely because of toxic green blue algae, exacerbated by California's drought, though the rest of the park remains open.

The East Bay Regional Park closed the lake on Monday, despite being cleared of the toxicity in February after the winter rains. The district runs a popular lifeguard program at the lake, and in years past, campers have been forced to spend their summers on the sand or grassy areas instead of swimming, or choose another lake to attend camp.

Unlike last summer though, Quarry Lakes in Fremont, which was closed for the same reason, reopened June 25. Swimming is allowed for people, but not for dogs, the district said in a statement. Shinn Pond in Fremont is off-limits for swimming both for dogs and people, the district said.

Lake Anza at Tilden Regional Park in Berkeley, Lake Del Valle and the Arroyo behind Shadow Cliffs contain blue-green algae, but harmful toxins haven't been detected for people, the district said.

Swimming is never allowed at Lake Chabot in Castro Valley.

So far this summer, here is what is safe and open for swimming with in the park district: Cull Canyon in Castro Valley, Contra Loma Lagoon in Antioch, Don Castro in Hayward, and Roberts Pool at Roberts Regional Recreation Area in Oakland.

It's common for toxic algae blooms to break out in warm weather, but the park district said the drought is likely making the situation worse. Warmer temperatures prevent water from mixing, allowing algae to grow thicker and faster, according to the Environmental Protection Agency. Also, warmer water is easier for small organisms to move through and allows algae to float to the surface faster. And algal blooms absorb sunlight, making water even warmer and promote more blooms.