LOS ANGELES COUNTY : Castaic Lake Algae Bloom Gives Water Bad Taste

An “especially large and persistent” algae bloom in Castaic Lake has produced odd-tasting water--but no health hazard--in parts of Los Angeles County, officials said today.

Metropolitan Water District spokesman Mark Beuhler said residents on the west side of Los Angeles County are most likely to notice the “musty” taste.

Because the algae present no health threat, there is no need for residents to boil the water, he said. But he recommended refrigerating the water to improve the taste.

Beuhler said MWD officials were trying to supply customers with water from the Colorado River or with a blend from Castaic Lake and other reservoirs.

He said the hot weather in recent days and the high nutrient level of Castaic Lake have spurred the algae growth, and with it an increase in a compound called geosmin. That compound, he said, is responsible for the bad taste and odor.

“Unfortunately, geosmin cannot be removed from water during the filtration process, and Castaic Lake is too large and too widespread to attempt to eradicate it in the reservoir,” Beuhler said.

“People with sensitive taste and smell can detect the compound in water levels as low as five parts per trillion,” he said. “By comparison, one part per trillion is equivalent to just 10 drops of geosmin in enough water to fill the Rose Bowl.”