COUNTYWIDE : Water’s Earthy Edge Has an Explanation

County residents who have noticed a strange taste in their tap water can blame the drought.

An increase in algae in Lake Mathews, a drinking water source for many county communities, has left a safe--albeit somewhat unpalatable--compound that the Metropolitan Water District of Southern California describes as tasting musty or earthy.

The problem occurs in warm weather when algae multiply.

Normally, the Metropolitan Water District dilutes the foul-tasting lake water by mixing it with water imported from Northern California, said Edward G. Means, MWD’s director of water quality.

But with the supply of imported water down because of the drought, the MWD--a water wholesaler--occasionally ships the lake water undiluted to community water districts. Lake Mathews is fed from the Colorado River.

“I want to stress that the musty off-taste is an aesthetic nuisance but not a health hazard,” Means said.

Sensitive people can detect the chemical given off by the algae in levels as low as 5 parts per trillion. One part per trillion is equivalent to a thimbleful of water in a stadium, MWD officials said.

Customer complaints are common when the level reaches 10 parts per trillion, according to the MWD.

The west end of the lake, where the algae levels are highest, is being treated with copper sulfate to control the growth, Means said.

The MWD supplies water to regional wholesalers, such as the Municipal Water District of Orange County, which in turn supplies it to local water districts. Customers in different parts of the county will have different taste problems, depending on how much of their local supply comes from the MWD.

Customers of the Irvine Ranch Water District, which supplies 100% MWD water to some areas not tied into underground supplies, have not been complaining about the water’s taste, district spokeswoman Joyce Wegner-Gwidt said Wednesday.