Somehow, almost 10% of all the water bound for Southern California taps--enough to supply hundreds of thousands of households--disappears each year, water officials said Tuesday.
Some water evaporates as it travels hundreds of miles in aqueducts from Northern California and the Colorado River. Additional water is lost through leaky pipes, and some water sneaks undetected through faulty meters, officials speculate.
But officials with the Los Angeles Department of Water and Power and the giant Metropolitan Water District say they cannot be sure where the so-called "unaccounted for" water actually goes.
With drought conditions and the threat of water rationing this summer, more attention is being focused on finding and capturing the missing water.
The MWD estimates that it loses about 2.5%, or about 2.1 billion gallons, of the water it brings to six Southern California counties every year. That is enough water to serve about 130,000 families for a year.
The Los Angeles DWP loses an estimated 8% of its water, or 1.8 billion gallons annually--enough to service 112,000 households.
Overall, MWD officials estimate that 9.2% of the water used by the scores of agencies in Southern California is "unaccounted for."
Concern over such disappearing water has spawned development of high-tech gear to search out leaks. With computers and sophisticated "hydrophone" listening devices, technicians can detect the distinctive sound frequency of escaping water and can track down leaks as small as dripping faucets.
San Francisco, which estimates that about 3% of its water is lost, has used a computerized leak-detection program for several years. Denver, which uses a similar system, loses just 6% of its water.
The Los Angeles DWP, which finds an average of 23 leaks in every 100 miles of pipe, is not among the converts to high-tech leak surveys.
"We tried leak-detection crews for two to three years after the 1977 drought," said Henry Venegas, assistant manager of engineering design at the DWP. Despite having more than 1,670 leaks a year, Venegas said the leak survey program "wasn't paying off" and was abandoned in the early 1980s.
Now the city concentrates on replacing aging water meters and sealing old water mains.
Since 1988 the city has replaced about 75,000, pre-1955 water meters and plans to retire an additional 75,000 of the slow-running instruments within the next two years at a total cost of about $2.5 million.
