Search for Southland’s Disappearing Water Grows

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.

Venegas said tests on the retired meters show them running 10% to 15% slow. That, he said, could explain up to one-half of the unaccounted-for water.

The city has also sought to put a concrete coating on water pipes in the older sections of the city. Last year, the DWP coated about six miles of pipe in concrete and has similar plans for this year, Venegas said. Since 1944, the city has concrete-coated more than 490 miles of pipe and has identified 2,200 more miles of pipe to be entombed. Over the next 25 years, the DWP plans to spend $250 million on the concrete project.

These efforts, Venegas said, have in recent years reduced leaks per 100 miles of pipe from 31 to 23. And, he added, the effort will cut the level of unaccounted for water considerably from the current 8% level.

“We’re sure of that,” Venegas said. “As we go along, every mile, every year an untold number of leaks are being eliminated from the system.”

The MWD, which has an aggressive leak-detection program, loses much of its water through evaporation on the long, open aqueducts it operates from Northern California and the Colorado River--enough water for 20,000 families.

As bad as these losses may sound, the DWP and most large Western water agencies have enviable records on a national basis.

More than 30% of the water pumped to New York City never gets to its intended destination, water industry officials said. And in New Orleans, lost water is estimated at 40% of the supply, according to officials with the American Water Works Assn., an industry trade group.

East Coast cities tend to have higher loss rates because their pipes are generally older and in greater disrepair than those in younger, West Coast cities, industry officials say. The sandy soil and mild climate of the West also helps keep pipe in good repair and the level of leaks down, they say.

Some level of losses are clearly acceptable, and inevitable. The Illinois Legislature recently adopted a law calling on water agencies to cut their unaccounted-for water to 10%.

And, some officials point out, while the water may be unaccounted for, it’s not necessarily lost forever.

“The good news,” said the MWD’s Mike Young, “is that it goes down to the aquifer and gets pumped out again.”