Huge leaks in aqueduct threaten New York water crisis

New York's water supply is being threatened by huge leaks in an ageing underground aqueduct that travels 85 miles from the mountains upstate to feed the taps and shower-heads of the city's eight million residents.

New York's water supply is being threatened by huge leaks in an ageing underground aqueduct that travels 85 miles from the mountains upstate to feed the taps and shower-heads of the city's eight million residents.

Alarm bells about the tunnel are being sounded just as the city and surrounding areas brace for what some experts warn could be its worst drought emergency in decades.

Much of the north-east of the United States, from Georgia to Maine, is experiencing one of the warmest and driest winters on record.

The concrete-lined tunnel, known as the Delaware Aqueduct, was opened in 1945. On average it supplies about half of New York City's water needs. In some seasons, 90 per cent of the water consumed in the five boroughs arrives through the tunnel. It hasn't been drained for repairs since 1958.

City engineers have known about the leaks for more than 10 years but they have largely kept quiet about the situation. The extent of the problem became public when a private group, Riverkeeper, obtained city documents through freedom of information laws. Details have been reported by The New York Times.

Preparations are under way to send a tiny, unmanned submarine along a 45-mile stretch of the tunnel equipped with cameras and other sensors to seek out the worst of the leaks.

Already, teams of deep-sea divers have been going down into the tunnel in a 12ft diving bell. The work involves descending the equivalent of 70 storeys in a 13ft shaft and is highly hazardous.

"It's been 12 years they've been aware of it," said Marc Yaggi, a lawyer for Riverkeeper. "And they've done virtually nothing about it except find out how much it's leaking. They need to get started fixing it immediately. It is just too great to let this go on much longer without taking really aggressive measures."

Not that there is anything that can be done fast enough to relieve the immediate drought pressures. New York City has had roughly half its normal rainfall this winter and drought restrictions will be implemented shortly, officials say. Already, restaurants cannot serve water unless customers ask for it. Car washing and watering gardens have been banned in neighbouring New Jersey.

Some of the water seeping from the aqueduct, meanwhile, can be seen rising like natural springs along the route of the tunnel. The most recent finds suggest that as much as 36 million gallons could be escaping from the tunnel every day.

That is fairly small, given the more than one billion gallons needed by New York City every day, but it is enough to supply the entire city of Rochester in upstate New York. After engineers warned that a complete collapse somewhere along the tunnel could not be ruled out, the city began to develop a contingency plan to bring supplies in from elsewhere. It would involve asking scores of towns upstate to stop tapping into the city's supply network and draw water locally. So drastic a scenario does not seem imminent, however.

The tiny, self-propelling submarine weighs 400 pounds, is 9 feet long and 16 inches across. When lowered into the tunnel this autumn, it will be programmed to stay dead centre in the tunnel as it surveys the 45-mile stretch where the worst leaks are believed to be.

It will use five digital cameras to record the inside of the tunnel lining. Other sensors will listen out for gurgling and rushing sounds. Even when the worst ruptures are identified, however, fixing them will present huge engineering challenges. Another miniature submarine may have to be developed to apply patches from inside the tunnel.