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IN MAY, a water main sprung a leak under downtown Singapore. In a dense island city with scarce water resources, an undetected leak could have been a disaster, damaging underground infrastructure like subways and sewers, possibly even eating its way up to street level before anyone noticed. But a network of sensors, the first of its kind, spotted the sudden drop in water pressure, traced its location and scrambled a team of engineers before damage could spread.

鈥淭he sensors spotted the drop in water pressure and scrambled engineers before the damage spread鈥�

Designed by a company called Visenti, a spin-out of the Massachusetts Institute of Technology, the Waterwise network is distributed across the Singaporean water grid. About 130 sensors take readings every millisecond, sampling the pressure far faster than existing systems, which typically sample once every few minutes. When a pipe springs a leak, the pressure change sweeps through the whole mains network. Visenti鈥檚 sensors pick up changes at multiple points across the network, sending the data to a central server that triangulates the signal back to the leak鈥檚 source.

The system can often tell more about what鈥檚 going on than on-site engineers. Ami Preis, a co-founder of Visenti, says the system measured the Singapore leak as a big one. 鈥淏ut when engineers got to the site they said the leak is not that big. Then they started digging there, and they saw the leak was as bad as we told them.鈥�

鈥淪ingapore is quite ahead of the game in managing water distribution,鈥� says Jean-Pierre Bardet, director of the Urban Water Institute at the University of Texas at Arlington. 鈥淭hey are on an island without much water, so they have to be creative about managing it.鈥�

Visenti鈥檚 sensor technology is now being rolled out to other big cities in Asia and Australia. Hong Kong and Melbourne have just installed their own networks, and Visenti is gathering data in Sydney as part of an upcoming deployment there.

As urban populations swell in the face of water supplies that are roughly static in quantity and geographical distribution, water grids need technology like this to keep up with demand.

There is plenty of room for improvement. In the US, many pipes date back to the mid-19th century. Water mains in Philadelphia, Pennsylvania, leaked a third of what they carried in 2009. In Cleveland, Ohio, the figure was 29 per cent.

Ireland is blessed with abundant fresh water resources, which may explain why it can afford to lose about 350 millilitres for every litre entering the grid. Many other countries face similar losses due to poor infrastructure (see graph).FIG-mg29942701.jpg

By catching leaks before they get out of hand, technology like Visenti鈥檚 can conserve water and save on the energy required to pump it.

Visenti also has sensors that go beyond keeping tabs on leaks: they measure pH, temperature, electrical conductivity and other properties that can be used to sniff out water contamination.

Nearly all urban water systems do this kind of monitoring as water enters the network, but almost none of them do so as it reaches the tap. Bardet says monitoring across a network can help assure customers that their tap water is safe and good to drink, something that鈥檚 especially important as desalinated and directly recycled waste water become an essential part of supply in growing cities.

Much of the world can鈥檛 readily have a water system with the same efficiencies as Singapore鈥檚, Bardet says. 鈥淚nfrastructure is not ready for it,鈥� he says. 鈥淚t鈥檚 ageing. It鈥檚 really hard to do new things with old pipes.鈥� Large amounts of money were spent to build water mains in developed countries, often more than a hundred years ago, but the same level of investment is not going into maintaining that infrastructure.

鈥淲ater infrastructure is not ready for modern technology. It鈥檚 hard to do new things with old pipes鈥�

鈥淥ne of the big challenges with water in the US is that it鈥檚 too cheap,鈥� says Eric Williams, a water engineer at the Rochester Institute of Technology in New York. 鈥淭here鈥檚 no economic incentive to care how much you use.鈥�

Not all solutions need to be high-tech, though. Situated in the Nevada desert, the city of Las Vegas has always been on a tight water budget. Its response has been to build a system that recycles nearly all water used indoors. Waste water is captured, treated, then pumped into a specially created marsh 鈥� called the Las Vegas Wash 鈥� which serves as a giant natural filter, before emptying into . The city then draws 鈥渘ew鈥� water from the lake, treats it, pumps it to homes and businesses, and the cycle continues.

Epidemic of failures

鈥淪ince 2002, we have reduced our water consumption by 123 billion litres,鈥� says Bronson Mack of the Las Vegas Valley Water District. 鈥淵et this community has grown by 480,000 people.鈥�

Bardet recently started applying epidemiological principles to the systems of pipes in the developed world鈥檚 major cities. He discovered that failures tend to propagate like disease outbreaks.

As an example, he cites a cascade of burst water mains in Los Angeles in 2009. 鈥淭he city had been very cautious not to break anything for a while, so when they started to do something they had an explosion,鈥� he says.

鈥淥nce there was a sudden disturbance in the system, the rest of it started to break left and right.鈥� One break allowed millions of litres to flood the campus of the University of California, Los Angeles, submerging cars and creating spontaneous waterfalls in front of buildings.

鈥淭hey couldn鈥檛 find the valve to shut down the pipe,鈥� Bardet says. 鈥淲ould you call the system smart when the warning signal takes hours to propagate through? They could have saved a lot of water and a lot of economic damage if you could reroute water within the system quickly.鈥�

This article appeared in print under the headline 鈥淪uper-smart grid spies out leaks鈥�