Water supply is vital to our lives along with food, and ensuring water supply during an emergency is one of the greatest concerns for earthquake-prone cities like Tokyo. We asked Toshimitsu Takaoka of the Bureau of Waterworks, Tokyo Metropolitan Government, to explain what measures are in place to prepare for the worst-case scenario.

Toshimitsu Takaoka is director of the Tokyo water supply section.

Tokyo has a network of some 17,000 miles (27,000 km) of water pipes––long enough to go two-thirds the way around planet earth! The whole network is carefully controlled and managed so that the 12.8 million residents of the city’s 23 wards never lack for water––even when an earthquake strikes.
Firstly, Tokyo extracts its water from rivers controlled by numerous dams, two of which belong to the city. Hence, there is never any danger that the water will run out. Secondly, the choice of water infrastructure––the pipes––is itself extremely important. The existing network is made of near-indestructible stainless steel alloy. Thanks to this new material, the incidence of leaks has been reduced from eight percent in 1998 to 2.7 percent in 2010. The next step was to devise joints that were almost impossible to break. We are in the process of renewing the entire network with this new joint technology. The idea behind this is that even if everything else fails, we will still be able to distribute water. With the right pressure, we can even overcome rising ground.

Left : Pipes joined together using the conventional technology. Right : New joint technology. The metal fitting and the protrusion get caught with each other during an earthquake, and this prevents the pipes from sliding out.

Tokyo’s 23 wards are equipped with 200 underground reservoirs through which drinking water flows under normal conditions. When there is an earthquake, trapdoors close automatically and the reservoirs fill up with enough water to supply the residents for three weeks––enough time to repair the network, even if only partially. These reservoirs are located strategically so that no one should have to walk more than one and a quarter miles (2 km) to get water. They are mostly built under hospitals, schools, sports centers––the very buildings that would be used as refugee centers during an emergency.
The Tokyo water-supply network is equipped with thousands of pumping stations that control the overall water pressure and assures adequate distribution throughout the city. We have installed small devices on the pumps to assist firefighters, especially in narrow lanes that are difficult to access with fire trucks. These devices can also be used in case of an emergency to create extra water supply points, which will reduce the need to transport water with motorized tankers, which would be a logistical nightmare in a city with such a high population density. With a major earthquake expected in the next few years, I am committed to providing the best emergency water-supply system possible. Water is the one element that we cannot do without during a natural disaster.

Photography / Satoru Naito Text / JQR Editorial Staff

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