The value of a raindrop

After battling both water scarcity and floods, the Sumida City in Tokyo has become a trailblazer in catching and using rainwater

Rain falling in the reservoir area is a must whereas rain falling in the communities is a nuisance, thinks the average person in Tokyo. Makoto Murase, director of urban affairs at Tokyo's Sumida City, is trying to change this.

Japan's capital uses 2 billion tonnes of water each year. The water comes from huge dams built far away in up-stream areas. Tokyo is short of water once every few years. And whenever that happens, it is time for another dam up-stream, leading to displacement and conflict with up-stream communities. At the same time, the 1,500 mm of rainfall it receives each year is not spared a thought. Almost 60 per cent of Tokyo's ground is covered - a city robed in asphalt and concrete. So when the rain falls, the overloaded and overflowing sewage system gives floods. This is the making of an irony of ironies: a parched city prone to floods.

Some 16 years ago, a serious flood inflicted heavy financial and health losses in Sumida City, one of the most densely populated wards in Tokyo. Floodwaters inundated many of the ward's buildings with sewage-contaminated water. For weeks people had no drinking water, as the city's drinking water tanks are installed underground.

The situation piqued Murase, who was then working in the public health centre of the local municipality, to find ways to utilise rainwater. "Rain is an incredibly important resource. It is essential to city planning and to mitigate water shortages, control flood and disasters," says Murase. "But," he laments, "society simply throws it away."

How should it be used? Build numerous mini dams -i-Murase's description of tanks that store rainwater - in cities. This not only reduces the city's water demand and reduces the pressure on water supply but also saves the environment. Large tracts of farm and forest land that large dams devour are also spared.

Moreover, rainwater is free. Its users save money. The civil servant thinks Tokyo is an ideal situation to reap the benefits of collecting rainwater as it is covered in concrete. Being the ideal for numerous cities around the world in terms of industrial development, Tokyo is now setting an example in the use of common sense in collection and utilisation of rainwater.

In the meantime, Sumida City has carried on with innovative measures to use harvest rainwater. Rainwater utilisation policies have been promoted with three aims: developing water resources in communities, restoring the regional natural watercycle, and ensuring water supply for emergencies. The ward office can boast of a rainwater utilisation system that covers half of the building's water needs and saves