Water

Tokyo, Japan

World leader in stopping water leakage

What is it?

Tokyo has one of the most efficient water systems in the world. In the past ten years, the city’s method of detecting and repairing leaks has halved the amount of water wasted from 150 million m3 water to 68 million m3 water. By focusing on same-day repairs, the leakage rate has been reduced to just 3.6%. These savings help reduce emissions by about 73,000 tCO2 per year.

How does it work?

Tokyo's water supply serves about 5 million m3 of water everyday to 12million citizens. The water is supplied by four rivers which flow into the Metropolitan area. Untreated water is taken from these rivers and purified through three processes - coagulation, sedimentation and filtration at local plants. It is then pressurised and supplied to customers as tap water through underground pipelines. The total length of distribution pipes is about 25,262 km in 2005.

The Bureau of Waterworks program aims to manage essential water resources in the most efficient way, conducting prevention and early repair of leakage. This stops collateral damage, which can potentially occur as a result of the leakage, such as subsidence of roads and muddying of the water.

Water supply is monitored 24 hours a day, seven days a week. Control of water leakage is one of the most critical aspects of Tokyo's system and all repair work for the leakages takes place on the same day. In 1985 there were about 58,000 cases of leakage repair - this dropped to about 21,000 in 2005.

Fig. Trend of Leakage Rate

Key results

• About 167,000 kWh of electricity reduced per year (compared to base year 1956)
• 2 billion yen (16.7 MUSD) reduction in electricity charges (vs. base year)
• Cost for leakage control is about 7.2 billion yen (60.3M USD) annually
• Prevented expense by leakage control is about 20.6 billion yen (172.4M USD)
• Emissions reduced by diminution of leakage rate is about 73,000 t CO2 (Equal to the amount of carbon dioxide emitted about 31,000 cars)

Application

Tokyo's model can be applied to other cities. It is highly successful in both reducing CO2 emissions and financially, in making energy savings. Tokyo's measures to control leakage can be adapted to other cities and can play a major role in curtailing CO2 emissions and climate change.