Leakage Prevention Guidebook - Bureau of Waterworks Tokyo ...

found, On the other hand, the new leakage increases gradually in accordance with time. This is referred to as the“repetition phenomenon” of leakage. As the solution to this repetition phenomenon may lead to leakage preventionmeasures, we are trying to understand this phenomenon. (Fig. 3)Leakage volume(m3/day)preventionvolumepreventionvolumeRepetitionvolumeRemainedleakagevolumeRemained leakage volumeThe second last time The last time ,owRecurring yearsFig.3Repetition of leakage1.2 ,ecessity of leakage preventionTokyo currently possesses water resources that supply a volume of 6.3 million cubic meters per day. This volumeincludes additional water supplied through yearly agreements with Kanagawa Prefecture and Kawasaki City as well asfrom the Sagami River, the stability of which is affected by the state of water in Kanagawa.Furthermore, due to the level of rainfall in recent years and the fact that planned dam construction is as yet incomplete,the actual supply from dams and other facilities in the Tone River system, which is responsible for roughly 80% ofTokyo’s water, is about 20% below initial estimates. These issues result in the low level of safety regarding drought.In consideration of these circumstances, we are required to work on securing stable water resources by water resourcesdevelopment such as development of dams, as well as to further promote measures for effective use of water and leakageprevention.On the other hand water distribution pipes installed within municipal Tokyo totals up to 26,000 kilometers as of FY2010,which is worth more than halfway around the world.Water pipes embedded under ground are constantly subject to a danger of leakage, and when leakage occurs, these pipespose risks of factors like secondary disasters including poor water flow, sagging road, inundation and so on.Leakage prevention measures are actively implemented as one of main initiatives of the Bureau, since such measureshave effects equivalent to a new water resources development, and that they prevent secondary disasters from occurring.- 2 -