Analysis for the Safety Supply of Raw Water to Meet with Serious Megacity Drought Eiji SHIBATA Fukuoka, a megacity in Japan, suffered severe shortage of its normal water supply, for a long period of time in 1978. This crucial experience led to the study of a new system which is adaptable to cover water supply being suffered by shortage of water frequently. Considering the difficulty of water resources development in Fukuoka's self-watershed, new water source was taken account in neighboring

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... rshed, where Fukuoka has not predominated water right yet . To solve this problem, the system requests that an occasional conditioning reservoir could be constructed somewhere. Specific water right which is valid only when source water is abundant should be admitted. On these conditions, the system is represented by either with the occasional conditioning reservoir, or without it. It was confirmed that the system was applicable to the circumstance of 1978's drought in Fukuoka, showing effective use of the occasional conditioning reservoir. Prior to apply the system in long time range , a model city, a model water supply system and model time series of water flow were settled to simulate a general circumstances.