Water supply alternatives to alleviate water shortage damages in urbanized watersheds are itemized and evaluated in terms of cost, life cycle energy (LCE), and damages. A newly developed stochastic model of precipitation and constructed GIS databases are applied to estimation of potential water resources in the Hakata bay watershed in Japan. Based on these results, water supply alternatives in the watershed are selected at several return periods on less annual precipitation in the order of minimizing cost, LCE, and damages. The water supply alternatives selected are cascade reuse in house, groundwater, two kinds of recycled water, and desalinated water. The storage water volume in the reservoirs at initial time, annual precipitation, and annual precipitation patterns are considered as three factors on water shortage from the water supply side. The unit values of cost, LCE, and damages are obtained to estimate damages of water shortage and to consider measures for water supply by applying the above three factors. Finally, based on statistical distribution of damages on water shortage, a new planning method to avoid water shortage is developed and how to decide a design precipitation level is proposed in terms of the return period of damages instead of that of precipitation.

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