求償性序率規劃應用於水資源長短期方案之綜合規劃

Abstract

一般而言水資源方案可分為長期方案及短期方案，其中長期方案為經常性使用之供水方案，而因應缺水事件之應變型方案稱為短期方案，就規劃的角度而言，長期方案其成本較易估計，而短期方案之施行與否決定於缺水事件，因此具有很大的不確定性，兩者之成本估計有本質上的不同。事實上長短期方案有一定程度的競合關係，而就整個水資源系統而言，兩者亦是並存，因此一個完整的水資源規劃必須能同時考量此兩類方案，以求的一個完整的最佳方案組合。 有鑑於此，本研究以求償序率規劃為理論基礎並結合水資源調配模式發展一水資源決策模式，可在同時考量長、短期方案之期望成本下建議出最佳的方案組合。針對上述問題，本研究以二階段方式進行考量，第一階段先以目前之水資源系統進行調配分析，以統計各種缺水事件之發生機率，第二階段再以此發生機率配合不同方案之成本與供水改善效率決定最佳之長短期方案組合。本研究以台北、桃園做為研究地區，台北地區用水需求中、高成長之情況，最佳組合方案中，長期方案皆為台北基隆雙向聯通管路工程及雙溪水庫，短期方案皆為第一、第二階段限水及台北盆地備用地下水井；桃園地區用水需求中成長之情況，最佳組合方案為短期方案之第一、第二階段限水及加強灌溉管理，用水需求高成長之情況除選用上述三種方案外，多選用停灌休耕方案。 傳統上水資源規劃長短期方案多分開考量，本研究發展之決策模式同時考量長短期方案，在最少總成本下滿足用水缺口，考量層面更更加完整實際，可提供決策單位更具體可行的參考。

For water resources management, short-time and long-term planning are usually trade-off. For long-term planning usually concerns about water supply and short-term planning usually faces responses for water shortage. The cost of the long-term planning is easier to estimate but the cost for short-term planning has high uncertainty. A complete water resources planning should consider both long-term and short-term issues for best management portfolios. This study applies Stochastic Programming with Recourse use to develop a decision making model for water resources management. Two-phase procedure is used in this study. In the first phase, the shortage probability is evaluated based on the current water distribution system. The second phase optimizes the decision portfolio based on the shortage probability and the cost for possible decisions. This proposed approach is applied to Taipei and Taoyuan areas. For Taipei, median and high growth of water needs are assumed. The optimized results show that the two-way water pipeline system is needed between Taipei and Keelung for long-term. Reduction of water supply and extraction of groundwater are needed actions for short term. For Taoyuan, under median growth of water need, reduction of water supply and irrigation management are needed. Under high growth of water need, additional fallow is needed. The result shows that a complete consideration of both long-term and short-term benefits can lead a better decision of water management.