Establishment of a Methodology for Evaluating the Carrying Capacity of Water Resource System under Climate Change

永續發展為在不超過環境承載力下，可持續滿足現在與下一世代之需求，本研究目的為推求短期(西元2010-2039年)受氣候變遷條件影響下水資源系統能負荷的供水承載力，確保社會經濟發展與規劃不會超過供水承載力。本研究採用缺水指數SI (Shortage Index)、缺水百分率日數DPD指標 (Deficit Percent Day Index)和農業供水指標AWS (Agricultural Water Supply Index)等做為水資源系統評估基準，並考量缺水容忍度、水文條件、以及水利設施，建立供水承載力推估流程。 本研究以系統動力學軟體Vensim建立頭前溪水資源系統動力模式，以模擬研究區域內水資源使用的情形。再利用IPCC所提供大氣環流模式輸出資料，模擬頭前溪流域在氣候變遷影響下可能河川流量變化情形，並依據供水承載力推估流程分析氣候變遷下頭前溪流域供水承載力變化情形。結果顯示，未來氣候變遷影響下，頭前溪流域水資源系統公共用水之供水承載力是呈現下降的情形；而農業供水承載力分析結果顯示，未來因為枯水期流量減少、豐水期流量增加的結果使得一期作農業供水承載力下降、二期作農業供水承載力提升之趨勢。 另外考量頭前溪為川流式灌溉系統，當乾旱發生時對灌溉可供水量影響較以水庫供水灌溉區域大，因此發展季節性預報技術應用於水資源管理。本研究藉由中央氣象局所提供之未來三個月溫度及降雨機率，以蒙地卡羅模擬的方式合成未來可能氣象資料，並進一步模擬其可能河川流量，進而分析未來農業水資源可能遭遇缺水風險，以供水資源調配決策之依據。Sustainable development aims to meet the needs of present and next generations without exceeding the carrying capacity of environment. The purpose of this study is to assess the carrying capacity of water supply system under climate change and ensure that the social and economic development and planning will not cause the overloading of water supply system in the future. First, an analysis framework for evaluating the carrying capacity of water supply system is established in this study. The framework considers hydrological conditions, tolerance of water shortage and water facilities, and shortage index(SI), deficit percent day index(DPD) and agricultural water supply index(AWS) are applied as criteria to evaluate the water shortage of water supply system. A water supply system dynamics model is established by the Vensim tool for the Touchien watershed. The results indicate that the carrying capacity of the water supply system has a decrease trend under climate change. In addition, the carrying capacity of agricultural water supply will decrease in first growing period due to the reduction of streamflow during dry period, while the carrying capacity will increase in second growing period because the increasing streamflow during wet period under climate change. Finally, the impacts of drought on streamflow irrigation area, such as the Touchien watershed, are more severely than the area irrigated by a reservoir. This study develops a seasonal forecast skill to strengthen water resources management to reduce the impacts. The forecast skill applies seasonal climate information with the lead-time of three months from Central Weather Bureau to estimate the risk of irrigation water shortage