氣候變遷對台中地區缺水風險之影響評估

Abstract

全球經濟之快速發展使溫室氣體之排放大幅增加，因而造成全球氣候變遷。而全球氣候變遷亦使區域之河川流量豐枯水期差異有擴大之趨勢，進而影響區域水資源之調配，因此探討氣候變遷對水資源之衝擊乃是目前重要課題。 本研究以蒙地卡羅法為基礎，整合氣象資料合成模式、地表逕流模式與地表水資源調配模式等，探討氣候變遷對台中地區缺水風險之影響，並以其評估氣候變遷對人工湖和越域引水工程等水資源調適策略效益之衝擊。其中氣象資料合成乃以一階馬可夫鏈配合雨量機率分佈模式進行，地表逕流模式則採用GWLF模式，地表水資源調配模式則以系統動力學為核心理論進行建置。 案例模擬結果顯示，氣候變遷將造成大甲溪與大安溪流域河川總流量增加，以及豐水期與枯水期流量之差異更為劇烈。台中地區在現有供水系統下，氣候變遷將使農業用水缺水情況更為嚴重，公共用水缺水情況則略有降低。若加入人工湖或越域引水工程等水資源調適策略，則可大幅改善台中地區無氣候變遷下之缺水情況，惟若再考量氣候變遷之影響，則農業與公共用水缺水情況皆會變差。本研究之分析方法與結果可做為因應氣候變遷，進行水資源調適策略評估選定之參考。

Rapid economic development has caused a worldwide greenhouse effect and induced global climate change. Climate change has also increased the fluctuation of regional river flow between wet and dry seasons, seriously impacting regional water resource management. The impact of climate change has thus become an important issue in regional water resource management. This study uses the Monte Carlo simulation method to evaluate the impact of climate change on water supply shortage in the Taichung area. The proposed model integrates weather generator, surface runoff, and water distribution models. This study uses this model to evaluate the impact of climate change on water shortage risk for existing water supply systems and the efficiency of adding two water supply measures, “artificial lakes” and “cross-basin water transport.” The weather data generator applies the first order Markov Chain and two probability distribution models including exponential distribution and normal distribution. The Generalized Watershed Loading Function (GWLF) model serves as a surface runoff model to simulate basin outflow. The water distribution model in this study was developed based on System Dynamics. Simulation results indicate that climate change has increased the annual river flow for both Ta-chia River and Da-an River basins. However, it has also increased temporal variations in river flow between wet and dry seasons. For existing water supply systems, this threatens the agricultural water supply but slightly improves the public water supply. Two additional water supply measures, “artificial lakes” and “cross-basin water transport,” can greatly reduce the risk of regional water shortage irrespective of climate change. As expected, the climate change will again increase the water shortage risk for both agriculture and public water uses. The results of this study are a valuable reference for the risk assessment of the impact of climate change on regional water supply.