建立氣候變遷對石門水庫供水與防洪能力之影響評估方法

Establishing a Methodology to Evaluate the Capabilityof Water Supply and Flood Mitigation of the Shihmen Reservoir under Climate Change

10.6342/NTU.2010.02518

何宜昕

氣候變遷 ； 石門水庫 ； 供水 ； 防洪 ； 高濁 ； Climate Change ； Shihmen Reservoir ； Water Supply ； Flood Mitigation ； High Turbidity

國立臺灣大學生物環境系統工程學系學位論文

2010年

碩士

童慶斌

繁體中文

近年來台灣地區極端水文事件發生明顯較過去頻繁且更為極端，對水庫功能造成嚴重的衝擊，本研究分別探討短期(2010-2039年)氣候變遷情境對石門水庫供水與防洪能力之影響，包含水資源不足缺水事件及暴雨來臨時高濁度入流對供水能力之影響與現有水庫防洪運轉規則下是否會有溢頂之危機。 本研究首先藉由變異點分析歷史長期時間序列，將變異點年份之前的資料視為與過去具有相同統計特性之基期，然後根據大氣環流模式模擬結果計算溫度及降雨之統計特性修正值以建立未來氣候情境，並藉由連續氣象資料合成模式繁衍未來氣候變遷下可能之日氣象資料與暴雨時雨量資料，採用童慶斌與連宛渝等(2009)發展之連續性水文模擬模式，進行日及小時兩種不同時間尺度之流量模擬。並以過去石門水庫於汛期所測得之濁度資料，對應尖峰流量統計關係而建立推估暴雨時期水庫之濁度方法，且考量平時和汛期水庫操作規則建立石門水庫運轉模式，以分析氣候變遷對平時供水能力、高濁度時期供水能力和防洪能力所造成之衝擊。 研究結果顯示石門水庫長時間供水能力，無氣候變遷情況下，未來石門水庫供水能力下降趨勢，長期而言，若需水量持續上升且氣候條件越漸嚴苛，水庫將面臨更嚴重之缺水情勢，枯水期勢必衝擊桃園地區產業發展，尤其以農業首當其衝；暴雨期間，分層取水設施對高濁度時期之供水能力將有顯著的改善；另外，防洪功能研究結果顯示石門水庫溢堤機會有增加的可能。

The frequency of extreme hydrological events in Taiwan have been obviously increasing recently and greatly impacted the function and operation of the reservoirs. The purpose of this study is to investigate the effects of climate change on water supply and flood mitigation capacity in Shihmen Reservoir. The effects including water shortages due to low flows and the high turbidity inflows in storm period and the risk of overflow under the current flood mitigation regulations are assessed in this study. First, the change point of climate is derived through analyzing the historic temperatures and rainfall data. The statistical properties of weather data in a period before the change point are served as baseline, and then the baseline statistical properties are adjusted to setup future climate scenarios according to the future temperature and rainfall changes projected by the outputs of General Circulation Models. Possible future daily and hourly weather data based on different climate scenarios’ statistical properties are generated by a continuous weather generator. The hydrological model developed by Tung and Lien (2009) is further used to simulate daily and hourly discharges. Historical relation between peak discharge and peak turbidity measured in the reservoir is constructed to project the possible turbidity in the future flood events. According to the Shihmen operational regulations for both ordinary days and event periods, the impacts of climate changes on water supply ability in drought period, in high-turbid period, and flood mitigation capability, are assessed. The results indicate that the water supply ability of Shihmen Reservoir may have decline trend because of less flow in dry periods. Furthermore, the climate change may exacerbate the shortage of water resource and impact the economics of Tao-Yuan region, especially agriculture. Withdrawing water from new water intakes during the high turbid period will significantly improve water supply ability. In addition, the results show that Shihmen Reservoir may increase the probability of overflow due to climate change.

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