行政院國家科學委員會補助專題研究計畫成果報告:水庫供水機能檢討評估與改善對策─以石門水庫為例─總計畫：水庫供水機能檢討評估與改善對策─以石門水庫為例

石門水庫於民國52 年興建於大漢溪中游，總蓄水量約2 億4 千萬 噸，原主要目標為提供灌溉防洪功能，然為因應目前整體民生及產業環 境改變，調節供應公共給水功能日趨重要。目前石門水庫每年供應民生 用水量約3億噸、工業用水量約1.5億噸及農業用水量約4.5億噸，總供 水9億噸約為水庫容量的四倍，顯見石門水庫在水資源調配的困難。 民國93年艾莉颱風期間，為石門水庫上游集水區帶來連續長時間高 強度降雨，造成水庫集水區大量土石崩塌，為石門水庫帶入將近2,000 萬立方公尺之淤積量，造成石門大圳進水口被大量泥砂掩埋而無法取 水，使得南桃園地區約三個星期無法供水，影響民眾生活甚鉅。經濟部 水利署等相關單位，雖已積極採取緊急因應措施以恢復供水。然而，大 量泥砂淤積減少水庫調蓄空間，必須研擬長期改善策略，方能維持水庫 永續經營，確保水庫正常供水機能。因此，國科會邀集相關學者組成本 研究團隊，分別由水文不確定性、自來水供需風險及備載應變、水資源 調度、颱洪期間水庫操作及環境影響等方向進行研就，作為水庫供水機 能檢討評估之依據，亦提出改善對策，提供主管機關做為未來加強水資 源運用或防災科技研究計畫核列之參考。The Shihmen Reservoir is built in the middle part of Da-Han River, a tributary of the Tam-Shiu River, for multiple functions, such as irrigation, flood mitigation, hydropower, and water supply. The reservoir was established in 1964 with the designed storage volume of 240 million m3. The rapid development in the Taoyuan County and its surrounding areas, which depend on the water supply from the Shihmen Reservoir, has increased the annual water demand to 900 million m3 due to the rapid development and urbanijation. However, the heavy rainfalls accompany with typhoons usually induce landslides and soil-erosion in the upstream catchments and decrese the reservoir’s capacity. The Typhoon Aere in August 2004 brought more than 1,600 mm of precipitation in upstream catchments and caused servere damage to the reservoir. More than 20 million m3 of sediments was estimated that flushed into the reservoir during the event. The turbidity of source water was too high to fulfill the minimum requirement of treatment for water supply. The waterworks were forced to be shutdown for three weeks and almost 2 million people suffered the unexpectable water shortage. Several emergency measures had been conducted by the Government to resume the water supply. The National Science Council of the Executive Yuan would like to offer scientific evaluations for improving the water supply function of the Shihmen Reservoir. A joint research group was teamed up by professors from universities and professionals from research institutes. The factors related to the water supply risk of the Shihmen Reservoir are analyzed, including the uncertainty in hydrology, the demand of water supply, the settling behavior of cohesive mud, the deposition and scour situations of the downstream channels, the capabilities of water treatment plants, regional water supply and storage, and the inter-regional management and support, and the treatment technique for the raw water with high turbidity. The provided suggestions will help the authorities to set long-term strategies for enhancing the water supply function of the Shihmen Reservoir