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Title: | 水庫防淤操作對供水營運風險影響之研究 Influences of the Reservoir Desiltation on the Risk of Water Supply Operation |
Authors: | 劉政其 Cheng-Chi Liu |
Advisor: | 闕蓓德 Pei-Te Chiueh |
Keyword: | 水庫防淤操作,數值模擬,排砂效率,庫容及供水量推估,風險分析, reservoir desilting operation,numerical simulation,venting efficiency,capacity and water supply estimatation,risk analysis, |
Publication Year : | 2023 |
Degree: | 碩士 |
Abstract: | 臺灣位於太平洋西北側,其海島型地形條件為地勢南北狹長,氣候易受海上產生熱帶氣旋影響,每年逢梅雨季及颱風季,於山坡地集水區發生的強降雨致使表土層沖蝕及土砂推移,上游河川水流挾帶大量泥砂進入水庫庫區,形成高濃度渾水或異重流並往大壩方向運移,庫區水體懸浮固體濃度驟增。作為影響河川污染指標主要因子,高懸浮固體濃度代表庫區渾水含有高濃度泥砂顆粒,長年的泥砂落淤累積導致水庫河床淤積、蓄水空間減少,除影響水庫蓄水、供水等基本功能,亦增加供水及淨水系統運作成本之負擔,對水庫下游區域公共、農業及工業的給水品質造成風險。
不同型態水庫皆需短期或長期性的水庫防淤策略,以減緩水庫淤積及穩定供水營運,常見的水庫防淤策略包括集水區保育、水庫通砂減淤、回復庫容及水資源調配,而工程方法則有水中浚渫、陸面開挖及建造防淤隧道等。作為臺灣具有最大容量的水庫,曾文水庫建庫設計容量逾7.4億立方公尺,然而因泥砂逐年淤積問題,庫容減少至今剩餘約5億立方公尺(2022年),且曾文水庫因本身缺乏民生用水的引水系統,需與烏山頭水庫串聯營運以供應嘉南大圳和其下游區域之水源。為有效解決未來曾文水庫蓄供水量缺乏的隱患,經濟部水利署南區水資源局近年防淤規劃之一係為利用抽泥、浚渫等工程手段形成之庫底主深槽,應用於導引、集中入庫渾水運移至壩前出水工入口處以提升防淤設施排砂成效,即為庫底導流槽設施。 為探討不同防淤操作情境、庫底導流槽設置前後對庫區懸浮泥砂傳輸現象變化之影響,以及對曾文水庫未來供水營運進行風險分析,本研究以曾文水庫為主要研究區域,蒐集庫區斷面地形資料、歷史颱風豪雨入流及入砂量歷線、出水閘門操作紀錄等資料,以二維數值模式建置水庫模型,應用數值模擬方法分析各水庫防淤操作情境在不同重現期流量、颱風豪雨事件下,庫區內泥砂運移行為及搭配防淤設施操作之排砂效率,並依據資料蒐集和模擬成果推估囚砂率曲線、未來庫容及供水量,建立風險分析方法以評估水庫淤積危害度和供水穩定度組合的風險程度,期望本研究相關成果未來可作為提供水庫管理單位實施防洪排砂運轉作業之參考,以改善集水區流域之水資源供應、提升水庫及下游區域水環境品質為永續目標。 Taiwan is located on the northwest side of the Pacific Ocean. The island's terrain extending from north to south is long and narrow. Due to its geographic location, the climate is often influenced by the tropical cyclones generated in the sea. Each year, excessive rainfall in the catchment area contributes to soil erosion during the rainy and typhoon seasons. Consequently, a significant volume of sediment streams into the reservoir region, generating high-concentration turbid water or density current causing a rapid increase of the suspended solids concentration in front of the dam. High suspended solids concentration in the reservoir area is a significant indicator of river pollution. In addition, the long-term sediment inflow is a cause of bed deposition and a decrease in the storage capacity, impacting the primary purpose of a reservoir and the cost of water supply and water purification. As a result, it endangers the quality of the water supply for domestic, industrial, and agricultural purposes and downstream regions. Reservoir management strategies to mitigate reservoir sedimentation and stabilize water supply operations can be classified as long-term or short-term, depending on the reservoir type. Standard reservoir sediment management methods include catchment area conservation, sediment reduction, capacity restoration, and water source allocation. The engineering methods include dredging, excavation, construction of desilting tunnels, etc. For example, the Zengwen Reservoir is the largest reservoir by volume in Taiwan, with a designed capacity of more than 740 million cubic meters. However, due to the sedimentation issue, its capacity has declined by about 200 million cubic meters. However, Zengwen Reservoir must be connected to Wushantou Reservoir to function as the primary water source for the Jianan Canal due to the requirement for a public water delivery system. Therefore, one of the strategies planned by the Southern Region Water Resources Office, WRA, MOEA for dealing with the risk of the Zengwen Reservoir's water storage capacity is to employ the dredged guiding channel constructed by dredging and excavating for guiding and directing the inflow of sediment into the reservoir and improving the venting efficiency of the desilting facilities. This study focuses on Zengwen Reservoir as the primary research area to discuss the influence of different desilting operation scenarios and dredged guiding channels on the suspended sediment transport phenomenon and analyze the risk of water supply operation of Zengwen Reservoir in the future. The study includes collecting data on reservoir terrain, historical hydrograph, records of gate operation, etc., and building a reservoir model by a two-dimensional numerical model. Study analysis includes the sediment transport behavior and the venting efficiency of desilting facilities during the flood events of the different return periods, Typhoons, and heavy rain. In addition, the results based on data collected and simulation include the trap efficiency curve, the reservoir capacity, and the water supply of Zengwen Reservoir, which aid in developing a risk analysis method to assess the risk level with the combination of reservoir sedimentation hazard and water supply stability. The study results can be referred to by reservoir management agencies for flood control and desilting operation. The sustainable goal is to improve the water resource supply of the catchment area and the water quality of the reservoir and downstream regions, which the planned strategy can achieve. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/87936 |
DOI: | 10.6342/NTU202301171 |
Fulltext Rights: | 同意授權(限校園內公開) |
Appears in Collections: | 環境工程學研究所 |
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