水庫濁水現象之研究---子計畫：水庫濁水含砂濃度之現場監測研究

Abstract

台灣地區水庫集水區週遭因地質條件不佳，加上近年來山坡地大量開發，水土 保持工作未落實以及氣候變遷等因素，造成大量山坡地沖蝕崩塌，使水庫多面臨颱 洪期間原水濁度過高及水庫淤積，導致防洪能力降低、給水能力不足等問題。為研 擬減緩或清除水庫淤積及降低原水濁度之策略，需分析泥砂在水庫內之運移、沖淤 和分佈的規律，而現場量測資料搭配數值模擬即是最佳的分析策略之一。泥砂移運 之觀測可分析泥砂分佈、運移之時間與空間行為，以提供模式參數率定與驗證之 用，以及未來排砂操作的即時資料回饋。既有之泥砂濃度量測技術無法同時達到高 濃度、多點資料擷取自動化、耐用性等需求。本研究的主要目的是以以被動式電磁 波時域反射法發展成本可行、高空間解析度、高時間解析度、高量測範圍、耐久性 的泥砂自動化觀測系統。研究首先建立基本泥砂取樣與超音波人工量測系統，作為 初期資料收集與後續監測技術開發驗證之工具；並以被動式電磁波時域反射法建立 寬頻的電學性質量測技術，藉以探討含砂濃度與寬頻電學性質之關係。接著改良現 有電學感測器之量測精度後，以石門水庫現址實際測試多點式電學感測技術，並配 合其他觀測技術，進行方法驗證及現場自動化監測實務問題探討。最後藉由各項觀 測資料，探討監測物理量與含砂濃度及其他環境因子之關係，以具體建議水庫濁水 含砂濃度之監測策略。

The climate change together with the unfavorable geological condition and land overuse has posed great challenge to river and water resource management in Taiwan. Typhoon Aere of August 2004 had caused the Shihmen Reservoir to silt up and suspend water supply for weeks due to excessive water turbidity. Excessive water turbidity during rainstorm and reservoir sedimentation are becoming serious problems to many reservoirs in Taiwan. Effective methods to monitor and simulate suspended-sediment transport in severe rainstorms are required to plan strategy for reducing turbidity of water supply and sedimentation in reservoirs. Observing the variation of suspended-sediment concentration with time and space can be used to calibrate and verify the numerical model and the real-time data can provide necessary feedback to operation of sediment routing. The main objective of this proposed study is to develop an automatic suspended-sediment monitoring system with high measurement range, high spatial and temporal resolution, cost effectiveness, and durability. A sediment sampler and ultrasonic device for suspended solid concentration will be used to collect data during rainstorms and verify the monitoring technique to be developed based on time domain reflectometry (TDR). Wide-band measuring technique based on TDR will first be developed to measure electric properties of turbid water at different frequencies. Relationship between wide-band electrical properties and suspended-sediment concentration will be established through laboratory investigations. Field probes with high sensitivity will be developed and tested in the field. An automatic monitoring system consisting of the newly-developed TDR probes and other conventional instruments will be installed in Shihmen reservoir. Optimal approach for suspended-sediment monitoring will be proposed based on the verification and comparison of different techniques as well as practical lessons learned from the case study.