圖書典藏及影音數位平台

阿公店水庫集水區大部分為青灰泥岩地形，質地鬆軟且吸水易化，每遇颱風豪雨即造成庫區大量沉滓運移入庫，自民國42年水庫開始運轉以來，每年約有50萬立方公尺之淤砂量淤積於庫底，至民國80年時，水庫淤積率已達71%。民國86年起辦理「阿公店水庫更新工程計畫」，進行水庫浚渫清淤1,160萬m3，庫區有效容量回復至1,837萬立方公尺，並改建溢洪管及灌溉管，實施空庫防淤操作以大量減少洪水時之沉滓落淤，以永續維持水庫之有效容量。然在水文、地文、泥砂運移等因素均具有相當高不確定性的情況下，上述更新工程的空庫防淤運轉規則，應可進一步依據實際操作成效進行檢討，以提升排砂效率。例如，由近年來防淤操作之觀察，在排洪通道地處於庫區邊陲位置，出流量有限(最大85 cms)的現況條件下，空庫防淤的成效實有取決於入庫泥砂的運移型態之現象；更新改善後的供水模式及操作運轉規劃則與影響水量與水質的水文、地文因子息息相關。因此，需要更深入的了解阿公店水庫更新改善工程完工後水庫空庫防淤操作的成效，藉由現場量測與水庫泥砂運移模式的分析，釐清入庫水砂在水庫內之運移、沖淤和分佈的規律，以提供本局後續推動提升阿公店水庫空庫防淤效率之管理策略擬定之參考依據。

Agondian Reservoir has been operated since 1953. 71% of the total storage volume was filled with deposited sediment in 1991. A reservoir renewal project was started in 1997. Empty flushing has been taken as the main measure to reduce sedimentation by flood events and to maintain the effective storage capacity sustainably. In order to realize the desiltation efficiency after finishing the renewal project, the project, “Sediment Observation and Efficiency Evaluation for Desiltation of Agongdian Reservoir by Empty Flushing” has been started in 2009. The transport, deposition and concentration distribution of the inflow sediment within the storage area is studied through on-site survey and numerical modeling. The results will be provided as the reference for promoting desiltation efficiency and management strategy. In this year (2014), the desiltation efficiency is analysis with concertration sampling. The project includes: 1. Data update and analysis 2. Concertration Sampleing 3. Desiltation efficiency is analysis. 4. Sedimentation analysis. 1,002 samples were taken in this year. For the rainfall event, include typhoon Matmo, “0810” event, and typhoon Fung-Wong, 481 samples were taken. The maximal sediment concentration at spill shaft is 31,946 mg/L by typhoon Matmo, and 3,000 mg/L by “0810” event. In peacetime, total 140 samples were taken at diversion works. The sediment concentration is about 500 mg/L. another 251 samples were taken with the mechanical disturbance. The sediment concentration is 15,000 mg/L. during the over-basin diversion, 130 samples were taken at inflow. The average sediment concentration is 1,300 mg/L. According the sampleing data, the desiltation efficiency of typhoon Matmo is 74% and 24% for “0810” event. It shows with the control of water level and mechanical disturbance could increase the desiltation efficiency. The topography shows the deposition fan still increase. But the variation of the main channel is not apparent with last year. And the effect of the mechanical disturbance to the downstream was also consider in this project. The result shows the increase of sediment concentration would risen the water level in 0.2 meter at the downstream. This would not increase the flooding risk of the downstream area. An extra sediment concentration sampling sensor is set at the spill shaft to show the immediate resuit. The survey results could be summarized to the points below. 1. From the aerophoto of upstream, it shows the deposition occurred at the upstream channel. And the sediment concentration during over-basin diversion is much higher than peacetime. These shows the survey of the upstream srea is necessary. 2. Tthe mechanical disturbance could increase the sediment concentration, it should be enhanced in the further 3. The main channel could provided a fast way for the high concentration flow, the main channel should be maintain. 4. Keep the water level at El.30 could increase the desiltation efficiency evident. With the control of the water level, the outflow should increase before the high concentration flow get in the reservoir. The time of the control could be much accurate wity another sediment concentration sampling sensor in the upstream.