德基水庫自1974年運轉至今，由於並未實施泥砂管理策略，經年累月下來，因泥砂淤積作用庫容已損失達25%，逐漸威脅到發電及供水功能，為能永續經營水庫，勢必要尋求有效之泥砂管理策略。本研究利用一維水理輸砂模式配合水庫水文概念模式進行水庫沖砂之模擬分析。
本研究使用自2008年到2016年實際水庫運轉紀錄並參考現行之水庫操作規則以建置德基水庫水文概念模式，並進行不同沖砂操作模擬，包含調整防淤操作天數、水位、調節性放流量以及調整水庫放流能力，以得出水庫在不同操作下對水位之影響，並使用此水位做為數值模式之下游邊界條件，以模擬不同操作策略下對水庫排砂之影響。數值模式模擬結果得知，當沖砂操作期越長，水位越低，會有較多之排砂量，然而當水位不完全洩降時，如1325至1330公尺，不宜進行長期沖砂操作，雖能排出較多之泥砂，但造成排出每單位泥砂所需耗水量增加，導致排砂效率下降。由計算不同操作情境下之水砂比得知，藉由擴大壩底出水口之放流能力，令水位於操作期內更全然下降，能使更多泥砂被排出，沖砂效率也有明顯之提升，也可藉由提高沖砂期間之調節性放水量使排砂量增多，但會使沖砂效率下降。SRH1D模式模擬結果預測，沖砂後於水庫三角洲會有較明顯之沖蝕情況，而於前坡段及壩前段則普遍發生淤積現象，其中又以壩前段淤積較為顯著。

Techi Reservoir, built in 1974, has no sediment management strategy. Accumulated sediment already exceeds 25% of reservoir capacity due to continuous sediment inflow. Thence, the power generation and reservoir storage have been severely impacted. In order to maximize the use and extend the life of this reservoir, a sustainable sediment management plan is needed. In this study, the 1D numerical model SRH1D was combined with the reservoir hydrological conceptual model to simulate a reservoir flushing operation.
In this simulation analysis, we use recorded reservoir operation reports from 2008 to 2016 as input data and refer to the current reservoir operation rules to establish the hydrological conceptual model. We simulated different operation scenarios adjusting factors such as the period of flushing, the maximum operation water level during flushing, the discharge capacity of the outlet as well as different regulation discharges during the flushing period. By doing so, we are better able to understand the influence of these factors on sediment release and reservoir geomorphology. The results of the numerical model show that the longer the operation period and the lower the water level, the more sediment release there will be. However, if the water level drawdown is incomplete, for instance drawn down to only 1325meters instead of 1320 or bellow, it is not advisable to implement longer flushing operation when considering water resource needs and conservation. Although there is more sediment release with longer operation, the flushing efficiency will be reduced due to the fact that water consumption per unit of sediment release has increased. The efficiency of flushing operation was predicted by comparing flushed water to computed sediment ratio. Results showed that modification of the bottom outlet by expanding the orifice area leads to more sediment flushing and improves flushing efficiency as the water level is able to be lowered more efficiently during the flushing period. In addition, increasing the regulated discharge from 86 to 115cms will flush more sediment but appears to reduce flushing efficiency. The SRH1D simulations predicted that most scouring will occur on the reservoir delta. Some scour sediment will not be flushed through the outlet but will deposit in the fore-set and bottom-set slope during the flushing process.

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