圖書典藏及影音數位平台

曾文水庫自蓄水以來，歷經多次颱風豪雨侵襲，水庫集水區洪水造成大量泥沙推移至蓄水區域內，其淤落之分佈情形及其可能對水庫產生營運之不利影響，有必要了解並因應。雖然本水庫每年皆以斷面法進行淤積測量，惟測量及成果計算費時約二個月時間，曠日費時且成果精度較不足。 由於98年8月莫拉克颱風來襲，超大豪雨造成水庫蓄水範圍土石坍崩，大量土石進入於水庫內。依據中心於98年10月委外辦理曾文水庫淤積測量工作，相較於97年測量結果，98年莫拉克颱風後淤積量為9,162萬立方公尺。其中呆容量部份（EL：171公尺以下）為1,379萬立方公尺，有效容量部份（EL：171公尺以上）為7,783萬立方公尺。自62年4月水庫蓄水以來至98年11月止累計總淤積量為25,781萬立方公尺，佔設計總容量74,840萬立方公尺之34.45%，累計年平均輸砂量為716萬立方公尺為預估年平均輸砂量561萬立方公尺之127.6%。 行政院亦特別制定「曾文南化烏山頭水庫治理及穩定南部地區供水特別條例」，以確保南部地區供水無虞。為有效執行曾文水庫之清淤排淤、集水區治理等計畫，亟需有精確之淤積測量資料配合各項計畫之執行辦理。 本計畫擬於100年度施做兩次淤積測量工作，第一次於5月底前（汛期前）辦理完成，第二次則預定於汛期過後辦理。並於計畫於第一次測量時，於蓄水面以上至EL.235M並再往外推30公尺水平範圍，以航拍技術配合空載光達（LiDAR），製作庫區數值地形模型及數值高程模型（DEM）等。

TsengWen Reservoir built in upstream of TsengWen River. The main objective is regulation and making full use of water resources of TsengWen River. TsengWen Reservoir not only to improve and expand of irrigated farmland in Southwest region, but also possesses with hydroelectric Power, water supply system and flood control etc. Since the reservoir water has gone through several typhoons and heavy rain hit. Reservoir watershed pushed to move large amounts of sediment to storage area caused by flood water. This situation will result unfavorable effect on operation of reservoir. In order to execute silt dredging engineering, and management of watershed effectively, so this plan use Airborne-LIDAR and Multibeam to obtain data, which with high accuracy and high density. According to the result to understand the reason and range of erosion and siltation, to be the basis for follow-up plans of the silt dredging engineering, management of watershed etc. This year executed two deposition measurements, which before and after flood period individually. The work project included: (1) Reservoir sedimentation surveying of below submerged line, (2) Airborne-LIDAR surveying of above submerged line, (3) Aerial photography operations of TsengWen Reservoir, (4) Digital Surface Model (DSM) and Digital elevation model (DEM) production of reservoir, (5) Reservoir volume calculation. From the measurement results indicate that this project before the flood period (2011.04) deposition measurements, Full of water (EL.227m) total volume and effective volume is 49,511’104 m3 (Water storage area is 1776 ha). After the flood period (2011.10) measurement results, Full of water (EL.227m) total volume and effective volume is 49,173’104 m3 (Water storage area is 1801 ha). Two measurement results stay volume (EL.171m) are all 0 m3 (Water storage area is 0 ha). The comparison measurement results of 2011.04 and 2010.04, total volume and effective volume increase 352’104 m3, stay volume increase 0 m3. The comparison measurement results of 2011.10 and 2011.04, total volume and effective volume reduce 338’104 m3, stay volume increase 0 m3. In order to analysis the erosion and siltation change situation in the area of plan. The comparison results with 2010.04 showed erosion near the dam and downstream region (section A-1~A-8). The deposition phenomenon occur in the sediment delta apex (section A-13) and tributary of the river of middle stream region (section A-8~A-16). In the dry water season due to the erosion by rainfall have erosion phenomenon in upstream region (section A-16~A-22).