保育減砂區位優選與量體評估之研究－以德基水庫集水區為例

Site Scanning and Volume Evaluation in Sediment Reduction and Conservation in the Deji Reservoir Watershed

10.29417/JCSWC.202206_53(2).0002

黃文政(Wen-Cheng Huang)；林政侑(Cheng-Yu Lin)；吳岳霖(Yue-Lin Wu)；陳炯勛(Jiong-Xun Chen)

德基水庫 ； 永久性沉砂設施 ； 沉砂效益 ； 可行性評估 ； 農塘 ； Deji Reservoir ； Permanent settling facility ； Sedimentation benefit ； Feasibility assessment ； Farm pond

中華水土保持學報

53卷2期（2022 / 06 / 01）

92 - 99

繁體中文

臺灣是一個海島國家，島內用水均需仰賴水庫供應，為維持水庫應有庫容量，政府對水庫集水區訂定年保育減砂量，期望可減少水庫淤積並延長使用壽命。故本研究針對臺中德基水庫集水區進行沉砂設施之「潛在區位」掃描，及「既有防砂壩」、「農塘」等沉砂設施調查，篩選適宜之永久性沉砂設施場址，並從土砂去化及生態探討場址設置之可行性。本研究共篩選出158處永久性沉砂設施場址，分別為「潛在區位」3處、「既有防砂壩區位」6處及「農塘區位」149處。其中以主流河段之「潛在區位」最具沉砂效益，惟德基水庫集水區範圍內有櫻花鉤吻鮭重要棲地，故基於生態考量，使其執行可行性降低；「既有防砂壩」以D29七家灣溪三號壩沉砂效益最高，但其位處於野生動物保育區，因此，本研究建議以沉砂效益次高之D31南湖溪二號壩，做為主要沉砂空間；「農塘」為本研究可行性與可操作性最高的設施，且農塘皆位處於道路方便之區位，後續可透過農地回填的去化方式，解決德基水庫集水區廣植蔬菜，土壤流失之問題。結果顯示，6座既有防砂壩共能提供約2.04萬立方公尺沉砂空間，約占總沉砂目標（33萬立方公尺）之6.2 %，農塘可營造之沉砂空間共約4.14萬立方公尺，約占總沉砂目標之12.55 %。

As Taiwan is an island country, water storage is predominantly dependent on reservoirs. To maintain reservoir storage capacity, the government has set annual targets for sediment reduction volume and conservation of reservoir watersheds. Therefore, in this study, the existing permanent deposit facilities and sedimentation facilities such as existing sabo dams and farm ponds in the Deji Reservoir catchment area were assessed to determine their suitability as permanent deposit facility sites. A total of 158 sites for permanent deposit facilities were selected, including three potential locations, six existing sabo dams, and 149 farm ponds. Of these, a potential location on the mainstream river offers the most sand-settling benefits. However, important Sakura habitat is present in the catchment area of the Deji Reservoir, and this ecological consideration reduces this site's potential feasibility. The D29 Qijiawanxi No. 3 dam has the highest sedimentation efficiency of existing sabo dams but is in a wildlife conservation area. The D31 Nanhuxi No. 2 dam is recommended as the main sedimentation space because it has the second highest sedimentation efficiency. Farm ponds are the type of facility with the greatest feasibility and maneuverability; this is because farm ponds are located on conveniently accessible roads. In the future, deforestation of farmland backfill may be a solution to problems concerning widespread vegetable planting and soil loss in the Deji Reservoir watershed. The results show that the six existing sabo dams can provide approximately 33,800 cubic meters of deposit volume, accounting for 10.2 % of the total sedimentation target (330,000 cubic meters). The farm ponds can provide a 41,400 cubic meter deposit volume, accounting for approximately 12.5 % of the total sedimentation target.

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