圖書典藏及影音數位平台

曾文水庫於民國98年8月8日遭受莫拉克颱風侵襲後，其水庫上游集水區邊坡崩坍嚴重，加速水庫淤積惡化情形，並嚴重影響水庫容量及水庫防洪運轉操作。為治理曾文、南化與烏山頭水庫及穩定南部地區供水，並緊急辦理相關水源設施之清淤、整建與新（擴）建工程及水庫集水區環境保育之相關措施，立法院通過「曾文南化烏山頭水庫治理及穩定南部地區供水特別條例」。為使曾文水庫後續相關治理計畫能維持水庫營運功能、保育上游集水區水域環境及穩定水庫供水能力，爰此，提出曾文水庫防洪防淤整體綱要計畫，針對上、中、下游防洪防淤整體計畫提出策略與建議，俾利作為後續計畫實施之參據。 經濟部水利署水利規劃試驗所(以下簡稱本所)依據經濟部水利署（以下簡稱 鈞署）民國100年2月1日經水源字第10015000710號函及民國100年3月24日經水源字第10015001770號函修正計畫名稱為「曾文水庫防洪防淤整體綱要計畫」，民國100年5月5日經水源字第10051076750號函修正計畫經費及期程，爰提本工作委託服務計畫書（修定稿），俾利工展。

Under the constrains of silt mitigation-and-removal technical feasibility as well as existing limiting conditions such as technical difficulty, regulation restriction and government financial condition, a long term average sediment inflow of 5,600,000m3 per year is used in this planning. This amount is identical to the value estimated in the approved “Tsengwen Reservoir Project Planning Report” and is slightly greater than the average annual siltation in the reservoir prior to Typhoon Morakot. For a sustainable operation of the reservoir, planning has been made to apply various measures to achieve a long-term average sediment removal rate equal to this amount. In other words, the goal of sediment removal in this master plan is, after completion of all recommended measures, long-term balance of sediment inflow and outflow will occur and will enable the reservoir to achieve a sustainable operation. Considering schedule of on-going sediment mitigation projects, three phase have been developed for Tsengwen Reservoir siltation prevention plan: 1. Phase 1 (2012~2015) The objective of this phase is to ensure water supply capability of the project and to restore the function of all facilities to a Pre-Typhoon-Morakot state. Furthermore, planning and design of sediment sluicing and flood discharge facilities are also carried out, in addition to conversion of PRO for sediment sluicing, construction of a new silt sluicing facility near the dam and improvement of intake structure, etc., as parts of integrated sediment reduction measures. 2. Phase 2 (2016~2027) This is the design and construction phase of newly planned sediment reduction projects. Facilities for upstream sediment diversion and reservoir sediment sluicing are being planned and would be designed and constructed in this phase. Furthermore, sediment dredging capacity would also be increased. The integrated measure shall achieve the goal of sediment inflow and outflow balance. 3. Phase 3 (after 2027) This is the phase that a sustainable reservoir volume will be achieved. In addition to projects constructed in Phase 2, new technologies which have been developed for silt removal shall be aggressively utilized to increase reservoir volume, with a long term goal to recover the lost reservoir volume. A reservoir volume of 435 millions has been set in this master plan as the volume that Tsengwen Reservoir shall be maintained after yr.2028. This is the expected reservoir volume at yr.2027 after all silt reduction projects have been completed. That is to say, from yr.2028 on, Tsengwen Reservoir can achieve the goal of 5,600,000m3 of sediment reduction. Although the purpose of this project is for silt reduction, the planned silt-removal structures will also increase flood discharge capacity and enhance flood operation safety. Tsengwen Reservoir shall take into account of development of new siltation prevention technology, silt sluicing operational efficiency, regulation changes, government financial condition and implementation schedule of other related projects (such as Tsengwen Transbasin Diversion Project) to review this planning once every 4 years and to make appropriate revision of the plan. The plan is to use the estimated inflow sediment quantity in the initially approved 「Tsengwen Reservoir Project Report」 as the silt prevention goal, with an objective first to maintain the planned reservoir volume and later to gradually increase the volume to a state following the dam construction.