圖書典藏及影音數位平台

近年因氣候變遷，導致水資源設施供水能力受到影響，且傳統水資源設施推動不易，桃園及新竹地區隨著人口成長、都市化的發展與產業結構的改變，用水需求量逐漸增加，造成桃園及新竹地區缺水風險高。 目前大漢溪水源利用率已達77％，石門水庫年運轉超過4次，且需備援新竹地區，造成石門水庫供水壓力高。本計畫探討石門水庫集水區是否有擴大之方案，如南勢溪是否尚有剩餘水量可引入石門水庫系統運轉，以提高區域供水穩定度及調配彈性，減輕石門水庫對大漢溪水源依賴，降低缺水風險，保障民眾用水權益。並基於環境變動因素，探討引水功能及工程可行性，評估是否可擴大推動效益。同時探討板二計畫及越域引水工程完成後區域供水情勢，提供未來政策推動之參考，爰此辦理「石門水庫擴大集水區規劃檢討評估」計畫。

1.Preface In recent years, the water supplement of Shihmen Reservoir is facing in a high-pressure situation. In order to solve the water supplement problem, this study reviews the water basin expansion planning around the Shihmen Reservoir. The conclusions of this study show that the residual flow of the nearby Nanshi River is enough to support the Shihmen Reservoir.The simple research flow chart can be shown as below: First, analyze the feasibility study of the water basin expansion of Shihmen Reservoir. Base on the results of feasibility study to determine a proper solution for expansion the water supply of the Shihmen Reservoir. Also, increase the water supply ability from Shihmen Reservoir to Bansin area, and Taoyuan area. The study results are showing in the following paragraph. 2.Basic data collection and evaluation From 2011 to 2018, Shihmen Reservoir supplied 412 millions m3 for agricultural water and 353 millions m3 for Water Corperation in average. Total water supply value for each target is about 760 millions m3, which is under tight condition because of its 200 millions m3 effective capacity and 4 times in a year use. Xindian River is one of main side stream within Tamsui River basin , and it’s main upstream are Beishi River and Nanshi River. The river length of Beishi River is about 50 km, and the basin area is 310 km2 , The slope rate of the river-bed is gentle, which is 1/100 in average. In 1987, Feitsui Reservoir was constructed at downstream of Beishi River; While the river length of Nanshi River is about 45 km, and the basin area is 332 km2 , The slope rate of the river-bed is 1/138 in average. 3.Evaluation of basin expansion for Shihmen Reservoir. Nanshi River basin located at northeast side of Mt. sylvia. During winter, the northeast monsoon brings a large amount of rainfall to recharge the Shihmen Reservoir, thus this area have higher develop potential. Feasible diversion program is the program A (Nanshi River Fushan- Shihmen Reservoir). According to the study results, program A provides 10.2×104 CMD of incresed water supply (develop scale 30CMS), which equivalent to 37.23 million per year. in the case of retaining water right around downstream area, Incresed water supply is up to 36.2×104 CMD if capacity of Gaotai Reservoir is taken into account. 4.The investigation of ditching facility in Nanshi River The principle of investigation of ditching facility will follow several basic conditions. (1)The water transmission by gravity. (2)As possble as narrowing the tunnel’s total length. (3)As possble as raising up transbasin diversion capacity. (4)Reducing the ditching facility construction funds. 5.Environment Impact analysis The engineering influence area involve aboriginal reserve and traditional domain. According to law principle, developement can only be conducted after approval of aboriginal tribe. Thus, closer attention to relevent regulation of aborigines’ right is necessary. On topic of ecology, diversion tunnel pass through underneath nature reserve. Environmental impact need further review on this ecological issue. 6.Engineering Content and benefit analysis Program A provides 10.2×104 CMD of incresed water supply; cost of the raw water is 23.4 NTD/m3; estimated construction cost is 14.6 billions NTD. The major benefit of this study are water supply, while secondary benefit is power generation. Benefit cost ratio (B/C) is 1.06. 7.Assessment of difficulty and strategy study on construction Program A is passing through a lot of formations. Miocene and Oligocene faults, and the which overburden more than 1,000 meters under the sea level. Facing the geothermal, gushing inflow, and the rockburst problem. To overcome these geological characteristics, the transbasin diversion tunnel are going to excavate with drilling and the blasting method. In addition, the shape of tunnel section is horseshoe and the full profile survey of the tunnel is lining. 8.Conclusion If program A (Fushan downstream- Shihmen Reservoir) is adapted, under the condition SI=0.5 for water supply system, years count of water deficient ratio above 5%, will decrease from 19 years to 15 years in Taoyuan area (shortage frequency reduct from once every four years to every three years). The years count of water deficient ratio above 10% will decrease from 4 years to 2 years (shortage frequency reduct from once every 15 years to every 30 years). Therefore, transbasin diversion could effectively lower the water supply pressure of Shihmen Reservoir and improve water supply stability. In this study, the plan has reserved growth need of water resource utilization based on“Northern Taiwan Water Resources Plans”. This plan is a longterm case, which means if there are water demand change result from Bansin area’s sociaty and economic condition, rolling review is recommended to the follow-up researches.