淡水河流域水資源永續性評估暨管理之研究

Abstract

本研究目的在藉由系統動力學理論，建立淡水河水資源系統動力模式，以評估流域水資源利用之永續性，研究範圍包含新店溪流域之臺北供水區及大漢溪流域之板新、石門供水區，再利用下游測站歷史流量資料及水庫歷年放流量驗證模式之合理性，接著採用年缺水指數(Shortage Index，SI)、農業可供水指標(Agriculture Supply Index，ASI)作為評估基準，求出在符合供水規劃準則之下最大可供水量，此最大可供水量定義為水資源系統之環境承載力，並訂出水資源永續發展指標，藉由指標的變化，進而探討淡水河流域水資源之永續性。 由現況分析結果發現台北地區之供水最為不虞匱乏，永續發展指標等於1；板新地區雖然永續發展指標等於1，但其供水情況較吃緊，若是未來需水量上升，並無相關規劃措施配合的話，會產生嚴重的缺水情形；至於石門地區由於本研究根據水利法規定，先滿足公共用水，再考慮農業用水，因此公共用水永續發展指標等於1，農業用水永續發展指標則等於0.04，建議末來可深入探討石門地區各標的用水使用的情形。 另考慮氣候變遷之預設情境，假設其需水情勢與2025年相同，探討在2025年若受到氣候變遷影響下水資源永續性的變化，且考慮台北區售水率的改善及自來水第五期擴建計畫中之直潭淨水場擴建計畫，根據初步規劃是將其中之53萬CMD支援板新地區，結果發現大部分的情境下是符合水資源利用的永續性，但由於氣候變遷影響之下，其環境承載力是呈現下降的情形；最後，本研究建立一套評估水資源利用永續性的機制，末來可利用此流程針對不同水資源政策作分析，透過需求總量管制的方式，以期望整體水資源系統能夠更符合永續發展之目標。

A system dynamics model was built for the TanHsui watershed. The model was used to evaluate sustainability of use of water resources. Study areas include water supply systems of Taipei, PanHsin and ShihMen. The stream flow record between 1991 and 1999 and release water from the Feitsui and ShihMen Reservoirs are used for the model verification. This study adopts two indexes, Shortage Index, SI and Agriculture Supply Index, ASI, to find the maximum water supply of water resource system. It is defined as carrying capacity. Furthermore, a Sustainable Development Indicator (SDI) is established to evaluate sustainability of use of water resource in TanHsui watershed. The results show that the SDI in all study areas is equal to 1, and it means the water supply system is sustainable. However, there is a difference between Taipei, PanHsin and ShihMen about water supply. In Taipei, it has a large surplus of water, but in PanHsin the water supply faces the stress of deficient water. According to Water Act, domestic use has the top priority of water usage and agricultural use has the second. Therefore the water supply meets domestic water use firstly in ShihMen area in this research. This research also considers the influence of climate change; it assumes that water demand is equal to that in 2025 when climate change happens. Besides, it considers the government’s policies in the future. The great part of results show that the water supply system under climate change is sustainable, but the carrying capacity shows a descendent trend.