利用Budyko framework評估現況與氣候變遷情境下台灣各流域水資源之變化

在氣候變遷的壓力下，預估水資源的變化以利水資源管理顯得格外重要，流域水資源的變化可以透過了解一個流域的降雨、蒸發散與流量的變化特性及趨勢而得。因此本研究使用TCCIP所產製0.05°×0.05°網格雨量與溫度資料(1960-2017年)，以及水利署監測(1960-2017年)與台電公司紀錄(1970-2017年)的歷年流量資料作為研究資料，分析全台107個流域的雨量、流量、蒸發散量、逕流係數等因子的變化趨勢，並建立集水區年時間尺度之雨量─流量線性關係式（年流量＝a×年雨量+b），此外利用TCCIP產製至世紀末的網格雨量及溫度資料，分析在AR5的34個GCM及4個RCP情境下，各流域於Budyko空間中的移動角度與向量長度並進行集群分析。結果顯示，全臺灣各集水區年流量在空間及時間上無顯著變化趨勢，然對應流量資料之年雨量卻普遍呈上升趨勢，並導致共有21個集水區的逕流係數達顯著下降的趨勢並主要集中在北區與南區，而逕流係數顯著上升的區域則集中於中區及東區；所有集水區的雨量與流量均呈現非常好的線性關係且達到顯著，R2值大於0.7的測站數高達71個，然而有25個流域發生流量高於雨量的狀況。在氣候變遷情境下全台流域於Budyko空間的變化可歸類於三種類型：集群1的流域共11個，該類流域在未來潛在蒸發散量增加的幅度最小，但年雨量的增幅最大，推論為最有可能遭遇洪患問題之流域；集群2的流域為27個，在未來其潛在蒸發散量將大幅增加，加上年雨量減少，推論將面臨嚴重水資源不足的問題；而集群3流域數量為37個，雨量與潛在蒸發散量的變化量介於前二者之間，但雨量增加量仍小於潛在蒸發散量的增加量，可能面臨水資源降低的問題。而本研究結果預期可作為未來全台各流域水資源管理的參考依據。

關鍵字

水資源管理；蒸發散量；集群分析；水文氣候

並列摘要

Under the stress induced by climate change, it is especially vital to predict the changes of water resources in the future. The changes of rainfall, evapotranspiration, and streamflow in the catchments are the prerequisite knowledge of water resources management. This study data includes the 0.05°×0.05° rainfall and temperature raster data, produced by TCCIP (1960-2017), and streamflow data, provided by Water Resource Agency (1960-2017) and Taipower (1970-2017). We analyze the trends of historical rainfall, streamflow, evaportranspirtaiton, and runoff coefficient for the 107 catchments in Taiwan. Rainfall-runoff relationships, i.e. annual runoff = a × annual rainfall + b, were also constructed. With the rainfall and temperature data til the end of the century provided by TCCIP, the movement of vector and direction of each catchment in Budyko space are calculated and clustered under the future climate senarios, incliding projections of 34 GCM for 4 RCP scenarios in AR5. The results show that there are no spatial and temporal trends for the annual runoff but there is overall increasing trend for the annual rainfall, leading to significant decreasing trend in runoff coefficient at 21 watersheds, mainly in Northern and Southern Taiwan. Every watershed has a very good rainfall-runoff relationship, and there are 71 watersheds where their relationships having R2 values greater than 0.7. However, the annual runoff data in 25 catchments is higher than the annual rainfall. The movement in the Budyko space of all catchments can be classified into three clusters. Cluster 1 of 11 catchments may suffer from flood in the future because it has the minimum increase in potential evapotranspiration but the maximum increase in rainfall among the three clusters. Cluster 2 of 27 catchments may face serious water shortage problems, because its potential evapotranspiration will increase significantly and the annual rainfall will decrease in the future. Cluster 3 of 37 catchments may face the problem of water resources reduction, because it has the second highest increase in rainfall and potential evapotranspiration among the three clusters, but the increase in rainfall is still less than increase in potential evapotranspiration. The results of this study could be a reference for the future water resources management in Taiwan.