台灣地區降雨豐沛，但是在空間及時間上分配不均，尤其在南部地區，枯水期和豐水期的降水量相當懸殊，根據統計有高達72 %之降水會形成河道逕流，顯示台灣河川流量變化的研究在水資源運用及分析上是非常重要的。本研究參考世界各地對河川流量變化研究之文獻，選出4種常用的統計方法，分別是檢定趨勢的 Mann-Kendall檢定法，檢定趨勢斜率大小的Theil-Sen 推估法，以及判斷有無改變點的Mann-Whitney-Pettit和Cumulative Deviation檢定法應用於台灣南部地區。本研究主要挑選南部地區流量測站之紀錄資料長度達30年以上，共9個流量測站，將上述4種統計方法應用於年平均流量、各月平均流量、高低流量、年平均基流量以及各月平均基流量等項目進行檢定。

流量與基流量檢定結果顯示，枯水期的流量檢定結果有超過7成的比例為上升趨勢，且多為顯著上升趨勢，位置集中於八掌溪、曾文溪與鹽水溪等於研究區域內較偏北邊的流域，而下降趨勢則集中於高屏溪的三地門測站與東港溪流域的潮州測站。於豐水時期，整個研究區域內的上升趨勢與下降趨勢比例則約為1：1。各個檢測項目的趨勢斜率(β)大多僅佔研究期間內常年平均流量的2 %，而低流量與枯水期的趨勢斜率(β)較大，可以達到研究期間常年平均流量的7.4%，顯示低流量與枯水期的改變量較顯著。於枯水期檢驗出的顯著改變點比豐水期還多，並且檢驗出的改變點年份有高達64 %的比例落於1990年至2000年間，改變點前後的改變幅度於低流量與枯水期項目較大。儘管於枯水期有檢驗出較多的上升趨勢，但流量仍遠遠不及豐水期。

The precipitation is concentrated in the wet season, which accounts for 90% of the total precipitation in southern Taiwan. Thus, the temporal and spatial distributions of precipitation are extremely uneven, making careful management of water resources in Taiwan crucial. According to the previous study, about 72% of the precipitation becomes river runoff which is one of the main water resource in human life. Therefore, it is an important issue to conduct on trends and variation of streamflow. Four statistical tests, such as Mann-Kendall test, Theil-Sen's slope estimator, Mann-Whitney-Pettit statistics, and Cumulative Deviation method are adapted to analyze the trend characteristics for 9 gauging stations in southern Taiwan.

The results of the streamflow and the baseflow both indicate that more than 70% increasing trends are found in the monthly average flow during dry period, and most of them are significant trends in the Bajhang River, Zengwun River, and Yanshuei River basins. The decreasing trends are centered in the Gaoping River basin and the Donggang River basin. The low-flow and dry period slope of the trend are significant, and they can be up to 7.4% of the long-term average flow. The change points in dry period are more than in wet period. Simultaneously, about 64% of the change points exists during 1990 to 2000 and the difference of the average flow after change points are significant in low-flow and dry period.

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