本研究探討氣候變遷對水庫集水區降雨特性造成之影響，分析石門水庫集水區1966~1990年、1991~2011年及1966~2011年各時期降雨變化，以Mann-Kendall趨勢檢定法進行雨量趨勢檢定，結果顯示雨量在1990年前增加趨勢集中於4月，1990年後無增加趨勢；減少趨勢由1、2及6月變至5及8月，得知氣候變遷造成雨量在時間分布上的改變，臺灣濕季為5~10月，乾季為11~羿年4月，顯示在乾濕季節交替時趨勢變化較為顯著。 一般雨量站雨量為點雨量，在水文分析上，區域內平均雨量為地區性在水資源工程設計與規劃之依據，故將點雨量轉換為面雨量。本研究將點雨量轉換為面雨量的方式為挑出所有雨量測站中可能最大降雨量為最大的測站作為基準點，將點可能最大降雨量乘上面積遞減因子最大值0.7轉換為面可能最大降雨量，由於面積遞減因子觀念考慮到研究區域之面積大小，推估之可能最大降雨量較能顯現出實際區域特性。計算結果可能最大降雨量建議值為1175.8mm，可能最大洪水量建議值為15675.5cms，本研究結果高於目前石門水庫之設計洪水量，顯示本研究較為保守，未來可作為石門水庫設計洪水之參考。 This study investigated climate change which affect of rainfall characteristics at Shihmen Reservoir catchment, and also analyzed the rainfall by the Mann-Kendall method some periods in 1966-1990, 1991-2011 and 1966-2011. According to the analysis result, the average annual rainfall in 1966 -1990 showed that the increasing trend occur in April, and the decreasing trend occur in January, February and June. For 1991-2011 is only had trend decreased which can seen in May and August, thus it can be concluded that climate change may affect the distribution of rainfall significantly. In Taiwan, dry season started from May to October, whereas wet season started from November to April. Hence, there was an obvious rainfall trends distribution which emerging in the dry and wet alternative. A standard used in a rain gauging station usually will be point rainfall. In aspect of hydrologic analysis, since an average regional rainfall is the basis for designing and planning water resource engineering, a point rainfall will be converted to a surface rainfall. By converting point rainfall into surface rainfall, this study picked out all maximum possible rainfall among rainfall gauging stations as standards and multiplied maximum possible point rainfall by above maximum values of area reduction factor, 0.7 in order to convert them into maximum possible rainfall. For area reduction factor it often considered the size of research area, so an estimated maximum possible rainfall would be more capable to show the actual area properties. This study suggested that PMP can adopt 1175.8mm, and PMF can adopt 15675.5cms. Since all research results in this study were above the design-flood inflow of Shihmen Reservoir, it showed that this study would be more conservative and could be used as a reference for future inflow projects.
