牡丹水庫集水區降雨分布與長期趨勢分析

Mudan Reservoir Watershed Rainfall Distribution and Long-term Trend Analysis

台灣雖然降雨充沛，但季節性差異極大以及極端降雨常造成洪災、旱災、山坡地崩塌等自然災害，而近半世紀氣候變遷造成水文循環改變，加劇以上現象，對集水區水資源應用造成極大衝擊，亦增加造成之人命傷亡及經濟損失。因此，掌握水庫集水區在氣候變遷下之降雨變化趨勢及空間分布，可為災害防治及集水區經營管理提供參考資訊。本研究應用Mann-kendall趨勢檢定分析牡丹水庫集水區降雨變化趨勢，降雨量資料取自水利署及氣象局雨量站，同時利用普通克利金法推估近年研究區內降雨分布。研究結果顯示整體降雨無顯著變化趨勢，但就雨量站而言，海拔較高之上游牡丹站地區年降雨量、豐水期雨量有明顯增加的趨勢，年最大連續不降雨天數有明顯減少的趨勢，而海拔較低之下游石門站地區的年不降雨天數則呈明顯減少的趨勢。

Although Taiwan has plenty of rainfall, the huge seasonal difference and extreme rainfall cause natural hazards, such as floods, droughts and landslides, to occur constantly. Climate change has changed the hydrological cycle nearly half a century, which does not only intensify the phenomenon talked above, but also impact the watershed's water resources applications enormously, leading to increasing casualties and economic losses. Therefore, understanding the reservoir watershed's rainfall trends and distribution under climate change could provide information for disaster risk reduction and watershed management. This study applies Mann-kendall test to analysis Mudan reservoir watershed's long-term rainfall trends. The precipitation data are captured from the Water Resources Agency and Central Weather Bureau's rainfall stations. The results show that the upstream Mudan station area has a significant increasing trend in annual precipitation and wet season precipitation, and significant decreasing trend in annual consecutive dry days. Furthermore, the downstream Shimen station area has a significant decreasing trend in annual dry days.