近年來台灣地區因氣候異常，極端洪水或枯旱現象日趨頻繁，當發生乾旱現象過於頻繁時，常會面臨水資源短缺或嚴重匱乏之窘況。惟一般對於如何明確定義乾旱而有所困擾，特別是因其研究對象及應用領域之不同而有所差異，例如農業、氣象及水文乾旱等。本研究之目的係探討降雨發生短缺而造成區域性之氣象水文乾旱現象，並發展乾旱嚴重性之評估研判方法，主要以雨水短缺而產生之現象來為乾旱事件進行定義。本研究首先採用乾旱延時曲線(Drought Duration Curves, DDC)之概念，藉以推求不同日數下移動平均降雨量之重現期距。此外，以不同日數下之移動平均降雨量來分析乾旱事件及判定其嚴重程度，並進一步推估集水區內乾旱特性之空間分佈，則可提供水文情勢研判及集水區經營管理之參考。 研究區域選定石門水庫集水區，主要分析對象為集水區域內10個雨量站之歷史日雨量紀錄，分別推求不同重現期距之DDC。在研究中，挑選主要三場乾旱事件作為本方法之驗證與應用。 由研究結果顯示利用乾旱延時曲線作乾旱事件嚴重程度之判定，若研究區域為水庫地區，配合水庫水位容量，更有助於乾旱特性之研析。因此，本方法未來可進一步發展，以作為長期水文情勢研判與乾旱預警上之參考與應用。 The phenomena of water resources deficit frequently come up these years in Taiwan. It is caused by the last increasing of water demand for social-economic development. On the other hand, climate change and irregular meteorological phenomena are also causing local drought events and extreme flood more and more. The ordinary are perplexing to how to clearly define the drought, especially the difference between research object and application territory has differences, such as agriculture, meteorology and hydrology of drought, etc.. This study aims to investigate meteorological hydrology drought resulted from a shortage of rainfalls, and advanced to determine the gravity of drought. This study adopts concept of the Drought Duration Curves at first, is it inquire into different number of days of moving average precipitation the return periods. In addition, analyze the incident of drought and judge its gravity with the moving average of precipitation under different number of days, and estimate the space distribution of the characteristic of drought, the reference that can offer the hydrology situation to study and judge and the upstream basin to manage. The upstream basin of Shihman Reservoir was chosen as a study area and different return periods of DDC of the project area were calculated by using daily rainfall records of 10 gauging stations. In this study, the return periods of a drought event made drawings, and there were three drought events used to test the application of this idea. From the researching results, Using the Drought Duration Curves to determined the order of severity of drought is more useful for studying the spatial characteristics of drought events Therefore, this method is worth as an advance study for detection of long-term hydrological situation and drought warning.
