Research On The Relationship Of Extreme Weather And Hydrological Events In The Basin Under The Regional Climate Background

Climate change has now become one of the hottest issues in the world. More and more hydrological workers started to research on the changes of hydrology and water resources caused by climate change. However, there is a little research on extreme hydrological event and its impact, and it is still at the early stage of research. The research on extreme events has developed in recent years because of the increasing frequency of extreme events brought by climate change and put people in real danger. In the context of climate change, the main content of this paper is to study the relationship of extreme weather events and extreme hydrological events. The preliminary research was carried out combining with Natural Science Foundation of China (The Sensitivity Research on the Hydrologic Processes to Extreme Weather Events NO.:51079131).In this paper, the calculating method of threshold was determined based on the definition of extreme weather events in IPCC. In accordance with the definition of extreme weather events, the definition of extreme hydrological events was defined based on summarization of the characteristics of hydrological events. And the threshold of extreme weather events and extreme hydrological events were defined. The data used in this paper are the daily meteorological data from 1975 to 2009 of 76 weather stations, the measured runoff data of hydrometric station and the meteorological data in the controlling basin of Nianyushan Reservoir. The distribution and changes of climate and extreme climate in Henan province has been analyzed and the correlativity and changes of extreme climate and hydrological events has also been analyzed in the controlling basin of Nianyushan Reservoir.The concept of extreme hydrological events has been defined in this paper. And according to the definition, the thresholds of extreme events were defined in the study area. The changing regularity and relationship of the extreme climate and hydrological events have been analyzed in small watershed under climatic background. Take the controlling catchment of Nianyushan Reservoir as an example, the occurring times of the extreme flood events and the extreme low-flow events which occurred respectively in flood season and non-flood season present a weak decreasing trend. There will be extreme precipitation events when the extreme flood events happen. But when the extreme precipitation events happen, there is a 45.7% chance of occurrence of the extreme flood events. There is a good correlation between the extreme flood events and the previous rainfall. The correlation between the extreme flood events and the sum of the rainfall three days ago is the highest. There are no correlation between the extreme low-flow events and extreme drought events. However, the correlation between the extreme low-flow events and days without precipitation is much better. The major influencing factors of the extreme hydrological events are the extreme precipitation events in the extreme hydrological events.