Study On Response Of Extreme Runoff Under Changing Environment In The Karst Basin

The impact of changing environment on the hydrological cycle is increasing,and the hydrological process in the basin has significant changes,which bring a lot of tests to the water supply,flood control and ecological environment.It is of important to explore the response of extreme runoff in the basin under changing environment.In view of this,this paper conducts research on the topic of "study on response of extreme runoff response under changing environment in the Karst Basin".The main work and results are as follows:(1)The paper uses a variety of statistical methods to analyze the trend,mutation and persistence characteristics of extreme temperature,extreme precipitation and extreme runoff in the Chengbi Basin.The results show that the extreme high temperature in the basin is significantly reduced,while the extreme low temperature is significantly increased,which made an abrupt change in 1997 and 1986.The Hurst index of extreme temperature is about 0.8,which is persistent.The decreasse trends of extreme precipitation and extreme runoff were weak,and they made abrupt changes in 2008 and 1980.The Hurst index of extreme precipitation is about 0.6,and the persistence is weak.The generalized Pareto distribution(GPD)distribution can be well fitted based on the super-threshold peak method,and it showed that the recurrence levels of extreme runoff in 10 years,100 years and 1000 years were 573.7m3/s,983.3m3/s and 1820.1m3/s.(2)Based on ArcGIS,the changes and transformation of land use types in the Chengbi Basin in 1980,1995 and 2010 were analyzed.The results showed that forest land,cultivated land and grassland were the main types of land use in the basin,and the area of cultivated land and grassland increased,while the forest land decreased.The transfor of land use between 1980?1995 and 1995?2010 are similar,but the transformation scale of previous was more obvious.(3)Construct a SWAT model for runoff simulation in the Chengbi Basin,simulate the daily runoff of the basin,and analyze the response of extreme runoff to climate change,land use change,and coupled climate and land use change.Base on this,use GPD distribution to study the POT sequence of coupled climate and land use change,and analyze its recurrence level.The results show that the decrease of temperature and the increase of precipitation will lead to the increase of extreme runoff in the basin,and the response of extreme runoff to precipitation changes is significantly higher than that of temperature;the reduction of forest land and the increase of cultivated land will lead to the increase of extreme runoff in the basin;The extreme runoff on land use scenario in 2010 is the most;the impact of climate change on the extreme runoff of the basin is significantly greater than that of the land use;the recurrence level of the extreme runoff in the basin is higher under the scenario of increasing precipitation.(4)The extreme runoff in the Chengbi Basin is highly responsive to climate change and has a strong dependence on precipitation.The watershed management should pay attention to climate change and formulate reasonable measures in the future.