Evolution Characteristics Of Mountainous Runoff And Its Response To Climate Change In Xiying River Basin

Based on the monthly precipitation and monthly average temperature,daily maximum temperature and minimum temperature data in Xiying River Basin from1961 to 2015,and monthly runoff discharge data of Jiu Tiao Ling hydrologic station from 1956 to 2015,this paper analyzed the evolution characteristics of climate change and mountainous runoff in Xiying River Basin by nonparametric Mann-Kendall test,wavelet analysis and model construction.On the basis of comprehensive analysis of the evolution characteristics of climate and runoff in Xiying River Basin in recent 55 years,the response process of mountain runoff to climate change is discussed in depth.Finally establish response and sensitivity evaluation model of runoff to climate change,and make a scientific prediction of runoff in different climate change scenarios.The results show that:(1)From 1961 to 2015,the precipitation of Xiying River Basin experienced the process of "decreasing in fluctuation-increasing slightly",and the whole precipitation showed a weak increasing trend.The annual average temperature and potential evapotranspiration were decreased first and then increased,and the overall trend was increased,the turning points of them were 1983.The precipitation,average temperature and potential evapotranspiration in the four seasons are all increasing.mutations of precipitation occurred in 2002,mutations of average temperature and potential evapotranspiration occurred in 1996,both of them have a common cycle of about 3a and 16 a.(2)From 1956 to 2015,the annual average runoff of Xiying River experienced a process of "slow reduction,rapid increase and rapid reduction",and the whole runoff showed a weak decreasing trend.Mutations occurred in 2002.Runoff discharge decreased in spring and summer,increased in autumn and winter,and summer is the main contributor to the decrease of annual runoff discharge.(3)The surface runoff discharge and the base flow discharge respectively account for66% and 34% of the mountain runoff discharge,the variation trend of them were consistent with the annual average runoff.The annual average surface runoff increased only in autumn,and summer is the main contributor to the decrease of annual average surface runoff.The annual average base flow decreased in summer and autumn and increased in spring and winter,and spring is the main contributor to the increase of annual average base flow.Mutations had all occurred in 2002,consistwith the precipitation,both of climatic elements and runoff have a common cycle of about 3a and 16 a.The annual runoff depth and annual precipitation show good positive synchronous variation characteristics,while the annual runoff depth are inversely asynchronous with annual average temperature and annual potential evaporation of Xiying River.(4)The average runoff coefficient of Xiying River in1961-2015 is 0.551,The changes of meteorological dryness and humidity in autumn and summer have the most significant influence on the hydrological dryness and humidity.The seasonal lag occured between meteorological drought and flood and hydrological drought and flood.Hydrological drought is easy to occur in summer and autumn,which lead to frequent annual hydrological drought.(5)The response of mountainous runoff discharge and its components to precipitation is strongest in autumn and weakest in winter.The response rate of surface runoff to precipitation is faster than that of base flow to precipitation at different time scales.The reaction of base flow to precipitation has hysteresis and insensitivity.(6)When the potential evapotranspiration and average temperature are constant,the increase of precipitation will cause the increase of runoff,when the precipitation and temperature are constant,the increase of potential evapotranspiration will cause the decrease of runoff,when the potential evapotranspiration and precipitation are constant,the increase of annual average temperature will cause the decrease of runoff,the increase of average temperature in summer and autumn will cause the increase of runoff.Annual runoff and autumn runoff are most sensitive to precipitation,summer runoff is most sensitive to potential evapotranspiration.