Response Of Runoff To Climate Change And Human Activity In Xiangjiang Basin

With the rapid development of social economy,the trend of global warming continues to intensify,and the characteristics of climate change are obvious.Meanwhile,the intensification of human activities has changed the water cycle process of river runoff.The Xiangjiang basin is affected by climate change and human activities,and floods and droughts frequently occur.It seriously restricts the social and economic development of Hunan.Therefore,the analysis of climate change and human activities is of practical significance for the study of Xiangjiang basin's water cycle.The main conclusions are as follows:Based on the data of 19 meteorological stations in Xiangjiang basin,the evolution characteristics of precipitation,runoff and potential evapotranspiration in Xiangjiang basin from 1961 to 2013 were analyzed by various mathematical statistics methods.The results showed that the annual distribution of precipitation in Xiangjiang River Basin was uneven,which was more frequent in spring and summer,and less in autumn and winter.The interannual variation trend of precipitation in 1961-2013 years was not obvious.Xiangjiang basin is the potential evapotranspiration distribution of the year showed a single peak in July,potential evapotranspiration;potential evapotranspiration in 1961-1995 years showed a significant downward trend after 1996,began to rise;Xiangjiang river basin runoff variation and precipitation is similar to that of annual distribution of spring and summer autumn and winter much less,the interannual change was not significant.Analysis of the interannual variation of precipitation runoff 1961 to 2013 extreme precipitation indices,continuous rain days decreased significantly during the year,30 years,the minimum flow minimum average flow rate increased significantly,95%percentile low flow frequency decreased significantly.Based on 1985-1995 years' meteorological and hydrological data and DEM,land use and soil data in Xiangjiang basin,SWAT hydrological model of Xiangtan hydrological station in Xiangjiang basin is established.The measured flow data based on 11 hydrological stations in the Xiangjiang River Basin are divided into 11 parameter areas,which are regular in 1986-1990 years and 1991-1995 years as the verification period.The simulation results show that the determination coefficient and Nash coefficient of 11 hydrological stations are all above 0.82,which proves that the model can better simulate the hydrological process of Xiangjiang basin and its tributaries.Using SDSM statistical downscaling model,we selected 1961-2013 meteorological data from 12 meteorological stations to simulate the downscaling of NCEP reanalysis data and the highest minimum temperature and precipitation of 12 stations.The reduced scale results show that SDSM can better simulate the highest minimum temperature in Xiangjiang River Basin,and the effect of rainfall simulation is general.Select the change features in CMIP5 CanEMS2 mode,RCP2.6 RCP4.5,RCP8.5 scenario analysis of Xiangjiang basin precipitation of 2014-2060 years,maximum and minimum temperature was significantly increased in RCP4.5 and RCP8.5 scenarios,the variation trend of precipitation was not obvious;compared with the reference period of 1961-2013 years,RCP2.6,RCP4.5,RCP8.5 annual precipitation under the relative reference period increased 1.93%2.9%,and 8.41%.Based on SWAT model and measured data,we quantitatively analyzed the impact of climate change and human activities on runoff change in Xiangjiang basin,and divided 1986-2013 years into two phases of 1986-1999 and 2000-2013 years.The results show that the main runoff change in Xiangjiang is mainly climate change,and the contribution rate is about 84..5%.The contribution rates of different factors in the tributaries are different.Human activities play an important role in increasing runoff in most basins.Combining the precipitation and temperature data of SWAT and SDSM after downscaling,the change trend of 2015-2060 years runoff in Xiangjiang three RCP scenarios is not obvious.Compared with the baseline period RCP2.6,RCP4.5 and RCP8.5 scenarios,the annual runoff increased by 5.41%,7.43%and 14.75%.