Research On Future Climate Change In The Nansi Lake Basin And Its Impact On The Runoff Of Typical Lake-entering Rivers

At present,the speed of global climate change is accelerating,and the problems caused by climate change have attracted the attention of all sectors of society.The hydrological cycle is greatly affected by climate change,and changes in temperature and precipitation may increase the probability of extreme hydrological events.Nansi Lake is the largest freshwater lake in North China.It is a multi-functional lake that integrates flood control,dehumidification and water supply.It is also the most important storage site in the East Route of the South-to-North Water Diversion Project.It plays a very important role in the local economy,social development and ecological environment.Therefore,it is important to understand the impact of climate change in the Nansihu Basin on runoff.In this paper,two typical tributary basins(Zhuzhaoxin River and Si River)in the Nansihu Basin are selected as research areas to estimate the impact of future climate change on runoff in the basin.Firstly,the SWAT distributed hydrological model is applied to the research area,and the SWAT-CUP software is used to calibrate the model and the analyze sensitivity of the parameters.Secondly,the SDSM is established by meteorological data and NCEP reanalysis data.The downscaling model studies the statistical relationship between regional predictors and forecasting quantities and verifies the accuracy of the simulations.Thirdly,the medium-low emission scenarios(RCP4.5)and high-emission scenarios(RCP8.5)in the CMIP5 model are input to the SDSM model to predict and analyze the future climate change of the study area.Finally,use the future climate data to drive the validated SWAT model,obtain the runoff of the future basin,and analyze the response of the basin runoff to climate change.The conclusions of the study are as follows:(1)The SWAT model is used to simulate the runoff in the Nansihu Basin.The R2 of the Zhuzhaoxin River Basin is 0.85,the Nash efficiency coefficient is 0.84,and the R2 of the Si River Basin is 0.83,and the Nash efficiency coefficient reaches is 0.82.Overall,the simulation results in Western Nansi Lake basin are better than those in the Eastern.The simulation results in the flood season are better than the non-flood period,and the model meets the applicability requirements.The model meets the applicability requirements.(2)Using SWAT-CUP for parameter sensitivity analysis,the sensitivity rankings in Eastern Nansi Lake basin(Si River Basin)are:EPCO.hru,ALPHA_BNK.rte,GWQMN.gw,etc.;The sensitivity rankings of in Western Nansi Lake basin(Zhao Zhaoxin River Basin)are:EPCO.hru,CH_K2.rte,SOL_AWC(1).sol etc.(3)Using the statistical downscaling model SDSM,the statistical relationship between the forecasting factors and the forecast variables is established.Through the calculation,the Nash efficiency coefficient of the temperature simulation results in the model verification period averages 0.95,and the Nash efficiency coefficient of the precipitation simulation results averages 0.85,which satisfies the applicability requirements.(4)Under the two scenarios of RCP4.5 and RCP8.5,the temperature and precipitation fluctuate,and the mean temperature and precipitation under the RCP8.5 scenario is greater than the RCP4.5 scenario.The maximum temperature rose by 2.1?(RCP4.5)and 4.3?(RCP8.5)at the end of the century;the minimum temperature rose by 2.2?(RCP4.5)and 4.5?(RCP8.5)at the end of the century;annual precipitation increased 46.5mm(RCP4.5)and 104.86mm(RCP8.5)at the end of the century.(5)The runoff of the Nansihu Basin is increasing in the future,and the growth rate in the flood season is large,and the mean value of runoff under the RCP8.5 scenario is greater than the RCP4.5 scenario.The runoff of Zhuzhaoxin River Basin will increase by 2.4%(RCP4.5)and 10.9%(RCP8.5)in short-term,and increase by 8.7%(RCP4.5)and 15%(RCP8.5)medium-term,and increase by 13.5%(RCP4.5)and 18.5%(RCP 8.5)in long-term;The runoff of Si River Basin will increase by 3.3%(RCP4.5)and 11.6%(RCP8.5)in short-term,and increase 9.5%(RCP4.5)and 20%m3/s(RCP8.5)in medium-term,and increase 14.8%(RCP4.5)and 25.6%(RCP8.5)in long-term.