Runoff Simulation Of Songhuaba Watershed Based On SWAT Model And Its Response Analysis To Future Climate Change

This study builds a distributed hydrological analysis model for the Songhuaba watershed based on the SWAT model.Based on parameter calibration,parameter sensitivity analysis,and model accuracy verification,it systematically simulates the hydrological cycle process in the Songhuaba watershed,and conducts water balance analysis and research on soil water,river runoff,and groundwater in the Songhuaba watershed.Design future climate change scenarios and analyze the simulation results of different climate scenarios to study the hydrological response under climate change and the impact of climate change on water resources.The research aims to provide reference for the rational development and optimal allocation of local water resources,and provide scientific basis for the rational development and utilization of water resources in the Songhuaba Basin.The main conclusions of this study are as follows:(1)Collect relevant data on land use,soil,and meteorology in the research area according to the input requirements of the model data,use Arc GIS and SPAW and other software to conduct preliminary data processing,and build a spatial database and attribute database of the SWAT model for the Songhuaba Basin distributed hydrological model.According to the characteristics of the watershed,the Songhuaba watershed is divided into25 sub watersheds in the model,with the Songhuaba hydrological station as the total water outlet of the watershed.On this basis,the sub watersheds are further divided,and 216hydrological response units(HRUs)are obtained.Based on this,a distributed hydrological analysis model for the Songhuaba watershed is established based on the SWAT model.(2)SWAT-CUP 2012 software was selected to calibrate the parameters and verify the accuracy of the model.The parameters were calibrated using the monthly scale runoff measured data of Songhuaba Reservoir from 2008 to 2013,and the model was validated using the monthly scale runoff measured data of Songhuaba Reservoir from 2014 to 2016.The results show that the regular runoff rates R~2 and Ens of Songhuaba Reservoir are0.8195 and 0.8171 respectively;The runoff verification period R~2 of Songhuaba Reservoir is 0.8404,and Ens is 0.8306,indicating that the R~2 between the model simulation results and the measured data is greater than 0.6,and Ens is greater than 0.5,indicating that the SWAT model has good adaptability in the Songhuaba Basin,and the model simulation accuracy can basically meet the research requirements.(3)Based on the characteristics of the Songhuaba watershed and the simulation results of the SWAT model,water balance analysis and research were conducted on soil water,river runoff,and groundwater in the Songhuaba watershed.The research results showed that the annual average rainfall in the Songhuaba watershed was 737.74mm,with actual evapotranspiration accounting for 43.2%of the total recharge,soil to groundwater recharge accounting for 28.3%of the total recharge,and lateral flow from surface runoff accounting for 19.6%of the total recharge,Soil moisture is in a negative equilibrium state;The annual average groundwater resources in the basin are 1.84×108m~3,groundwater in a negative equilibrium state;The main sources of river runoff in a watershed are surface runoff and underground runoff.It can provide technical support for the rational development and optimal allocation of local water resources.(4)The SDSM statistical downscaling model is selected,and the relationship between the forecast amount and the forecast factors is established through SPSS using multiple stepwise regression analysis and multiple collinearity diagnostic analysis.The relationship between regional climate and large-scale environmental factors is established.The model is calibrated and validated.The results show that the correlation coefficient and Nash efficiency coefficient of temperature simulation are above 0.75 on average,The correlation coefficient and Nash efficiency coefficient of precipitation simulation are both above 0.6on average,and the simulation accuracy of the model can meet the applicability requirements,allowing for the estimation of future climate scenarios in the Songhuaba Basin.(5)SDSM downscaling model is used to design future climate change scenarios,and the simulation results of different climate scenarios are analyzed to drive SWAT model to obtain the runoff change of Songhuaba basin.The prediction results indicate that the runoff in the Songhuaba Basin is positively correlated with precipitation and weakly negatively correlated with temperature.Overall,the monthly runoff in the future will first decrease and then increase in the near future(2020 to 2050),and in the long term(2051 to 2100),it will increase.Moreover,the average runoff under the SSP5-8.5 scenario is greater than that under the SSP3-7.0 scenario,and the average runoff under the SSP2-4.5 scenario is greater than that under the SSP1-2.6 scenario.