Study On Runoff Response Under Extreme Scenarios In Dawen River Basin Based On SWAT Model

In recent years,the problem of water resources and water environment is one of the research hotspots of global environmental issues.Climate change and the underlying surface of the watershed are important factors that affect the hydrological cycle,their changes make the evolution of hydrological elements complex and uncertain.In particular,activities such as unreasonable land use patterns of human beings change the structure of the underlying surface,so the study of their effects on the hydrological process is of great significance to the sustainable development of regional economy and society.In this study,typical small and medium-sized watersheds(the control range of Dawenkou Station)are selected as the research object the trend、catastrophe and periodic characteristics of precipitation and runoff at representative hydrological stations are analyzed,and the SWAT model of typical small and medium-sized watersheds in Dawen River Basin is constructed.The parameter sensitivity analysis and calibration of SWAT-CUP model are used to comprehensively evaluate the applicability of SWAT model in the basin through the evaluation index of the model.On this basis,the future climate change scenario and the impact of human activities(different land use patterns)are simulated by using the calibrated model,the response of typical watershed hydrological runoff process to climate and land use change is quantitatively analyzed.The research results can provide a reasonable and effective theoretical basis for the protection of ecological environment,water resources planning and management in Dawen River Basin.The main conclusions are as follows:(1)Taking Dawenkou Station and Laiwu Station in Dawenhe River Basin as representative hydrological stations the trend、abrupt change and period of runoff are analyzed.The results show that from 1984 to 2016,the runoff of Dawenkou Station and Laiwu Station has an upward and downward trend,respectively.There are mutation points.The runoff of Dawenkou station and Laiwu station is periodic,and the first main period corresponds to the time scale of 27 years.(2)The typical small and medium-sized watershed of Dawenhe River Basin is simulated by SWAT model.The watershed is divided into 70 sub-basins.The sensitivity and uncertainty of the parameters are analyzed by SWAT-CUP,and the measured data of Dawenkou Station and Laiwu Station from 1990 to 2016 are used to calibrate and verify.Among them,Dawenkou Station Nash coefficient Ens=0.84,determination coefficient R~2=0.80,Laiwu Station Nash coefficient Ens=0.66,determination coefficient R~2=0.84.It shows that the SWAT model has good applicability in the study area.From 1990 to 2016,the average precipitation of typical watersheds in Dawen River Basin was 670mm and the surface runoff was 134mm.(3)Based on the trend and abrupt change analysis of meteorological data(air temperature and precipitation)in Dawen River Basin from 1990 to 2016,the precipitation showed a downward trend,the decline rate was about 51.8mm/10a,the temperature showed an upward trend,and the average temperature increased by about 0.39℃/10a.Considering the dynamic characteristics of meteorological elements and climate model,eight combinations of temperature change and precipitation change in four scenarios are set up to simulate runoff.Through the analysis of the total amount of runoff under different climate scenarios,the results show that the impact of precipitation change on runoff is higher than that of temperature on runoff.Precipitation increases by 10%and runoff increases by an average of36%.When the temperature increases by 1~oC,the average runoff increases by about 30%.(4)According to the trend of land use change in 1990、2000、2005、2010 and 2015,three extreme land use change scenarios are set up.The simulation results show that with the increase of land use area of township industrial and mining residents,the impervious area increases and the runoff increases the most.(5)In the typical small and medium-sized watersheds of the Dawen River basin,runoff has varying degrees of response to land use and climate change,with an increase of 10%in precipitation and 1~oC or 2~oC in temperature and an average increase of 38%in runoff.Under the land use scenarios of the three extreme scenarios,the average increase of runoff is about14%,so the response of runoff to climate change is more significant.