Impact Of Changing Environment On Watershed Runoff And Simulation Analysi

Environmental change conditions are increasing and their effects on runoff have become a hot topic of research in the hydrological community.The distinction and definition of the impact of climate change and human activities on runoff in the changing environment also adds difficulty to the research.Therefore,the study of how to distinguish and define the impact of both,and how to analyze the impact of the changing environment on runoff qualitatively and quantitatively and the magnitude of the impact is of great significance to the deployment of water resources in the basin.In this study,the Yongcui River basin was selected as the study area.Firstly,the trend analysis of precipitation,runoff and other hydrological characteristics was conducted,and the results of the trend analysis were used to analyze the sudden change in runoff and evaporation and calculate the contribution rate;secondly,the sudden change analysis was used to obtain the sudden change year,and a stepwise regression model was established before and after the sudden change year to calculate the effect of precipitation on runoff before and after the sudden change year,and the results were used to describe the effect of climate change on runoff.The SWAT model is used to describe the impact of human activities on runoff by changing land use and calculating the magnitude of the impact of land use on runoff.The main results of this study are as follows:1.The trend analysis of precipitation and runoff and abrupt change analysis of runoff at Beltling(II)station,runoff trend at Yulin,Xinguang and Xinshuguang stations,and abrupt change analysis of evaporation in the whole basin were analyzed by M-K trend test,sliding average method,accumulation curve method,and comparison of slope change of accumulation,and it was concluded that runoff showed an increasing trend and evaporation showed a decreasing trend,and the abrupt change years were2001 and The sudden change years are 2001 and 2011.2.The contribution rate of precipitation to runoff before and after the mutation point was calculated separately,and the magnitude of the effect of precipitation on runoff was 39.08% after the mutation year to before the mutation year.A stepwise regression model was established to calculate the effect of precipitation on runoff before and after the abrupt change in runoff year as 15.79% increase in runoff during the abundant water period and 28.84% decrease during the dry water period.3.The SWAT model was established for the study area,and the best fit was achieved at the Yulin station,which was used to adjust the reference for the integrated watershed,and the model could be applied to the Yongcui River basin after the adjustment.The four parameters with strong model sensitivity were saturated infiltration coefficient,baseflow a-factor for riverbank storage,infiltration rate of the main channel,and shallow groundwater threshold for generating baseflow.4.The model with completed parameters by rate setting was substituted into four periods of land use data,four periods including 2000,2005,2010,and 2020,keeping the rest of the database unchanged,to simulate the effect of human activities on runoff,and the results of the study showed that runoff showed a very small decrease from 2000 to 2010 as the area of forested land increased,but as the area of forested land increased again from 2010 to The results show that runoff decreases minimally from 2000 to 2010 as the area of forested land increases,but increases again from 2010 to 2020 as the area of forested land increases.