Runoff Variation And Attribution Analysis In The Upper And Middle Huai River Basin

In recent years,the hydrological cycle under the background of human activities and climate change has become a hot research topic in hydrology.Research and quantification of the contribution rate of human activities,land use/underlying surface changes and climate change to the runoff changes is of great significance to the rational planning and utilization of water resources and the protection of regional water resources security.This paper takes the middle and upper reaches of the Huai River Basin(above the Bengbu Station)as the research area.First,the MK test,Moving t-Test,R/S analysis method is used to analyze precipitation and potential evaporation sequences from 1958 to 2018 and the runoff sequence from 1958 to 2016.The change trend,and the mutation point of the runoff series was determined in 1990,and the runoff series was divided into the base period and the change period.During the change period(1991-2016),the multi-year average runoff decreased by 8.66%compared with the baseline period(1958-1990).A land use transfer matrix is used to analyze land use changes and their impact on runoff changes.From 1980to 1995,the largest transfer of land use area occurred on the conversion of cultivated land to residential land,reaching 664 km~2.Secondly,the transfer of grassland to cultivate land and forest land reached 259km~2 and 241km~2 respectively.The larger forest land and water area showed a downward trend in the corresponding runoff changes,and the year when the grassland area decreased significantly corresponds to the time of the runoff point of the runoff sequence.(1)Establish a SWAT hydrological model in the middle and upper reaches of the Huai River Basin,set different simulation schemes to simulate the corresponding runoff,and quantitatively evaluate the runoff changes caused by climate change,land-use changes,and human activities.(2)Based on Budyko's hydrothermal coupling equilibrium theory,the elastic coefficient method is used to calculate the sensitivity of precipitation,potential evaporation,and underlying surface parameters.(3)Quantitative analysis of the contribution rate of climate change and human activities in runoff changes based on Budyko's water-heat coupling equilibrium theory.(4)Combine two methods of attribution analysis of runoff change for comprehensive evaluation.The research results show that:(1)In the SWAT hydrological simulation method:the contribution rate of climate change,land-use change,and the impact of human activities during the change period is 28.25%,-1.45%,and-70.30%,respectively.The main factors that causes changes in runoff.(2)Based on Budyko's hydrothermal coupling equilibrium theory:The elastic coefficients of precipitation,potential evaporation,and underlying surface parameters in the base period and the change period are 2.11,1.10,-1.10,and 2.36,-1.36,and-1.07,respectively.(3)Among the various factors that lead to changes in runoff,the contribution rates of climate change,underlying surface changes,and direct effects of human activities are 37.13%,-53.53%,and-9.34%,of which the underlying surface changes are the main causes of runoff reduction.(4)Climate change is a secondary factor that causes runoff change.Except for climate change that contributes positively to runoff change,the contribution rates of land use/underlying surface changes and human activities are both negative.Due to the limitations of analysis methods and the different attributes of land-use and underlying surface definition,the difference between the evaluation results of the two attribution analysis methods is mainly reflected in the changes in land use/underlying surface and the absolute value of the contribution rate of human activities.Both of these research methods provide references for exploring the nature of the watershed and quantitatively evaluating the mechanism of runoff changes.