| In recent years,water cycle process and water resources situation in the middle reaches of the Yellow River have changed significantly,human activities and climate change are considered to be the key factors affecting the process of runoff generation.A large number of water and soil conservation measures were implemented and the implementation of policies(e.g.,Grain for Green Project)has resulted in significant improvements in vegetation conditions in most areas of the middle reaches of the Yellow River.In the background of population growth and the changing characteristics of the underlying surface,studying the impact of changes in climate and underlying surface conditions on the runoff generation mechanism of the basin has become a hot issue in the study of hydrology.Under the support of the China National Key R&D Program during the 13th Five-year Plan Period(Grant No.2016YFC04020203)"Change mechanism and trend prediction of water and sediment in the Yellow River Basin" and National Natural Science Foundation of China(Grant No.51979250).This paper selected Jialu River Basin and Jingle Basin as the research objects,based on traditional hydrological methods and long series of measured rainfall and runoff data,the runoff generation patterns of basin and influencing factors are analyzed,combined with modern remote sensing technology,the discriminant system for the spatial distribution of runoff generation patterns in basin was constructed.The research content and results are as follows:(1)Discrimination and analysis of runoff generation patterns in typical basins.Starting from the mechanism of the traditional runoff formation process,based on the combination of runoff components of the flood and the comprehensive identification index of the runoff generation pattern,the changes in the runoff generation pattern of the Jialu River and Jingle basins were distinguished in three stages.The study found that:the runoff generation pattern of the two basins are still dominated by superpermeability runoff,but in recent years,the proportion of floods dominated by superpermeability runoff has been gradually decreasing gradually,while the proportion of floods dominated by mixed runoff and saturation excess runoff have been increasing step by step,indicating that the runoff generation patterns in the two basins have changed in recent years.(2)Attribution analysis of changes in runoff generation patterns in basins.The K-means clustering method is used to classify rainfall events in the basin into three types,and to determine the degree of influence of different types of rainfall on runoff generation.At the same time,the reduction effect of vegetation coverage at different stages on runoff generation in the basin was quantitatively analyzed.Based on the constructed non-linear regression model between runoff coefficient and influencing factors,combined with the spatial data processing function of ArcGIS,the control variable method is used to analyze the influence of vegetation coverage and antecedent precipitation on the spatial distribution of runoff coefficient and the runoff coefficient was used as an intermediate variable to discuss the impact of changes in underlying surface factors on the runoff generation mechanism of the basin.(3)Research on the spatial distribution of runoff pattern and its influence on runoff process.Based on the soil type,topography and land use data,establish a basin runoff generation pattern spatial distribution discrimination system to identify the spatial distribution characteristics of runoff generation patterns in the basin.Through comparative analysis with the proportion of different runoff components in the floods,the rationality of the spatial distribution of the runoff generation pattern was verified.And according to the runoff generation capacity of different runoff patterns,based on the measured rainfall and runoff data,the influence of the spatial distribution of different runoff patterns on runoff generation in the basin is analyzed... |
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