| The Kuye River Basin has the vital impact on flood and sediment in the Yellow River Basin.Due to the large-scale human activity in the basin,the underlying surface of the watershed has undergone great changes,resulting in huge changes in the hydrological cycle.In recent years,watershed runoff has been decreasing,and flood frequency and peak flow have also been decreasing.In view of this,by discussing the dual effects of climate change and human activities on the hydrological process of the Kuye River Basin,it is of prime importance to optimize tactics for rational implementing of water resources and promote the long-term development of the basin.By identifying the evolution law of the rainstorm and flood characteristics in the basin from 1960 to 2018,this paper focalizes the Kuye River Basin,and achieves the quantitative assay through DTVGM model that the reduction degree of the flood process caused by the variation of the underlying surface.Its main conclusions are as follows:(1)In the light of the remote sensing data of land use in the Kuye River Basin in 1980,1990,2000 and 2015,the area changes and spatial transformation laws of different land use types in the study area were analyzed,and the change pattern of the substrate was analyzed as a whole by combining the data of leaf area index in the basin from 1982 to 2018 and the construction of water conservancy and water protection measures in the basin from 1960 to2018.The results show that large-scale human activities have greatly changed the circumstance of the underlying surface.The variation in land use are reflected in the mutual transformation of various land uses in the watershed.The vegetation changes are reflected in the continuous increase in leaf area index and the large-scale construction of various water conservation facilities in the basin.(2)The changes in the pattern of storm floods in the basin were analyzed based on the storm flood data of the study area from 1960-2018.Precipitation in the study area shows significant interdecadal differences in terms of precipitation amount,intensity and frequency of occurrence,with a trend of decreasing from the 1960 s and 1970 s to the lowest value in the 1980 s and 1990 s,and gradually increasing after 2000;changes in floods in the basin show a significant and continuous decreasing trend in the annual maximum sub-flood flow and annual frequency of occurrence,and the annual maximum sub-flood flow and annual frequency of occurrence of floods in the three hydrological stations from 2000 to 2018 show a significant and continuous decreasing trend.The annual maximum sub-flood flow at all three hydrological stations from 2000 to 2018 decreased sharply to less than 1/7 of the average value in the 1960 s and 1970 s,and floods of large and medium magnitude almost ceased to occur.The sudden change year of the basin’s storm flood change characteristics was identified by the mutation test method as 1998,and the storm flood relationship diagrams were established sequentially.It was found that the flood peak flows after the mutation point were all smaller than those before the mutation point,indicating that the storm flood relationship in the basin had changed.(3)Based on the DTVGM model,the model simulation parameters were calibrated and verified for the rainstorm and flood with good correspondence between the reference period and the change period of the Kuye River Basin.And it was found that its simulated flood peak error was about 10%,and the ENS was greater than 0.65,indicating that the DTVGM model could meet the basic requirements for simulating the flood process in the basin.The results show that: no matter it is the base process or the change process of the simulation in the study area,under the influence of the change of the underlying surface conditions of the river basin,the flood peak flow shows a significant decrease,and its attenuation rate is about 40%. |
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