| In recent years,water resources in the Source Region of the Yellow River(SRYR)have become scarce and soil erosion has become increasingly serious under the influence of climate warming and intense human activities.Therefore,understanding the changes of runoff and sediment in the SRYR and predicting the future water and sediment allocation have great theoretical and practical significance to water resources planning and management,efficient and healthy development of the economy,and ecological protection in the basin.The SRYR is taken as the study area.Based on the data of DEM,land use,soil,meteorology,and slope,the SWAT model of runoff and sediment in the SRYR was established,and then the model was calibrated and validated.During the period of calibration and validation,the decisive factor R~2 and the Nash efficiency coefficient NSE of runoff and sediment volume were all greater than 0.5 at the four hydrological stations in the study area----Huangheyan,Jimai,Maqu,and Tangnaihai.R~2 and NSE of the Tangnaihai Station reached more than 0.7.The percent deviation PBIAS range of runoff at the four hydrological stations ranged from-15%to 15%,and the sediment PBIAS ranged from-30%to 30%.The results show that the SWAT model has good applicability in the simulation of runoff and sediment in the SRYR.Use the SWAT model with a good utilization rate to explore the changes of soil erosion in the SRYR.On the time scale,the intensity of soil erosion in the watershed gradually increased,and the amount of soil erosion in the entire study area was as high as 4.75×10~8 t;On the spatial scale,87.99%of the area in the study area is mild soil erosion,and its soil erosion modulus is less than 2500 t/(km~2·a).The southeastern area of study area covered by grass,northwest source region and covered by the Ice and snow were subjected by severe soil erosion.At the same time,based on the change characteristics of the sediment volume,duration from 1960 to 1974 as the base period and duration from 1975 to 1990 as the changing period,the model reduction method was used to carry out sediment attribution analysis.It was found that the contribution rates of climate change and human activities to sediment volume were 23.1%and76.9%,respectively.According to the changing characteristics of meteorological elements and land use types in the SRYR,16 climate models and 3 land use change scenarios were set up to analyze the sediment response to the environmental change in the SRYR.The analysis results of changes in land use types show that the changing trends of runoff and sediment under different land use are basically the same.The changing rate of sediment under L1,L2,L3 scenarios is-34%,15%and 49%,respectively.The soil erosion intensity increases-20.45 t/(km~2·a),9.9 t/(km~2·a)and 19.16 t/(km~2·a),respectively.The increase of the area of wetlands and wasteland will increase the runoff and sediment production in the watershed and intensify soil erosion.Conversely,the increase of grassland area will reduce the runoff and sediment load and reduce the soil erosion intensity in the basin.The increase of grassland area can effectively control the soil erosion in the SRYR and improve the ecological environment.The analysis results under climate change show that when the rainfall increases by 30%and the temperature decreases by 2?,the runoff,sediment and soil erosion intensity of the study area are the largest,while the rainfall decreased by 30%and the temperature increased by 2?,the runoff,sediment and soil erosion intensity in the study area were the smallest.The analysis of runoff and sediment under different climate models found that increased precipitation and lower temperature are important factors leading to increased runoff,sediment and soil erosion intensity in the SRYR.The change of precipitation is directly proportional to the change of sediment volume and soil erosion intensity,and the change of temperature is inversely proportional to the change of sediment quantity and soil erosion intensity. |
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