Temporal-spatial Change Of Soil Erosion In Watershed In Upperreaches Of Shahe,Shallow Mountainous Areas In Beijing

Soil erosion is one of the more serious ecological problems faced by humans.Since the 20th century,China has earried out a large number of soil and water conservation and ecological restoration work.The shallow mountainous area is an excessive area of mountainous and plain areas,and it is a fragile ecological environment,The ecological environment protection in shallow mountainous areas is the focus of regional soil and water conservation work.Studying change of the soil and water loss after the implementation of regional water conservation measures and identifying key areas can provide a scientific basis for further strengthening the ecological clean small watershed management.This paper selected the Wangjiayuan small watershed in the upper reach of Shahe River within the lower mountainous area of Beijing as the study area.Based on the collected digital elevation model(DEM),land use(2007 and 2017)and soil types and other base data,the change of soil erosion in the study area from 2007 to 2017 was simulated using the China Soil Erosion Model(CSLE)and SWAT model,and the simulation results are compared with each other.Based on the CSLE simulation results,the temporal and spatial changes of soil erosion were analyzed,and the driving factors were discussed.The final analysis results are as follows:(1)The average annual erosion modulus of SWAT model and CSLE model was 338.65 t/(km2·a)and 310.81t/(km2·a),respectively.The correlation coefficient R2 and relative error Re of the two sets of simulation results are 0.985 and 4.57%,respectively.The overall SWAT simulation results are relatively large,mainly because the SWAT sin,ulation results increased dramatically during the peak year and this increase will continue for some time.(2)Based on CSLE simulation,the annual erosion modulus of the study area increaseed first and then decreased from 2011 to 2017,and the area where soil erosion was prone to occur was on the northwest.Soil erosion was obvious correlated with slope gradient and land use types,The average annual erosion modulus is bare land,gentle slope,and medium coverage area is the area where soil erosion is easy to occur.