Study On The Uncertainty Of Benefit Evaluation Of Soil And Water Conservation Comprehensive Management

Soil erosion is serious in mountainous areas of Beijing.In order to control soil erosion,the state launched the beijing-Tianjin Sandstorm Source Control Project phase II in 2012,comprehensively controlling 135 small watersheds in Beijing.In order to scientifically analyze and evaluate the effect of comprehensive control of small watershed,the state has decided to carry out the monitoring work of soil and water conservation benefit of small watershed control project in Beijing,and evaluate the benefit of small watershed as a unit.The complex terrain,diverse erosion forms and difficult data acquisition in Beijing mountainous area bring a lot of uncertainties to the quantitative assessment of soil erosion management.In this paper,based on the monitoring project of the benefits of comprehensive soil and water conservation in small watershed in 2017,the Beijing soil loss equation and SCS-CN model were used based on remote sensing and GIS technology,combined with the data of rainfall process,sediment loss and yield recorded by soil loss monitoring stations such as Tanghekou.The benefit of water transfer and soil conservation in Laoyugou watershed is calculated and analyzed with uncertainty.The main research results are as follows:(1)The sources of uncertainty affecting benefit evaluation are systematically summarized,in addition to the soil and water loss phenomenon of the natural uncertainty,the main sources of uncertainty are: the measured data error,error of spatial and temporal resolution,without considering other factors,soil conservation measures,and the errors induced by uncertainty and model parameter uncertainty,the uncertainty of model structure.All kinds of uncertain factors interact with each other and the error transfer accumulates,which jointly affect the evaluation result of comprehensive soil and water conservation management.(2)The relative sensitivity analysis of each factor of Beijing soil loss equation was carried out,and the uncertainty analysis of spatial interpolation method of rainfall and calculation method of rainfall erosivity was carried out.The results showed that the relative sensitivity of rainfall erosivity factor was the highest,and it was the easiest to introduce uncertainty,which was the main factor affecting the evaluation of comprehensive soil and water conservation management benefits.The quality of spatial interpolation results is mainly related to the density of rainfall stations,nearby rainfall stations and watershed area.The greater the density of rainfall stations,the smaller the relative error of spatial interpolation results.Different spatial interpolation methods have less influence on the interpolation results.(3)By interpolation calculation of different rainfall,the uncertainty of soil conservation benefit in Laoyugou watershed in 2018 is 9.92%,the value range of soil conservation benefit is0.95%-20.80%,the uncertainty of water conservation benefit is 10.73%,and the value range of water conservation benefit is 1.32%-22.77%.In 2019,the uncertainty of soil conservation benefit is 8.81%,and the value range of soil conservation benefit is 6.57%-24.18%.The uncertainty of water conservation benefit is 10.00%,and the value range of water conservation benefit is 8.03%-28.02%.After comprehensive treatment,the soil conservation benefit of water transfer in Laoyugou small watershed is increasing year by year.