Soil Erosion Calculation In A Watershed Based On MUSLE Model

Soil erosion is a main type and mode of non-point source pollution while water and soil loss is the main drive force of non-point source pollution in watershed. Researching a quantitative evaluation method of soil erosion in watershed scale with the technology of Remote Sensing and Geographic Information System has important meaning to the management of water and soil resources and non-point source pollution in watershed.As a calculation model of soil erosion in watershed scale, MUSLE is widely used in the simulation and calculation of water and soil loss process in watershed scale, because it takes comprehensive account of numerous factors such as soil erodibility, slope length and grade, vegetation cover and management measures, surface runoff and so on. With the MUSLE at the core, we developed a disturbed model of soil erosion in watershed scale which can be used for the rapid calculation of non-point source pollution on the basis of the analysis of watershed soil erosion process. The research content and results are as follows:(1) On the basis of the analysis of soil erosion process in watershed scale, we analyze the fundamental principles of MUSLE, research the method of how to calculate the value of the factors involving in the model such as soil erodibility, slope length and grade, vegetation cover and management measures, surface runoff and so on, study the method of river sediment hydraulics calculation based on sediment deposition and erosion, summarize the relative theory of distributed calculation of soil erosion and sediment transmission in watershed scale and finally build a fundamental theory framework;(2) We research the model structure of distributed calculation of soil erosion and the method of data organization. With the idea of module modeling, we build a distributed soil erosion model in the watershed scale at the core of slope sediment yield module and river sediment transmission module using the language of C# on the background of Microsoft Studio.NET; Utilizing the function of spatial data processing of GIS, we develop functional modules such as data obtaining and organization, visible display and result calibration with the help of ArcGIS Engine;(3) In order to evaluate the precision and applicability of the model, we choose the zhongtianshe watershed and lianshuihe watershed as the study areas to calculate the amount of soil erosion and drainage basin sediment yielding in the two watersheds with the model.While simulating the process of erosion In Zhongtianshe watershed from 2009 to 2014, the accuracy is affected by some artificial cultivation measurements such as declogging, building the dam and etc. However, if eliminating the data which is affected by artificial measures, the determination coefficient (R2) and Nash coefficient (Ens) can reach 0.96 and 0.89 in the aspect of annual sediment production; In terms of monthly sediment production, R2 and Ens can reach 0.92 and 0.69. These approve that the model developed in our research has high accuracy and good applicability. In order to further validate the accuracy, we simulate the process of erosion in Lianshuihe watershed from 2000 to 2009. It turned out that R2 and Ens can respectively reach 0.88 and 0.84 in annual sediment production while the R2 and Ens are respectively 0.9 and 0.82 in monthly sediment production. According to the above, the model is not only suitable for applying in these two study areas, but also has high precision.