Spatial Distribution Characteristics of Soil Erosion in Lancang River Basin
澜沧江流域土壤侵蚀的空间分布特征

Soil erosion has become one of the major environmental and agricultural issues around the world. It will not only result in land degradation and decline of soil fertility due to the direct loss of solid particles and organic matter, but also cause mudslides, landslides and other geological disasters. Moreover, it will also give rise to sand deposit and water pollution in river, impact on the regular flood discharge of the river, and reduce the life cycle and efficiency of hydropower projects. The Lancang River originates on the Qinghai-Tibet Plateau and is a famous transboundary river running throughout six countries. The Lancang River Basin experiences large regional differences in climate as it flows from north to south. Temperature and precipitation increase from north to south, and decrease with increasing elevation. The diversity of physiographic settings result in a variety of soil types and ecosystems. However, the ecological environment of the Lancang River Basin is very fragile, and soil erosion is very serious in the middle and upper reaches. Therefore, it is necessary to study the soil erosion and the spatial distribution characteristics of it in the basin. Based on GIS and RUSLE model, the paper studied the soil erosion and its spatial distribution in Lancang River Basin. The results showed that the annual amount of soil erosion was 1.13 billion ton and the soil erosion modules was 68.63 t·hm-2 in the basin. Accordingly, it was concluded that the basin was belong to the intensive erosion areas. Zhaqu River was the most serious erosion area and the eroded soil accounted for 24.94% of the total; followed by Angqu River and Ziqu River, and accounted for respectively 18.00% and 11.70%. The degree of soil erosion in the basin was closely related to the slope and elevation. The soil erosion modules averagely increased 33.34 t·hm-2 as the slope stepped up to the next level, while the soil erosion aggravated 2.3 times as the elevation increased 1000 m. 60.86% area of the basin suffered soil erosion with different degrees. The intense erosion areas were mainly located in regions where the elevation was more than 3000 m and the slope of 15~35°.These areas are also the key areas in preventing the soil erosion and geological disasters, such as landslides. Although there still exists controversy in the application of RUSLE model in the large-scale complex terrain region, it can achieve sound results at least in this study.