Soil Erosion and Its Relationship to the Spatial Distribution of Land Use Patterns in the Lancang River Watershed, Yunnan Province, China

Abstract

The Lancang River Watershed is one of the most biologically diverse areas in the world. The river flows through Yunnan Province, China, which suffered serious deforestation since the 1980s; this in turn led to increased soil erosion in the region. To investigate the influence of the spatial distribution of land use and slope on soil erosion in the Lancang River Watershed, the Soil and Water Assessment Tool (SWAT) model was used to establish hydrological models using two-phase land use maps (1975 and 1985), a soil map, and meteorological data from 11 gauging stations. The satisfactory values of Nash-Sutcliffe efficiency <i>E_ns</i> and correlation coefficient R 2 during the calibration and validation period indicated that SWAT can be used in this area to simulate the average annual soil erosion under different land use scenarios change. By comparing soil erosion rate under different land use scenarios change, forests and grasslands had similar effects on preventing soil erosion. A parameter, soil erosion increment ( E i ), was used to assess the effects of slope on soil erosion. The results revealed that variation in sediment yield was more sensitive to land use change for slopes exceeded 25 ° than for slopes being 0 ° - 15 ° . The spatial distribution of land use also had a relationship to soil erosion. Compared with the soil erosion rate in each sub-watershed using two-phase land use maps, the soil erosion rate increased when the percent cover of natural vegetation decreased. The results of this study provide baseline data for soil conservation and protection of the environment and ecology of the Lancang River Watershed in Yunnan Province.