Abstract
Soil erosion is one of the most critical eco-environmental issues in the Poyang Lake basin, China. The purpose of this study is to discover the spatial pattern of soil erosion, and predict soil loss and sediment yield, and evaluate soil loss impacts on main reservoirs by using Universal Soil Loss Equation (USLE), GIS and Remote Sensing (RS). Firstly, five erosion factors including rainfall erosivity (R), soil erodibility (K), topographic factor (LS), cover and management factor(C), and conservation supporting practice factor (P) were calculated and analyzed, respectively. Secondly, annual soil erosion and its spatial distribution were evaluated, and sediment yield was subsequently predicted. Next, soil erosion was classified into five erosion categories according to Industry Standard of Water Resources of China. Then, the relationship among soil erosion, landform and land use and land cover (LULC) were analyzed. Finally, the influence of soil erosion on main reservoirs in the basin were assessed. The result showed that: 28.3% of the total watershed area appears soil loss; the average annual soil loss amount is approximate 2.7 × 107 t; soil erosion modulus ranged from 0 to 394.8 t/ha/y, with a mean value of 1.82 t/ha/y. 71.7% of the watershed area are undergoing minimal erosion, primarily appear in surrounding the lake area, both sides of river valley and plains of five main rivers; 24.1% of the watershed area are undergoing low erosion, mainly found in the west, east, central hilly and mountain areas; 3.4% of the watershed area was observed moderate soil erosion; 0.83% of the watershed area are undergoing high, very high and extreme soil erosion, which located in the northeastern and northwestern corner, and the upstream of the Ganjiang river and Fuhe river sub-watershed. Low and moderate soil erosion most frequently occurred at the plains and hills zone in this basin. Soil loss happens on needleleaved forest, rainfed croplands and shrub land use type are greater than that of other LULC types; soil erosion modulus descends on the different land use types, orderly by bare lands, grass lands, shrub lands, rainfed croplands, needleleaved forest, spares vegetation, broadleaved deciduous forest, artificial surface, irrigated croplands and water bodies. Present main reservoirs are undergoing a big threat from the upstream sediment load, especially as the Qiyi, Da’ao, Qixing and Tuolin reservoir.
Highlights
Soil erosion is one of the most critical environmental issues because of its adverse economic and ecological influence [1]
The equation may be expressed in non-dimensional terms as: sediment delivery ratio (SDR)=Sy/T (4) Where, Sy is the sediment yield at the watershed outlet or point of interest, and T is the total soil loss defined as the total eroded sediment on the areas eroding above the watershed outlet or point of interest
By using the average annual sediment data observed by hydrological stations, and multiplying Universal Soil Loss Equation (USLE) model output by the SDR as simulated sediment yield, we calculated absolute error and relative error to evaluate the accuracy of soil erosion data from the USLE model output (Table 4)
Summary
Soil erosion is one of the most critical environmental issues because of its adverse economic and ecological influence [1]. The loss of top soil results in lower yield and higher production costs. Soil erosion has become one of the most crucial ecoenvironmental issues in China [4]. According to results of the 2nd national soil erosion remote sensing survey, the area of soil loss was 3.56 × 106 Km2 in 2003, accounting for 37.1% of the total land area of China, in which the area of water erosion reached at 1.65 × 106 Km2, accounting for 46.3% of the total soil erosion area [5]. The overall situation of soil loss is difficult to be controlled at the current developing stage in China. Eco-environment damage often happen after temporarily controls soil erosion in many regions of China. While the conditions of soil erosion were improved in some key management districts, there was overall deterioration [6]
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