以黄土高原典型丘陵沟壑区——延河流域为研究区, 基于GIS和RS技术, 利用2001-2010年延河流域水文站月降雨量数据、MODIS NDVI数据、DEM数据、土壤类型数据和土地利用数据,率定了修正的通用土壤流失方程(RUSLE)的相关参数,计算了研究区2001-2010年逐年的土壤侵蚀模数, 利用杏河水文站实测的泥沙数据, 验证了模型的有效性,分析了延河流域土壤侵蚀强度的时空变化特征。结果表明,2001年到2010年延河流域土壤侵蚀模数呈减小趋势,2001年土壤侵蚀模数最大,为6 596.72 t/(km2·a),2008年土壤侵蚀模数最小,减小到2 485.46 t/(km2·a),降低62.32%;2009年由于暴雨冲刷,土壤侵蚀模数显著增大;2010年土壤侵蚀模数和2006、2007年相差不多;土壤侵蚀强度分布比例变化明显,土壤侵蚀强度为强度、极强、剧烈的面积比分别由16.21%、21.93%和12.36%降低为10.85%、4.58%和0.39%。土壤侵蚀强度等级转移矩阵表明大部分地区的土壤侵蚀强度向低一级转移,2001-2005年31.68%的面积土壤侵蚀强度降低一级,2005-2010年42.13%的面积土壤侵蚀强度降低一级。
Soil erosion has become a worldwide environmental problem because it could threaten soil structure, agricultural production, water quality, and so on. During the past decade, much effort has been made to control soil erosion in the Loess Plateau, thus the distribution of soil erosion intensity in this region has experienced a great change. So it is necessary to take more effective soil and water conservation measures and realize the sustainable utilization of water resource by knowing soil erosion changes. Based on RUSLE model, soil erosion changes from 2001 to 2010 in the Yanhe Watershed, a typical hilly-gully region on the Loess Plateau, were studied with the support of GIS and RS. The data set used in the model includes monthly precipitation, MODIS NDVI data, DEM, land use and soil type maps. Having localized the coefficients in RUSLE, the gauged data from Xingzihe Hydrological Station was used to verify the model and the proved reasonable results were produced with this model. The annual soil erosion modulus and the temporal and spatial change of soil erosion intensity in the Yanhe Watershed were analyzed. The main conclusions are as follows: Firstly, in the period 2001-2010, soil erosion in the Yanhe Watershed experienced a decreasing trend from the maximal value of 6596.72 t/(km2穉) in 2001 to the minimal value of 2485.46 t/(km2穉) in 2008, decreased by 62.32%; the soil erosion modulus increased obviously in 2009 because of heavy rainfall. Secondly, the distribution of soil erosion intensity changed obviously and the area ratio of intense, extremely intense, and most intense soil erosion decreased from 16.21%, 21.93% and 12.36% to 10.85%, 4.58% and 0.39% respectively. Thirdly, the transformation matrix of soil erosion intensity indicated that the soil erosion intensity transformed from high level to low level in most of the area with 31.68% of the total area of the watershed from 2001 to 2005 and 42.13% from 2005 to 2010. The distribution pattern of soil erosion intensity during the past decade revealed in this study could provide support for soil and water conservation and ecological environmental construction in the study area and even in the similar watersheds of the Loess Plateau.
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