BackgroundWater induced soil erosion is the most prevailing form of land resources deterioration in the highlands of Ethiopia, where huge amount of fertile soil is being lost annually. The purpose of this study was to estimate and map mean annual soil loss rates in the Gedalas watershed of the Blue Nile Basin, Northeastern Ethiopia. The estimation was carried out by using RUSLE model coupled with local perceptions. Soil, land use/cover, DEM, rainfall and support practice data were used as an input parameters. The raster layers were processed to present the required input parameters in ArcGIS platform and finally the inputs were multiplied together to quantify annual average soil loss rate and generate intensity maps of the watershed.ResultsThe estimated annual mean soil loss rate of the watershed was found to be 37 t ha−1 year−1, which is more than two times higher as compared to the maximum tolerable soil loss value (16 t ha−1 year−1) and the annual erosion rates range from 0 to above 935 ton ha−1 year−1. The annual mean soil loss values below 5 ton ha−1 year−1 were rated as very slight, while those above 50 ton ha−1 year−1 were categorized as very severe soil erosion risk. Areas experiencing values between these two were further classified into slight, moderate, and severe erosion zones. Soil loss in more than 1/3rd of the study area (36.4%) was below moderate (< 15 t ha−1 year−1). Nearly one-fourth (25.5%) of the watershed area experienced moderate (between 15 and 30 ton t ha−1 year−1) soil loss values. Only 14% of the watershed areas were classified under severe to extremely severe (> 30 t ha−1 year−1) soil erosion risk zones. While 62% of the watershed still undergoes from very slight to moderate levels of soil loss, yet 72.6% of soil erosion occurred in zones less than 3200 m in elevation which represents more than half (51%) of the total surface area of the watershed. The study also demonstrated that the northeastern parts of the watershed suffer more from high soil erosion risk due to steep slope and rugged landforms of the area. Similarly, 43% and 35% of soil erosion occurred on cropland and grasslands areas, respectively.ConclusionThe quantitative soil loss estimation results and farmers’ perception of soil erosion revealed that soil erosion has still remained significant problems in the watershed. The results underscore the urgent need for comprehensive and site-specific SLM practices in the watershed.

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基于 RUSLE 模型和当地感知的埃塞俄比亚青尼罗河流域 Beshillo 流域土壤侵蚀图和严重程度分析

背景水土流失是埃塞俄比亚高原土地资源退化最普遍的形式，每年都在流失大量肥沃的土壤。本研究的目的是估算和绘制埃塞俄比亚东北部青尼罗河流域 Gedalas 流域的平均年土壤流失率。估计是通过使用 RUSLE 模型结合局部感知进行的。土壤、土地利用/覆盖、DEM、降雨和支持实践数据被用作输入参数。对栅格图层进行处理以在 ArcGIS 平台中显示所需的输入参数，最后将输入相乘以量化年平均土壤流失率并生成流域强度图。结果发现流域的年平均土壤流失率估计为37 吨公顷-1 年-1，与最大可容忍土壤流失值（16 t ha-1 year-1）相比，它高出两倍以上，年侵蚀率范围从 0 到 935 吨 ha-1 year-1 以上。年平均土壤流失值低于 5 吨公顷-1 年-1 的被评为非常轻微，而高于 50 吨公顷-1 年-1 的被归类为非常严重的土壤侵蚀风险。经历这两者之间的值的区域进一步分为轻度、中度和重度侵蚀区。超过 1/3 的研究区域（36.4%）的土壤流失低于中等（< 15 t ha-1 year-1）。近四分之一 (25.5%) 的流域区域经历了中等（15 到 30 吨 t ha−1 年−1）土壤流失值。只有 14% 的流域区域被归类为严重到极严重（> 30 t ha-1 year-1）土壤侵蚀风险区。虽然 62% 的流域仍然处于非常轻微到中等程度的土壤流失，但 72.6% 的土壤侵蚀发生在海拔小于 3200 m 的区域，占流域总表面积的一半以上 (51%) . 研究还表明，流域东北部由于该地区坡度陡峭和地形崎岖，遭受更高的水土流失风险。同样，43%和35%的土壤侵蚀分别发生在农田和草地区域。结论定量土壤流失估算结果和农民对土壤侵蚀的感知表明，流域土壤侵蚀仍然是严重的问题。结果强调了在流域中迫切需要针对特定​​地点的综合 SLM 实践。然而，72.6% 的土壤侵蚀发生在海拔小于 3200 m 的区域，占流域总表面积的一半以上 (51%)。研究还表明，流域东北部地区由于坡度陡峭和地形崎岖，更容易遭受高水土流失风险。同样，43%和35%的土壤侵蚀分别发生在农田和草地区域。结论定量土壤流失估算结果和农民对土壤侵蚀的感知表明，流域土壤侵蚀仍然是严重的问题。结果强调了在流域中迫切需要针对特定​​地点的综合 SLM 实践。然而，72.6% 的土壤侵蚀发生在海拔小于 3200 m 的区域，占流域总表面积的一半以上 (51%)。研究还表明，流域东北部地区由于坡度陡峭和地形崎岖，更容易遭受高水土流失风险。同样，43%和35%的土壤侵蚀分别发生在农田和草地区域。结论定量土壤流失估算结果和农民对土壤侵蚀的感知表明，流域土壤侵蚀仍然是严重的问题。结果强调了在流域中迫切需要针对特定​​地点的综合 SLM 实践。研究还表明，流域东北部由于该地区坡度陡峭和地形崎岖，遭受更高的水土流失风险。同样，43%和35%的土壤侵蚀分别发生在农田和草地区域。结论定量土壤流失估算结果和农民对土壤侵蚀的感知表明，流域土壤侵蚀仍然是严重的问题。结果强调了在流域中迫切需要针对特定​​地点的综合 SLM 实践。研究还表明，流域东北部地区由于坡度陡峭和地形崎岖，更容易遭受高水土流失风险。同样，43%和35%的土壤侵蚀分别发生在农田和草地区域。结论定量土壤流失估算结果和农民对土壤侵蚀的感知表明，流域土壤侵蚀仍然是严重的问题。结果强调了在流域中迫切需要针对特定​​地点的综合 SLM 实践。结论土壤流失定量估算结果和农民对土壤侵蚀的认知表明，流域土壤侵蚀问题仍然存在。结果强调了在流域中迫切需要针对特定​​地点的综合 SLM 实践。结论土壤流失定量估算结果和农民对土壤侵蚀的认知表明，流域土壤侵蚀问题仍然存在。结果强调了在流域中迫切需要针对特定​​地点的综合 SLM 实践。