The implementation of soil and water conservation (SWC) measures in the Ethiopian Highlands is a top priority to reduce soil erosion rates. However, the effectiveness of these measures for different hillslope gradients and land use conditions remains poorly understood. This study addresses this knowledge gap by determining support practice (P) and cover-management (C) factors of the Revised Universal Soil Loss Equation for commonly used SWC structures in semi-arid environments. The factor values were calculated on the basis of soil loss data collected with 21 large runoff plots installed in rangeland and cropland sites. The P- and C-factors were calculated following the recommended procedures. Results show P-factors ranging from 0.32 to 0.74 for stone bunds, from 0.07 to 0.65 for trenches, and from 0.03 to 0.22 for stone bunds with trenches. Reduced storage capacities due to sediment deposition resulted in significant declines of the effectiveness of SWC structures over time. For example, the average P-factor value for trenches increased from 0.1 in the first year after installation to 0.51 after 3 years. C-factor values ranged from 0.23 to 0.82 in rangeland and from 0.03 to 0.35 in cropland. For rangeland, this large variability is due to vegetation cover changes caused by grazing. In cropland, C-factors vary with crop types and tillage practices. The results of this study not only aid in modelling and quantifying the short-term impacts of SWC structures on soil erosion rates but also highlight the importance of considering temporal variations of the effectiveness of SWC measures.

中文翻译：

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确定埃塞俄比亚北部牧场和农田石堤和沟渠的 RUSLE P 和 C 因子

在埃塞俄比亚高地实施水土保持（SWC）措施是降低水土流失率的首要任务。然而，这些措施对不同山坡坡度和土地利用条件的有效性仍然知之甚少。本研究通过确定半干旱环境中常用 SWC 结构的修订通用土壤流失方程的支持实践 (P) 和覆盖管理 (C) 因素来解决这一知识差距。因子值是根据在牧场和农田场地安装的 21 个大型径流地块收集的土壤流失数据计算得出的。按照推荐的程序计算 P 和 C 因子。结果显示，石堤的 P 因子范围为 0.32 至 0.74，沟渠为 0.07 至 0.65，带沟渠的石堤为 0.03 至 0.22。由于沉积物沉积而导致的存储容量降低导致 SWC 结构的有效性随着时间的推移而显着下降。例如，沟槽的平均 P 因子值从安装后第一年的 0.1 增加到 3 年后的 0.51。C 因子值在牧场中介于 0.23 至 0.82 之间，在农田中介于 0.03 至 0.35 之间。对于牧场而言，这种巨大的变化是由于放牧引起的植被覆盖变化。在农田中，C 因子因作物类型和耕作方式而异。这项研究的结果不仅有助于模拟和量化 SWC 结构对土壤侵蚀率的短期影响，而且还强调了考虑 SWC 措施有效性的时间变化的重要性。