BackgroundThe use of existing land use/cover type exerts more pressure on the natural dynamism of the watersheds and hydrology due to continued cultivation and mis-management of land resource. The objectives of this study was to assess the combined effects of land use/cover types and slope gradient on watershed hydrology in terms of sediment and nutrient losses/transport from HRU of each land use/cover types. Integrated soil and water assessment tools (SWAT) model with Arc-GIS was used for simulation of sediment and nutrient loss by using land use/cover, soil, slope and climatic data as input. Analysis of variance (ANOVA) for mean comparison and correlation was used for data analysis.ResultCombined effects of urban land and slope gradient produced more sediment than other land use/cover types followed by cultivated land. In cultivated land as slope gradient increased values of sediment and nutrient losses also increased until it reaches to 30% slope and then declined. In Forest and grassland sediment loss increased until 15% slope then after declined, but in urban land as slope gradient increases sediment and nutrient loss are also increased.ConclusionCultivated land and difference in its slope gradient had more significant effect on watershed dynamics and hydrology in terms of loss of fertile top soil from upland, downstream water quality reduction and sedimentation of water structures than others land use/cover types and need to avoid steep slope and continuous cultivation and implementing integrated watershed management strategies in order to keep the natural dynamism of the watersheds.

中文翻译：

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埃塞俄比亚奥罗米亚东沃勒加区 Chancho 和 Sorga 子流域的土地利用/覆盖类型和坡度梯度对沉积物和养分流失的综合影响

背景 由于土地资源的持续耕作和管理不善，现有土地利用/覆盖类型的使用对流域和水文的自然活力施加了更大的压力。本研究的目的是评估土地利用/覆盖类型和坡度梯度对流域水文的综合影响，从每个土地利用/覆盖类型的 HRU 的沉积物和养分损失/运输来看。通过使用土地利用/覆盖、土壤、坡度和气候数据作为输入，使用带有 Arc-GIS 的综合水土评估工具 (SWAT) 模型来模拟沉积物和养分流失。数据分析采用方差分析(ANOVA)进行均值比较和相关性分析。结果城市土地和坡度梯度的联合效应比其他土地利用/覆盖类型产生更多的泥沙，其次是耕地。在耕地中，随着坡度的增加，泥沙和养分损失值也增加，直到坡度达到 30%，然后下降。森林和草地的泥沙流失量增加到坡度15%后下降，而城市土地随着坡度的增加泥沙和养分流失也增加。结论耕地及其坡度差对流域动力学和水文的影响更为显着与其他土地利用/覆盖类型相比，高地肥沃的表层土壤流失，下游水质降低和水结构沉积，需要避免陡坡和连续耕作并实施综合流域管理策略以保持流域的自然活力.