Abstract
Excessive soil loss and sediment yield in the highlands of Ethiopia are the primary factors that accelerate the decline of land productivity, water resources, operation and function of existing water infrastructure, as well as soil and water management practices. This study was conducted at Finchaa catchment in the Upper Blue Nile basin of Ethiopia to estimate the rate of soil erosion and sediment loss and prioritize the most sensitive sub-watersheds using the Soil and Water Assessment Tool (SWAT) model. The SWAT model was calibrated and validated using the observed streamflow and sediment data. The average annual sediment yield (SY) in Finchaa catchment for the period 1990–2015 was 36.47 ton ha−1 yr−1 with the annual yield varying from negligible to about 107.2 ton ha−1 yr−1. Five sub-basins which account for about 24.83% of the area were predicted to suffer severely from soil erosion risks, with SY in excess of 50 ton ha−1 yr−1. Only 15.05% of the area within the tolerable rate of loss (below 11 ton ha−1yr−1) was considered as the least prioritized areas for maintenance of crop production. Despite the reasonable reduction of sediment yields by the management scenarios, the reduction by contour farming, slope terracing, zero free grazing and reforestation were still above the tolerable soil loss. Vegetative contour strips and soil bund were significant in reducing SY below the tolerable soil loss, which is equivalent to 63.9% and 64.8% reduction, respectively. In general, effective and sustainable soil erosion management requires not only prioritizations of the erosion hotspots but also prioritizations of the most effective management practices. We believe that the results provided new and updated insights that enable a proactive approach to preserve the soil and reduce land degradation risks that could allow resource regeneration.
Highlights
The Ethiopian plateau, the source of the Blue Nile, contributes about 86% of the flow to the main Nile River [1]
The performance of Best Management Practices (BMPs) in reducing sediment yield of the Finchaa catchment is comparable to the results reported by Demissie et al [26], with a reduction of SY by 35% after the application of filter strips
Study on how the BMPs continue to perform under the future climate change scenarios is required to achieve sustainable soil and water management in the future. Both statistical analysis and the hydrographs of simulated and observed streamflow and sediment yield through calibration and validation revealed that the Soil and Water Assessment Tool (SWAT) model is capable of simulating the hydrological regime of the Finchaa catchment
Summary
The Ethiopian plateau, the source of the Blue Nile, contributes about 86% of the flow to the main Nile River [1]. The basin accounts for 20% of Ethiopia’s land area, with the major share of the country’s irrigation and hydropower potential targeted by the development centers Despite this potential, soil erosion and its consequences have become a serious challenge to the highland catchments [2,3,4,5,6]. The continuous soil erosion adversely affects soil and water resources, hinders agricultural productivity and reduces the products and services that improve livelihoods. This in turn spurs interest in the effects on water resources based on which many nations like Ethiopia conduct their development activities
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