Derege T. Meshesha, Atsushi Tsunekawa, Mitsuru Tsubo, and Nigussie Haregeweyn
Soil erosion, Land degradation, USLE model, Soil conservation
Land degradation as result of soil erosion is a serious problem in the CRV (Central Rift Valley) of Ethiopia. The severity of degradation has caused agricultural production to be declined over years and food insecurity and poverty to be worsened in the region. However, there has been no systematic study of this problem or of possible management solutions of soil erosion. To meet this need, we analyzed soil erosion rates from 1973 to 2006, identified erosion hotspots, and proposed possible soil conservation scenarios. We assessed the soil loss dynamicity using the universal soil-loss equation and geographical information system software. We characterized the watershed in terms of the erosion severity, topography, and land use to identify hotspots and proposed, modeled, and evaluated various watershed management scenarios to mitigate the problem. Soil erosion increased markedly from 1973 to 2006, with annual rates of 31, 38, and 56 t ha-1 in 1973, 1985, and 2006, respectively, as a result of vegetation degradation in the period. The observed soil erosion rates are far from the tolerable rate of soil loss of the country and hence require urgent soil conservation interventions, especially in the hotspot areas. We proposed eight scenarios for reducing soil losses and evaluated their effectiveness. Rehabilitating degraded land (using exclosures and planted vegetation) and installing stone erosion-control structures (stone bund) in cropland reduced the total soil loss by 12.6% and 63.8%, respectively. Treating hotspot areas with annual soil loss of more than 20 t ha-1 by integrated management (erosion-control structures and exclosures) was the most effective approach, reducing soil loss by 87.8%.
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