Most soil loss estimation studies in Ethiopia have focused at plot level and some at micro- to milli-watersheds (< 10000 ha). However, these studies may not represent the entire area of a macro-watershed (> 50,000 ha) which is very essential for development planning. The aim of this study was, therefore, to calculate the soil loss rate and analyze the spatial distribution of soil erosion and locate the erosion high susceptible areas at the macro-watershed scale so as to help for regional development planning. The study area was the macro-watershed of the Geba River (5,133 km²). The RUSLE model, the most practical method of estimating soil erosion potential, was applied in this study. The results of the analysis showed that the average soil loss in the entire watershed was 6.34 ton ha-1y-1, while 7.31 ton ha-1y-1 was from arable land. These estimates are within the tolerable soil loss (2 - 18 ton ha-1y-1) for Ethiopia put forward by Hurni. Taking the global soil formation rate at 1 ton ha-1y-1, the soil in the study area was being lost 6 or more times faster than the rate of renewal and sustainability. More than 84% of the study area was classified under very slight soil loss (< 5 ton ha-1y-1). However, about 5% of the watershed was suffering from severe (25 – 45 ton ha-1y-1) or very severe soil loss (≥ 45 ton ha-1y-1). The highest soil loss was estimated from calcaric Fluvisol and areas with a slope steeper than 30%.
Keywords:
Soil erosion, Macro-watershed, USLE, North Ethiopia.
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