The sustainability and service life of reservoirs depends on the amount of sediment storage. Reservoir sedimentation is a critical problem in reducing the service life of dams. The sedimentation problem is the consequence of watersheds sediment supply to the river networks and then to the reservoir. River bank sediment deposition is another consequence of excess sediment supply from the upstream watersheds. The deposition of sediment on bank of a river causes change in flow regime and as result

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... flooding may happen to the adjoining areas. The degree of severity of river bank sediment deposition or reservoir sedimentation can be analyzed with the availability of information on the sediment load from the upstream watersheds. Physically based models are appropriate tools for sediment modelling and prediction at the outlet point of a watershed. Nevertheless, the applicability of the existing physically based models is limited to data availability which restricts their application to data scarce areas. Therefore, this research has been undertaken to analyze the fundamental watershed soil parameters, geomorphologic parameters and hydrologic parameters and thereafter suggest an alternative sediment yield estimation method that can be applied to data scarce areas. A Soil erodibility estimation equation has been derived from soil data of the Upper Awash basin in Ethiopia and has been evaluated for its applicability to the FAO (1998) world soil database. The evaluation has been made with reference to the equation of Williams et al. (1984). According to the evaluation result, for 80 % of the World Soil Database the relative error of the proposed equation as compared to the equation of Williams et al. (1984) has been estimated to be less than 20 %. This indicates that with easily measurable soil parameters like the percentage of sand, silt and clay, a reasonable soil erodibility factor can be predicted. SWAT2005 model has been applied to the Awash basin and two selected subbasins (Fincha and Gudar) of the Blue Nile basin. The [...]