Effects of Watershed Characteristics on River Flow for The Case Of Ribb and Gummara Catchments
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Date
2011-10
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Addis Ababa University
Abstract
In this study the effect of watershed characteristics on annual outflow contribution of Ribb
Catchment is evaluated. The Gummara catchment, which is adjacent to the Ribb catchment
and is equivalent in terms of area but a long year annual flow of more than double of Ribb
was taken for comparison in the whole process of evaluation. ILWIS model was used for
detail evaluation of the physical watershed characteristics (PCC) for both watersheds. The
effects of physical catchment characteristics were analysed and characteristics which have
high differences (Rainfall and soil) were identified. Distributed physically based hydrological
model known as soil and water assessment tool (SWAT) has been applied for evaluation of
PCC with significant differences. The model was calibrated and validated over the gauged
upper reaches of catchments of Rib and Gummara. The model was calibrated for the period
from 1998-2004 and validated for the period from 2005-2007. The performance of the model
was evaluated on the basis of performance rating criteria, coefficient of determination, Nash
& Sutcliff efficiency, and volumetric error. The overall performance of the two models gives
satisfactory result. The physical catchment characteristics which have high differences
(Rainfall and Soil) in the two watersheds were evaluated and tested by creating different
scenarios in the calibrated and validated models and the result shows soil has a great effect in
lower annual flow of Ribb watershed followed by rainfall.
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Keywords
Gummara;Catchments