Sediment Yield Prediction Using Hydrological Models in Upper Gilgel Abbay and Megech Watersheds, Upper Blue Nile Basin, Ethiopia

Abstract

Soil erosion, land degradation and loss of agricultural soils are major problems in Upper Blue Nile Basin of Ethiopia. The parameter efficient semi-distributed watershed model (PED-WM), soil and water assessment tool (SWAT) and the generalized watershed loading function (GWLF) are tested for the prediction capability of sediment yield in the Megech and Upper Gilgel Abbay watersheds. Model calibration and validation for the suspended sediment yield for Upper Gilgel Abbay and Megech watersheds was applied from 1997-2007 and 2008-2012; and 2000-2010 and2011-2014, respectively. NSE, R2 and PBIAS were used to evaluate the model performance. The monthly time step model efficiency of PED-W for Upper Gilgel Abbay watershed was found R², NSE and PBIAS (0.89, 0.77, -8.5) and (0.82, 0.81, 5.87) and for Megech watershed (0.85, 0.71, 6.54) and (0.83, 0.72, 12.1) during calibration and validation periods, respectively. On the other hand, the SWAT model efficiency for Upper Gilgel Abbay watershed was (0.84, 0.84, -2.7) and (0.62, 0.62, 3.5) and for Megech watershed (0.64, 0.63, 17.9) and (0.63, 0.60, 27.9) during calibration and validation period respectively. Whereas the efficiency of GWLF model was obtained (0.76, 0.58, -21.24) and (0.76, 0.60, -5.2) for Upper Gilgel Abbay watershed and (0.76, 0.57, 22.42) and (0.73, 0.58, 20.89) were for Megech watershed during calibration and validation period respectively. The result shows that almost all model performance ranges from satisfactory to very good agreement. The overall model performance indicated that PED-WM model was more appropriate model to predict sediment yield than SWAT and GWLF models.