Abstract:
The objective of this study was to evaluate sediment prediction capability of SWAT and PED-W models in range of scale of watershed size. The study was conducted for AnditTid (4.84km2),Temcha (410.1km2) and Gumara (1271km2) in Blue Nile basin. The calibration and validation were carried out using the different model objective function at the outlet of watersheds having sixteen years measured data for both models by taking limbering-up, calibration and validation (2000,2001-2010 and 2011-2015) respectively. The common model efficiency criteria for SWAT model results of sediment load during calibration and validation in monthly time steps for the Andit Tid,Temcha and Gumara (NSE=0.88,0.65,0.78) and (NSE=0.92,0.86,0.85). In case of PED-WM during calibration and validation in monthly time for AnditTid, Temcha and Gumara (NSE=0.90,0.82,0.83) and (NSE=0.92,0.80,0.90) respectively. There were good agreement between measured and predicted flow and sediment load and also it was confirmed using both graphical technique and quantitative statistics. Difference in the model behavior depends on the runoff mechanism. For SWAT model the main runoff generation process is infiltration excess and could predict better monthly discharge and sediment load than daily time steps. PED-W model saturation excess is the main runoff mechanism and could predict the maximum extent of runoff area 6% (5% saturated and 1% degraded) with regardless of ranges of watershed. The overall model performance indicated that PED-WM was relatively accurate for prediction of discharge and sediment load. However, PED-WM is a simplified spreadsheet coupled with the water balance and it requires very few calibration parameters to simulate discharge and sediment and also it is important in data limiting environment as compared to SWAT, but more work is desired to account for contributions from gullies, which can cause high influxes of sediment load. Generally, outputs of this study may help planners and decision makers to take relevant soil and sediment measures to diminish frightening soil loss and land degradation troubles in the Blue Nile basin.