Abstract:
Hydrological models are influential tools for simulating the effect of watershed processes
and management on soil and water resources. The main objective of this study was
comparative hydrological modeling of Maybar watershed using SWAT-WB and SAWT-CN
in order to understand hydrological components of Watershed and to evaluate the
performance of the models for simulating stream flow. The Arc SWAT interface
implemented in the ArcGIS software was used to delineate the sub-basin, combine the data
layers and edit the model database. The effective depth of the soil profile values for seven
soil types was assigned based on the topographic index of the watershed. The hydro
meteorological data collected from nearby stations and the missed data were filed by
arithmetic mean and simple interpolations. Sensitivity analysis was conducted for both
SWAT-WB & SWAT-CN. The sensitivity result showed base flow alpha factor & maximum
canopy storage are the most sensitive parameters for SWAT-WB &SWAT-CN respectively.
The models were calibrated and validated on Maybar watershed using Sequential Uncertainty
Fitting and Generalized Likely-hood Uncertainty estimation for SWAT-WB &SWAT-CN.
Sequential Uncertainty Fitting gives good result compared to Generalized Likely-hood
Uncertainty estimation. SWAT-WB was performed slightly better during calibration than
SWAT-CN with the value of Sequential Uncertainty Fitting of (0.91 &0.87) for SWAT-WB
& SWAT-CN respectively. In the validation period SWAT-WB was also performed better
than SWAT-CN with the value of Sequential Uncertainty Fitting of (0.85&0.78) for SWAT
WB and SWAT-CN respectively. All sources of uncertainty captured by bracketing more
than 33% for SWAT-WB & 51% of SWAT-CN. Base- flow (64.2% - 71.46%) is an
important component of the total discharge compared to surface runoff in the study area.
Based on the statistical indicators, the evaluation indicates that SWAT-WB &SWAT-CN had
very good performance for both month calibration and validation period. The statistical result
revealed that if properly calibrated SWAT-WB can be used more effectively than SWAT-CN
in Monsoonal climate like Ethiopia.
