COMPARATIVE HYDROLOGICAL MODELING OF MAYBAR WATERSHED USING SWAT-WB AND SWAT-CN, AWASH BASIN, AMHARA REGION

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.