RAINFALL - RUNOFF MODELING A COMPARATIVE ANALYSES: SEMI DISTRIBUTED HBV LIGHT AND SWAT MODELS IN GEBA CATCHMENT, UPPER TEKEZE BASIN, ETHIOPIA

Abstract

In Ethiopia, there are large numbers of hydrological modeling works have been conducted in different basins under different climate, land use, soil, geology. The applied models have different structure to simulate discharge. Their ability in simulating discharge in a comparison approach has not yet been explored. Thus conducting comparative analyses of models and identifying better models which represent realistic simulation is important for proper development and management of water resource for the cathment. The main objective of this study was to compare HBV light semi distributed and SWAT models in predicting streamflow in the Geba catchment upper Tekeze basin. The various modelling procedure (i.e input data, sensitivity analsis, calibration, validation and uncertainty assessment) were employed to test the models ability in predicting the discharge at the outlet of Geba catchment. However, to have better understanding of model parameter performance, sensitivity analysis of model parameters were performed manually by trial and error procedure. The results shows that K2 , MAXBAS , BETA are more sensitive than other model parameters in HBV light model and CN2, GWQMN and SOL_AWC are more sensitive parameters in case of SWAT. The calibration results of HBV light and SWAT as evaluated by E NS , R 2 and PBIAS are 0.70, 0.71 and 0.73, 0.81, 11%

respectively. Moreover, an E NS , R 2 and PBIAS of 0.71, 0.72 and 0.72, 0.72, 4.1% were obtained during validation Period for HBV light and SWAT models respectively. From the uncertainity plot for HBV light most of the simulated flow are inside the 95PPU with high predictive uncertainity band as comparsion with the SWAT CUP uncertainity analysis by SUFI 2 and from the uncertainity plot in SWAT model most of the simulated hydrograph is outside the upper and lower band and less predictive uncertainiy. These mentioned results depicted that both models are well reasonably simulated the discharge of Geba catchment. And from uncertainity and identifiability of parameter applying HBV light model could be effective in simulation of runoff for sustainable water resources management and development in the watershed runoff by considering sensitivity, model performance, parameter identification and uncertainity analysis.