Evaluating two GIS-based semi-distributed hydrological models in the Bhagirathi-Alkhnanda River catchment in India

The hydrological models are used for simulating the runoff of a river basin based on available rainfall data and other parameters. Over the years, several hydrological models have been developed in different parts of the world. Two such semi-distributed hydrologic models are SWAT and HEC-HMS. In this study, a comparative analysis has been carried out to evaluate the performance of these two distributed hydrological models as a flood forecasting tool. The Alkhnanda and Bhagirathi rivers, which flow into the Tehri Reservoir, Uttarakhand and pass through Tehri, Uttarkashi and Chamoli districts of Uttarakhand, India, are selected for the analysis. The performance of these two models is evaluated by using standard statistical methods. The comparative analysis of these two models shows that the SWAT model is performing slightly better in comparison to the HEC-HMS model, especially in the lean period. The underestimation of peak discharge may be due to the contribution of significant snowmelt discharge during the rainy season. The models are also used to predict future discharge under different climate change scenarios. The future prediction shows that the peak discharge of Alkhnanda may be increased by 27 and 47% under RCP4.5 and RCP8.5, respectively.