Process-based Hydrological Modeling to Analyse Sub-basin Response Under Extreme Rainfall Events in Koyna River Basin, Maharashtra

The understanding of floods has become more complex as the changing climate has made the floods more unpredictable, recurrent, and intensified. The present study focuses on the analysis of behavior of the sub-basins under the extreme rainfall events. For this purpose, an extreme flood event of 2019 in Koyna River Basin located in the Upper Krishna River Basin, Maharashtra was considered. The hydrological responses of the sub-basins of Koyna River basin during this flood event were obtained using a Process-based Soil and Water Assessment (SWAT) hydrological model. The model was configured using the topographical, land use, soil and metrological parameters, respectively. Fathom FABDEM hydrologically corrected DEM were used to delineate the watershed with an outlet near Karad City, just downstream of the Warunji gauging station. The Indian Metrological Department (IMD) 0.25⁰ * 0.25⁰ daily gridded rainfall data and minimum and maximum temperature were used to set up the model. The simulation runs were taken to obtain the responses of the sub-basins for the period of 2016 to 2020.  The study reveals high value of Coefficient of Correlation (R²) being equal to 0.72 indicating that the simulated runoff is closely related with the observed runoff at Warunji Gauging station. The configured hydrological model would be useful in predicting the sub-basin responses under climate change so that the proper planning and preparedness can be made to evolve the robust policies for handling severe floods in the future.

Keywords: Climate Change, Extreme events, SWAT, FABDEM, Koyna River.