Quantifying Flood and Drought Hazards on a Large Data Scarce Indian River Basin

India has experienced several devastating climate extremes during recent decades. Floods and droughts are among the most dangerous geohazards and constitute a serious menace for public safety leading to human and economic losses. For example during the August 2018 Kerala floods 483 people died and 140 were missing, whereas the 2016 drought hit about 10 states and affected about 330 million people. In this work we quantified the flood and drought magnitude and frequency in the large Netravati river basin in India combining: 1) gauged data (rainfall and evapotranspiration), 2) satellite data (CHIRPS), and 3) a parsimonious semi-distributed hydrological model. Netravati is one of the west flowing rivers in the Western Ghats (WG) of India, which is one of the biodiversity hotspots in the world, draining out an area of about 3150 km2 at Bantwal gauging station before reaching the Arabian Sea. The mean annual precipitation over the basin is about 4000 mm mostly occurring during southwest monsoon (June – September). It is characterized by a humid and tropical climate with a temperature range of about 20 to 35 ºC. The hydrological model has been calibrated and validated on the river basin outlet and an independent validation has been carried out for two internal gauged stations. Results provided satisfactory performances with Nash-Sutcliffe and Kling-Gupta-efficiencies higher than 0.8. Secondly, return periods of floods and droughts have been computed based on commonly used statistical analysis and validated against measured data. Finally, based on simulated river discharge, results have been extended to ungauged locations in order to provide an estimate of the potentially exposed population.