Applicability of reanalysis data in calibrating a hydrological model in a data-scarce mountainous watershed

Understanding the hydrological processes of mountainous regions is crucial for watershed management. The increased frequency of floods in the Himalayan region emphasizes the need to set up a hydrological model in this region. The complex topography and climate patterns of the Himalayas, with a few hydrometeorological stations, make modeling the region challenging. Therefore, the study of hydrological responses using a fully distributed hydrological model in this region is very rare. This study aims to address the challenges of data scarcity in mountain regions using alternative data for observed discharge data for the calibration of the hydrological model. We assess the utility of reanalysis surface runoff data (RSRD) from ERA-5 in calibrating a fully distributed hydrological model WATFLOOD. Six water balance components at nine land-cover classes are analyzed using the WATFLOOD model. The results show that the RSRD can be used as an alternative for the discharge data for calibration of the hydrological model. The evaluation of water balance components shows changes corresponding to wet and dry years. We verified simulation results using observed data, revealing the limitations of calibrating a hydrological model with RSRD.