Uncertanity in water budget derived form the reanalysis products in the Indian sub-continental river basins

Understanding of water budget in river basins is important for water resources planning and management. However, water budget and associated uncertainty is not well quantified for the river basins in the Indian sub-continent basins partially because lack of availability of observed data related to water budget components (precipitation (P), evapotranspiration (ET), and total runoff (R)). The reanalysis products provide valuable information that can be used for water resources planning and management, however, our understanding is limited about the uncertainty in the water budget and its closure in the reanalysis products. In this study, an attempt is made to analyse the uncertainty in different water budget components derived from reanalysis products (CFSR, ERA-I, ERA-I/L, JRA55, MERRA and MERRA/L) and to compare them with the Variable Infiltration Capacity (VIC) model forced with observed climate forcing. The water budget from the reanalysis products is analysed for 18 sub-continental river basins. Results show that all the reanalysis products show regional and temporal variability in water budget components, which can be attributed to bias in the input forcing and land surface model parameterization related to soil and vegetation. Air temperature is found to have the best temporal correlations (> 0.79) in all the reanalysis products followed by precipitation and total runoff. owever, a large uncertainty was noticed in ET from the reanalysis products, which in turn affects water storage and water budget closure in the Indian sub-continental river basins. Substantial improvements were observed in ET estimations when we forced the VIC model with the forcing obtained from the reanalysis products, which indicates that the land surface parameterization of soil and vegetation can improve the water budget.