Abstract
Study region: The Ganges-Brahmaputra (GB), a major river basin of the Indian Sub-Continent (ISC), is the host of more than 700 millions people.
Study focus: In addition to monsoons and strong climate variability, GB is facing growing demands for freshwater availability by a continually growing population and rapidly developing of agricultural and industrial sectors. The management of water resources is thus of highest priority and, in the context of current over-abstraction of groundwater, accurate estimates of terrestrial freshwater storage are essential. We propose a multi-satellite approach to estimate surface freshwater storage (SWS) and subsurface water storage (SSWS, groundwater + soil moisture) variations over GB. Basin-scale monthly SWS variations for the period 2003-2007 show a mean annual amplitude of similar to 410 km(3), contributing to about 45% of the Gravity Recovery And Climate Experiment (GRACE)-derived total water storage variations (TWS). During the drought-like conditions in 2006, we estimate that the SWS deficit over the entire GB basin in July-August-September was about 30% as compared to other years. The SWS variations are then used to decompose the GB GRACE-derived TWS and isolate the variations of SSWS whose mean annual amplitude is estimated to be similar to 550 km(3). This new dataset of water storage variations represent an unprecedented source of information for hydrological and climate modeling studies of the ISC. (C) 2015 The Authors. Published by Elsevier B.V.