Résumé
We present a methodology combining information from complementary remote sensing datasets and hydrological modelling for the monitoring of surface and groundwater variations in two large drainage basins, the Negro and the Mekong rivers. Spatiotemporal variations of surface waters can be determined combining observations from satellite imagery (i.e. JERS-1, SPOT VGT, multisatellite products) and radar altimetry (i.e. Topex/Poseidon, ERS-1&2 RA, ENVISAT RA-2). The orbital characteristics and the type of sensors present advantages and drawbacks depending on the nature of the study region, and account for the spatial and temporal resolutions, and the accuracy of the surface water storage estimates. Water stored in aquifers is isolated from the total water storage measured by GRACE by removing the contributions of both the surface reservoir derived from satellite imagery and radar altimetry, and the root zone reservoir simulated by hydrological models.