Interannual variations of river water storage from a multisatellite approach: a case study for the Rio Negro River basin

International audienceSpatio-temporal variations of water volume over inundated areas located in a large river basin have been determined using combined observations from a multi-satellite inundation dataset, the Topex/Poseidon (T/P) altimetry satellite, and in situ hydrographic stations for the water levels over rivers and floodplains. We computed maps of monthly surface water volume change over the period of common availability of T/P and the multisatellite data (1993-2000). The basin of the Negro River, the largest tributary in terms of discharge to the Amazon River, was selected as a test site. A strong seasonal signal is observed with minima in October and maxima in June. A strong interannual component is also present, particularly important during ENSO years. The surface water change was estimated to be 167 ± 39 km3 between October 1995 (low water) and June 1996 (high water). This result is consistent with previous estimates obtained for the 1995-1996 hydrological cycle over the same area using the JERS mosaic data. The surface water volume change is then compared to the total water volume change inferred from the GRACE satellite for an average annual cycle. The total water storage for the Negro River basin is almost equally partitioned between surface water and the combination of soil moisture and groundwater. The water volume changes are also evaluated using in-situ discharge measurements and the GPCP precipitation product (correlation of 0.61). The results show the high potential for the new technique to provide valuable information to improve our understanding of large river basin hydrologic processes