CoAuthors

Ayan Fleischmann (IPH/UFRGS, Brazil); Taina Conchy (UEA, Brazil); Stéphane Calmant (LEGOS UMR5566 IRD/CNES/UPS/CNRS, France); Vinicius Siqueira (IPH/UFRGS, Brazil); Marielle Gosset (GET UMR5563 CNES/IRD/CNRS/UPS, France); Rodrigo Cauduro Dias de Paiva (IPH/UFRGS, Brazil); Walter Collischonn (IPH/UFRGS, Brazil); Joecila Santos da Silva (UEA, Brazil)

Real-time monitoring of discharges in the Congo River basin is not straightforward given the strong geomorphological diversity, the relatively low level of knowledge of hydrological processes and the size of the basin, spreading on several countries. In this study, we built stage/discharge rating curves based on: 1) the discharges given by the distributed MGB-IPH hydrodynamic model forced by GPM TAPEER precipitation product, and 2) satellite altimetry SWE (Surface Water Elevation) time series from SARAL and Jason-2 missions at each crossing between a river reach and a satellite ground track (the so-called virtual stations – VSs). Within the MGB-IPH, we included a simple representation of lakes, improving the discharge estimates in the upper Congo. Simulated discharges were validated against both in-situ discharge data (coarse) and SWE from altimetry for the overlapping period (namely 2011-2016).
At the locations with available discharge data, the model was found to perform very well (Ens higher than 0.7 and volume error lower than 10%). The high quality of the RCs all over the basin showed that the TAPEER rainfall estimate used as input to the MGB-IPH model permitted to represent well the hydrological and hydrodynamic processes, even for the most upstream ungauged locations. Some discrepancies, observed in simulated discharges with other rainfall inputs, were discarded thanks to this dataset.
The Jason-2 RCs can now be used routinely to derive discharges in near real time (NRT) from forthcoming Jason-3 SWE observations, with a temporal sampling of one every 10 days and at almost a hundred of potential VSs. In addition, the combination with observations coming from former missions flying on the same orbits (T/P for Jason-2, ENVISAT and ERS-2 for SARAL) permitted to produce long term discharge time series, prerequisite for climate-change studies.