Large - scale hydrologic and hydrodynamic modelling of the Amazon River basin 2 3 4 Rodrigo

22 23 In this paper, a hydrologic/hydrodynamic modelling of the Amazon River basin 24 is presented using the MGB-IPH model with a validation using remotely-sensed 25 observations. Moreover, the sources of model errors by means of the validation and 26 sensitivity tests are investigated and the physical functioning of the Amazon basin is 27 also explored. The MGB-IPH is a physically-based model resolving all land 28 hydrological processes and here using a full 1D river hydrodynamic module with a 29 simple floodplain storage model. River-floodplain geometry parameters were extracted 30 from SRTM DEM and the model was forced using satellite-derived rainfall from 31 TRMM3B42. Model results agree with observed in situ daily river discharges and water 32 levels and with three complementary satellite-based products: (i) water levels derived 33 from ENVISAT altimetry data; (ii) a global dataset of monthly inundation extent; and 34 (iii) monthly terrestrial water storage (TWS) anomalies derived from GRACE. 35 However, the model is sensitive to precipitation forcing and river–floodplain 36 parameters. Most of the errors occur in westerly regions, possibly due to the poor 37 quality of TRMM 3B42 rainfall dataset in these mountainous and/or poorly monitored 38 areas. Also, uncertainty in river-floodplain geometry causes errors in simulated water 39 levels and inundation extent, suggesting the need for improvement of parameter 40 estimation methods. Finally, analyses of Amazon hydrological processes demonstrate 41 that surface waters governs most of the Amazon TWS changes (56%), followed by soil 42 water (27%) and ground water (8%). Moreover, floodplains play a major role in stream 43 flow routing, although backwater effects are also important to delay and attenuate flood 44 waves. 45 46 ha l-0 08 73 16 5, v er si on 1 15 O ct 2 01 3