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Comparison Between GRACE-Derived Water Stock Variations and ENVISAT Water Stages in the Amazon Basin
Vaz De Almeida, F.1; Santos da silva, J.2; Ramillien, G.3; Calmant, S.4; Seyler, F.5; Blitzkow, D.6; Cazenave, A.7
1USP / IRD; 2UFRJ / IRD; 3CNRS/LEGOS; 4IRD/LEGOS; 5IRD/LMTG; 6USP; 7CNES/LEGOS

Since 2002, the GRACE space mission collects space and time gravity variations all over the Globe. In the Amazon basin, these time variations of the gravity can be converted into water mass variations, hence into equivalent height (hereafter GEH), at a 10 day interval. We compare these GEH with the time variations of water stages at in-situ gauge stations. Both datasets present corelated variations with the hydrological cycle. Yet, the linear coefficient between each pair of series varies spatially. At first order, large (>10) values are found uptream the rivers, decreasing downstream, when a -expected- minimum value of 1 is found at the mouth of the Amazon. In order to have a closup view, we also compared the GEH with stage time series derived from ANVISAT at 35 virtual stations regularly spaced along 1900km of the Rio Negro, second contributor to the Amazon. Doing so, we observe that this coefficient does not decrease regularly along the river course but presents local extrema. We present temptative explanations of these patterns in terms of hydrology, geology, pedology and flow accumulation altogether.

 

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