The River Amazon water contribution to the Atlantic Ocean

The mean interannual discharge of the River Amazon in the Atlantic Ocean has been estimated using two methods, independent but complementary. After having defined, in the most logical way, the eastern limit of the Amazon basin, the water balance from Óbidos was established for the 1972-2003 period. The mean interannual discharge at the mouth would be 205,000 m3os-1. A second method was based on ten sets of flow measurements done at the mouth from 1997 to 2008, which correlated very well with the corresponding discharge values observed in Óbidos. This method indicates an interannual flow at the mouth of 208,000 m3os-1, including 6,000 m3os-1 that represent the derivation from the Amazon River towards Rio Para (and the Ocean) by the furos, channels that run in the River Amazon's old arm. With an uncertainty of plus or minus 6%, the interannual contributions of the River Amazon to the Ocean, over the 1972-2003 period, would represent 17% of the total volume of fresh water entering the oceans worldwide.Original Abstract: Cette etude determine, par deux methodes, independantes mais complementaires, le debit moyen interannuel de l'apport liquide de l'Amazone a l'ocean Atlantique. Apres avoir defini, le plus logiquement possible, la limite Est du bassin amazonien, l'etude etablit le bilan hydrologique de l'Amazone depuis Óbidos jusqu'a l'ocean, sur la periode 1972-2003. Le debit moyen interannuel a l'embouchure serait de 205 000 m3os-1. Une seconde methode se base sur dix series de mesures de debit effectuees a l'embouchure de 1997 a 2008 qui se correlent tres bien avec les debits observes a Óbidos. Cette methode indiquerait un debit interannuel a l'embouchure de 208 000 m3os-1, en y incluant les 6 000 m3os-1 que represente la derivation de l'Amazone vers le Rio Para (et l'Ocean) par les furos, canaux qui coulent dans l'ancien bras de l'Amazone. Avec une incertitude de plus or minus 6 %, les apports interannuels de l'Amazone a l'ocean, pour la periode 1972-2003, representeraient 17 % des apports mondiaux en eau douce.