Amazonian deforestation: its influence on the Amazon discharge at Obidos (Brasil)

This survey completes our earlier work on the evolution of the Amazon discharge at Óbidos from 1903 to 1999. The impact of this deforestation on the mean annual discharge was estimated using a water balance approach from 1940 to 2003. The evolution of the runoff coefficient indicates that there was a 5% increase in the mean annual discharge over the 22 years from 1981 to 2003. The number of strong floods was five time higher during this period than it was before. On the other hand, it seems that there is no influence of the deforestation on the low flows. Key-words: South America, Amazon catchments, Óbidos, rainfall, discharge, water balance, deforestation.Original Abstract: Cette etude complete l'ebauche publiee dans Evolution du debit de l'Amazone a Óbidos de 1903a 1999. L'impact de ce deboisement sur les debits moyens annuels est mis en evidence en utilisant le bilan hydrologique, calcule de 1940 a 2003. L'evolution du coefficient d'ecoulement permet d'estimer a 5 % l'augmentation du debit moyen annuel sur 22 ans (1981-2003). Le nombre de fortes crues a quintuple. Par contre, aucune influence du deboisement sur les etiages n'a ete decelee.