Climate Variability and Change—Hydrological Impacts (Proceedings of the Fifth FRIEND World Conference held at Havana, Cuba, November 2006), IAHS Publ. 308, 2006, 220–225.

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Impact of the Amazon tributaries on major floods at Óbidos

JOSYANE RONCHAIL¹, Jean-Loup Guyot², Jhan Carlo Espinoza Villar², Pascal Fraizy², Gérard Cochonneau³, Eurides De Oliveira⁴, Naziano Filizola⁴ & Juan Julio Ordenez⁵

1 Université Paris 7- Denis Diderot and Laboratoire d’Océanographie et du Climat (LOCEAN-IPSL), case 100, 4 Place Jussieu, F-75005 Paris-France

josyane.ronchail@lodyc.jussieu.fr

2 Institut de Recherche pour le Développement and Universidad Agraria La Molina, casilla 18 1209, Lima 18, Peru

3 Maison de la Télédétection, 500 rue J.F. Breton, F-34093 Montpellier Cedex 05, France

4 Agência Nacional de Águas, Setor Policia, CEP 70610-200, Brasília, Brasil

5 Servício Nacional de Meteorología y Hidrología, Cahuide 785, Lima 11, Peru

Abstract Major flooding of the Amazon river (with discharge over 250 000 m3 s-1) is analysed, using daily discharge at

(a) Óbidos, the lowest gauged station on the Amazon River, 800 km from the ocean,

(b) Six gauge stations located on the main tributaries and characterized by different discharge regimes.

During the 1984–2001 period major flooding on the main stream was related to the following features:

(a) greater than usual high water in the Solimões River, the largest tributary,

(b) delayed discharge peaks in the southwestern tributaries and the Amazonas River (Peru) and/or advanced discharge peaks on the Negro-Branco River,

(c) unusual February–April discharge peaks in the western and northwestern tributaries, particularly in the Negro River.

These two last features contribute to the simultaneous inflow of a great quantity of water from all the tributaries in April–May and may favour major flooding of the Amazon River at Óbidos.

Key words Amazon River; Óbidos; flooding; discharge; Brazil; Peru

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