Abstract ID: 68

Regional Runoff Changes in the Amazon Basin and Relationships With Rainfall (1974 - 2004)

Former hydrological studies in the Amazon Basin generally describe the annual discharge variability on the main stem. Though, the downstream Amazon River only represents the mean state of the Amazonian hydrological system. That is why we dedicate this study to the analysis of the variability of regional runoff extremes in the Amazon basin, using a new data set that include daily discharge in the main 15 sub-basins and monthly rainfall data in more than 700 raingauge stations. This data base has been compiled in the mark of the Hydrogeodynamic of the Amazon Basin program (HYBAM), a partnership between Amazonian countries institutions (Agencia Nacional de Aguas in Brazil, Servicio Nacional de Meteorologia e Hidrologia in Peru and Bolivia, Instituto Nacional de Meteorología e Hidrologia in Ecuador and Instituto de Hidrologia, Meteorologia y Estudios Ambientales in Colombia) and the French Institute for Research and Development (IRD). We show that during the 1974-2004 period the stability of the mean discharge on the main stem, in Obidos, is explained by opposed regional features: a diminution of the low stage runoff, particularly important in the southern sub-basins, and an increase of the high stage runoff in the north-western region, the rainiest part of the basin. These changes are observed since the beginning of the nineties. We also point out that the changes in discharge extremes in the sub basins are closely related to the regional pluriannual rainfall variability.

Session:  Feedbacks to Climate - Land cover, surface hydrology, and atmospheric feedbacks. (A)

Presentation Type:  Oral