Sep 15, 2009

Contrasting regional discharge evolutions in the Amazon basin (1974–2004)

Jhan Carlo Espinoza Villara, Jean Loup Guyotb, Josyane Ronchailc, Gérard Cochonneaub, Naziano Filizolad, Pascal Fraizye, David Labatf, Eurides de Oliveirag, Juan Julio Ordoñezh, Philippe Vauchele
Journal of Hydrology
  • States that former hydrological studies in the Amazon Basin generally describe annual discharge variability on the main stem; however, the downstream Amazon River only represents the mean state of the Amazonian hydrological system
  • This study therefore uses a new data set including daily discharge in 18 sub-basins to analyze the variability of regional extremes in the Amazon basin, after recalling the diversity of the hydrological annual cycles within the Amazon basin
  • Applies several statistical tests in order to detect trends and breaks in the time series
  • Shows that during the 1974–2004 period, the stability of the mean discharge on the main stem in Óbidos is explained by opposite regional features that principally involve Andean rivers: a decrease in the low stage runoff, particularly important in the southern regions, and an increase in the high stage runoff in the northwestern region
  • Finds that both features are observed from the beginning of the nineties
  • Finds that these features are also observed in smaller meridian sub-basins in Peru and Bolivia
  • Shows that the changes in discharge extremes are related to the regional pluriannual rainfall variability and the associated atmospheric circulation as well as to tropical large-scale climatic indicators