Variability in the discharge of South American rivers and in climate / Variabilité des débits de rivières d'Amérique du Sud et du climat

Abstract

Changes in trend and quasi-periodicities are sought in the time series of river discharges in all major South American basins. The relationship between trends and quasi-periodicities found and climate variations on interannual and longer time scales are discussed. Consideration of multiple rivers gives insight into the geographical extent of hydrological signals and climate impacts. It is found that the streamflow of all major rivers of South America has experienced an increased trend since the early 1970s. It is suggested that this simultaneity may reflect the impact of a large-scale climate change. All the time series of river streamflows that were analysed show El Niño-like periodicities. Only for La Plata Basin do these explain a larger part of the total variance than the other quasi-periodicities. There are two other quasi-oscillations in the time series analysed: one of them with a longer period—around 17 years—and the other of about 9 years. Previous work has related these oscillations to sea-surface temperature anomalies in the Atlantic Ocean.