River streamflows provide an integrated view of a drainage basin response to variations in regional hydrology and climate, as well as anthropogenic activities. This paper examines the variability of the large rivers in South America’s La Plata drainage basin, one of the largest in the world. It is shown that the rivers capture the change reported in the regional climate during the 1970s, and are significantly influenced by sea surface temperature (SST) anomalies in the Pacific and Atlantic Oceans on interannual and interdecadal time scales. In particular, it is shown that the streamflows are influenced by El Niño/Southern Oscillation, interannual SST anomalies in the western tropical Atlantic, and interdecadal SST variations in the tropical North Atlantic.

The predictability of cyclic components in the time series of the Paraná River streamflow is discussed. A predictive model is constructed and a prediction is made for the decade starting in 1999. The results suggest increased probability of below-average flows in the Paraná until 2006. A new method to monitor water river behavior using satellite altimetry to estimate water level heights over continental surfaces is presented. The method is applied to describe the behaviors of the Paraná and Paraguay Rivers in the period 1993-2001.