Hydrological processes interconnecting the two largest watersheds of South America from multi-decadal to inter-annual time scales: A critical review

The hydrological aspects of the Amazon and the La Plata basins are interconnected through southward moisture transport performed by the Low-Level Jet east of the Andes and the South Atlantic Convergence Zone. Remote effects of sea surface temperature variability in the Pacific and the Atlantic are of varied periodicities, from multi-decadal to inter-annual time scales. Major oscillations thus far detected are Atlantic Multi-decadal Oscillation, Pacific Multi-decadal Oscillation, North Atlantic Oscillation, Atlantic Dipole, Antarctic Oscillation, and the El Nino Southern Oscillation. In the multi-decadal, inter-decadal and decadal time scales, the effects of climate variability over the hydrological processes that interconnect the Amazon and La Plata watersheds are felt predominantly in the South American Monsoon season, while on the inter-annual scale the effects vary along the year. The hydrological memory in Amazonian soils is also responsible for the inter-annual variability of hydrology of the Amazon Basin. Due to the effects of soil water on evapotranspiration, the hydrological memory can affect the supply of moisture to the La Plata Basin, influencing the inter-annual variability of this basin. The implications of the observed oscillations to the hydrological and climatological variability in the two basins are discussed and synthesized in this article. Hypotheses for future research are formulated.