Extreme discharge events in the Parana River and their climate forcing

The largest discharge anomalies of the Parana River were examined focusing on the contribution from the subbasins and on the climate forcing of these events. Major discharge anomalies at Corrientes originated in the central and southern Upper Parana basin with relatively small contributions from the Paraguay river and the northern Upper Parana basin. About two thirds of the major discharge anomalies in Corrientes occurred during El Nino events while none was registered during La Nina events. Major discharge anomalies related to El Nino occurred either in the spring of the year of El Nino onset or in autumn of the following year (autumn (+)) accompanying the precipitation signal of El Nino in eastern subtropical South America. The signal during autumn (+) is the most relevant as five out the six top discharges of the Parana River at Corrientes occurred in this season. The remaining third of the major discharges not related to El Nino took place during the austral spring or austral summer of neutral periods. In each of these seasons, they share a common sea surface temperature anomaly pattern in the proximity of the South American coasts.