ISLA Federico Ignacio
congresos y reuniones científicas
ENSO-triggered floods in South America
Congreso; EGU General Assembly 2016; 2016
ENSO-triggered ﬂoods altered completely the annual discharge of most watersheds of South America. Anomalousyears as 1941, 1982-83 and 1997-98 signiﬁed enormous discharges of rivers draining toward the Paciﬁc but alsoto the Atlantic Ocean. These ﬂoods affected large cities as Porto Alegre, Blumenau, Curitiba, Asunción, Santa Feand Buenos Aires. Maximum discharge months are particular and easily distinguished at those watersheds locatedat the South American Arid Diagonal. At watersheds conditioned by precipitations delivered from the Atlanticor Paciﬁc anticyclonic centers the ENSO-triggered ﬂoods are difﬁcult to discern. The ﬂoods of 1941 affected70,000 inhabitants in Porto Alegre. In 1983, Blumenau city was ﬂooded during several days; and the Paraná Rivermultiplied 15 times the width of its middle ﬂoodplain. The Colorado River in Northern Patagonia connected for thelast time to the Desaguadero-Chadileuvú-Curacó system and therefore received saline water. ENSO years modifyalso the water balance of certain piedmont lakes of Southern Patagonia: the increases in snow accumulations causehigh water levels with a lag of 13 months. The correlation between the maximum monthly discharges of 1982-83and 1997-98 at different regions and watersheds indicates they can be forecasted for future ﬂoods triggered bysame phenomena. South American rivers can be classiﬁed therefore into ENSO-affected, and ENSO-dominated,for those within the Arid Diagonal that are exclusively subject to high discharges during these years.