Identification of extreme hydrological events in the Parana River basin

Extreme events (droughts and floods) are climate conditions that occur periodically in a geographic region, limiting productive and recreational opportunities as well as human activities in general. In terms of intensity and frequency, in extreme cases they can cause loss of human life as well as economic damages nationally due to the allocation of vast resources to recovery. The present work uses the Standardized Precipitation Index to evaluate dry and wet events in the Parana River basin upstream from Posadas (934 000 km2). Several dry and wet events during 1901-2002 were detected based on this index. The worst drought identified in the study area occurred in all the sub-basins during 1963-1964, with different degrees of severity. The most severe wet event occurred in 1982-1983 in most of the sub-basins, with a significant temporal differences. This methodology was based exclusively on rain gauge data and provides a useful tool to study and compare the results obtained.