Observed impact of climate change on Brazilian rivers

Abstract

Historical series of Brazilian main rivers natural flow, published by the National Electric System Operator (ONS), present clear regional patterns of long-term variations since 1931. As these flows result from the water balance in the upper catchment of each measurement station, it is possible to determine the causes of these long-term regional patterns: significant changes in vegetal coverage (typically deforestation) and climate changes (mainly in average rainfall and temperature). In a large part of the national territory, encompassing approximately the NE, SE and South regions, long-term variations of average flows in the last four decades were mainly due to climate changes associated with anthropogenic global warming. As these changes in climate parameters will persist for at least the next twenty years, the hydrological diagnosis of long-term variations enables to elaborate reliable projections for future flows over the next two decades, with less error margin than indirect methods based on downscaling of global climate models (GCMs).