ABSTRACT
The Paraná River Basin has already been subject to considerable variability in climate and hydrology in the past, and considerable changes can be expected in the future, based on projections from Global Climate Models (GCMs). According to those projections, temperature will rise in the whole region while precipitation will increase in the east and south of the basin and decrease in the north and northwest parts of the basin. However, there is still a considerable disagreement between different GCMs regarding the magnitude of the changes in precipitation and even in the direction of change (positive or negative) in some regions. In this chapter, we describe the results of a large-scale integrated assessment of climate change impacts on hydrology that were obtained by running a continental-scale hydrological model with input from 25 GCMs. Model results show that there is general agreement that rivers that flow from north to south within the Paraná headwaters, which lie mostly within Brazil, will probably face reductions in discharge. The same trend is predicted for rivers that flow from the west, a region that already has a dry climate. There is no agreement among model predictions, however, about the future changes in the discharge of the main Paraná River itself, except for a projected decline in discharge in the reach upstream of its confluence with the Paranapanema River in Brazil. The northern part of the Paraná River Basin is projected to become drier, as expressed by the aridity index, which is the ratio between potential evapotranspiration and precipitation. Potential impacts on agriculture, hydropower and navigation are discussed, and results are compared to previous regional or local studies found in the literature.
