Regionalização dos impactos das mudanças climáticas nos regimes de chuva e vazão na bacia hidrográfica do Xingu.

Abstract

The impacts of climate change should influence the intensification of extreme events in the coming decades, such as floods and droughts. Therefore, this work aims to generate regionalized future scenarios of climate change for rainfall in the Xingu River Basin (XRB), in the 2021-2080 horizon and to evaluate its impacts on monthly streamflow and possible consequences on energy production at the Belo Monte hydroelectric plant. A statistical downscaling to obtain the future series of rainfall in the XRB was used and from these derive the streamflow using the Principal Component Regression technique, duly calibrated and validated for the Altamira station, a reference for Belo Monte. The ensemble of four Global Climate Models (CanESM2, CNRM-CM5, MPI-ESM-LR and NORESM1-M) and two climate scenarios (RCP 4.5 and RCP 8.5) were used. Trends and rainfall extremes indices in the XRB in the period from 1980 to 2016 were also evaluated. Most of the indices showed a positive trend in the northern part and a negative trend in the southern part of the BHX. Large portions of XRB showed these trends with statistical significance, with homogeneous results in many of them, especially the R95p, R20, SDII and PRECTOT indices. Future projections for RCP 4.5 and RCP 8.5 scenarios were unanimous in pointing out a significant reduction in rainfall in the rainy season and a slight increase in the dry season in XRB compared to the reference period (1981-2010). Consequently, the projections also pointed to reductions in streamflow in Altamira and reduction in the energy generation potential in Belo Monte in the two periods analyzed (2021-2050 and 2051-2080). The RCP 4.5 scenario presented the largest reductions in rainfall and streamflow rates in the two periods compared to the RCP 8.5 scenario. In light of this scenario, by 2080, an annual reduction in the energy generation potential in Belo Monte of 21.3% is expected compared to the reference period and the utilization of 38.8% of the maximum installed potential. The increasing demand for water consumption to meet the multiple uses of the basin, associated with climate change, should influence the availability of water for energy generation in Belo Monte. This information can help decision makers to adopt energy policies and mitigation measures to the possible impacts of these scenarios and reinforce the need for investments in other sources of renewable energy to compensate for the losses of hydroelectric production in Belo Monte in the future.