Análise da vulnerabilidade energética dos aproveitamentos hidrelétricos do sistema interligado nacional frente às mudanças climáticas e aos padrões de usos consuntivos da água

Abstract

Climate change (CC), resulting from natural processes, has been intensified by anthropogenic activities, mainly due to the increased emission of greenhouse gases (GHGs). These changes have affected several sectors of society, including the environment, water resources, and electricity generation, among others. The latest climate assessment reports published by the Intergovernmental Panel on Climate Change (IPCC) indicate future reductions in precipitation in some regions of Brazil, an increase in the frequency and intensity of extreme events such as droughts and floods—particularly in the North and Northeast regions—and a rise in global average temperatures. These factors, combined with changes in water consumption patterns, which are also influenced by climate conditions, may further impact the Brazilian Electric Sector (BES) due to its strong dependence on hydropower generation. This study assesses the impacts of climate change and water demands on streamflows in the main river basins and hydropower plants in Brazil, as well as their effects on electricity generation. For this purpose, the MGB-IPH hydrological model was applied to simulate the historical period (1970–2014) and future scenarios (2015–2100) under climate change conditions. The simulations were driven by projections from five climate models from the NASA Earth Exchange Global Daily Downscaled Projections/Coupled Model Intercomparison Project Phase 6 (NEX-GDDP/CMIP6) dataset, considering two greenhouse gas emission scenarios, namely the Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5), as well as projections of consumptive water uses provided by the Brazilian National Water and Basic Sanitation Agency (ANA). The energy assessment proposed in this study is based on Natural Inflow Energy (NIE), since this variable is directly related to streamflows at hydropower plants. The results show that all five climate models consistently project reductions in streamflows for the future scenarios at the major hydropower plants evaluated. However, the models differ regarding the magnitude of these reductions. The NIE projections obtained with the CanESM5 model indicate the largest decreases, reaching reductions of up to 100% in the Paraguaçu River Basin. In contrast, the projections generated by the INM model indicate positive variations, with increases approaching 10%. For the remaining climate models, reductions in NIE average around 20%. The most significant findings of this study highlight how climate change and increasing water consumption may affect hydropower generation and further increase the vulnerability of the sector. Therefore, the results presented here can provide valuable information to support planning and decision-making by responsible agencies, enabling the implementation of measures to mitigate future impacts on hydropower generation and enhance the resilience of the Brazilian electricity sector.