Avaliação dos impactos das mudanças climáticas sob a segurança hídrica do sistema Cantareira

Abstract

The impacts of climate change pose a threat to water security of supply reservoirs and can affect the provision of potable water. Hydrological drought events exemplify this threat and have been occurring more frequently in various regions worldwide. Understanding these impacts is essential for water resource management aimed at ensuring water security. However, there is a lack of comprehensive studies exploring the impacts of climate change in this context. In this study, we investigate the impacts of climate change on the water security of the Cantareira system, the primary water supply system for the São Paulo Metropolitan Region (SPMR) and one of the largest in the world. First, using daily observed precipitation and evapotranspiration data, we calibrated and evaluated a conceptual hydrological model, achieving satisfactory statistical metrics. To represent possible future climate change scenarios, we considered two emission scenarios from the CMIP6 project (SSP2-4.5 and SSP5-8.5) and used a set of future projections generated by an ensemble of 10 Global Climate Models (GCMs). These data were used to drive the hydrological model to simulate streamflows for the study area. Consequently, future streamflow values were analyzed, and water security was assessed from the perspectives of excess, scarcity, and vulnerability. Our results indicate that streamflow is expected to exhibit greater annual variability, with significant increases in simulated flow between December and March, and slight decreases between May and July. The results highlight risks associated with excess water and flooding, with January being the wettest month, while the analysis of water security indicators identifies August and September as the most vulnerable months. Overall, our analysis exposes the fragility of the Cantareira system's water security and provides technical and scientific information that can be utilized in developing strategies to address future water insecurity.