Resumo:
Global climate changes are the result of both natural interferences and the influence of human activity, and their effects have become increasingly evident. Addressing the idea of abundance, which for a long time supported the culture of water waste, its undervaluation as a resource, and the postponement of necessary investments to optimize its use, is an urgent matter. Current projections indicate significant changes in the temporal and spatial distribution of water resources, and the increased frequency and intensity of disasters amplify this pressure, highlighting the need for mitigation plans to ensure the sustainable use of water resources. In this context, the role of the State (federal, state, and municipal governments) as the main manager of public policies involving water security and availability is crucial. The trends shown in the scenarios studied across various models must be considered by decision-makers, evaluating the impact on river flows and water availability, for the application of management tools and the development of action plans that enable adaptation and mitigation of impacts. In this regard, the Santo Antônio River basin was modeled using the Large-Scale Hydrological Model (MGB-IPH) to understand the climatic influence of CMIP6 projections, applying greenhouse gas emission scenarios SSP2-4.5 and SSP5-8.5. The objective of the study was to adjust the model to the basin and, through simulations, understand the trends in future water availability for the periods 2021 to 2060 and 2061 to 2100. The model was calibrated for each of the seven sub-basins, analyzing the three objective functions and the consistency between observed flows and those generated by the model. Overall, the results were satisfactory, with good adjustments, except for the calibration of the sub-basin located downstream of a hydroelectric plant, a fact that is understandable and inherent to existing hydrological models. With the projected flow series for the sub-basins, flow duration curves were developed and evaluated, as well as the variation of Q95, used as a characteristic flow to represent water availability. Thus, in general, the models suggest flow reductions throughout the basin, for any scenario or period.
