Atualização das curvas IDF vigentes para municípios da bacia do Rio Taquari-Antas e análise comparativa frente aos impactos dos eventos climáticos extremos de 2023 e 2024

Abstract

This study aims to update the Intensity-Duration-Frequency (IDF) curves used in municipalities in the Taquari-Antas River Basin, in the state of Rio Grande do Sul, considering the extreme weather events recorded in 2023 and 2024. IDF curves are essential tools for designing hydraulic projects and urban planning, being based on historical precipitation series. Over the years, an intensification in the frequency and magnitude of extreme events, such as heavy rainfall, has been observed due to global climate change. The study involves a comparative analysis between the current curves and new curves, the latter developed by including the most recent heavy rainfall episodes, assessing whether the previous models still adequately represent the region's hydrological behavior. The municipalities whose IDF curves had been developed in the study by Bortolin et al. (2020) were evaluated, and those with new historical series available for updating were selected. Therefore, seven cities were selected using rainfall data from the National Water and Sanitation Agency (ANA), extended through 2024 and covering the most extreme events of great magnitude that occurred in Rio Grande do Sul. Based on the annual daily maximums, a data series was obtained for the selected municipalities in the basin, to which statistical probability distribution methods were applied. The values were disaggregated for different durations, allowing the generation of new IDF curves and subsequent comparative analyses. Comparison with current models highlighted the importance of incorporating more recent data into the analyses to ensure greater safety and efficiency for infrastructure in the face of increasingly recurring new climate scenarios. With this in mind, the study also applied the IPH Technical Note (2024), which establishes hydrological criteria for climate change adaptation for extreme precipitation and flow in the Southern Region of Brazil. Thus, the work was conducted to meet the most up-to-date technical criteria, developing new IDF curves for the municipalities evaluated and contributing to hydrological adaptation to the challenges posed by climate change. Comparative validations revealed that, in addition to the inclusion of new periods in the historical series, the incorporation of the three extreme events between 2023 and 2024 suggests possible changes in rainfall patterns in both the most frequent and the most extreme events. Although the results do not show significant variations in all cases, differences stand out in the shortest return times (2 and 5 years) and also in the longest (50 and 100 years). For long return times, these differences indicate that rare, large-scale events may be becoming more likely, recurrent, and intense. For short return times, the results suggest that frequent rainfall tends to be less intense, producing lower precipitation volumes in the same time interval, but maintaining the same frequency of occurrence. [resumo fornecido pelo autor]