Long-term rainfall variability and trends in Brazilian state capitals and implications for urban water supply (1958–2024)

ABSTRACT This graphical abstract summarizes the study of long-term rainfall variability and trends across Brazilian state capitals from 1958 to 2024 using TerraClimate data. It illustrates the methodological workflow, including the application of the Mann-Kendall test, Sen's slope estimator, and Trend-Free Pre-Whitening (TFPW). The figure highlights spatial differences in rainfall trends, with increasing patterns in the North and South regions and decreasing trends in the Northeast. It also emphasizes that seasonal trends are more pronounced than annual trends and shows the implications of these findings for urban water supply management under climate variability. Understanding long-term rainfall variability is essential for urban water supply planning and climate adaptation in Brazil. This study analyzes annual and seasonal rainfall variability and trends in the 26 Brazilian state capitals and the Federal District using monthly TerraClimate precipitation data from 1958 to 2024. The novelty of this research lies in its integrated nati onwide assessment over a 66-year period, including both annual and seasonal trend analyses and their implications for urban wa ter supply. Descriptive statistics were used to characterize rainfall variability, while the Mann–Kendall test and Sen’s slope est imator were applied to detect long-term trends. Serial autocorrelation was evaluated, and the Trend-Free Pre-Whitening proced ure was applied when necessary. Results reveal strong spatial heterogeneity in rainfall patterns across Brazil. Significant incre asing annual rainfall trends were identified in Belém, Florianópolis, and Porto Alegre, whereas decreasing trends were observe d in Salvador, Aracaju, and Teresina. Seasonal analyses showed increasing precipitation during austral summer (DJF) in northe rn capitals and decreasing winter (JJA) rainfall in parts of Central-West and Southeast Brazil. These findings emphasize the im portance of incorporating long-term rainfall variability and seasonal trends into urban water management and climate adaptation strategies.