Evaluation of pluviometric and fluviometric indices in the Paraíba do Sul river basin

Rainfall and river flow indices in the Paraíba do Sul river basin from 1962 to 2022 were evaluated to characterize extreme maximum flow and rainfall events. Data were collected from pluviometric and fluviometric stations in 10 municipalities using the HIDROWEB platform. Extreme values for rainfall and flow were identified using the 99th percentile and the Gumbel distribution, respectively. The Mann-Kendall test analyzed trends in extreme events and historical time series. Results indicated that extreme events were mostly not statistically significant. However, the historical series showed a balance of positive and negative trends in precipitation, while all flow trends were negative. A spatial distribution map of accumulated rainfall averages was created using the Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) platform, revealing spatial rainfall heterogeneity across the basin. Additionally, a double-mass graph from CHIRPS data compared changes within sub-basins to the basin's average. This work concludes that while there is a trend of decreasing streamflow in the Paraíba do Sul basin, precipitation levels have not shown a corresponding decrease, suggesting that the reduction in streamflow is not primarily due to meteorological factors.