Climatological characterization and observed trends in precipitation extremes indicators in the Paraná Hydrographic Region, Brazil

Abstract Brazil’s water resources management is strongly influenced by the availability and temporal distribution of surface water, particularly in regions with high socioeconomic activity. The Paraná Hydrographic Region (PHR) stands out in this context due to its dense population, advanced economic development, and substantial water demand across multiple sectors. Variations in precipitation directly affect river discharge and reservoir storage, making rainfall variability a key factor in regional water availability and long-term planning. Given its socioeconomic and environmental importance, this study aims to develop a precipitation extremes climatology in the PHR and identify trends over recent decades. Daily precipitation data from the Brazilian Daily Weather Gridded Data, covering the 1961 to 2020 period, are analyzed. The Mann-Kendall statistical test and Sen’s Slope are employed to detect the significance and magnitude of trends, respectively. Results reveal apparent spatial and temporal variations in precipitation extremes across the PHR. The southern portion shows significant increasing trends in total precipitation (PRCPTOT), intensity (SDII), and the frequency of extreme events (R95p, Rx1day). In contrast, the northern region displays greater seasonality. Summer experiences the highest rainfall totals, while winter records the lowest. Additionally, there is a prevailing trend of increasing consecutive dry days (CDD) in the northern region, indicating a growing risk of prolonged droughts. Meanwhile, a reduction in consecutive wet days (CWD) in the north and eastern areas points to more frequent interruptions in the rainy periods. This study contributes to enhancing climate monitoring and integrated water resource management in the context of climate change in the PHR.