Climate Change in Sergipe, Northeast Brazil: Hydrological Trends in Recent Decades

ABSTRACT Analysing spatial and temporal variability in climate is not just an academic exercise; it is also crucial for identifying hydrological trends, assessing climate change, and understanding the environmental vulnerability of a region. These analyses also help in projecting future water availability and susceptibility to desertification. The Northeast of Brazil (NEB), characterised by prolonged droughts and intense rainfall events, could greatly benefit from such research. In Sergipe, the smallest state in NEB, some studies have revealed trends indicating a decrease in annual rainfall and increasing extremes in maximum and minimum temperatures, accompanied by signs of climate change in arid zones. Therefore, this study aimed to evaluate the temporal variability of precipitation ( P ), evapotranspiration (ETo), and the aridity index (AI) in Sergipe's watersheds, as well as to assess changes in their spatial distribution across the territory. The results showed that, over the past six decades, Sergipe did not exhibit statistically significant tendencies in the P variables: total annual precipitation, total precipitation in the wettest quarter (WQT), and total precipitation in the driest quarter (DQT). However, spatial analysis revealed changes in the dynamics of these variables. Five watersheds presented a statistically significant increase in ETo annually and during the DQT. Spatially, an expansion of ETo occurred in areas highly susceptible to desertification, particularly in the São Francisco watershed and at the headwaters of the Piauí and Real rivers. These findings suggest a trend of decreasing water availability in the region, emphasising the need for immediate policy intervention to mitigate the risks and damage caused by prolonged droughts.