Investigating the Impacts of Climate Change on Hydrological Extremes in The Madeira River Basin, Amazonia: an emphasis on the unprecedented drought-flood transitions over the last decade

Droughts and floods are natural phenomena in the Amazon, arising from the spatial and temporal variability of rainfall distribution. However, anthropogenic climate change and forest degradation, summed to large-scale climatic events, have intensified their frequency, intensity and onset, pushing the Amazon region to a critical tipping point. The Madeira River, the largest and most significant tributary of the Amazon River, is particularly vulnerable to these extremes. Notable droughts in 2005, 2010, 2015-2016 and 2023-2024, alongside major floods in 2014 and 2021, highlight the increasing variability of hydrometeorological patterns, severely impacting water resources, ecosystems and communities. This study evaluates the environmental and social impacts of climate change on the Madeira River Basin, emphasizing changes in hydrometeorological patterns and their repercussions in droughts and flood events. Daily observed data on precipitation, streamflow, and water level from stations operated by the National Water and Sanitation Agency (ANA) were analyzed. A 50-year historical dataset (January 1975 to August 2024) across 14 locations was used to calculate the Standardized Precipitation Index (SPI) and the Standardized Streamflow Index (SSI) to assess the magnitudes, duration, and period of occurrence of flood-drought events. The findings reveal escalating impacts of hydrological extremes on ecosystems and communities. Rising temperatures and extreme events disrupt the basin’s ecological recovery processes, reducing soil moisture, altering evapotranspiration rates, and stressing biodiversity. Communities face reduced water availability, compromised hydroelectric energy production, and restricted transportation for riparian populations reliant on river systems for livelihoods. Correlations between SPI and SSI were analyzed to understand the interactions between climatic and hydrological variables, offering insights into the basin’s response mechanisms to drought and flood events. These insights are critical for guiding adaptive strategies and managing water resources in a changing climate. Furthermore, the study highlights the importance of developing and refining early warning systems to mitigate risks, enhance resilience and support sustainable management in the face of hydrological extremes.