Trends, Patterns, and Persistence of Rainfall, Streamflow, and Flooded Area in the Upper Paraguay Basin (Brazil)

The decrease in river streamflow and rainfall volumes due to climate change and/or variability has been affecting several environmental and socioeconomic aspects of the Pantanal floodplain in Brazil. This study analyzed 37-year-long (1986-2023) hydrological time series of rainfall, streamflow and flooded areas in three contributing basins of the Pantanal floodplain (Jauru - JB, Taquari-TB and Miranda-MB), revealing distinct hydrological trends influenced by climate systems and ENSO patterns. Significant decreasing trends in rainfall and streamflow were observed in the northern JB and TB basins, while the southern MB basin showed increasing behavior. As a consequence, the downstream flooded areas in the Pantanal floodplain showed a decreasing trend in the period. Long-term memory processes (Hurst phenomenon) were identified in the time series of the basin flooded surface and also in the Paraguay river stage data, indicating a persistent and aggregated reduction in the hydrologic variables, affecting both the ranching and fishing activities in the region, and the regional ecology. These findings reinforce the need for adaptative management strategies to tackle the impacts of water surface loss, increasing fire risk, and climate variability in the Upper Paraguay basin.