Increasing floods and droughts raise concerns about an accelerating water cycle. This study analyzes streamflow data in major South American tropical river basins and shows that water use and deforestation have amplified climate change effects on streamflow extremes over the past four decades. Drying (fewer floods and more droughts) is aligned with decreasing rainfall and increasing water use in agricultural zones and occurs in 42% of the study area. Acceleration (both more severe floods and droughts) is related to more extreme rainfall and deforestation and occurs in 29% of the study area, including southern Amazonia. The regionally accelerating water cycle may have adverse global impacts on carbon sequestration and food security.

Vinícius B. P. Chagas, Pedro L. B. Chaffe, Günter Blöschl