Climate drives observational changes in hydrological extremes across most global regions

Public summary

* Drought and flood flows concurrently increase or decrease across most global regions.

* Human activities mainly affect Alaska, Central America, the Amazon region, Northern and Central Europe.

* Regions in the Southern Hemisphere are primarily governed by climatic factors.

Abstract

Identifying the common dominant drivers of hydrological extremes (floods and droughts) occurring in the same regions within a single year is crucial for developing effective adaptive strategies in response to such events. However, this aspect remains insufficiently explored in current global assessments. To address this gap, we analyze changes in drought and flood flow in the same regions, along with their potential dominant drivers, across 9,531 global hydrological stations, for the period 1980–2014. Our findings indicate a simultaneous increase (constituting 28.14%) or decrease (constituting 33.36%) in both drought and flood flow across the majority of global regions. Regions such as Alaska, Central America, the Amazon region, and Northern and Central Europe are primarily influenced by anthropogenic activities, including water withdrawal and changes in vegetation cover. In contrast, other regions, particularly in the Southern Hemisphere, are predominantly influenced by climatic factors, including atmospheric water balance and its seasonal variability. By identifying these common drivers, the study provides critical insights for developing targeted adaptive strategies to mitigate the impacts of hydrological extremes.