Climate drives observational changes in hydrological extremes across most global regions

Area of Science:

• Hydrology
• Climate Science
• Environmental Science

Background:

• Understanding drivers of hydrological extremes like floods and droughts is vital for adaptation.
• Global assessments often overlook common drivers of co-occurring extremes within the same regions.
• This study addresses the gap in identifying shared drivers of annual drought and flood flow changes.

Purpose of the Study:

• To analyze changes in drought and flood flow in common regions globally.
• To identify the dominant drivers of these co-occurring hydrological extremes.
• To provide insights for developing targeted adaptive strategies.

Main Methods:

• Analysis of drought and flood flow data from 9,531 global hydrological stations (1980-2014).
• Identification of simultaneous changes in drought and flood flow within the same regions.
• Attribution of dominant drivers (anthropogenic vs. climatic) to observed hydrological changes.

Main Results:

• A majority of global regions show simultaneous increases (28.14%) or decreases (33.36%) in both drought and flood flow.
• Anthropogenic activities (water withdrawal, vegetation changes) are key drivers in regions like Alaska, Central America, the Amazon, and Northern/Central Europe.
• Climatic factors (atmospheric water balance, seasonal variability) predominantly influence regions in the Southern Hemisphere.

Conclusions:

• Hydrological extremes often co-occur, driven by either anthropogenic or climatic factors depending on the region.
• Identifying these common drivers is essential for effective, region-specific adaptive strategies.
• The findings offer critical insights for mitigating the impacts of concurrent floods and droughts globally.