Impacts of climate change and human activities on global groundwater storage from 2003 to 2022

• GRACE and ERA5 data reveal significant global groundwater storage changes from 2003 to 2022. • Around 81% of global regions showed significant groundwater storage variability. • Over 3.4 billion people are affected by groundwater declines in the past 20 years. • Unsustainable groundwater extraction for irrigation is a key driver of depletion trends. Groundwater is integral to land surface processes, significantly influencing water and energy cycles, and it is an important resource for drinking water and ecosystems. Climate change and anthropogenic impacts have an ever-increasing influence on the water cycle and groundwater storage in recent decades. This study leverages GRACE and ERA5-Land data to analyze groundwater storage variability from 2003 to 2022, with a 1° spatial resolution. Approximately 81 % of global regions have shown significant groundwater storage changes, with 48 % experiencing declines and 52 % observing increases. Approximately 3.4 billion people live in regions where groundwater has significantly declined over the past 20 years. Findings indicate considerable global groundwater changes, with depletion hotspots (>20 mm/year) in northern India, the North China Plain, eastern Brazil, and around the Caspian Sea. Standardised Precipitation-Evapotranspiration Index (SPEI) trends exhibit a stronger influence on groundwater storage change than precipitation trends, highlighting the critical role of evapotranspiration. Groundwater depletion is driven primarily by agricultural irrigation and over-abstraction, with population density playing a relatively smaller role. GRACE data facilitates global monitoring, underscoring the need for long-term dynamic observation to inform sustainable groundwater management policies crucial for regions facing groundwater depletion to ensure long-term freshwater resource sustainability.