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

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 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 3.2 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, the Middle East, and around the Caspian Sea. Analysis by climatic region showed that the most pronounced groundwater declines occurred in arid and semi-arid areas with an aridity index between 0.1 and 0.5, highlighting regions with sparse vegetation and fragile ecosystems. In terms of climate change, compared to precipitation, meteorological drought and wetness are the primary climatic factors influencing the distribution of groundwater storage. Groundwater depletion is primarily caused by unsustainable extraction, especially for irrigation. 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.