Asia's 'Water Tower' Is Losing 24 Billion Tonnes of Groundwater a Year, Satellite Study Finds

Groundwater beneath High Mountain Asia -- the vast, glacier- and snow-fed mountain region often called the 'Asian Water Tower' -- is being depleted at an alarming pace, according to a new satellite-based study. The region supplies water to farming, cities and ecosystems across more than a dozen downstream countries, and researchers estimate its groundwater storage is now declining by about 24.2 billion tonnes a year.

The study, led by Prof. Shudong Wang of the Aerospace Information Research Institute of the Chinese Academy of Sciences (AIRCAS) and published in Environmental Research Letters, tackled two long-standing obstacles to understanding the region's groundwater: sparse on-the-ground measurements and extremely complex mountain terrain. To get around them, the researchers built an artificial intelligence (AI) powered assessment model that combines data from multiple satellites, Earth system modeling and explainable AI to reconstruct about 20 years of groundwater storage changes.

The results show that roughly two-thirds of High Mountain Asia saw declining groundwater storage between 2003 and 2020, with the largest losses in heavily populated downstream basins with high irrigation demand, including the Ganges-Brahmaputra, Indus and Amu Darya basins. Some inland areas at higher elevations saw localized increases instead. Climate-related factors, especially changes in the cryosphere -- the planet's frozen water in ice and snow -- explained nearly half of the variation, while human groundwater withdrawals, particularly for irrigation, have become an increasingly important driver since 2010.

The researchers project that if current water-use patterns continue, groundwater losses will keep accelerating; increased glacier melt could temporarily slow the decline around the 2060s, but that buffering effect cannot continue indefinitely and would be followed by faster losses.