Asian Water Tower Losing 24 Billion Tonnes of Groundwater Annually

The High Mountain Asia region, known as the “Asian Water Tower,” is losing approximately 24.2 billion tonnes of groundwater each year. This finding comes from a new satellite-based study. The region supplies water to more than a dozen downstream countries. This water supports agriculture, urban areas, and ecosystems for hundreds of millions of people.

Researchers at the Aerospace Information Research Institute of the Chinese Academy of Sciences (AIRCAS) led the study. They developed an artificial intelligence (AI) model to analyze groundwater changes. This model combined satellite observations, Earth system modeling, and explainable AI. The goal was to overcome limited ground data and complex mountainous terrain.

The AI model reconstructed two decades of groundwater storage changes across High Mountain Asia. It identified the main drivers of these changes. The study found that about two-thirds of the region experienced declining groundwater storage between 2003 and 2020. The most significant losses occurred in densely populated agricultural basins. These include the Ganges-Brahmaputra, Indus, and Amu Darya basins. Some higher-elevation inland areas showed localized increases in groundwater storage.

Climate-related factors account for nearly half of the observed groundwater storage variation. Changes in the cryosphere, which includes glaciers and ice caps, play a crucial role. Human groundwater withdrawals are also a significant cause of depletion. This is especially true in downstream agricultural regions that rely on irrigation. The impact of human water use became more pronounced after 2010.

Researchers project that groundwater losses will continue if current water use patterns persist. Increased glacier melt might temporarily slow the decline around the 2060s. This “buffer effect” is not sustainable. It is expected to be followed by accelerated losses. Continued groundwater depletion threatens agricultural areas downstream that depend on these reserves.

The research combined remote sensing, hydrological knowledge, and interpretable AI. This approach addresses challenges in studying High Mountain Asia. The findings were validated against thousands of groundwater well measurements and independent datasets. The National Key R&D Program of China and the National Natural Science Foundation of China (NSFC) funded this research.