Underground water tends to stay out of view. It moves slowly, often unnoticed, and is rarely part of public conversation. Yet beneath the Himalayas and the Tibetan Plateau, it plays a steady role in supporting life far beyond the mountains.

A study, “Assessing groundwater sustainability across high mountain Asia using remote sensing”, looks at how this hidden water has been changing over the past two decades. The researchers draw on satellite observations, climate models, and artificial intelligence. Rather than tracking dramatic events, it follows quieter shifts beneath the surface. Over time, those shifts begin to add up.

What emerges is not a sudden collapse, but a gradual thinning. Across much of the region, groundwater appears to be declining, shaped by long term climate pressure and continued use, with effects that travel well beyond the highlands.

Groundwater storage declined across most of Asian mountains from 2003 to 2020

High Mountain Asia does not behave like a single system. Water moves through snow, ice, soil and rock at different speeds. Some of it appears quickly in rivers. Some of it lingers underground for years.

The study suggests that this balance has been changing since the early 2000s. From 2003 onwards, groundwater levels fell across roughly two thirds of the region. The pattern is uneven. Losses are more pronounced in lower elevation basins, especially where farming depends heavily on pumping.

In these areas, groundwater increasingly compensates for rainfall that arrives late, falls unevenly, or does not come at all.

Satellite data reveals steady groundwater loss

Direct measurements underground are sparse. To fill the gaps, the researchers turned to satellites that detect subtle changes in Earth’s gravity. These shifts reflect changes in how much water is stored below the surface.

The satellite signals were combined with climate modelling and machine learning to separate natural variability from human influence. The results point to an average loss of around 24 billion tonnes of groundwater each year.

In parts of the Ganges Brahmaputra and Indus basins, most monitored wells show declining levels. These are also places with dense populations and intensive irrigation, where demand rarely pauses.

Climate pressure and human use combine

There is no one factor that causes the drop. Climate change is one of the factors as it causes higher temperatures and changed rainfall patterns. Weather changes are less predictable when it is wet, while evaporation is getting higher in the warmer atmosphere.

On the other hand, ice melting and the thawing of frozen ground are giving off more water, which may even locally slow down the drop in groundwater until about the 2060s. adds short, term supply but also signals long, term change in the system itself. The overuse of water by humans is another reason for the problem.

In most areas, pumping out water is being done at a rate that is higher than the ability of the natural environment to replenish the water.Eventually, a great deal of people cannot look away from the problem of the water deficit.

Glacier melt offers limited relief

For now, melting ice can appear to ease pressure. Extra water reaches rivers and, in some cases, seeps underground. The study suggests this may slow groundwater decline in certain regions until around the 2060s.

That contribution fades as glaciers retreat. Once ice reserves shrink, the additional flow diminishes. Where demand remains high, groundwater losses are expected to accelerate again.

Future risks grow after mid-century

Looking ahead, the picture is mixed. Some high and remote areas may continue to gain water for a while. Many populated basins are projected to face increasing stress.

Groundwater often acts as a quiet reserve during dry years. When it is depleted, recovery can take decades, sometimes longer. The study does not offer sharp warnings, but it leaves a sense of narrowing margins. What happens next depends less on any single trend than on how pressures continue to accumulate.

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