The research was led by Prof. Shudong Wang of the Aerospace Information Research Institute of the Chinese Academy of Sciences (AIRCAS). The team sought to overcome two major obstacles to understanding groundwater in the region: limited on-the-ground data and the extremely complex mountainous landscape. The findings were recently published in Environmental Research Letters.

AI and Satellites Reveal Two Decades of Change

To build a clearer picture of what is happening underground, the researchers created an artificial intelligence (AI) powered assessment model that combines observations from multiple satellites, Earth system modeling, and explainable AI.

Using this approach, they reconstructed about 20 years of groundwater storage (GWS) changes across High Mountain Asia. The system also helped identify the main forces driving those changes and allowed the researchers to explore how groundwater risks could develop under future scenarios.

The results show that roughly two-thirds of HMA experienced declining groundwater storage between 2003 and 2020. The largest losses occurred in heavily populated downstream basins where irrigation demands are high, including the Ganges-Brahmaputra, Indus and Amu Darya basins. Some inland areas at higher elevations, however, experienced localized increases in groundwater storage.

Climate and Human Water Use Drive the Decline

Climate-related forces explain nearly half of the observed variation in GWS, with changes involving the cryosphere playing an especially important role.

At the same time, human withdrawals of groundwater have become an increasingly significant source of depletion, particularly in downstream agricultural regions that rely heavily on irrigation. The influence of human water use became even more pronounced after 2010.

Researchers also project that groundwater losses will continue if current patterns of water use remain in place. In some locations, increased glacier melt could temporarily reduce the pace of groundwater decline around the 2060s. But this “buffer effect” cannot continue indefinitely and is expected to be followed by faster losses.

If present water use patterns do not change, groundwater depletion could accelerate further, increasing the threat to agricultural areas downstream that depend on these reserves.

A New Way to Track Groundwater in Mountain Regions

For the analysis, the researchers used a framework guided by existing scientific knowledge while also drawing on large amounts of observational data. Information from multiple satellite sensors was used to estimate GWS changes over the past 20 years.

The framework incorporates a lightweight Transformer architecture designed to account for hydrological memory and delayed effects within mountainous catchments. The researchers also used explainable machine learning methods to determine the physical factors associated with the groundwater changes identified by the system.

To test the reliability of the results, the team compared its findings with thousands of measurements from groundwater wells as well as independent datasets. Those comparisons provided additional support for the study’s conclusions.

By combining remote sensing observations, established hydrological knowledge, and interpretable AI methods, the framework helps address long-standing difficulties in studying High Mountain Asia, including rugged terrain and incomplete information about human water use.

The research was funded by the National Key R&D Program of China and the Key Program of the National Natural Science Foundation of China (NSFC).

During a total solar eclipse, the Moon completely blocks the bright disk of the Sun, making the much fainter solar corona visible. The corona is the Sun’s extremely hot outer atmosphere, and during most eclipses it appears white or silvery. Some people watching last week’s eclipse did see this familiar pearly color. In Spain, however, observers were treated to something different. The corona took on an unusually rich golden hue.

Why the Eclipse Looked Golden

The timing of the eclipse played an important role. In Spain, totality occurred while the setting Sun was already close to the horizon. When the Sun sits that low in the sky, its light must travel through much more of Earth’s atmosphere before reaching an observer.

Along that longer path, molecules in the air scatter shorter wavelengths of visible light, especially blue. This is the same basic process that helps make sunsets appear orange and red. With more blue light removed, the warmer colors that remain become much more noticeable.

Conditions that day added another layer to the effect. An unusually large amount of smoke in the air from nearby forest fires acted like an additional atmospheric filter. Smoke particles scattered even more of the remaining blue wavelengths, intensifying the golden tones in the visible light surrounding the eclipsed Sun.

A Pink Solar Prominence Stood Out

The remarkable featured image was created using multiple exposures and HDR processing. HDR, or high dynamic range imaging, combines exposures with different brightness levels so that both very bright and very faint details can be preserved in a single image. The photograph was captured last week from Benavente, Spain.

Not everything around the Sun was transformed into gold. A large prominence remained visible along the Sun’s left edge. Solar prominences are enormous structures of glowing plasma that extend outward from the Sun’s surface and are often shaped by powerful magnetic fields.

This prominence emitted strongly in light associated with hydrogen, allowing its original bright pink color to survive despite the atmospheric filtering. Against the unusually golden corona, the vivid pink structure made an already rare eclipse scene even more striking.