Chinese dam near India border a ticking geological bomb, finds Beijing-backed study

A study by geologists affiliated with China's state-run geological survey has found that the under-construction Medog Hydropower Station on the Brahmaputra River in Tibet sits atop an active fault line, raising fresh concerns over the structural safety of what is set to become the world's largest hydropower project. The dam is just 50 km from China's border with Arunachal Pradesh.

The dam in Medog county had come to light over a debate about whether Beijing could control the Brahmaputra's flow into India. That came after India suspended the Indus Waters Treaty with Pakistan. Beijing and Islamabad claim their ties to be an "iron-clad, all-weather friendship".

According to a report by the South China Morning Post (SCMP), citing a paper published in Mandarin in the journal Sedimentary Geology and Tethyan Geology under the supervision of the state-owned China Geological Survey, researchers identified the active Paizhen Fault directly beneath the Medog dam site on the Yarlung Tsangpo, the name by which the Brahmaputra is known in Tibet.

The study, which was conducted by geologists from the Chengdu University of Technology, the Civil-Military Integration Centre of the China Geological Survey, and the Middle Yarlung Zangbo River Natural Resources Observation and Research Station, has warned that this fault could significantly undermine the structural stability of the mega-dam.

WHAT IS THE MEDOG DAM CHINA IS BUILDING CLOSE TO INDIA?

The Medog Hydropower Station is a planned 60,000-megawatt run-of-the-river hydroelectric project on the Yarlung Tsangpo river (the Brahmaputra in India) in Tibet's Medog County.

Originating in the Angsi Glacier in western Tibet, the Yarlung Tsangpo travels 1,625 km in the China-controlled territory of Tibet and enters India after the Great Bend near the Namcha Barwa peak. Then, as the Brahmaputra, it flows for 918 km within India and another 337 km in Bangladesh, where it is called Jamuna, and empties into the Bay of Bengal.

With an estimated cost of more than 1 trillion yuan (about $137 billion), it is set to become the world's largest hydropower facility, producing around 300 billion kilowatt-hours of electricity annually—roughly three times the output of the Three Gorges Dam. Approved by China in December 2024, construction began in July 2025, with commercial operations targeted for 2033.

But if the Chinese state-affiliated researchers are to be believed, this gigantic dam is being built on what is, for all intents and purposes, a geological time bomb.

WHAT IS THE PAIZHEN FAULT THAT THREATENS MEDOG DAM?

According to the SCMP report, the researchers said the Paizhen Fault, which has remained active since the Pleistocene epoch—the geological period that began about 2.6 million years ago and included the Ice Age—poses a significant risk to the mega-dam because it continues to show signs of tectonic activity.

"The Paizhen Fault, which has been highly active since the Pleistocene, will have a major impact on the structural stability and construction of nearby structures, including dams, roads, bridges and tunnels, as well as the reservoir area," they wrote, warning that future fault movement could compromise the safety of the project.

Researchers also noted that the Pai village area, where the Medog dam is being built, lies within one of China's most earthquake-prone regions. Ancient lake sediments indicate the fault was active as recently as 9,500 years ago, while the magnitude 6.9 earthquake that struck Tibet in 2017 at the northern end of the fault provided further evidence of its continuing seismic potential.

The study said repeated movement along the fault has already damaged the underlying geology. "This makes the foundation bearing capacity and structural stability of nearby engineering projects more susceptible to damage," the researchers wrote, explaining that the fault has fractured surrounding rocks and weakened their mechanical properties.

In practical terms, this means the ground beneath the project is less capable of supporting the immense weight of a 60,000-megawatt dam and its water reservoir and could be more vulnerable during earthquakes or other seismic events.

RESERVOIR OF MEDOG DAM COULD TRIGGER LANDSLIDES, SLOPE COLLAPSES

The team also warned that the terrain surrounding the reservoir consists of unstable material with a "loose structure and weak cohesion". They said that once the reservoir is filled, prolonged water saturation, combined with fault activity and earthquakes, could "extremely easily" trigger landslides and slope collapses.

"Under regional seismic action, landslides and collapses can easily be induced, threatening the safety of engineering facilities and personnel," they wrote, adding that "structural stability safeguards must be strengthened" through measures such as slope reinforcement and retaining barriers during both construction and operation.

The findings come as India and Bangladesh continue to monitor the project's downstream implications. While the dam has sparked fears that China could manipulate water flows, hydrologists say the greater concern is the geological risk posed by the location rather than Beijing's ability to cut off the river.

"Any attempt to divert the flow would be counterproductive as it would result in upstream floods because of sediment accumulation," economist and water expert Nilanjan Ghosh of the Observer Research Foundation told India Today Digital. He added that China cannot simply “turn off the tap” because the Yarlung Tsangpo contributes only around 10–15% of the Brahmaputra's total flow, with the river gaining most of its volume from tributaries and monsoon rainfall after entering India.

That said, with a Beijing-backed study itself warning that the world's largest dam is being built atop an active fault line in one of the Himalayas' most earthquake-prone regions, perhaps the more pressing question is not whether China can stop the Brahmaputra's flow, but what the consequences would be if a massive dam—and the enormous reservoir behind it—were to fail.

- Ends