China's plan to build world's biggest dam on Brahmaputra near Arunachal Pradesh hits an 'Ice Age fault': Report

Beijing's own scientists have flagged that the site of its record-breaking hydropower project on the Yarlung Tsangpo sits directly on a fault line that has been shifting since the Ice Age, a disclosure that adds a fresh dimension to India's long-running concerns over the dam.

China is pressing ahead with construction of what will be the largest hydropower project on Earth, built on the Yarlung Tsangpo in Tibet, the river that becomes the Brahmaputra once it crosses into Arunachal Pradesh and flows on through Assam and into Bangladesh. But a new report has surfaced an uncomfortable detail buried in the project's own backyard: geologists working under a Chinese state body have concluded that the dam is coming up right on top of an active fault.

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What the Report Says

According to the South China Morning Post, a study published last month in the Chinese-language journal Sedimentary Geology and Tethyan Geology, carried out with the backing of the state-run China Geological Survey, identifies the Paizhen Fault as running directly beneath the hydropower project's construction zone. The research was conducted jointly by scientists from Chengdu University of Technology, the Civil-Military Integration Centre of the China Geological Survey, and a river research station based in the middle stretch of the Yarlung Tsangpo.

The researchers describe the Paizhen Fault as having remained highly active since the Pleistocene epoch, more commonly known as the Ice Age, and say this activity is capable of undermining the structural stability of everything being built in the vicinity, the dam itself, along with roads, bridges, tunnels and the reservoir. Their central finding is that the fault has already fractured and weakened the surrounding rock, leaving the ground less able to bear the load of major engineering structures.

The terrain around the planned reservoir was also flagged as loosely structured and poorly bound together, a combination the scientists say sharply raises the odds of large-scale slope collapse once the area is submerged and exposed to prolonged water contact alongside ongoing seismic activity.

A Fault That Never Really Slept

Perhaps the most striking part of the study is its timeline. The researchers trace the fault's activity from the Early Pleistocene all the way through to the current Holocene epoch, with sediment evidence pointing to movement as recently as roughly 9,500 years ago, geologically speaking, almost yesterday. As a real-world reference point, the team cited the magnitude 6.9 earthquake that hit Milin in Tibet in 2017 as proof that the fault remains capable of generating destructive tremors.

The region itself sits within one of the most seismically restless stretches of the Himalayas, where the Indian and Eurasian tectonic plates are still grinding against each other. The study's authors argue that construction crews will need to significantly reinforce slopes and put up retaining structures to guard against landslides and collapse, both while building the dam and after it becomes operational.

Why This Matters for India

For India, this isn't just a technical footnote from a foreign construction site, it strikes at the heart of an issue New Delhi has been raising for years. The Brahmaputra is a lifeline for the Northeast, feeding agriculture, drinking water supplies, fisheries and hydropower generation, and sustaining the livelihoods of millions across Assam and Arunachal Pradesh before the river moves on into Bangladesh. Any structural failure, sudden water release, or long-term disruption at the dam site upstream could send shockwaves far beyond China's borders.

New Delhi has consistently pushed for greater transparency from Beijing on the project, along with proper consultation as a downstream and co-riparian state, citing worries about water security and ecological damage. China has so far maintained that the dam's purpose is purely power generation. But the fact that its own state-backed researchers are now on record warning about active fault lines beneath the site gives India's demands for openness a harder scientific edge to stand on.

The Scale of the Project

To put the ambition of the project in perspective, the dam is expected to generate around 300 billion kilowatt-hours of electricity every year,roughly three times the output of the Three Gorges Dam, currently the world's largest. Construction officially got underway last year, and the project has already positioned itself as one of the most geopolitically sensitive infrastructure builds in Asia, given its location on a river that three countries depend on.