Explained: Why is China's largest dam in Tibet a potential ‘water bomb’ for India?

China is not a signatory to international water-sharing treaties and this limits India's ability to legally restrain Beijing from altering the flow.

China greenlit the construction of what is slated to be the world's largest hydropower project on the Yarlung Tsangpo River in Tibet last December, raising serious alarm bells across the Indian subcontinent. 

China has approved construction of the world’s largest hydropower dam on Tibet's Yarlung Tsangpo river — a project that has raised alarm in India over its potential downstream impact.(Representative image)

Officials have expressed apprehensions that the proposed dam would give Beijing significant power to regulate or even divert the flow of the trans-border river, which enters India through Arunachal Pradesh before flowing into Assam and Bangladesh.

In a recent interview with news agency PTI, Arunachal Pradesh chief minister Pema Khandu warned of the dangers posed by the project, saying, “It is going to cause an existential threat to our tribes and our livelihoods. It is quite serious because China could even use this as a sort of ‘water bomb’.”

Dubbed the Great Bend Dam, the 60,000 MW dam will have a power capacity three times that of the massive Three Gorges Dam, also in China.

Why Chinese dam could be a ‘water bomb’ for India

The Yarlung Tsangpo is not just a Tibetan river; as it crosses into India, it becomes the Siang in Arunachal Pradesh, and further downstream in Assam, it merges with tributaries such as the Dibang and Lohit to become the Brahmaputra—a river lifeline for millions in India and Bangladesh.

An infrastructure project of this scale in the ecologically fragile Himalayan zone poses multidimensional threats. Indian officials and regional stakeholders fear environmental degradation and a strategic vulnerability that could allow China to manipulate water flow into India.

The potential for weaponising water is not new in geopolitical strategy. A 2020 report by the Lowy Institute, an Australian think tank, warned that Chinese control over rivers originating in Tibet could give it a powerful hold over India’s economy and agriculture.

“If the dam is completed, our Siang and Brahmaputra rivers could dry up considerably,” Arunachal CM flagged.

The concern here is not hypothetical. China is not a signatory to international water-sharing treaties. This limits India's ability to legally restrain Beijing from altering the flow of the transboundary river.

Khandu said if China had been a signatory to such agreements, the project might have been beneficial for India.

“Suppose the dam is built and they suddenly release water, our entire Siang belt would be destroyed. In particular, the Adi tribe and similar groups... would see all their property, land, and especially human life, suffer devastating effects,” he explained.

What is India’s counterplan?

In response, India has initiated steps to secure its own water security through the Siang Upper Multipurpose Project—a proposed 10 GW hydropower plant in Arunachal Pradesh, said Prema Khandu. This dam will act both as a power generator and a strategic buffer.

He added that the decision came after extensive consultations with the central government. “The Arunachal Pradesh government has conceived a project called the Siang Upper Multipurpose Project, which will serve as a defence mechanism and ensure water security,” he said.

Though China has not shared any official updates, Khandu believes construction may already be underway. India’s own project could help regulate water availability and act as a safeguard during potential floods induced by China’s dam. “In the future, if China releases water, there will definitely be flooding, but it can be controlled,” he added.

Recognising that the dam’s impact will be most felt by indigenous and local populations, the Arunachal Pradesh government is involving tribal communities in its planning. “I am going to arrange a meeting very soon to raise further awareness about this issue,” said Khandu, referring to consultations with the Adi tribes and others along the Siang River.

He also emphasised that India cannot afford to remain passive. “Who will make China understand? Since we cannot make China see reason, we should focus on our defence mechanisms and preparations. That is what we are fully engaged in at the moment.”

Environmental and geological red flags

Despite assurances from Chinese authorities that the dam would not cause major environmental damage, there is little clarity on the actual impact, especially with regard to community displacement and ecological disruption. For reference, China relocated around 1.3 million people over the 17 years it took to complete the Three Gorges Dam project.

A report by news agency ANI suggested that the Great Bend Dam would require extensive tunnelling—up to 420 km—through the Namcha Barwa mountain range to divert the river’s flow. This region lies on an earthquake-prone tectonic boundary, which adds to the project's risks. 

Chinese experts themselves have raised alarms over potential landslides and tremors. BBC quoted one senior engineer from the Sichuan provincial geological bureau in 2022: “Earthquake-induced landslides and mud-rock flows are often uncontrollable and will also pose a huge threat to the project.”

This hydropower megaproject, with a projected cost of $127 billion, is being framed by Beijing as part of its push for carbon neutrality by 2060. However, for India, the stakes go far beyond clean energy.