On a football pitch ringed by misty mountains, the air rang with fiery speeches as an Indigenous community protested against a planned mega-dam, India’s latest move in its contest with China over Himalayan water.

India says the proposed new structure could counteract China’s construction of a likely record-breaking dam upstream in Tibet by stockpiling water and guarding against the release of weaponised torrents.

But for those at one of the possible sites for what would be India’s largest dam, the project feels like a death sentence.

“We will fight till the end of time,” said Tapir Jamoh, a resident of the thatch-hut village of Riew, raising a bow loaded with a poison-tipped arrow in a gesture of defiance against the authorities. “We will not let a dam be built.”

Jamoh’s homeland of the Adi people lies in the far-flung northeastern corner of India, separated from Tibet and Myanmar by soaring, snowy peaks.

Proposed blueprints show India considering the site in Arunachal Pradesh for a massive storage reservoir, equal to four million Olympic-sized swimming pools, behind a 280-metre (918-foot) high dam.

The project comes as China presses ahead with the $167bn Yaxia project upstream of Riew on the river known in India as the Siang, and in Tibet as the Yarlung Tsangpo.

China’s plan includes five hydroelectric power stations that could produce three times more electricity than its vast Three Gorges dam, the world’s largest power station, though other details remain scant.

Beijing says it will have no “negative impact” downstream.

“China has never had, and will never have, any intention to use cross-border hydropower projects on rivers to harm the interests of downstream countries or coerce them,” the Chinese Ministry of Foreign Affairs told the AFP news agency.

The area around the village of Riew is one of the shortlisted sites for India’s response mega-dam, a project that people like Jamoh feel is the more immediate threat to them. “If the river is dammed, we also cease to exist,” said the 69-year-old Jamoh. “Because it is from the Siang that we draw our identity and culture,” he added.

Despite a thaw between New Delhi and Beijing, the two most populous nations have multiple areas of disputed border manned by tens of thousands of troops, and India has made no secret of its concerns. The river is a tributary of the mighty Brahmaputra, and Indian officials fear China could use its dam as a control tap to create deadly droughts or release a “water bomb” downstream.

China rejects that, saying “the hype surrounding the Yaxia Hydropower Project as a ‘water bomb’ is groundless and malicious”.

India’s dam could produce 11,200-11,600 megawatts of hydropower, making it the country’s most powerful and helping to scale back emissions from its coal-dependent electricity grid. The dam would create a giant reservoir of 9.2 billion cubic metres, but the exact area flooded depends on its final location.

The Adi people, like Jamoh, consider the river sacred and depend on its life-giving waters for their lush lands dotted with orange and jackfruit trees.

They fear the dam will drown their world. “We are children of the Siang,” said Jamoh, who was the former headman of Riew, before being forced to quit by local authorities for protesting against the dam.

The dam, residents are convinced, would drown dozens of villages. “If they build a huge dam, the Adi community will vanish from the map of the world,” said Likeng Libang, from Yingkiong, a town that even officials say is likely to be entirely underwater.

“The Adi will be totally displaced,” he added. “We will be nowhere.”

NHPC, India’s public hydroelectricity utility, did not respond to AFP’s requests for comment.

India’s “dam-for-dam” approach may be counterproductive, said Anamika Barua, a transboundary water governance expert at the Indian Institute of Technology Guwahati. “Diplomatic engagement, transparent water-sharing agreements, and investment in cooperative river basin management would yield more durable and equitable outcomes than reactive infrastructure building,” she said.

Building mega-dams in earthquake-prone Arunachal Pradesh is also risky, said Barua. But India’s construction drive of massive dams suggests it will not back down on this project. Two other big dams overcame local resistance.

“If the dam must be built, I hope I die before that day comes,” said bow-and-arrow-wielding Jamoh.