PARONG: India fears a planned Chinese mega-dam in Tibet will slash water flows on a major shared river by up to 85 per cent during the dry season, according to four sources and a government analysis, prompting New Delhi to fast-track plans for its own massive dam to mitigate the effects.
The concerns were described in an undated Indian government analysis of the Chinese dam’s impact, the specifics of which Reuters corroborated with four sources and is reporting for the first time.
In December, China announced it would build the world’s largest hydropower dam in a border county just before the Yarlung Zangbo river, which originates in Tibet’s Angsi Glacier, crosses into India.
That triggered fears in New Delhi that its longtime strategic rival could weaponise its control of the river, known as the Siang and Brahmaputra in India.
New Delhi says Beijing’s plans may cut water flow by 85pc in dry season
New Delhi estimates the Chinese dam, which broke ground in July and will cost nearly $170 billion, will allow Beijing to divert as much as 40 billion cubic meters of water, or just over a third of what is received annually at a key border point, according to the sources and the document.
The impact would be especially acute in the non-monsoon months, when temperatures rise and lands become barren across swaths of India.
For example, the major regional city of Guwahati, which is dependent on water-intensive industry and farming, would see a 25pc reduction in supply, the analysis shows.
In response, senior Indian officials have been holding meetings to accelerate construction of the Upper Siang Multipurpose Storage Dam this year, including one organised in July by Prime Minister Narendra Modi’s office, according to two of the sources, who spoke on condition of anonymity to discuss sensitive government matters.
India’s largest hydropower company in May moved survey materials under armed police protection near a prospective site for the project, which would be the country’s biggest dam, if completed.
A spokesperson for China’s foreign ministry said the hydropower projects “have undergone rigorous scientific research on safety and environmental protection, and will not adversely impact the water resources, ecology, or geology of downstream countries”.
Modi’s office and the Indian ministries responsible for water and external affairs did not respond to Reuters’ questions. State-owned hydropower major NHPC also did not return a request for comment.
The proposed Upper Siang project in India would alleviate the impact of China’s dam with its projected 14 billion cubic meters of storage capacity, allowing India to release water during the dry season.
This would reduce the impact on Guwahati to an 11pc reduction in supply, according to the document and sources.
The Indian project could also mitigate any move by Beijing to release devastating torrents of water.
According to the document, the Indian dam would be able to fully absorb any excess water released from a breach in Chinese infrastructure. India is considering a proposal to keep 30pc of its dam empty at any time to account for such surges, two of the sources said.
India’s foreign ministry has said that top diplomat S. Jaishankar raised concerns about the dam during a meeting with his Chinese counterpart on Aug 18.
Meanwhile, India has itself been accused by Pakistan of weaponising water.
Delhi this year suspended its participation in a 1960 water treaty with Islamabad and may divert flows from another key river from its downstream neighbour. An international tribunal ruled India must follow the agreement, but Delhi claims the panel has no jurisdiction.
Published in Dawn, August 26th, 2025
