Tsering Dhundup
DHARAMSHALA, Aug 27: India has raised alarm over China’s planned construction of the world’s largest hydropower dam in Tibet, warning that the project could reduce water flows of the Brahmaputra River by as much as 85% during the dry season, according to a government analysis and four sources familiar with the matter. The findings, corroborated by Reuters, have prompted New Delhi to fast-track its own mega-dam in Arunachal Pradesh as a strategic countermeasure.
The concerns, laid out in a confidential government report, mark the first time the potential scale of impact from Beijing’s project has been revealed. In December, China announced plans for the $170 billion hydropower dam in Medog County, Tibet, on the Yarlung Tsangpo just before it enters India as the Siang and later becomes the Brahmaputra. Work reportedly began in July.
According to Indian estimates, the Chinese dam could divert up to 40 billion cubic metres of water annually—nearly one-third of the river’s natural flow at a key border point. The impact would be most severe in the non-monsoon months, with the regional hub of Guwahati projected to face a 25% decline in water supply.
Officials fear Beijing could “weaponise” control over the transboundary river, which supports agriculture, industry, and millions of livelihoods across India’s northeast. Indian External Affairs Minister S. Jaishankar reportedly raised the issue with his Chinese counterpart Wang Yi during their August 18 meeting.
Beijing has dismissed New Delhi’s fears, with a foreign ministry spokesperson insisting the project “has undergone rigorous scientific research” and “will not adversely impact” downstream countries.
In response, Prime Minister Narendra Modi’s office convened high-level meetings in July to accelerate work on the proposed Upper Siang Multipurpose Storage Dam. Surveying began under heavy security in May, reflecting the project’s strategic importance.
If completed, the dam would be India’s largest, with a storage capacity of 14 billion cubic metres. It is designed to release water during the dry season to offset shortages while also serving as a safeguard against sudden floods from Chinese infrastructure upstream. Plans under review propose maintaining the reservoir at 70% capacity to absorb potential surges.
However, India’s counter-dam faces strong resistance at home. When NHPC surveyors arrived in Arunachal Pradesh’s Parong village in May, local Adi villagers destroyed equipment, looted police camps, and blocked access roads.
The project could submerge at least 16 villages, directly affecting around 10,000 people and impacting over 100,000 in total. Despite the opposition, the state government, led by Modi’s party, has declared the dam essential for “water security and flood moderation”.
Authorities are negotiating compensation packages, with plans to spend more than $3 million on education and emergency infrastructure. Some villages have recently allowed NHPC to resume preliminary work.
Experts caution that both Chinese and Indian dams in the region carry serious risks. “The Chinese dam is being built in a zone of high seismicity and extreme weather events,” said Sayanangshu Modak, a scholar of India-China water relations at the University of Arizona. “Such conditions can trigger landslides, mudslides, or glacial lake outburst flooding. It’s a legitimate safety concern that requires dialogue.”
The Brahmaputra, Tibet’s longest river, sustains millions across Tibet, India, and Bangladesh. Already under pressure from climate change and melting Himalayan glaciers, the river has become the latest flashpoint in tense Sino-Indian relations.
While China aims to generate power from its project by the early-to-mid 2030s, India’s Upper Siang dam is still years away from construction. Experts warn that this timeline gap could leave India vulnerable to sudden water releases from upstream, compounding the risk for downstream communities.
The Colorado river does not reach the Sea of Cortez. That is another transnational river.