China’s New Mega-Dam in Tibet Could Spark Water War with India

The Yarlung Tsangpo River, known as the Siang in Arunachal Pradesh and Brahmaputra in Assam, flows through Bangladesh. China has begun constructing the world’s largest hydropower dam in Tibet, raising concerns in India that it could reduce water flow in a major river by up to 85% during the dry season. According to four sources familiar with the matter and an Indian government analysis reported by Reuters, India is fast-tracking plans for its own dam to mitigate the adverse effects of China’s project.

Since the early 2000s, the Indian government has considered projects to control water flow from Tibet’s Angsi Glacier, which sustains over 100 million people in China, India, and Bangladesh. However, these plans have faced strong resistance, sometimes violent, from residents of Arunachal Pradesh, who fear their villages will be submerged and their way of life destroyed.

In December 2024, China announced plans to build the world’s largest hydropower dam in a border region where the Yarlung Tsangpo River enters India, triggering significant concern in New Delhi. China, India’s long-standing strategic rival, claims parts of Arunachal Pradesh as its own, raising fears that Beijing could weaponize control over the river, which originates at the Angsi Glacier and flows as the Siang and Brahmaputra through India and Bangladesh. In May, India’s largest hydropower company, NHPC, moved survey materials under armed police protection to the prospective site of the Upper Siang Multipurpose Storage Dam, which, if completed, would be India’s largest dam. Two sources, speaking anonymously due to the sensitivity of the matter, revealed that senior Indian officials have been holding meetings to accelerate construction, including one organized by Prime Minister Narendra Modi’s office in July. An Indian government analysis highlights concerns about the Chinese dam’s impact. Although Beijing has not released detailed construction plans, India estimates the project, which began in July and costs nearly $170 billion, could divert up to 40 billion cubic meters of water annually—over a third of the water received at a key border point. The impact would be most severe during the dry season, potentially reducing water supply to Guwahati, a major regional city reliant on water-intensive industries and farming, by 25%. The Upper Siang project, with a storage capacity of 14 billion cubic meters, could reduce this shortfall to 11% by releasing water during dry periods.

The Upper Siang dam is also designed to counter sudden water releases from China, mitigating flood risks. India is considering keeping 30% of its dam empty to absorb unexpected surges.

China’s Foreign Ministry spokesperson claimed the hydropower project has undergone rigorous safety and environmental assessments and will not harm downstream water resources, ecology, or geology. However, India’s Prime Minister’s Office and relevant ministries did not respond to inquiries. India’s Foreign Ministry noted that External Affairs Minister S. Jaishankar raised concerns about the dam during a meeting with his Chinese counterpart on August 18.

In May, when NHPC moved survey materials to Parong village in Arunachal, angry locals, primarily from the Adi community, damaged equipment, vandalized a nearby bridge, and looted police tents. These communities rely on farming paddy, oranges, and limes. Meanwhile, Pakistan, a Chinese ally, has accused India of weaponizing water by suspending the 1960 Indus Waters Treaty and considering diverting another river’s flow, a move Delhi defends despite an international tribunal’s ruling. **Development or Destruction?** At least 16 villages could be submerged by the Upper Siang dam, directly affecting around 10,000 people, with community leaders estimating over 100,000 could be impacted. Odoni Palo Pabin, a grocer from Parong, said, “We grow paddy, cardamom, jackfruit, and pears to support our families and educate our children. We will fight this dam to the death.” Arunachal’s Chief Minister, aligned with Modi’s BJP, called China’s dam an “existential threat,” emphasizing the Upper Siang project’s role in ensuring water security and flood control. The state government plans to discuss compensation for affected families. India’s history of activism against large dams suggests the Upper Siang project could face years of delays or downsizing. Even if approved, construction could take a decade, likely after China’s dam begins generating power in the early-to-mid 2030s.

Experts warn that building large dams in seismically active Tibet and Arunachal could pose significant risks. Sayanangshu Modak, a researcher at the University of Arizona, said, “China’s dam is being built in a seismically active area prone to extreme weather events, raising risks of landslides, glacial outbursts, or mudslides. India’s concerns about dam safety are entirely valid, and both countries should engage in dialogue.”