India fears the Chinese mega-dam in Tibet could reduce water flows on a major river by up to 85% during the dry season, according to sources and a government analysis seen by Reuters. This has prompted India to fast-track its own dam projects to mitigate potential effects. Since the early 2000s, India has considered controlling water flow from Tibet’s Angsi Glacier, which supplies over 100 million people downstream in China, India, and Bangladesh. However, resistance from residents of Arunachal Pradesh, fearing submersion and loss of their way of life, has impeded progress.
In December, China announced its intention to build the world’s largest hydropower dam in a border county upstream of the Yarlung Zangbo River before it enters India. The move has sparked concerns in New Delhi that Beijing could leverage control over the river for strategic advantage. Known as the Siang and Brahmaputra in India, the river originates from the Angsi Glacier. Additionally, India’s leading hydropower firm has already protected survey materials with police near a potential site for the Upper Siang Dam, which could be the largest in the country if built.
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Senior officials have discussed accelerating construction plans, including a July meeting organized by Prime Minister Narendra Modi’s office. A leaked analysis from the Indian government, confirmed by sources, estimates that the Chinese dam might divert as much as 40 billion cubic meters of water each year, which accounts for over a third of the water at a crucial border point. This impact would be particularly severe in non-monsoon months when water is scarce.
India plans to build its own dam to store water and release it during dry periods, potentially reducing water shortages for cities like Guwahati by 11%. The Indian dam could also help mitigate flooding from Chinese releases. At minimum drawdown levels, the dam could absorb excess water from breaches.
