China Begins Building World's Largest Dam, India Plans Counter In Arunachal Pradesh

China has officially begun construction of the world's largest hydroelectric dam on the lower reaches of the Yarlung Tsangpo river in Tibet, a mammoth project situated barely 50 kilometres from the  Arunachal Pradesh border.

In direct response to the Chinese dam, India is pushing forward with the Siang Upper Multipurpose Project (SUMP), an 11,000 MW hydroelectric and flood-control mega-dam proposed on the Siang river in Arunachal Pradesh's Upper Siang and Siang districts. Driven by state-run NHPC, SUMP would become India's largest hydropower project if built, generating an estimated 47 billion units of electricity annually at a projected cost of approximately US$13 billion (roughly Rs 1.5 lakh crore).

The comparison between the two projects starkly illustrates India's challenge. While China's 60,000 MW Medog Hydropower Project is already under active construction, SUMP remains firmly in pre-feasibility studies, with pre-construction work yet to commence. China's planned project is widely reported to far exceed SUMP's capacity.

India is now trying to accelerate its own strategic response while closely monitoring Beijing's every move on the contested river.

The Yarlung Tsangpo, which enters Indian territory as the Siang river before widening into the Brahmaputra, is a lifeline for millions across Arunachal Pradesh and Assam. Experts warn that a dam of this magnitude upstream could fundamentally alter water flows, devastate local ecosystems, cripple agriculture and unleash catastrophic and unpredictable flooding downstream.

In a formal written response to the Lok Sabha, the Centre confirmed it is "carefully monitoring all activities relating to the Brahmaputra river basin, including Chinese plans for hydropower exploitation," and pledged to implement necessary preventive and corrective measures to safeguard lives and livelihoods in downstream areas. New Delhi has also consistently pressed Beijing on transparency, data sharing, and prior consultation on all transborder river projects, demands that have so far yielded limited results.

Beyond power generation, SUMP is specifically designed to control seasonal flooding downstream and protect Indian territories from the risks posed by upstream diversions, a dual purpose that highlights its geopolitical significance as much as its economic value.

New Delhi is simultaneously strengthening flood forecasting systems, river monitoring networks and infrastructure resilience across the Northeast to manage risks in the interim.