Twice the size of three gorges: What 60,000 MW China's Tibet mega-dam means for Assam and Arunachal

The construction of a gigantic 60,000 megawatt (MW) hydroelectric dam project in Tibet by China has raised several security and environmental issues for India downstream. India plans the 11,200 MW Siang Upper Multipurpose Project (SUMP) in Arunachal Pradesh to defend against any water manipulation or flooding by Chinese authorities. This project can accommodate up to 9.2 billion cubic meters (bcm) of the river water.

China's $167B mega-dam on the Yarlung Tsangpo

Construction of the Yarlung Tsangpo mega-dam project started in the lower reaches of the river in Tibet on July 19, 2025, involving an expenditure of about 1.2 trillion yuan ($167.8 billion).

Capacity: The five stages of this dam project have a combined electricity generation capacity of 60,000 MW, which is more than twice the production capacity of the Three Gorges Dam.

Downstream impact: The Yarlung Tsangpo directly drains into India after changing its name to the Siang River and joins the Brahmaputra in Assam.

India's biggest fear: Water impoundment unilaterally by Beijing in drought months or release in huge volumes in monsoon months can create serious flooding threats for Northeast India.

Defence strategy of India: Siang upper multipurpose project

The Deputy Chief Minister of Arunachal Pradesh, Chowna Mein, stressed that the proposed Siang Storage Dam is specifically designed as a hydro-buffer against any disruption from upstream areas.

Storage capacity: The proposed 280- to 300-meter-high Siang Storage Dam would have the ability to store 9.2 billion cubic meters of water.

Regulating flow: The proposed reservoir project would help regulate the flow of water by storing excess flow coming from Tibet and releasing consistent flows during the winter season.

Delays in approval and local ecological Opposition

Despite being a crucial project for India, the Siang Dam project is at its initial stage and needs clearance before its execution.

The Chief Minister of Arunachal Pradesh, Pema Khandu, said that the Preliminary Feasibility Report (PFR) of the project will help determine if the selected location is geologically and ecologically feasible or not. Local indigenous tribes have expressed opposition to the plan by saying that they would be displaced and their ancestral lands and forests would be submerged.

Whether India's 9.2 bcm reservoir can fully neutralise a 60,000 MW mega-structure upstream depends on final engineering specs and actual operational protocols adopted by Beijing.