Explained: China's mega dam on Brahmaputra and India's downstream risks

China has begun building a massive dam on Yarlung Zangbo near Arunachal Pradesh, raising strategic concerns for India as Beijing eyes economic and energy gains

China has reportedly begun constructing what it is calling the world’s largest hydropower project on the Yarlung Zangbo River in Tibet, just across the Line of Actual Control from Arunachal Pradesh. Situated in Medog (Metok) County and near Mainling/Nyingchi, the dam will be a series of five cascade hydroelectric stations, collectively known as the Medog or Yarlung Tsangpo mega-dam.

 

When completed, which is projected for the 2030s, it will connect to China's power grid as the river flows south to Arunachal Pradesh and through India and Bangladesh as the Brahmaputra.

 

Why is China building a dam near Arunachal Pradesh?

 

The Chinese government describes the project as an integral part of its clean energy and climate objectives. The project is incorporated in China's 14th Five-Year Plan and long-term development plans up to 2035. The dam project aims to produce electricity, which would be equivalent to the entire United Kingdom's needs in one year, according to the Reuters report. Beyond renewable energy targets, the project may also serve flood-control functions and act as a stimulus for domestic investment, infrastructure growth, and jobs.

 

 

What will be the benefits for China?

 

The expected scale of power generation is massive. The combined annual output is projected at 300 billion kWh, far surpassing the Three Gorges Dam, and covering roughly the yearly electricity consumption of the UK.

 

With an estimated cost between $167 billion and $170 billion (1.2 trillion yuan), the project is expected to boost Chinese construction, equipment, and bond markets. Furthermore, the project is expected to contribute to China’s carbon-cutting goals and may provide downstream flood mitigation. Meanwhile, control over a major tributary will provide China the geopolitical leverage and potential influence over transboundary water flows.

 

Why is India worried?

 

India is worried that China's upstream control of the Brahmaputra's waters could allow China to control water levels as a tactical weapon of sorts. Pema Khandu, the Chief Minister of Arunachal, called the dam a "ticking water bomb" and a threat to life. His concerns stem from Beijing not having signed up to any international river-sharing agreements and not knowing what its future plans might be.

 

The risks downstream include reduced flow (the sediment captured is critically important to irrigation), problems with the ecosystem, and more extreme dry seasons. There are also significant risks, including floods, from sudden discharge of water in the case of planned storage (for electricity generation, for example) or accidents (including maintenance issues and emergencies). All of which is concerning for India's north-east.

 

Additionally, the project stretches across a seismically active Himalayan gorge — which heightens landslide, flood, and ecological hazard, potentially devastating downstream regions.

 

Does it challenge India’s geopolitical position?

 

This project is near a contested territory in Arunachal Pradesh. India is concerned that China's unilateral actions could redefine control over shared water resources and geopolitical influence. Flow reduction could impair drinking water, crop yields, and riverine ecosystems in Assam and beyond. With increased dependence on a dam controlled by China, India may find itself politically constrained. Additionally, the project risks militarising water policy in an already fragile Himalayan border context.

 

How is India responding to China’s dam construction?

 

To counter China’s influence, India is fast-tracking hydropower in Arunachal. Plans include the 11,000 MW Upper-Siang Multipurpose Project (SUMP) at a cost of around Rs 1.5 trillion, with a reservoir capacity of 9.2 billion cubic metres, likely to strengthen India’s water rights under international norms.

 

Additional projects like Subansiri Lower (2,000 MW) and Dibang (2,880 MW, tallest concrete gravity dam) are under various stages of planning and construction.

 

India relies on the 2006 Expert-Level Mechanism, through which China shares real-time flood-season hydrological data for Brahmaputra and Sutlej.

 

Meanwhile, Assam Chief Minister Himanta Biswa Sarma has publicly stated that despite concerns, there’s no immediate threat—citing the river’s multiple sources, including Bhutan and local rainfall.

 

Conversely, organisations in Arunachal like SIFF and ex-CM Nabam Tuki, along with student bodies in Assam, have pressed for thorough impact reviews, transparency, and the declaration of Assam's flood issues as a national emergency.

 

How has the world responded to China’s action?

 

Bangladesh has raised questions about a reduction in water supply and flow variability. However, China states the project is expected to have no negative effects on countries downstream.

 

Meanwhile, environmental organisations have raised concerns regarding the dam's potential to influence a sensitive ecological zone, highlighting the potential for earthquakes and other natural disasters, given its location in the Himalayas.

 

While India and Bangladesh have formally raised the issue with China, there has been little overt international censure or coordinated global diplomatic response so far. The project is seen as an extension of China’s broader infrastructure and strategic ambitions rather than a direct provocation warranting sanctions or collective action.

 

Moreover, the lack of enforceable worldwide agreements on rivers permits China to move ahead without any serious accountability from the rest of the world.

 

For India, this is a multi-faceted challenge. The downstream risks for India include everything from water shortages to environmental damage, along with border tensions. As a response, India is increasing hydropower and flood control investment plans, while also utilising diplomatic engagement, data-sharing, and political mobilisation as diverse strategies to stake its own claims.