Why Siang project matters for India as China builds mega Brahmaputra dam, and why Arunachal locals are up in arms

India’s Siang Upper Multipurpose Project, or SUMP, is a proposed 11,200-megawatt dam and reservoir project in Arunachal Pradesh. It is designed to generate electricity and store and regulate water. China’s Medog project is a reported 60,000-megawatt hydropower project on the Yarlung Tsangpo in Tibet.

These projects are connected because the Yarlung Tsangpo becomes the Siang after flowing through the Himalayas into Arunachal Pradesh. It then enters Assam as the main channel of the Brahmaputra, before continuing into Bangladesh. This creates one continuous river system across three countries.

Their shared river links energy planning with water security. China’s project is upstream, while SUMP would be downstream in India. India sees its project as a way to strengthen storage and river management, while local communities fear its effects on land, villages, livelihoods and cultural heritage.

The proposed SUMP is planned to generate 11,200 megawatts of electricity. China’s Medog project is reported at 60,000 megawatts. On power generation alone, Medog would therefore be much larger than SUMP. This difference is why Arunachal Pradesh Deputy Chief Minister Chowna Mein said the projects should not be compared only by generating capacity.

The storage comparison points in the other direction. Figures cited by Mein put SUMP’s live storage at around 9.2 billion cubic metres. The Chinese project is estimated to have about 5.5 billion cubic metres. Live storage is the portion of a reservoir that can be actively used to manage releases.

This means SUMP is presented as a water-management project as well as a power project. Its larger cited live-storage capacity could help India hold back and regulate incoming water. The government says this could support flood management in the Siang basin and downstream Arunachal Pradesh and Assam.

India views SUMP as more than an electricity project because China is developing major hydropower infrastructure upstream on the Yarlung Tsangpo. The Medog project’s location in Tibet has raised concerns in India about how Chinese dam operations could affect downstream water flows. New Delhi therefore links SUMP to national security and river management.

The proposed Indian project would combine power generation with storage and controlled releases. Its cited live-storage capacity is around 9.2 billion cubic metres, compared with an estimated 5.5 billion cubic metres for Medog. By retaining some incoming water, SUMP could provide India with a larger tool for managing flows in the Siang basin and farther downstream.

The strategic concern is not only the size of the dams. It is also the possibility of sudden releases or reduced flows during dry periods. In June 2025, Kiren Rijiju called SUMP a strategic necessity. The project has therefore become part of India’s response to China’s upstream plans.

Dam operations upstream can change when and how much water reaches downstream areas. Water held behind a dam may reduce flows at some times, while a sudden release may create a sharp rise downstream. This matters along the Yarlung Tsangpo, which becomes the Siang in Arunachal Pradesh, the Brahmaputra in Assam and continues into Bangladesh.

The article notes concerns about reduced flows during dry periods and sudden releases from China’s Medog project. Separate research by Chinese scientists reconstructed runoff from 1325 to 2020 using tree-ring data. Their warning was that runoff could increase during this century, potentially raising the frequency of high-flow events, including floods.

A reservoir such as SUMP could hold back some incoming water and release it in a controlled way. Under suitable conditions, that can moderate peak flows in the Siang basin and downstream Arunachal Pradesh and Assam. However, the cross-border river means operations and changing runoff patterns remain important concerns for India and Bangladesh.

Members of the indigenous Adi community and other local groups oppose SUMP because they fear losing homes, ancestral land and traditional livelihoods. They also worry about environmental damage and threats to cultural heritage. For residents of the Siang Valley, these are immediate risks, unlike the project’s broader strategic and electricity benefits.

Opposition has focused on preliminary survey work for the project’s pre-feasibility report. Protesters have demanded that the survey stop. They want affected communities consulted before the project moves forward. Their objection is therefore directed both at the possible dam and at the process being used to prepare it.

The dispute intensified in October 2026, when demonstrations escalated into clashes in parts of Arunachal Pradesh. Reports said protests in Pasighat involved stone-pelting, injuries to police personnel and damage to public and private property. The conflict shows how strategic arguments can collide with local concerns over land, consent and survival.

Live storage means the portion of a reservoir available for managing water releases. It is not simply the total space behind a dam. This usable volume gives operators room to retain water, release it when needed and adjust flows for different conditions.

For example, if heavy runoff enters a reservoir, operators may hold back some of it instead of allowing the entire surge downstream immediately. They can then release water in a controlled manner. Under suitable conditions, this can moderate peak flows and help reduce flood risks in downstream areas.

The state government says SUMP could provide around 9.2 billion cubic metres of live storage. It argues that this capacity could help regulate flows in the Siang basin and downstream Arunachal Pradesh and Assam. The benefit depends on reservoir operations and incoming water conditions, while local communities remain concerned about submergence and displacement.

A transboundary river is a river that crosses or forms part of the boundaries of more than one country. Its water does not stop at a national border. Activities upstream can therefore influence communities, ecosystems and water availability far downstream.

The river in this case begins as the Yarlung Tsangpo in Tibet. It becomes the Siang in Arunachal Pradesh, enters Assam as the Brahmaputra’s main channel and then continues into Bangladesh. A dam or reservoir in one country can alter the timing, volume or speed of water reaching the next country.

That makes upstream control politically and environmentally important. India is concerned about possible sudden releases or reduced flows from China’s Medog project. New research also points to potentially higher runoff and more high-flow events. India’s SUMP is presented as a response involving storage and regulation, while local opposition highlights the environmental and social costs within Arunachal Pradesh.