Siang Upper Multipurpose Project: Why Arunachal Pradesh Is Divided Over an 11,200 MW Dam
People in parts of Arunachal Pradesh are protesting against the proposed Siang Upper Multipurpose Project (SUMP), an 11,000 to 11,200 MW hydropower and water storage dam on the Siang river.
The planned reservoir would hold about 9.2 billion cubic metres of usable water (live storage). This would make it one of the largest storage reservoirs in India.
The protests started as objections to survey work and pre-feasibility studies (early tests that check whether a site is suitable). They have now grown into clashes between villagers and security personnel. In late September 2026, villagers in Geku in Upper Siang district clashed with security forces, and four people were arrested.
The Arunachal Pradesh government says the dam is not only about electricity. It says the dam can store and control the river's water, which matters because China is building a giant hydropower project upstream on the same river (called the Yarlung Tsangpo in Tibet).
The project is still at the pre-feasibility stage. If it is found technically possible, it will still need a Social Impact Assessment, an Environmental Impact Assessment and a Detailed Project Report (DPR) before any construction can be considered.
Siang Upper Multipurpose Project (SUMP): India's Storage Dam on the Siang
The Siang Upper Multipurpose Project, or SUMP, is a very large dam proposed on the Siang river in Upper Siang district of Arunachal Pradesh. The Siang is the name of the Brahmaputra river when it first enters India from Tibet. The project plans to produce about 11,000 to 11,200 MW of electricity and to store about 9 billion cubic metres of water behind a dam nearly 300 metres high. It is called "multipurpose" because it is meant to do several jobs at once: make electricity, control floods and act as a water store for India.
The protests are happening because SUMP is still at the survey stage, and every survey now meets local resistance. The state government presents the dam as India's answer to China's Medog project upstream. The protesters stress the loss of land, culture and safety. How this conflict is handled will decide whether the project moves on to the SIA, EIA and DPR stages.
India-China Transboundary River Cooperation: The Brahmaputra Data-Sharing Mechanism
India and China share several big rivers that start in Tibet and flow down into India. The most important are the Brahmaputra (Yarlung Tsangpo) and the Sutlej (Langqen Zangbo). India and China have no water-sharing treaty for these rivers. Instead, they cooperate through a few simple arrangements: agreements (MoUs) under which China shares river data during the flood season, and an Expert Level Mechanism (ELM) where officials from both sides meet to discuss river issues.
The Arunachal government defends SUMP mainly as a water-security tool against China's Medog dam. This argument is strong because India and China have no water treaty, and even the simple flood-data MoU for the Brahmaputra has lapsed since 2023. Without reliable data from upstream, India wants its own large reservoir to absorb sudden water releases.
Environmental Impact Assessment (EIA) Notification, 2006
The EIA Notification, 2006 is the main rulebook that decides whether a big project in India can be built. It is issued under the Environment (Protection) Act, 1986. It says that listed projects, such as large dams and hydropower plants, must get an environmental clearance before any construction starts. The process studies the project's likely harm to nature and people and lets the public raise objections at a hearing.
SUMP has not reached the EIA stage yet; it is still in pre-feasibility. If the studies show it is possible, NHPC will have to prepare an EIA report and hold a public hearing in the affected area. That hearing will be one of the main formal places where the Adi villagers can record their objections.
- Siang Upper Multipurpose Project: 11,000 to 11,200 MW; about 9.2 BCM live storage; dam height about 300 m; cost about ₹1.13 lakh crore
- Location: Upper Siang district, Arunachal Pradesh; developer: NHPC
- Status (October 2026): pre-feasibility stage; next steps are SIA, EIA and DPR
- Late September 2026: clash between villagers and security forces at Geku; four arrests
- Main protest group: Siang Indigenous Farmers' Forum (SIFF); main community affected: Adi tribe
- China's Medog project: about 60 GW; approved December 2024; construction began 19 July 2025
- Brahmaputra flood-data MoU with China expired 5 June 2023; ELM on trans-border rivers set up in 2006
- Siang + Dibang + Lohit meet near Sadiya (Assam) to form the Brahmaputra