Why India’s answer to China’s mega dam is facing resistance in Siang valley

The Siang Upper Multipurpose Project, or SUMP, is a proposed 11,200 MW hydropower and water-management project. NHPC would implement it across Arunachal Pradesh’s Siang belt. The project matters because it is presented as both an energy project and a possible response to China’s upstream dam plans.

SUMP would cover Upper Siang and East Siang districts. The Siang enters Arunachal Pradesh near Gelling and travels 294 kilometres before joining the Dibang and Lohit at Sadiya in Assam. Together, those rivers form the Brahmaputra.

The idea dates to 1983, and the project became a national project in 2008. In September this year, the Cabinet approved a pre-feasibility survey. Indigenous communities, including Adi and Galo groups, oppose the plan because they fear flooding, displacement and damage to their cultural and economic ties with the river.

SUMP is planned as an 11,200 MW project across three districts: Upper Siang and East Siang. Its scale is national, but its immediate footprint would be concentrated in the Siang valley, where Indigenous communities live beside the river.

The Siang Indigenous Farmers Forum estimates that the reservoir could submerge 27 villages and displace over 1.5 lakh people. The article presents these figures as the forum’s estimate, not as a final assessment. The project is still at the pre-feasibility stage, so its exact impacts have not been settled.

Its proposed live storage is 9.2 billion cubic metres. The size of that reservoir is central to the dispute because it could cover villages, fertile paddy fields and heritage sites. The government says further studies would clarify the project’s feasibility and consequences before any construction decision.

The Centre and Arunachal Pradesh government see SUMP as more than a power project. They say it could strengthen national water and energy security, regulate seasonal floods in the Siang-Brahmaputra basin and support long-term development. Arunachal Pradesh has about 40% of India’s untapped hydropower potential but only 2,115 MW of installed capacity.

The strategic backdrop is China’s planned 60,000 MW mega dam at Medog, upstream in Tibet. The Siang is called the Yarlung Tsangpo in Tibet. Arunachal Pradesh says SUMP could help regulate flows and counter the possible impact of the Chinese project.

The state has also declared 2025-2035 the “Decade of Hydropower.” Yet the cross-border rationale has intensified local concerns rather than settling them. Indigenous groups fear the project could damage homes, farmland, heritage and river-based livelihoods, while the government says consultation and further studies must continue.

If SUMP’s reservoir is built as proposed, opponents fear it could transform the valley’s landscape and daily life. Several groups say villages and fertile paddy fields could go underwater. That would threaten homes, food security and traditional livelihoods tied to farming and the river.

The Siang Indigenous Farmers Forum estimates that 27 villages could be submerged and over 1.5 lakh people displaced. It also warns that heritage sites, including Kekar Moying, associated with the Anglo-Abor battle, could be lost. These impacts explain why opposition focuses on ancestral land as well as compensation.

The government has not approved construction. Surveys and a pre-feasibility assessment are underway, and some villages have signed agreements to allow survey work. Opponents allege that surveys occurred without community consent and criticise central-force deployment. The government says it will provide clarity, support affected people and hear their concerns.

A dam’s megawatt rating measures potential electricity generation, not the amount of water stored behind it. Storage depends mainly on the reservoir’s physical size and design. That is why a project with lower power capacity can still hold more water than a higher-capacity project.

The key mechanism is the height, or “head,” from which water falls. A steep drop gives moving water more energy and can produce more electricity with less stored water. Chief Minister Pema Khandu said China’s Medog project may generate more power because of the Great Bend’s steep drop, even though its reported storage is lower.

The article compares Medog’s estimated 5.5 BCM storage with SUMP’s planned 9.2 BCM. It also cites Etalin: 3,097 MW with 7.5 MCM of storage, versus Dibang’s 2,880 MW with roughly 4 BCM. These figures show why capacity alone cannot reveal storage.

A pre-feasibility report, or PFR, is an initial assessment of whether a proposed project appears technically workable and what consequences it might have. For SUMP, it is meant to establish whether the plan deserves deeper investigation. It does not itself authorise building the dam.

The report would help examine the project’s basic feasibility and potential implications. The Cabinet’s decision in September was to carry out this survey, not to approve construction. The distinction matters because the project remains uncertain and communities are already challenging the survey process.

If SUMP is considered feasible, it must undergo further scrutiny. The next steps listed in the article include a Social Impact Assessment, an Environmental Impact Assessment and preparation of a Detailed Project Report. Some villages have signed agreements for survey work, while the government says the process should be comprehensive and transparent.

A hydropower dam stores or channels water and releases it through equipment that spins as the water moves. In standard hydropower systems, turbines turn generators, which produce electricity. The article focuses on two factors behind that output: how much water moves through the system and how far the water falls.

More flow means more moving water is available to generate power. A greater height, called the water head, gives the falling water more energy. Khandu explained that the steep drop at the Great Bend of the Yarlung Tsangpo helps China’s project generate substantial power. This is why megawatts and storage capacity are not interchangeable measures.

The article’s comparisons illustrate the point. Etalin could generate 3,097 MW with only 7.5 MCM of storage, while Dibang could generate 2,880 MW with roughly 4 BCM. SUMP’s lower capacity than Medog does not automatically mean less stored water.