Binish Thomas (Special Correspondent)
India faces a new strategic worry along its northeastern frontier. China has begun building what is meant to be the world’s largest hydropower project on the Yarlung Tsangpo river, the upper stretch of what India calls the Brahmaputra.
The site is in Medog (Motuo) County in Tibet, close to Arunachal Pradesh. The border dispute between the two countries has never been fully settled, so a project this large and this close adds to the tension.
The River and the Project :
The river rises on the Tibetan plateau as the Yarlung Tsangpo, makes a sharp U-turn at the “Great Bend” near Medog, then enters Arunachal Pradesh as the Siang. In Assam it becomes the Brahmaputra, and in Bangladesh it is called the Jamuna. The dam is being built near that bend.
The project is planned at 60,000 megawatts, nearly three times Three Gorges, and is designed to exploit the roughly 2,000-metre drop of the river around the Namcha Barwa massif.
China announced the plan in December 2024, and work reportedly began in July 2025. It is a series of five cascade hydropower stations, projected for completion in the 2030s. Cost estimates run to roughly 1.2 trillion yuan (about US$167 billion).
Why Is It Seen as a Threat? :
1. Location and geology : The dam is in a seismically active region of Medog County, bordering Arunachal Pradesh. Earthquakes, landslides and glacial lake bursts are real hazards in this part of the Himalayas, and a failure upstream would send a huge surge downstream with little warning.
2. Control over the flow : Sources in India’s power ministry have said China could divert Brahmaputra water once the dam is built, which could cause shortages or flood-like conditions in Arunachal Pradesh and Assam.
There is no water-sharing treaty between India and China, so India depends largely on data sharing and goodwill. Arunachal Chief Minister Pema Khandu has called it a “water bomb”.
3. Border tension : The dam’s closeness to the contested border ties water security to the territorial dispute. Any sudden release or restriction of water could also be read as a strategic signal.
What If There Is an Accident or Sudden Release?.
The most exposed areas would be:
• Arunachal Pradesh: the Siang valley, including Tuting, Upper Siang, Siang and East Siang districts, would be hit first and hardest by a flash flood.
• Assam: the Brahmaputra valley is already flood-prone every monsoon, with erosion and displacement. A surge would worsen this.
• Meghalaya: one assessment lists Meghalaya among the areas whose people could be affected.
• Bangladesh: the river continues there as the Jamuna, so it is a downstream victim too.
The river system supports nearly 130 million people and about six million hectares of farmland.
Impact on Farming in Assam and Arunachal Pradesh :
• Dry-season shortage: the dam could reduce water availability in the dry season and worsen flood risk during the monsoon. That would hurt irrigation for winter and spring crops.
• Loss of silt: reduced sediment flow could seriously affect soil fertility in the floodplains of Assam and Bangladesh. The river’s silt is what keeps the valley’s farmland fertile.
• Fisheries and livelihoods: Assam’s opposition leader Debabrata Saikia has warned of worse flooding and soil erosion, threatening agriculture, fisheries and rural livelihoods.
• Hydropower and drinking water: flow changes could also affect hydropower generation and drinking water, especially in the northeastern states.
The Other Views
• The Brahmaputra is not fed by Tibet alone. Most of its water comes from Bhutan, Arunachal Pradesh and rainfall in Assam. The monsoon, not Tibet, supplies the bulk of the flow in Assam.
• Assam Chief Minister Himanta Biswa Sarma said in July 2025 that the dam may even help Assam. China has defended the project.
This is a contested area of analysis. The real impact depends on dam design, how it is operated, and whether China shares data.
India’s Response: The Siang Upper Multipurpose Project :
India is pushing an 11,000 MW hydropower and flood-control dam on the Siang in Arunachal Pradesh, in response. Arunachal’s deputy chief minister has argued it could help regulate downstream flows and reduce flood risk.
The project is controversial locally. Sections of indigenous communities oppose it over displacement, environmental and livelihood concerns, and protests escalated on October 23 with a 12-hour bandh. The unrest reportedly turned violent, with buildings torched. Some villages have given consent for survey work.
What India Should Do :
• Push for a binding water-data sharing agreement, with year-round hydrological data, not just monsoon-season data.
• Build flood early-warning systems and strengthen disaster preparedness in Arunachal Pradesh and Assam.
• Commission independent environmental and seismic assessments of its own dams, and win local consent before building.
• Raise the issue with Bangladesh to build a joint downstream position.
The dam is a serious concern, but it is not yet a proven weapon. The main risks are an accident in a quake-prone zone, reduced silt and dry-season flow, and the lack of any trust-based water agreement.
India’s best answer is a mix of diplomacy, preparedness and carefully planned infrastructure that also respects its own tribal communities.
