Every year, when monsoon rains feed the Yarlung Tsangpo in Tibet, the same water that Tibetans call their “sorrow river” becomes the Brahmaputra in Arunachal Pradesh, the Luit in Assam, and one of the world’s great ecological systems before crossing into Bangladesh as the Jamuna. This single river – fed by Himalayan glaciers, monsoon rains, and dozens of tributaries – is simultaneously a Chinese geopolitical asset, India’s most flood-prone waterway, Bangladesh’s agricultural lifeline, and one of the last truly wild river systems on earth. The decisions being made about it in Beijing, New Delhi, and Dispur will shape the lives of 130 million people across three countries for the next century.
The River’s Geography: From Tibetan Plateau to the Bay of Bengal
The Brahmaputra is one of the longest rivers in the world, with a total length of approximately 2,900 kilometres. It begins as the Yarlung Tsangpo on the Tibetan Plateau at an altitude of over 5,000 metres near the Chemayungdung glacier, flowing east along the Himalayan range for most of its Tibetan course. At the Great Bend near Namcha Barwa, it makes a dramatic U-turn and plunges south through one of the world’s deepest gorges – the Tsangpo Gorge, sometimes called the “Grand Canyon of the Himalayas” – before emerging into Arunachal Pradesh. In this descent from Tibet to the plains, the river drops roughly 3,000 metres over just 200 kilometres, making it one of the fastest-moving large rivers in the world.
Entering Assam, the Brahmaputra becomes wide, braided, and unpredictable. The Assam plains are geologically young and seismically active – the 1950 earthquake, measuring 8.6 on the Richter scale, was one of the largest recorded in the 20th century and dramatically altered the river’s channels and sediment load. The river carries an enormous sediment burden, estimated at over 700 million tonnes annually – among the highest of any river in the world – which it deposits on the floodplain creating and destroying islands, shifting channels, and building soil in some areas while eroding it in others. The Majuli island in Assam, the world’s largest river island, has been losing land to Brahmaputra erosion for decades. The river then crosses into Bangladesh, where it merges with the Ganga (Padma) and Meghna before emptying into the Bay of Bengal through one of the world’s largest deltas.
China’s Mega-Dam: The Motuo Project
In November 2020, China approved plans for a hydropower project at Motuo (Metog) on the lower Yarlung Tsangpo – precisely at the Great Bend where the river makes its dramatic descent. The project, planned to have a capacity of approximately 60,000 megawatts, would be the largest hydropower project in the world if completed – dwarfing the Three Gorges Dam’s 22,500 MW. China’s state-owned PowerChina and other entities have been conducting feasibility studies in the area for years. The project is positioned as part of China’s commitment to peak carbon emissions before 2030 and carbon neutrality before 2060.
India’s concerns about the Motuo dam are multiple and serious. First, there is the question of flow regulation: a dam of this size would give China the ability to regulate the volume of water entering India’s territory downstream. During a conflict or diplomatic standoff, this represents a potential strategic leverage point of enormous significance. China and India have no bilateral water treaty on the Brahmaputra – only a memorandum of understanding for sharing hydrological data during the flood season (June to October), which China has periodically suspended during moments of diplomatic tension, most recently in 2017 during the Doklam standoff. Second, there is the question of sediment: the Tsangpo Gorge produces extraordinarily high sediment loads from the steep, geologically active terrain. A dam of this size would trap enormous quantities of sediment, fundamentally altering the sediment regime of the Brahmaputra in India and potentially starving the downstream floodplain and delta of the nutrient inputs that sustain its agricultural productivity.
Flooding, Erosion, and Assam’s Living Disaster
Assam floods every year. This is not a failure of state capacity or climate change alone – it is the natural hydrological character of the Brahmaputra system, which has been flooding the Assam plains for as long as the plains have existed. What has changed is the scale of human exposure to flooding. Assam’s population has grown substantially since independence, and settlement has extended into floodplains and river islands that were previously understood to be temporary or cyclically inundated. The 2022 Assam floods affected roughly 4.7 million people across 28 districts. The 2020 floods were similarly devastating. These are not exceptional events; they are recurring ones.
The erosion problem is distinct from but related to flooding. The Brahmaputra erodes roughly 8,000 hectares of land in Assam annually on average – some estimates are higher. Communities living on river islands (chars) or on the main bank face not just flood damage but the permanent loss of agricultural land as the river shifts. Char communities in Assam are among the most marginalized in India – predominantly Bengali-speaking Muslims and some Hindu communities, with limited access to permanent land records, education, and government services due to the temporary and shifting nature of their habitat. The political dimensions of char erosion and displacement feed into Assam’s complex ethnic and immigration politics in ways that go well beyond water resource management. See also our reporting on India’s water governance failures.
India’s Own Dam Plans in Arunachal
India’s response to China’s upstream dam plans has included accelerating its own hydropower development on the Brahmaputra and its tributaries in Arunachal Pradesh. The National Hydroelectric Power Corporation (NHPC), SJVN, and private developers have permissions for dozens of projects in the state. The Lower Subansiri project on the Subansiri River, a major Brahmaputra tributary, has been under construction for over two decades and remains incomplete amid sustained opposition from downstream farmers and fisherfolk in Assam who argue that the project’s environmental impact assessment did not adequately assess flood risk and downstream ecological effects. The political economy of hydropower development in Arunachal involves the state government, which stands to gain royalties and employment, the developers who stand to earn from power sales, and the downstream communities in Assam who bear the risks.
The Bhupen Hazarika Setu – the Dhola-Sadiya bridge inaugurated in 2017, spanning the Lohit tributary of the Brahmaputra with a total length of 9.15 kilometres – represents a different kind of state intervention in the river basin: connectivity infrastructure that opens Arunachal to economic development and has strategic implications for troop and supply movement along the China border. The bridge’s name honours the legendary Assamese musician and filmmaker Bhupen Hazarika, who sang about the Brahmaputra’s power and the lives it shaped. The juxtaposition of his river poetry with the bridge’s strategic purpose captures the multiple registers in which the river operates in the public imagination.
| Country/State | Status | Key Issues |
|---|---|---|
| China (Tibet) | Motuo mega-dam planned (60 GW) | Flow regulation, sediment trapping, no bilateral treaty |
| Arunachal Pradesh | Multiple projects in various stages | Downstream flood risk, ecological impact on Assam |
| Assam | Downstream user, bears flood/erosion risk | Annual flooding, char erosion, lower Subansiri opposition |
| Bangladesh | Downstream delta dependent on flow | Seasonal flows, sediment for delta maintenance, salinisation |
Climate Change and the Glacial Retreat Question
The Brahmaputra is one of the most glacier-fed rivers in Asia. Approximately 50 percent of its total annual flow is estimated to come from snowmelt and glacial melt from the Tibetan Plateau and eastern Himalayan glaciers. Climate change is already affecting this. Glaciers in the eastern Himalayas and on the Tibetan Plateau are retreating at measurable rates. In the short to medium term, glacial retreat typically increases meltwater flows – a “peak water” phase – before the long-term decline as glaciers lose mass and eventually disappear from lower elevations. Modelling studies suggest that the Brahmaputra basin may already be near peak water for glacier-fed flow in some sub-basins, with significant flow declines possible over the second half of the 21st century.
The implications for agriculture in Assam and Bangladesh, for the ecology of the delta, and for the geopolitics of water sharing are profound. A dam at Motuo that was designed for a specific flow regime will function very differently as that regime shifts. Flood management in Assam, calibrated to current hydrological patterns, will need systematic revision as both peak flows and base flows change. Bangladesh, which is already highly vulnerable to sea-level rise and salinity intrusion in the delta, faces the compounding threat of reduced freshwater flows to push back brackish conditions. These are not speculative futures; they are the scenarios that hydrological modellers are already working with, and the current generation of political decisions about dams and water sharing will be inherited by communities living through these changes.
The Diplomatic Deficit: No Treaty on the Most Important River
India and China have no binding bilateral treaty on the Brahmaputra – a remarkable fact given that both nations are downstream of each other on different tributaries and that the river serves as the lifeline of an entire Indian state. The 2002 and 2008 MOUs on hydrological data sharing were practical but minimal – they cover only monsoon-season flood data and have been suspended during political tensions. China has repeatedly declined India’s requests for a comprehensive water-sharing framework, in part because China does not consider itself bound by the 1997 UN Convention on the Law of Non-Navigational Uses of International Watercourses, which it has not ratified.
India is in a weaker bargaining position than it might appear. It is simultaneously seeking Chinese cooperation on the Brahmaputra while being downstream of China on the river – the structural asymmetry of upstream-downstream relationships in international water law is difficult to overcome without broader diplomatic leverage. The 2017 Doklam standoff and the 2020 Galwan clash have made any cooperative water framework politically difficult domestically in both countries. Yet the alternative – a future where a massive Chinese dam regulates flows into India without any agreed framework, during a period of climate-driven flow variability that neither country fully understands yet – is considerably worse. This is a diplomatic problem that India needs to solve before the Motuo dam is built, not after.
What This Means for India’s Future
The Brahmaputra is simultaneously a geopolitical challenge, a climate vulnerability, and a human rights issue for millions of people in Assam’s char communities and across the downstream basin. Pressure for a comprehensive India-China water framework needs to come from civil society, researchers, and elected representatives – not just diplomatic channels. The Ministry of Jal Shakti’s annual reports on Brahmaputra basin management are public documents worth tracking. Source: Central Water Commission, Brahmaputra Basin Report; ICIMOD Himalayan Glaciers: Climate Change, Water and Livelihoods; Expert Group on Brahmaputra River System reports.
The Northeast India Dimension: Floods as Policy Failure
Assam’s annual flood cycle is not just a natural disaster – it is also a policy failure accumulated over decades. The embankment system built along the Brahmaputra since the 1950s to protect floodplains was designed for a river hydrology that has since changed substantially. Many embankments are poorly maintained, inadequately designed for current flood peaks, and some have been shown to worsen flooding in specific locations by preventing natural drainage. The 1954 flood was the reference event for much of the embankment planning; the 2022 floods significantly exceeded those parameters in some districts. The Central Water Commission estimates that Assam needs 5,000 additional kilometres of flood embankments to protect all at-risk settlements – a figure that reflects decades of infrastructure deficit.
Flood insurance coverage for farmers in Assam’s Brahmaputra floodplain remains minimal. The Pradhan Mantri Fasal Bima Yojana has low penetration in the highest-risk areas precisely because the actuarial risk is too high for private insurers to cover without prohibitive premiums. The result is that the agricultural losses from Brahmaputra flooding – which can be substantial for farmers growing winter paddy, mustard, and vegetable crops on riverine land – are borne largely by the farmers themselves, with state ex-gratia payments that never fully compensate. This is a structural vulnerability that links the geopolitics of upstream dam-building in China to the kitchen economies of the poorest farming families in Assam. See also our analysis of India’s water crisis management approaches for the broader context of river basin governance.
The Bangladesh Stakes
Bangladesh sits at the confluence of three major river systems – the Brahmaputra (Jamuna), the Ganges (Padma), and the Meghna – and is probably the country most severely affected by any changes in their flow regimes. The Bangladesh delta supports a population of approximately 170 million people at high density on land that is largely within 5 metres of sea level. Reduced freshwater flow from the Brahmaputra system would increase salinity intrusion into coastal and estuarine areas, threatening both agriculture and drinking water in the southwestern delta. Increased peak flows during monsoon, potentially amplified by upstream dam releases, would worsen an already severe flood risk. The construction of the Motuo dam in China without any international water-sharing agreement in place represents a significant existential risk for Bangladesh that has been insufficiently acknowledged in the international climate and water diplomacy conversations dominated by upstream nations.