The Carbon Curtain: China's Yarlung Tsangpo Dam Turns a River Into Leverage

In July 2025, construction formally began on what will become the largest hydropower project in human history. Located at the great bend of the Yarlung Tsangpo in Tibet, the Medog hydropower station is planned to generate 60,000 megawatts of electricity once operational, roughly three times the installed capacity of China's Three Gorges Dam and approximately equal to the entire annual power output of the United Kingdom.

Illustration by The Geostrata

The projected annual generation of 300 billion kilowatt-hours will, by Beijing's account, serve the country’s push to peak carbon emissions before 2030 and achieve full carbon neutrality by 2060. 

Built into the same concrete tunnel that will generate that electricity is something else entirely: the ability to control when, how fast and in what volume a river flows across an international border into India and Bangladesh. These two things are the same asset. 

THE PLEDGE AND ITS ARCHITECTURE

China formally announced its dual carbon targets at the United Nations General Assembly in September 2020, committing to peak carbon dioxide emissions before 2030 and reach carbon neutrality before 2060. These pledges form the basis of Beijing's positioning at successive COP summits as a responsible major power committed to the global energy transition. 

Hydropower occupies a structural role in this architecture. China’s 14th Five-Year Plan for renewable energy set a target for hydropower to supply 17.4% of national electricity generation by 2025, up from 16% in 2021, with a further 40 gigawatts of new capacity to be added in both the 14th and 15th planning periods.

Hydropower currently accounts for roughly 425 gigawatts of China's 1,950 gigawatt generation fleet, more than any other country on earth. The Medog project is the logical ceiling of this expansion; the most accessible dam sites in Sichuan and Yunnan are already near saturation, making the Yarlung Tsangpo Great Bend the last large undeveloped site with extraordinary hydraulic potential. 

The geography of Medog is exceptional. Within 50 km, the river descends approximately 2000 m through the world's deepest Canyon. Engineers plan to bore a tunnel through Namcha Barwa Mountain to divert part of the river through five cascade underground hydropower stations. The electricity generated will not serve Tibet’s modest local demand. It will travel via ultra-high-voltage direct-current transmission lines to Eastern and Central China, feeding industrial loads thousands of kilometres away.

THE RIVER'S PATH AFTER THE GREAT BEND

The Yarlung Tsangpo does not stop at the Tibetan border. After the great bend, it crosses into India’s Arunachal Pradesh, where it becomes the Siang, then collects the Dibang and Lohit tributaries in Assam to form the Brahmaputra, before entering Bangladesh as the Jamuna and draining into the Bay of Bengal. Over 130 million people across India and Bangladesh depend on the river system for agriculture, fisheries, drinking water and floodplain ecology.

A cascade of dams at a river’s steepest elevation drop produces a specific hydrological capability. Reservoir storage allows an upstream operator to hold back water during periods when downstream agriculture depends on seasonal flow. Controlled release from the large storage volumes can send high discharge pulses downstream with little warning, producing flash flood conditions in valleys with no storage infrastructure to absorb the surge.

China shares hydrological data with India and Bangladesh only during monsoon months and with documented delays. No binding water-sharing treaty exists between China and either downstream state, and no joint monitoring mechanism operates at the dam site.

Studies have found that the Medog site is unnecessary for China's emissions targets and that

its transmission costs to eastern provinces exceed those of available alternative sites. The choice of this specific location, the last point before the river leaves Chinese territory, is not explained by climate accounting alone.

This is the core of the emissions-as-leverage argument. Beijing has never disclosed Medog’s reservoir operating data or agreed to a binding release schedule, and that omission is what turns a hydropower station into a control point on India’s and Bangladesh’s water supply. 

INDIA READS THE INFRASTRUCTURE CORRECTLY

India’s response is the clearest evidence of how New Delhi reads the upstream project. Within weeks of China's construction announcement, the Indian government accelerated discussions around the Siang Upper Multipurpose Project in Arunachal Pradesh, a proposed 11,000 megawatt storage dam across the Upper Siang and Siang districts.

At an estimated cost of approximately 1.5 lakh crore rupees, it would become India's largest hydropower project if built. The National Hydroelectric Power Corporation is leading pre- feasibility surveys, and the Arunachal Pradesh administration has described the project in explicit national security terms.

A large Indian reservoir on the Siang, placed between the Chinese dam and the population centres of Assam, would function as a hydrological buffer. If Medog's operators released an abnormal discharge volume, sufficient Indian storage capacity could absorb the surge before it reached the densely settled floodplains of Assam.

The proposed Indian reservoir would hold approximately 9 billion cubic metres and would be designed partly for this attenuation function. In mid-2025, India also announced a broader initiative to construct over 200 dams across its northeast with a combined planned capacity of 75 gigawatts, mirroring the upstream Chinese expansion in both scale and geography.

India is simultaneously framing its hydropower push in green energy language, describing the Siang project as a clean energy initiative supporting the country's 2070 net-zero commitment. The project will generate hydroelectric power. But the stated rationale from Arunachal Pradesh's administration is explicit about a second purpose: establishing prior-use rights on the river, asserting hydrological sovereignty, and building a physical deterrent against upstream flow manipulation.

Both countries are building dams on the same river. Both are calling them clean energy. The audiences for these claims are entirely different.

THE DATA CHINA DOESN'T SHARE

The absence of a binding agreement between China and India is not an oversight. China has declined a formal treaty governing the Yarlung Tsangpo, offering instead a memorandum of understanding for limited seasonal data sharing. A memorandum carries no enforcement mechanism. It can be suspended or narrowed at the upstream operator's discretion, which creates leverage. Hydrological data on the Yarlung Tsangpo has been classified as a national security matter.

Detailed information on reservoir operations, sediment projections and discharge scheduling remains unavailable to downstream governments. In a basin where glacial lake outburst floods are an increasing risk and where agricultural planning in Assam and Bangladesh depends on seasonal flow predictability, this is an advantage to whoever controls the reservoir. 

Climate governance institutions have not addressed this gap. The United Nations Framework Convention on Climate Change (UNFCCC) has no mandate over transboundary water infrastructure, so Medog’s renewable-energy classification places it outside the scrutiny that a water-control structure would otherwise face.

The 1997 UN Watercourses Convention, which establishes equitable utilisation and no-significant-harm principles for shared rivers, has not been ratified by China. Climate commitments and transboundary water governance sit in separate legal silos, and the Medog project occupies the space between them.

Bangladesh receives the Brahmaputra at its most downstream point, shaped by every upstream decision made in Tibet and Assam and yet neither country’s planning documents account for it. It has no storage infrastructure and treaty rights over river flow. Already among the world's most climate-vulnerable countries, facing rising seas and intensifying cyclone frequency, a destabilised Brahmaputra adds existential water risk to a state with no seat at the upstream table.

ONE RIVER, ONE PLAYBOOK

The Medog project is one data point in a pattern visible across river systems where China sits upstream. On the Mekong, Chinese dams have been documented to hold back water during downstream droughts and release it without advance notice to lower riparian states. The climate commitment framing is newer, but the underlying pattern is the same: to build infrastructure that works as both an energy asset and a flow-control mechanism. Beijing resists binding data-sharing agreements while reporting the project as a contribution to global decarbonisation. 

Medog’s scale is what separates it from the rest of the pattern. 60,000 megawatts of capacity will displace a real, countable volume of coal fired generation, the kind of number Beijing can report at COP without exaggeration. That is exactly what makes the dam’s second function easy to miss. A project this large does not need help looking legitimate. 

India's response confirms the importance of the infrastructure. The Indian government is building the dam worth 1.5 lakh crore rupees, not just out of consideration that it is an important climate project. The reason is that the construction of such a large infrastructure, which controls the final 50 kilometres of the transboundary river before it crosses into the territory under dispute, is itself an important strategic consideration. 

Emissions diplomacy is real, but the leverage hidden behind it is hard to miss.

---

BY NISHQA TEAM GEOSTRATA

info@thegeostrata.com