China's construction of the world's largest hydropower facility on the Yarlung Tsangpo River, known downstream as the Brahmaputra, has once again raised questions in India regarding water security, seismic stability, environmental consequences, and the strategic impact of Beijing's growing control over infrastructure on the transboundary river.
This project, known as the Medog Dam or Yarlung Tsangpo Hydropower Project, is being built in the scenic 'Great Bend' of the river in the Medog county, Tibet. Here, the river makes a sharp U-turn before entering Arunachal Pradesh as the Siang River. The construction site is located near the eastern border of India, close to settlements such as Gelling, Norbuling, and Bishing.
According to the South China Morning Post (SCMP), Chinese Prime Minister Li Qiang called this hydropower project a 'project of the century' during the groundbreaking ceremony. The dam is situated in the lower reaches of the Yarlung Tsangpo in Medog County, Tibet, in one of the deepest river valleys in the world. Over nearly 50 kilometers, the river drops by approximately 2000 meters, creating one of the world's richest hydropower resources.
Scientists warn that this project could negatively affect one of the world's richest mountain ecosystems. According to SCMP, the complex will consist of five cascading hydroelectric power stations capable of generating about 300 billion kilowatt-hours (kWh) of electricity annually, more than three times the annual output of China's Three Gorges Dam. The newspaper estimates the total cost of the project at around 1.2 trillion yuan (approximately 167 billion US dollars), making it the most expensive hydropower project in history.
The Brahmaputra is one of Asia's most vital transboundary rivers. In Tibet, it is known as the Yarlung Tsangpo; in Arunachal Pradesh, as the Siang (or Dihang); and in Bangladesh, as the Jamuna. The river flows through China, India, and Bangladesh before emptying into the Bay of Bengal. With a length of about 2900 kilometers, it feeds a basin covering approximately 580,000 square kilometers, which is shared by China, India, Bhutan, and Bangladesh, with China holding the largest share of this basin.
The Brahmaputra is the ninth largest river in the world by water discharge and one of the world's largest braided rivers. It is vital for irrigation, agriculture, transport, fishing, and hydropower in northeastern India and Bangladesh.
Hydrologists argue that China cannot completely stop the flow of the Brahmaputra into India, as the river receives significant additional water from heavy monsoon rains and numerous tributaries after entering Arunachal Pradesh and Assam. Nevertheless, experts note that the massive upstream reservoir will allow China to control the timing and volume of water releases to some extent.
According to a Reuters report on India's hydropower strategy, New Delhi fears that the Chinese dam upstream on the Yarlung Tsangpo could reduce dry season flow by up to 85% under certain operating scenarios, although there is no public evidence of China intending to do so. Indian officials and strategic analysts worry that Beijing may gain more leverage by controlling key upstream infrastructure. Experts also distinguish between water diversion and flow regulation, pointing out that China's project is described as a hydropower dam, not a diversion scheme.
India's concern goes beyond mere water availability. SCMP reports that New Delhi is increasingly viewing this project through the lens of national security, as the river flows through Arunachal Pradesh, which China considers 'South Tibet'. Indian officials and analysts fear an increase in Beijing's influence. Arunachal Pradesh Minister Pema Khandu recently called the project a potential 'water bomb', warning that the flow could 'significantly dwindle' during reservoir filling, and sudden releases could increase the risk of downstream flooding.
Experts also point to the absence of a comprehensive agreement on the joint use of the Brahmaputra between India and China.
Beyond geopolitics, the project's location has attracted intense scientific scrutiny. According to a PTI report citing SCMP, Chinese geologists have discovered an active fault line beneath the hydropower project that could affect its long-term structural stability. These findings were published in the Chinese journal Sedimentary Geology and Tethyan Geology under the direction of the Geological Survey of China. The study showed that the Paicheng Fault, an active geological fault in the Eastern Himalayas, remains active since the Pleistocene epoch. Researchers warned that prolonged tectonic activity has weakened the surrounding rock formations, making the foundations of dams, bridges, roads, tunnels, and reservoir infrastructure more vulnerable. They noted that the 'Paicheng zone is located within the Yarlung Tsangpo hydropower station reservoir area downstream' and cautioned that earthquakes could trigger landslides and rockfalls threatening engineering infrastructure. A 2017 earthquake of magnitude 6.9 in Milingen was cited as evidence of the region's seismic activity.
Chinese authorities consistently reject claims of risks to downstream countries. PTI reports that Beijing has repeatedly stated that the hydropower project has undergone extensive geological surveys and meets the highest engineering standards. An official statement from China in December 2024 deemed the project safe and emphasized the priority of environmental protection. A spokesperson for the Chinese Ministry of Foreign Affairs, Mao Ning, stated that the project has undergone decades of scientific research and environmental assessments, and that China will continue to maintain contact with downstream countries, strengthening cooperation in disaster prevention and mitigation. Chinese officials also insist that the project will not adversely affect downstream water flow.
Scientists warn that the project could impact one of the world's richest mountain ecosystems. A geologist from Sichuan, Fan Xiao, described the Yarlung Tsangpo Grand Canyon as a rare hot spot of biodiversity in a geologically unstable region. He warned that the construction of multiple mega-hydroelectric plants with high dams, large reservoirs, and extensive tunnel systems could increase the risk of landslides and cause irreversible environmental damage. Fan also questioned official claims that large hydropower projects are entirely 'green', arguing that long-term geological and environmental costs remain uncertain. Researchers also expressed concern over the displacement of local communities and potential impacts on culturally significant Tibetan sites.
Concerns over China's management of transboundary rivers are not new. In a written response to the Rajya Sabha on February 8, 2018, the Ministry of External Affairs (MEA) confirmed that China had not provided hydrological information for either the Brahmaputra (Yarlung Tsangpo) or the Satluj (Langchen Tsangpo) during the 2017 flood season, despite existing bilateral Memoranda of Understanding (MoUs). At that time, the then-Minister of State for External Affairs, Gen. (Dr.) V.K. Singh (retired), stated that China had informed India that the break was due to 'technical reasons'. The MEA stated that India continues to monitor transboundary rivers for any anomalies and regularly raises issues related to the rivers through the India-China Expert Level Mechanism (ELM), established in 2006, as well as diplomatic channels.
China resumed data exchange on the Brahmaputra on May 15, 2018, according to the bilateral MoU, which requires Beijing to provide water discharge information during the rainy season from May 15 to October 15. The resumption followed concerns in India after China suspended data exchange during the 73-day standoff in Doklam in 2017. Although many analysts linked the suspension to deteriorating bilateral relations, Beijing claimed the break was due to the modernization of hydrological monitoring stations in Tibet. Data exchange resumed after the 11th meeting of the India-China Expert Level Mechanism on Transboundary Rivers in Hangzhou in March 2018, after which Chinese Foreign Ministry representative Lu Kang announced the continuation of cooperation on hydrological information. The initial MoU on hydrological data exchange for the Brahmaputra was signed in 2002 and extended in 2008 and 2013. India and China also have a separate agreement concerning the Satluj River, originally signed in 2005 and extended in 2010.
Some analysts believe the project could alter the strategic balance between China and India. Sayanangshu Modak, a researcher from the University of Arizona, noted that the project will demonstrate China's engineering capabilities and strengthen its strategic influence in the region. He also observed that India has accelerated the construction of downstream dams as part of its own strategy to strengthen water usage rights. Security analyst Ni Lexion from Shanghai told SCMP that while China views the project as an internal matter, the dam could give Beijing an additional geopolitical lever due to its upstream location. However, Liu Zongyi, a senior researcher at the Shanghai Institutes for International Studies, countered that concerns about China's ability to manipulate river flow are exaggerated, and the project will not fundamentally change bilateral relations.
India responded by accelerating hydropower development in Arunachal Pradesh. Reuters reported that New Delhi approved investments exceeding $4 billion for two major hydroelectric projects along the Brahmaputra. The Kamala project, rated at 1720 MW and valued at 260.7 billion rupees, will be developed jointly by NHPC and the Government of Arunachal Pradesh. The Kalai-II project, rated at 1200 MW and costing 141 billion rupees, will be implemented by THDC India Ltd in partnership with the state government. Reuters also reported that India plans to develop over 76 GW of hydropower capacity in the Brahmaputra basin by 2047 through a $77 billion power transmission investment program.
The construction of the Medog Hydropower Station, which is the world's largest hydropower project, raises serious concerns among Chinese state geologists. According to a study conducted by scientists, this station is located directly above an active fault line in Tibet.
The project site is only 50 kilometers from the border between China and Arunachal Pradesh. This fact has raised new alarms regarding the safety of the giant dam. Previously, the dam itself was already a subject of debate concerning China's ability to control the flow of the Brahmaputra River, especially after India suspended the Indus Water Treaty with Pakistan.
According to the report published in the journal Sedimentary Geology and Tethyan Geology in Chinese under the auspices of the Chinese State Geological Survey Institute, the active Paicheng fault runs beneath the Yarlung Tsangpo River, where the Medog Dam is being built. In Tibet, the Brahmaputra River is known as the Yarlung Tsangpo. The study was a joint effort by geologists from Chengdu University of Technology, the Geological Survey of China's Center for Civil-Military Integration, and the Mid-Yarlung Tsangpo Natural Resources Research Station.
Scientists warned that this fault could critically affect the strength of the dam. The Medog Hydropower Station is a 'run of the river' type project with a capacity of 60 thousand megawatts, being built in the Medog County in Tibet on the Yarlung Tsangpo River. This river originates from the Angsi Glacier in western Tibet and flows 1625 kilometers across China.
After passing through the Great Bend near Namcha Barwa peak, the river enters India, where it is called the Brahmaputra. It flows 918 kilometers in India and then 337 kilometers into Bangladesh, where it is named Jamuna, before emptying into the Bay of Bengal. The total estimated cost of the project is 1 trillion yuan, equivalent to approximately 137 billion US dollars, making it the world's largest hydropower project. Annually, it will produce about 300 billion kilowatt-hours of electricity, almost three times more than the Three Gorges Dam.
China approved this project in December 2024, and construction began in July 2025, with a planned full commissioning by 2033. However, according to the Chinese state scientists themselves, this massive dam is being built over a geological 'ticking time bomb.'
The report states that the Paicheng fault has been active since the Pleistocene period, which began about 2.6 million years ago and included the Ice Age. Scientists note that this fault remains constantly active and could have a significant impact on the stability of the dam, roads, bridges, tunnels, and reservoir. They warn that future fault displacements could jeopardize the safety of the entire project.
Researchers also pointed out that the Pai area, where the Medog Dam is being built, belongs to one of China's most seismically active regions. Analysis of ancient lake sediments showed that this fault was active up to 9500 years ago. The fault's activity was confirmed by a magnitude 6.9 earthquake that occurred in the northern part of this fault in Tibet in 2017.
The study also emphasized that frequent displacements of this fault have already weakened the geological structure of the area. Scientists reported that the surrounding rocks have disintegrated and lost their strength. Simply put, the bearing capacity of the ground to support such a massive 60,000-megawatt structure and its huge reservoir has decreased compared to the initial assessment, especially during seismic events.
The team of scientists also cautioned that the ground around the reservoir has a loose and weak structure. When the reservoir is filled with water, combined with the influence of the fault and earthquakes, the risk of landslides and collapses significantly increases. Specialists insist on the necessity of strengthening safety measures, such as slope reinforcement, both during construction and operation.
India and Bangladesh are closely monitoring this situation, as the project could affect the river flow downstream. Nevertheless, experts believe that the main problem is not China's ability to stop the water flow, but the dangerous geological condition of the area.
Nilanjan Ghosh, a water expert at the Observational Studies Fund, noted that any attempt to change the direction of the water flow would lead to adverse consequences, as it could cause upstream flooding due to sediment accumulation. He also added that the Yarlung Tsangpo accounts for only 10–15 percent of the total volume of the Brahmaputra; the rest comes from tributaries and monsoon rains in India, meaning China cannot completely block the water.
Thus, despite China's own state research acknowledging that the world's largest project is built over an active fault line in one of the most seismically dangerous zones of the Himalayas, the main question is not about controlling the Brahmaputra's flow, but about the catastrophic consequences that could arise in the event of the collapse of such a giant dam and its reservoir.
A serious threat has resurfaced in the Harshil area of Uttarkashi. The memory of the disaster in Dharali-Harshil last year is still fresh, but local residents claim that permanent safety measures have not yet been implemented. The population remains anxious due to the rising water levels in the Bhagirathi River and ongoing erosion, forcing them to monitor the river's flow every night. Local residents warn that if effective protective measures are not taken soon, the existence of Harshil itself could be jeopardized.
Vinod Kumar Suman, Secretary of the Disaster Management Department, reported that work to strengthen the banks is accelerating due to the rising water levels in the Bhagirathi River in the Harshil area. Meanwhile, District Administrator Prashant Arya conducted an inspection, issuing directives to ensure the safety of the riverbank, remove obstructing trees, and maintain constant monitoring of vulnerable zones. He emphasized that public safety is the highest priority, and all departments are working in coordination.
Dr. CS Tomar, Director of the Meteorological Department, forecasts that this monsoon season may be slightly weaker, with expected total rainfall at 90–92 percent of the normal level. However, he noted that episodes of very heavy rain cannot be ruled out, which could lead to rapid rises in the water levels of rivers and temporary streams. Under such conditions, vigilance is required from both the public and the administration.
Senior Geologist Dr. MPS Bisht stated that the re-formation of a lake in Dharali cannot be ruled out. He explained that such situations are characteristic not only of one location in the mountains but also of many others. Small channels descending from the mountains carry huge amounts of debris and deposit it into the main river, forming alluvial cones. This process applies to small tributaries such as Alkanda, Bhagirathi, Kali Ganga, and Yamuna, which carry a lot of silt and form such cones.
Previously, people settled in these areas, believing that flat land had formed along the river, and built houses there without paying attention to the negative aspects. Dr. Bisht reminded that the incident in Dharali is not isolated; similar situations have occurred before and can happen again. Debris accumulated in the glacial zone will move downstream again with increased rainfall. When the speed of its movement slows down, it settles in the main current, creating a 'bottleneck' effect in the Bhagirathi River. This narrows the channel, slows the flow, leads to the formation of whirlpools, and the gradual formation of a large lake.
Dr. Bisht urged the authorities to exercise special control over all such choke points where small tributaries join the main river. He also noted that the Dharali area should have been completely cleared, but after partial work, it was left in its previous state. He warned that during rainfall, debris would be brought in, and a similar dam structure would form again. He cited the Jala area as an example, where a lake of about 14 kilometers formed previously, swallowing three villages, and warned of the possibility of similar disasters in the future.
