South of the Brahmaputra near the Indian border lies an active fault line under the world’s largest hydroelectric project being built by China. Worryingly – this alert is not from any foreign agency or Indian expert. A new study by geologists affiliated with China’s state-owned enterprise highlights this dire geological hazard.
The study, sponsored by the state-run China Geological Survey, said an active landslide called the Pigeon Fault runs through the construction area of a large hydroelectric project downstream of the Yarlung Changpo River. The research was conducted by scientists from Chengdu University of Technology, China Geological Survey Civil Military Integration Center and Yarlung Changpo River Research Center. According to them, the movement of faults can seriously affect the stability of dams as well as roads, bridges, tunnels and reservoirs.
According to the researchers, the Pigeon fault was very active since the Pleistocene era, which began about 2.6 million years ago. Geological samples have shown evidence of its movement around 9,500 years ago. In geological terms, 9,500 years is not a long time; Therefore, it is not considered as a dead or inactive fault. A magnitude 6.9 earthquake in the Milin region in 2017 was also cited as an example of current seismic activity in the region.
This fault movement has already fractured and weakened the adjacent bedrock. As a result, the weight-bearing capacity of large structures may be reduced. The slopes on both sides will remain wet for a long time after the water has accumulated in the reservoir. A combination of weak rock, fast flowing water, heavy rainfall and earthquakes will increase the risk of large landslides or landslides. So scientists suggest strengthening hillsides, building retaining walls and continuous earthquake monitoring.
However, the study did not say that the dam would definitely collapse. Geological hazards are not the same thing as specific disasters. Advanced engineering techniques, proper construction and continuous monitoring can reduce risk. But building the world’s largest hydroelectric project on top of one of the world’s most earthquake-prone regions, extremely steep mountains, weak bedrock and active faults, is no ordinary engineering project. Assam and Bangladesh can pay for even the slightest mistake here.
China officially began construction on the project on July 19, which will consist of five phased hydroelectric plants with an investment of about 1.2 trillion yuan, or about $168 to $170 billion. The goal is to generate about 300 billion kilowatts of electricity per year, which is about three times the annual output of the Three Gorges Dam. As the river drops nearly 2,000 meters in about 50 kilometers, China plans to use the huge height difference to generate electricity.
The project is commonly referred to as ‘run-of-the-river’ or a system where river water is diverted through tunnels to generate electricity. Such projects may have less water storage capacity than typical large reservoir-based dams. But ‘river racing’ is not without danger. Five major stations, long tunnels, reservoirs, mountain cutting and massive explosive construction could put new pressures on already unstable terrain. Due to the lack of public disclosure of its complete design, reservoir capacity and water management regulations, it is difficult to independently verify the true level of risk.
History also clearly testifies to the dangers of this region. The magnitude of the 1950 Assam-Tibet earthquake was an earthquake, one of the strongest earthquakes in the world, causing massive landslides in an area about 330 km long and 100 km wide. The hills break up and form natural dams blocking some of the Brahmaputra’s tributaries. Later, the temporary dam collapsed and the water destroyed villages and killed many people in Assam. In other words, earthquakes followed by landslides, river dams and then flash floods – these ‘cascading disasters’ or one disaster after another are not just theoretical risks in the region.
Recent scientific studies have also shown the risk of glacial collapse, landslides and debris blocking rivers in the Yarlung Changpo Grand Canyon. A sudden collapse of a natural dam caused by mountain debris can have an impact hundreds of kilometers downstream. However, the same study suggests that the impact of such southern floods may not be greater than the local monsoon floods in Assam in many cases. This finding shows that accurate location-based models and real-time data are more necessary than creating panic.
Another big question for India is water security. Most of the Brahmaputra’s total annual water comes from Assam and Arunachal Pradesh and its tributaries such as Subansiri, Lohit, Dibang and Manah. Therefore, China will dry up the entire Brahmaputra at the flick of a switch – such claims are exaggerated. However, during the dry season, the timing, amount and importance of precipitation from Tibet increases. Not only the total amount of water per year, but also the amount of water in any given season is equally important for agriculture, river biodiversity, fish, water transport and the natural flow of rivers.
In 2025, an internal Indian government assessment seen by Reuters feared that the project’s capacity to divert about 40 billion cubic meters of water a year could reduce the amount of water flowing into India during the dry season by up to 85 percent. But this is a rash assessment on the Indian side; Whether China actually plans to withdraw such water could not be independently confirmed. China’s Ministry of Foreign Affairs has claimed that the project will not have any harmful effects on water resources, the environment or geology, and will not divert water.
Blindly believing China’s claims or declaring every Chinese project a ‘water bomb’ – neither is enough. The main problem is lack of information. There is no binding water sharing agreement between India and China on the Brahmaputra. In earlier arrangements, China provided information on rainfall, water level and flow during floods in India. However, India’s Ministry of External Affairs informed Parliament in August 2025 that the provision of information would be suspended from June The two countries agreed to hold an expert-level meeting in early 2025 to discuss resuming information exchange.
By June 2026, China has pledged to strengthen water resources information and communication with Bangladesh. But real security in the Brahmaputra basin requires simultaneous real-time information exchange between three countries – China, India and Bangladesh. Diplomatic assurances alone cannot prevent earthquakes or floods.
India has proposed the High Siang Multipurpose Project in Arunachal Pradesh to counter the potential impact of Chinese projects. The proposed Indian dam is planned to store about 14 billion cubic meters of water. According to the government, it will intercept sudden inflows from China and provide water in dry weather. But the project risks submerging at least 16 villages and directly affecting around 10,000 people. Many of the local tribals are opposing the project to protect their land, culture and livelihood.
So, one mega dam in China is another mega dam in North India – this equation does not completely solve the problem. Both the projects will be built in the same earthquake-prone Eastern Himalaya region. Blocking the river with a series of massive dams in the name of protection can further endanger the river’s normal sediment flow, fish breeding, riparian agriculture, forest areas and the lives of local communities.
India’s demand will not be limited to the question of whether China will release or stop the water after this new geological report. India has to demand from China a complete seismic design, fault map, reservoir capacity, tunnel location, dam breach model, emergency release rules and disaster management plan for the project. Also, security checks by independent international experts and joint early warning systems of India, China and Bangladesh are essential.
Finally, this project is not just a domestic power project in China. Cross-border rivers, such as danger. China alone may benefit from power generation, but a major mistake, landslide or structural failure could cost billions of people in Arunachal, Assam and Bangladesh. That is why it is not enough to say ‘faith’ in the case of the Brahmaputra – transparent data, scientific testing, collective monitoring and binding international norms are needed. In the case of the world’s largest dam built on an active fault, opacity itself is a major risk.