Recent Nepal floods highlight Himalayan vulnerabilities and cascading disaster risks. China's Yarlung Tsangpo dam project faces scrutiny due to its geologically unstable location. The dam's operation could influence downstream river flows and water security for India. Chinese scientists have warned about the project's seismic and landslide risks in the region. India faces managing combined risks from infrastructure, climate change, and border proximity.
The rain came down relentlessly, turning quiet mountain streams into raging torrents and narrow roads into muddy rivers. Across Nepal, floodwaters and debris swept through homes, roads and hydropower facilities, leaving behind broken bridges, stranded communities and villages cut off from the outside world. In the mountains, where steep slopes already make life precarious, swollen rivers, landslides and collapsing rock can quickly turn a natural hazard into a cascading disaster. For communities living along narrow Himalayan valleys, a sudden rush of water, ice and debris can leave little time to escape. The recent flash floods in Nepal have brought these vulnerabilities sharply into focus. Search teams have battled heavy rain and thick layers of debris while looking for people believed to be trapped in tunnels, hydropower projects and underground power facilities along the Bhotekoshi River. But the devastation has also raised a larger question: what happens when the already fragile Himalayan environment is combined with increasingly large infrastructure projects, including dams, tunnels, highways and hydropower facilities? That question has particular significance for India because the Himalayas are not confined by political boundaries. Rivers, glaciers, mountain systems and geological faults cut across China, Nepal, Bhutan and India. A disaster originating in the high mountains can therefore have consequences far beyond the point where it begins. It is against this backdrop that China's massive hydropower project on the Yarlung Tsangpo, known downstream as the Brahmaputra, has come under renewed scrutiny. The project, being built in Tibet's Medog County at the dramatic Great Bend of the river, is expected to become the world's largest hydropower project. Its location, however, adds another layer of concern. The project sits in one of the world’s most geologically challenging regions, marked by steep Himalayan terrain, active faults, earthquakes, landslides, glaciers and extreme weather. These natural risks make the dam not just a massive engineering undertaking, but also a strategically sensitive project located upstream of one of India’s most important rivers.
Why the Brahmaputra is so important
China formally began construction of the Yarlung Tsangpo River Lower Reaches Hydropower Project in July last year. The mega-dam is being built in Medog County, near the river’s Great Bend, where the Yarlung Tsangpo makes a dramatic U-turn before entering India. China calls the Brahmaputra the Yarlung Tsangpo. After crossing into Arunachal Pradesh, the river is known as the Siang or Dihang before flowing through Assam and eventually entering Bangladesh, where it is known as the Jamuna. The project is located in one of the world’s deepest river gorges. Over a stretch of about 50 kilometres, the river drops nearly 2,000 metres, creating enormous potential for hydropower generation. The project is expected to comprise five cascade hydropower stations and generate more than 300 billion kilowatt-hours of electricity annually, more than three times the annual generation of China’s Three Gorges Dam, according to reports cited in the material. With an estimated cost of around 1.2 trillion yuan, or about $167.8 billion, it is set to rank among the world’s most expensive infrastructure projects. Chinese Premier Li Qiang has described it as the “project of the century”. But the significance of the project extends far beyond its size or power-generation capacity. The Brahmaputra is far more than a river. It is an economic, ecological and strategic lifeline for millions of people across the eastern Himalayas and South Asia. Originating on the Tibetan Plateau, the river flows through China, India and Bangladesh before emptying into the Bay of Bengal. It stretches for roughly 2,900 kilometres and drains a basin of about 580,000 square kilometres shared by China, India, Bhutan and Bangladesh. One of the world’s largest rivers by discharge, the Brahmaputra is also known for its vast braided channels. Its waters support agriculture, irrigation, fisheries, transport, hydropower and ecosystems across the region. For India, the river becomes particularly important after entering Arunachal Pradesh and Assam. The Brahmaputra and its tributaries sustain communities, farmland and ecosystems across the Northeast, while also bringing the region some of its most destructive floods. That is what makes China’s position upstream so significant for India. Beijing cannot simply stop the Brahmaputra from flowing into India. By the time the river reaches Arunachal Pradesh, it has already begun receiving substantial water from rainfall and tributaries, with flows rising sharply during the monsoon. The concern is therefore less about China being able to permanently cut off the river and more about whether a large upstream hydropower system could influence the timing and volume of flows. The operation of reservoirs, tunnels, power stations and other infrastructure could potentially affect seasonal water releases. For India, this raises questions not only about water security, but also about access to reliable hydrological information and the ability to prepare for sudden changes in river flows, particularly during periods of heavy rainfall or extreme weather.
China began construction of the Yarlung Tsangpo River Lower Reaches Hydropower Project in July last year.
What did experts find
The study, published in the Chinese-language journal Sedimentary Geology and Tethyan Geology and supervised by the state-owned China Geological Survey, examined the Paizhen Fault in Tibet. According to the researchers, the fault has remained highly active since the Pleistocene epoch, or Ice Age, and continues to show evidence of geological activity. Geological dating of ancient lake sediments suggests that movement along the fault occurred as recently as about 9,500 years ago. The researchers warned that repeated movement along the fault had fractured and weakened surrounding rock formations. This could make major engineering structures in the area more vulnerable to geological hazards. "The Paizhen area is located within the reservoir area of the Yarlung Tsangpo downstream hydropower station," the paper said. The researchers said the fault could have a significant impact on the structural stability and construction of nearby infrastructure, including dams, roads, bridges and tunnels, as well as the reservoir area. They also cited the magnitude 6.9 earthquake that struck the Milin area of Tibet in 2017 as evidence that the region remains seismically active. "Under regional seismic action, landslides and collapses can easily be induced, threatening the safety of engineering facilities and personnel," they said. The scientists recommended reinforcing vulnerable slopes and installing retaining structures to reduce the risk of landslides and collapses during construction and after the project becomes operational. The research was conducted by scientists from the Chengdu University of Technology, the Civil-Military Integration Centre of the China Geological Survey, and the Middle Yarlung Zangbo River Natural Resources Observation and Research Station. The findings are significant because they come from Chinese researchers working within China's own geological and scientific institutions. They do not establish that the project is unsafe or that a disaster will occur. But they underline the difficulty of constructing and operating a mega-project in a region where geological instability is an inherent feature of the landscape.
China began construction of the Yarlung Tsangpo River Lower Reaches Hydropower Project in July last year.
Is China capable of ‘stopping’ the Brahmaputra?
The idea that China could simply stop the Brahmaputra from reaching India is often overstated. Srijan Pal Singh, author, former Advisor for Policy and Technology to former President APJ Abdul Kalam, CEO of Homi Lab and founder of Kalam Centre, said the more realistic concern was China's ability to influence the timing of flows and the lack of transparency surrounding the management of the river. "The real concern, therefore, is less about China cutting off the Brahmaputra and more about transparency, reliable data-sharing, and India's ability to anticipate and manage sudden changes in flow," Singh had earlier told TOI. He said that while a significant share of the Brahmaputra's annual flow is generated within India through monsoon rainfall and tributaries, the lean-season flow originating in Tibet remains strategically important. Singh also cautioned against viewing the project solely through the lens of water diversion. "Any large dam on an international river has both economic and strategic implications," he said. He added that control over upstream infrastructure could itself create strategic influence even without physically restricting the river. "It is not necessary to stop the flow of water for leverage to exist. The ability to regulate flows, collect hydrological data, or alter the timing of water releases can shape the decisions of downstream countries, particularly during periods of tension or extreme weather," he said. The distinction matters because the principal challenge for India is not simply the quantity of water but the predictability of that water. During the monsoon, India needs accurate information about upstream river conditions to prepare for floods. During the dry season, information about river flows becomes equally important for agriculture, water management and ecosystems.
What India is concerned
India’s concerns over the Medog project go beyond water security. The Yarlung Tsangpo flows from Tibet into Arunachal Pradesh. A mega infrastructure project on the river, close to the disputed border, therefore has an inevitable strategic dimension. The biggest concern may ultimately be geological. The project lies in the eastern Himalayas, along the collision zone of the Indian and Eurasian tectonic plates. The region is marked by active faults, steep slopes, fractured rock, earthquakes and frequent landslides, all of which pose challenges for a mega-dam and the infrastructure needed to support it. The 1950 Assam-Tibet earthquake, estimated at magnitude 8.7, remains a stark reminder of the region’s seismic potential. It caused widespread destruction across Tibet and Assam and killed thousands of people. The Chinese geological study has added to concerns over the site. Researchers found that repeated fault activity had weakened rock formations and recommended measures such as reinforcing vulnerable slopes and constructing retaining structures to reduce landslide risks.
China’s own geologists have raised the alarm.
Writing in Project Syndicate, Brahma Chellaney, professor emeritus of strategic studies at the New Delhi-based Centre for Policy Research, said the warning from Chinese scientists was particularly significant. “The geologists conclude that the terrain has a 'loose structure and weak cohesion' and warn that fault movement or an earthquake could easily trigger large-scale instability, threatening both the reservoir and surrounding infrastructure,” Chellaney wrote. “Ironically, the latest evidence suggests that China's scientific establishment understands the dangers of building the unprecedented super-dam more clearly than its political leadership appears willing to acknowledge. Now that China’s own geologists have raised the alarm, Beijing must embrace transparency and accept transboundary responsibilities before a potential water bomb is fully assembled upstream,” Chellaney wrote on X. There are also concerns about the possibility of reservoir-triggered seismicity, in which the weight of water stored behind a large dam can affect pressure and stress along existing faults. China’s 2008 Wenchuan earthquake has often been cited in this debate. Scientists have differed over the extent of the Zipingpu reservoir’s role, but some studies have suggested that the reservoir may have contributed to triggering or advancing seismic activity. The concern, therefore, is not only whether an earthquake could damage the dam. A major earthquake could also trigger landslides, rockfalls and failures across the surrounding infrastructure. Singh said advances in engineering have significantly improved dam safety but cannot completely remove geological risks. “Modern engineering can design dams to withstand very strong earthquakes. Advanced materials, flexible structural designs and continuous monitoring systems have greatly improved dam safety. However, no engineer can completely eliminate geological risk,” he said. The region has also witnessed glacier collapses and landslides. Sayanangshu Modak, a researcher at the University of Arizona, cited the massive 2021 glacier collapse near the Great Bend, which temporarily blocked the river and sharply raised water levels, SCMP reported. Long-term safety, he added, would depend on continuous monitoring, regular assessments and the ability of the project to withstand not only earthquakes but also landslides, rockfalls and extreme weather events.
What does Nepal’s recent disaster show?
The August 26 disaster in Nepal offers a stark example of how Himalayan hazards can interact. The evidence available so far points to a glacier-rock collapse and massive debris avalanche rather than a conventional monsoon flood. The collapse triggered an ice-rock avalanche that temporarily blocked the Bhotekoshi River, sending a huge volume of ice, rock, mud and water downstream and causing widespread destruction. The avalanche reportedly travelled at around 50 metres per second. Such events demonstrate the cascading nature of Himalayan disasters. A glacier collapse or earthquake can trigger a landslide; a landslide can block a river; and the sudden failure of that blockage can send a destructive surge of water and debris downstream. Infrastructure located along the river corridor, including roads, bridges, hydropower stations and settlements, can then become part of the disaster chain. The 2015 Nepal earthquake provided another warning. Research following the quake found that earthquake-triggered landslides were a major cause of damage to hydropower infrastructure and estimated that about a quarter of existing, constructed and planned Himalayan hydropower projects faced a high probability of moderate-to-severe earthquake damage.
The August 26 disaster in Nepal.
How climate change is adding to the risk
