A ticking time bomb? The unseen dangers of China's mega dam on Brahmaputra

The devastating floods in Nepal are a reminder of how vulnerable the Himalayan region is to natural disasters that are becoming increasingly difficult to predict. But they also pose another question: What happens when such fragile terrain becomes a site for large hydropower projects, including one that will be the largest upon completion?

This question becomes pertinent for India as China goes ahead with its Great Bend (Medog) Hydropower Project on the Yarlung Tsangpo river, which enters Arunachal Pradesh as Siang before opening up in Assam as the Brahmaputra. It is being built in one of the world’s most geologically fragile regions, where earthquakes, landslides, glacial lake outbursts, extreme rainfall and other cascading disasters are major risk factors.

Notably, one of the hydropower projects badly damaged in the Nepal floods—the Upper Trishuli 3A Hydropower Project—was being partly funded by China’s Exim Bank. Currently, a large number of people are trapped in its tunnels.

The seismic potential of the Brahmaputra basin is much higher. The catchment area is much larger, which means the flood threat multiplies. It is also an erosion-prone area and, therefore, highly landslide-prone.

While the immediate debate in India has centred on whether China will be able to manipulate the Brahmaputra’s flow, what is also crucial to see is how much it can impact the region’s downstream in the case of a natural disaster. While such projects can trigger avoidable flood disaster, they can also act as force multipliers. For instance, in the Chamoli disaster in 2021, every person who died was either working in hydropower or died because of the hydropower project. Similarly, during the glacial lake outburst in Sikkim in 2023, hydropower projects suffered the most damage—largely because of negligence—and ended up compounding the disaster.

The issue with the Great Bend Project is that we don’t know its basic dimensions. What is this project? What is the height of the dam? What is the hydropower component? What is the number of units? What is the length of the headrace tunnels (used to transport water from the reservoir to the power station)? How much water is going to flow through it? What is the storage capacity of the dam? Is there a diversion capacity?

Even to understand the central concern of how much China will be able to bend the Brahmaputra river through the project and how it will impact downstream areas, these questions are crucial.

It is India’s right to get this information from China. The claim that India is trying to neutralise the impact by building the Siang Upper Multi-purpose Project doesn’t hold water, because you don’t even know what you are neutralising.

If it’s a purely hydropower project, which is what it seems like at the moment, during monsoons they can’t do much in terms of reducing downstream flows. Same is likely to be the case during summers, because of melting. In winter, however, its capacity to manipulate the flow could be higher.

However, in case the project itself faces a certain problem, its impact will be much bigger in the downstream areas.

Bhutan is also in the Brahmaputra basin, but China is not known to be building any projects in the catchment area of Bhutan’s rivers. So it is primarily India and Bangladesh that are concerned. As far as Bangladesh goes, in regular operation, the project might not make much difference, but it could be impacted if there is a disaster. Hence, the most impact will be borne by India, that, too, mostly Arunachal Pradesh.

Another issue is the secretiveness of the Chinese when it comes to such disasters. In Siang, for example, in June 2000 there was a massive landslide that blocked one of the tributaries of the Yarlung Tsangpo. It created a huge reservoir.

The Chinese army had to prepare a road leading to it and then take heavy machinery to breach it. All this preparation took several weeks. India came to know about it only when that water arrived after the breach.

There are no international norms that mandate China to share such data with downstream countries. Whatever norms exist, China is not known to be following them. There is the 1997 UN Convention on the Law of the Non-Navigational Uses of International Watercourses, but China, India and Bangladesh have not signed it.

Take the case of the Mekong River and the longstanding geopolitical, environmental and hydrological dispute between China and countries like Thailand over the former’s upstream control of the river.

China is the upstream country with respect to most rivers that flow from it, and it has not signed any water-sharing agreement or information-sharing agreement with anybody.

Hence, what is required is some kind of a joint disaster-warning mechanism between India, China, Nepal and Bangladesh. There should also be, as far as trans-boundary rivers are concerned, a multilateral effort to conduct research, monitor and share information. If it is not possible multilaterally, at least it should be bilateral to begin with.

India should ask China to conduct joint research because there is so much happening in terms of climate change and its impacts in this region. In fact, India has a right to ask for a joint India-China impact assessment of the Great Bend project, and it should do so publicly.

So far, we have been talking about glacial lake outbursts or flash floods. Now there is a new situation where there could be something like a hanging glacier and an avalanche coming from melting permafrost.

India has significant leverage in terms of trade with China. It is actually importing much more from China than it is exporting. India is a much bigger market.

Frankly, it doesn’t help to go for a big hydropower project when there is no justification for it. In fact, every disaster provides us with more reason why we should not be going for such projects.

India should definitely be demanding a common water-management mechanism. But that could be the next step; the first step should be information about shared rivers.

The writer is coordinator, South Asia Network on Dams, Rivers and People.