Why India’s plans to counter China’s mega dam in Tibet may falter

The Yarlung Tsangpo river originates in the mountains of western Tibet, and flows eastwards through the Tibet Autonomous Region.

It then enters Arunachal Pradesh, where it is known as the Siang. Then, it flows further downstream to Assam, from when it is widely known as the Brahmaputra.

This river is currently the site of an intensifying conflict between India and China over the control, ownership and use of its waters.

While the threat of competition for this water has always loomed large, it began to take firmer shape in July, when China began construction of a 60-gigawatt hydropower project in Medog, just 30 km north of Arunachal Pradesh. The dam is set to be the world’s largest in terms of hydropower capacity – the current largest one, the Three Gorges Dam, also in China, has a capacity of 22.5 gigawatts.

These plans have alarmed India. Ministers have described the dam as a “water bomb” that China can weaponise – either by withholding water to India, or suddenly releasing it in large volumes, which can wreak destruction downstream.

In response, India has been pushing forward with plans to build the 11-gigawatt Siang upper multipurpose project in Arunachal Pradesh’s Siang district. The dam at Siang could help mitigate some of these probable risks of the Chinese dam, Indian authorities have argued.

The government had been considering the project since 2017, when the Niti Ayog proposed it. In February 2022, the Ministry of Jal Shakti formed a technical group to finalise the dam’s height. A month later, they recorded their findings in a report, asserting that the Siang Upper dam “will act as a flood cushion in case of sudden release of flood due to breach in natural and man made storages” in China’s proposed dam at Medog.

The document noted that the dam would also help regulate glacial floods on the river, and thus minimise losses to local livelihoods.

But experts warn that the Indian dam will be of limited use in these respects.

Rather than offer any protection from China, India’s dam will only serve as a marker of its claims over the river, experts argued. As India sees it, “if they do not construct a dam on the Brahmaputra, then we will not have water rights over the river”, said Sumit Vij, assistant professor at Netherlands-based Wageningen University, who has worked extensively on the Brahmaputra basin.

The dam has also raised fears of damage to the local environment and destruction of livelihoods. Thirteen villages in Arunachal Pradesh are to be completely submerged, including agricultural fields where the Adi community grows ginger, cardamom, and paddy. Locals are also concerned that the dam will restrict sediment flow in the river.

Communities in the region have been protesting against the project since 2024, noting that the government was pushing it through without adequately consulting them, and by deploying armed forces and police to quell objections.

Such conflict is regrettable, particularly since, to achieve the tangible results of the kind the government seeks, “there has to be a diplomatic solution, a dialogue solution, and not a dam solution”, Vij noted. He added, “If they get into this dam race, India will harm its own environment much more than what is expected to be harmed by China.”

Scroll emailed the Ministry of Jal Shakti, seeking responses to questions about the rationale behind the construction of the dam and its planned functions. This story will be updated if it responds.

Flood moderation or hydropower generation?

The government intends for the Upper Siang dam to perform more than one function. Arunachal Pradesh Chief Minister Pema Khandu said the dam “is not just about generating power, but also about maintaining the natural flow of the Siang river and mitigating potential flood risks from water releases by China”.

But experts argue that such a goal is unrealistic.

If the Siang dam’s main function is to mitigate against the risk of floods, they said, other functions, such as hydropower generation, would have to take a back seat.

A key reason for this is that since the Siang dam is a hydropower project, water levels of its reservoir would typically be kept high. Soumya Dutta, a visiting senior fellow at Impact and Policy Research Institute who works on energy and climate, noted that “for creating electricity, dam officials keep the reservoir levels at full capacity to maximise the energy potential”.

If China withheld water or released excess water, the Siang dam would allow India to “moderate these daily cycles of peaks and troughs of water for a few days”. But because it would have a limited buffer capacity, “beyond that, if there is a heavy rainfall or a sudden release, the dam will not be able to hold it back”, Dutta explained.

This risk is exacerbated by the geographical limitations the Siang dam will face. Dutta noted that a crucial feature of a dam designed for flood control is a large reservoir. The government is proposing to build a reservoir in Siang – but the geography of the region will only allow for a narrow and deep reservoir, as opposed to the wide ones found in some dams elsewhere in India, like the Nagarjuna Sagar dam, jointly operated by Andhra Pradesh and Telangana to control floods.

In such broad reservoirs, flood control can be carried out even by keeping water levels “just a little low”, Dutta said. In deep reservoirs, however, maintaining a buffer capacity to guard against floods would mean necessarily keeping water levels much lower, which would impinge on hydropower generation capacity.

Dams that prioritise hydropower generation are, in fact, generally prone to causing flooding when there is a sudden inflow of water into their reservoirs – Dutta noted that many independent experts argued that is what happened in the 2018 floods in Kerala.

Indeed, concerns about the construction of the Siang dam do not only revolve around its efficacy – but also about the effects that it might have downstream in Assam, if the dam releases large volumes of water to prevent flooding around it. “Unfortunately, there is no bioregional understanding of rivers,” in India, said Mirza Zulfiqur Rahman, visiting associate fellow at Delhi-based Institute of Chinese Studies.

Such an approach takes into account the fact that “if you create something upstream of the river basin, it will have an impact downstream, and also vice-versa”, he added.

More deliberation needed

The canyon where the Medog dam will be built is one of the deepest in the world, and plunges to depths of more than 5,000 metres. The river’s fall over this canyon generates massive amounts of energy, making it an ideal site for a large hydropower plant.

China has spent decades studying the site and drawing up plans for the dam’s construction. Experts fear that if India now rushes to catch up with its neighbour, its own dam will not be built in the most optimal way.

“China has spent years studying the geomorphology and understanding the advantage of gradient that it has to build the dam there,” said Rahman.

In this regard, India is “15-20 years behind China”, Rahman said. At the moment, the government is attempting to conduct a survey, based on which it would draw up a “pre-feasibility report” of the dam in Siang.

This is only one of the first steps of the process, Rahman explained. “You need to have a long-term research analysis in order to back up your structural interventions,” he said. This work would have helped India understand the area’s hydrology more precisely, and identify potential sites for the dam.

He further explained that such research could have helped minimise the likelihood of protests among local communities, since information about the project could have been communicated to people on the ground in a timely way. At present, he argued, sufficient hard data about the project has not been shared with local communities, which is leading to increased speculation among them.

“If India would have invested time and money in understanding the river basin in the last 20 years, India could have been in a much better position to design a dam that could perhaps counter the Medog dam,” Rahman said.

No treaty

India and China both feel a strong need to demonstrate ownership over the river in this region, experts noted, because there is no international law, transboundary institution, or treaty for the Brahmaputra basin that inscribes how its water should be shared.

All the four countries that use the basin – China, Bhutan, India, and Bangladesh – have diverse interests, ranging from hydropower generation to flood management and economic development. But so far, discussions between them on cooperating over the river have been limited.

In 1997, more than one hundred countries came together to adopt the United Nations Convention on the Law of the Non-Navigational Uses of International Watercourses, which sets out a framework for countries that have to share waters. It mandates that signatories have to share hydrological, meteorological, hydrogeological and ecological data with each other, and that conflicts be resolved “with special regard being given to the requirements of vital human needs”. But other than Bangladesh, none of the other countries in the Brahmaputra basin signed to be party to it.

“That made it very clear that India and China did not want to engage in a multilateral diplomatic negotiation where there could be a third-party mediation,” said Vij. “It could have allowed for a more just, equal playing field for all actors, but the downside is that it would take longer time to negotiate between the countries.”

Instead, India and China signed a memorandum of understanding in 2002 aimed at helping India take steps towards flood control and mitigate the risks of disasters. Under this memorandum, China would provide hydrological information of the river to India in both the flood and non-flood season. This memorandum was renewed in 2008 and 2013 – China temporarily paused it in 2017 after the two countries clashed in Doklam, and renewed it again in 2018. But the memorandum expired in June 2023 and has not been renewed since.

In any case, Vij noted that as a mechanism, a memorandum of understanding “can be a weak institutional mechanism for water-sharing”. Rahman added that while agreements act as “bricks of confidence building”, they are not as strongly backed by international law, and can be withdrawn more easily.

In contrast, under international law, treaties are typically far more comprehensive, and carry more weight. Thus, they usually “lead to cooperation and better understanding between the riparian states”, said Vij.

Indeed, though India and China signed the memorandum, the process of sharing data has been fraught, Vij, Mirza Rahman and Anamika Barua wrote in a 2017 paper. Such sharing is typically a means of building trust between countries, but “in the specific case of the Brahmaputra the lack of a data sharing procedure at the basin level has fostered mistrust between the riparian countries and hindered regional cooperation”, he wrote.

Further, he noted, “The power asymmetry between the countries and the broader political context, which currently considers all hydrological data relating to international borders as classified, make the process of sharing data complex.”

That has left the two countries in a race to create large infrastructure in the Himalaya, which can be disastrous not just to the topography, but also to local indigenous populations. “In the way the dam construction is going on, it probably will not have an impact on what the Chinese are doing as much as it will have on their own population, people, nature and ecology,” said Vij.