New Delhi, once again, has asked China to resume the flow of hydrological data for the rivers that flow through its largely unmarked border, and this time it does so with much more seriousness than in diplomatic jargon. During the 36th meeting of the Working Mechanism for Consultation and Coordination on India-China Border Affairs, which is taking place in New Delhi this week, India is seeking an early meeting of the Expert Level Mechanism on trans-border rivers and has called for the Chinese side to provide technical details of the projects it is constructing on the Yarlung Tsangpo in Tibet. The demand is not new, India had been making a variant of it since 2018, but the circumstances have changed drastically, and that is what makes this round different.

China is now constructing the world's biggest hydropower dam in a valley only 50 kilometres from the Indian border in Arunachal Pradesh, in the vicinity of Medog county in Tibet. The project was approved and ground-breaking was conducted by Premier Li Qiang in July last year in Nyingchi and is expected to cost more than 1.2 trillion yuan ($167-178 billion), and will produce an installed capacity of 60,000 megawatts, with an annual capacity of about 300 billion kilowatt-hours. As a comparison, it would be, by far, the largest hydro power station in the world, by far, and it will be built over the next 10 years. Once the river enters into the Arunachal Pradesh it is called Siang, as it reaches Assam it is called Brahmaputra and when it reaches Bangladesh it is called Jamuna and finally flows into the Bay of Bengal after merging with the Ganga. That one river system is the source of drinking water, irrigation and fisheries for tens of millions of people in three countries.

The size of the structure is alarming, but so is the lack of information surrounding it, which is what scares Indian planners. China has been withholding hydrological information on the river during the flood season since June 2023, due to the frosty relations since the Galwan incident in 2020, as revealed in the submissions to Parliament last year. Created in 2006 specifically for this kind of data exchange, the Expert Level Mechanism is not a treaty to be honored, and goodwill has been lacking. India's forecasting capacity for floods in Assam and Arunachal is hugely hampered without real-time flow data and its forecasting capacity for sudden water releases is equally limited. There's also the harder-edged concern that the dam is in one of the world's most seismically active regions: a zone where the Indian and Eurasian plates are still grinding and if it was to fail or if it was to be tampered with, the consequences would be impossible for any downstream government to insure against.

Rather than wait for Beijing to cooperate, New Delhi has sought to create its own leverage. The Siang Upper Multipurpose Project in Arunachal Pradesh is the answer India is looking for: It is being developed by NHPC, with a capacity of 11,000 megawatt and a reservoir capacity of around nine billion cubic metres, with an estimated cost of 1.13 lakh crore rupees (around 13 billion dollars). The government has openly said that the project is for two purposes: first, to produce electricity, and second, to buffer the sudden flooding or withdrawal of river water due to Chinese activities upstream. It's significant that a hydropower project is being sold as a national security initiative, not as an economic opportunity. The plan has also encountered strong opposition from locals. Twenty-seven villages in the Adi tribal belt are reportedly in danger of being flooded and over one hundred thousand members of the tribe are at risk of being displaced, and central paramilitary troops have been deployed to prevent survey teams from leaving. That is, the project is creating its own domestic political price, but also portraying it as being strategically necessary.

On both sides the economics are suspect. At nearly 180 billion dollars, it's more than five times and thirteen times the size in capacity, respectively, of India's dam, and a sign of how vastly different river geography is, as well as a larger asymmetry in the amount of capital that each state can raise to build frontier infrastructure. The project is also a means of regional development for Tibet and a showcase of engineering prowess in China, where the economic returns would be slim in many places, but the project is financed with state money and is guaranteed by the nation's sovereign debt. India's economic calculations are more precise, constrained by budget limitations and other factors such as environmental clearance and land rights litigation, which Beijing's economic model has to deal with less.

In addition to the bilateral optics, this is rapidly becoming a template model of how power is exerted over water in Asia where there is no binding water-sharing law, unlike the Indus, Mekong or Nile systems to varying extents without the constraints of a legal framework. Bangladesh is the furthest downstream nation, and has expressed its too-soft concern about the Jamuna's importance in flood control and agriculture. Water diplomacy will, however, sit awkwardly with other two main topics trade and de-escalation of the border since Chinese President Xi Jinping is likely to be in New Delhi for the BRICS summit in September.