Why China's proposed mega dam spells concern for India

There are many types of aggression in international politics, and some of them are driven by water. In 1951, when China formally occupied and annexed Tibet to make it an integral part of the People's Republic, it gained control over major river systems and became the dominant power in control of Asia's water map.

With that annexation, China today sits upriver of major water sources of South and South East Asia, making its southern neighbours, including India, jittery every time Beijing plans to build another dam on any river that rises in the highlands of Tibet. The rivers Indus, Brahmaputra, Irrawaddy, Salween, Yangtze, and Mekong, flowing into Pakistan, India, Bangladesh, Myanmar, Laos and Vietnam, all rise in the Tibet Autonomous Region of China.

China is considered a country with the most dams, with some estimates putting the number at close to half of the world's 50,000-odd dams categorised as large dams. Some dams in China are bigger than 'large', and they are so huge that they can only be called mega dams. Take, for example, the dam that China built on the Yangtse River called the Three Gorges, the world's largest hydroelectric dam with a generating capacity of 22,500 megawatts. The second-largest hydroelectric dam in the world got commissioned in 2021, just days before the 100th anniversary of the Chinese communist party. The Baihetan Dam on the Jinsha River, a tributary of the Yangtze, is also said to be the world’s biggest arch dam.

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Now, there has been talk of China building another super dam, bigger than anything in existence, on the Yarlung Tsangpo that becomes the River Brahmaputra in India. This dam will be built in the Medog region, where the Yarlung Tsangpo takes a U-turn and begins its descent into India. The dam is part of China's 14th 5-year plan and will have 3 times the capacity of the Three Gorges Dam. For India, the concern is not the capacity of electricity but the nature of the dam and the river it will be built upon - the Yarlung Tsangpo/Brahmaputra.

The river flows in China for about 1,600 kilometres from its headwaters near Mount Kailash in Tibet, then 900 odd kilometres in India first as Siang and then as the Brahmaputra before joining with the Teesta and entering Bangladesh to carry on for a little over 300 kilometres as the Yamuna, till its confluence with the Ganges at Goalando.

The region where China plans to build the biggest dam that the world has ever seen is in south-eastern Tibet, where the river bends sharply and rushes through one of the most dramatic gorges in the world. The Yarlung Tsangpo gorge stretching over 500 kilometres is carved out of granitic bedrock, which reaches 17,000 feet above sea level at some places, making it three times deeper than the Grand Canyon.

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The concern in India and Bangladesh is about how much of the water of the Brahmaputra and the Yamuna would get blocked by the massive dam that China will build in this Yarlung Tsangpo canyon. Some experts are of the opinion that this may not be so worrisome a factor because the longer stretch of the Yarlung is located in the rain-shadow zone to the north of the Himalayan range and receives much less rainfall compared to the south part of the river.

This means that the average annual precipitation from snowmelt and meagre rainfall that the river receives in Tibet is about 300mm. But after the U bend, as the river moves towards the foothills and into India, the average annual precipitation, mainly rainfall, is 3,000 mm or more. The river flow increases by about 10 times between where it comes out of the canyon and when it reaches Guwahati halfway down the Brahmaputra valley in Assam. There are also at least 7 very healthy tributaries of the Brahmaputra that contribute to its massive flow.

So even if China were to dam the Yarlung Tsangpo it would not greatly affect the amount of water that the Brahmaputra would carry, and it is unlikely that the Chinese dam would substantially impact the economies of India or Bangladesh. However, the real matter of concern has more to do with environmental impact and the deadly outcome in case of an accidental breach at the future dam.

The Medog region sees heavy monsoon, landslides and avalanches are common occurrences, and many instances of flash floods have been recorded here. Add to that the suspect tectonicity of the Eastern Himalayas, meaning that the chance of an earthquake is not rare in this region. So, imagine what could happen if a mega dam built here bursts because of an earthquake; the devastation that it would cause in Arunachal Pradesh, Assam, and even in Bangladesh with a wall of water, like a Tsunami, with terrible force sweeping everything in its path.

In 1975 the Banqiao Dam, in China, collapsed killing an estimated 230,000 people. The dam had burst after incessant rains, sending a wall of water nearly 20-foot-high and over 11-km-wide surging downstream, bursting 62 other dams downriver drowning 26,000 people within a few hours. There is certainly no comparison between the near primitive engineering of the Banqiao and what China is capable of now, but that will not stop people downriver of a mega dam from worrying. Engineering can never guarantee a failsafe promise against nature, and a mega dam on the Yarlung Tsangpo will always carry with it the danger of a mega disaster in the event of an earthquake or landslide.

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