Can China turn off India's tap, hit land formation?

India Today

4 hours ago

It's impossible that anyone who has taken a train to Guwahati and crossed the Saraighat Bridge hasn't been left amazed by the width of the Brahmaputra. It looks like a sea. Just to imagine that the mighty Brahmaputra gushes as a stream, called Yarlung Tsangpo, in Tibet is unimaginable for millions of Indians. But that's the fact and the visual answer to the question -- can China turn the Brahmaputra tap off for India?advertisementThe idea that China, being the upper riparian country, might be capable of controlling the flow of the Tsangpo-Brahmaputra river system was brought up by Pakistan after India suspended the Indus Waters Treaty (IWT).That scare-mongering was promptly addressed by Assam Chief Minister Himanta Biswa Sarma. But what do research data and experts suggest? Can China block or divert the flow of Yarlung Tsangpo and hit India's water supply?
Diverting the flow of a high-sediment river like the Brahmaputra won't be just about the water, it would also hit soil formation downstream."If India does something like this that they stop the flow [of rivers] to Pakistan, then China can also do the same thing," Rana Ihsaan Afzal, a senior aide to Pakistani Prime Minister Shehbaz Sharif, told Geo News on May 23.advertisementHis remarks caused some consternation given the fact that China is constructing the 60,000-MW Medong Dam on the Yarlung Tsangpo at the Great Bend, near the India-China border.Experts rule out any possibility of China blocking or diverting water, and say a bigger worry should be that the massive dam -- one of the biggest in the world -- is coming up in a calamity-prone area in China-controlled Tibet.Economist Nilanjan Ghosh, who has studied the Tsangpo-Brahmaputra River System for close to two decades, says that it has never been China's position to block the flow of the Brahmaputra, albeit it aims to build run-of-the-river dams."Any attempt to divert the flow would be counterproductive as it would result in upstream floods because of sediment accumulation," Ghosh, Vice President, Development Studies at the Observer Research Foundation (ORF), tells India Today Digital.The expert says China won't be able to "turn off the tap" as the Brahmaputra is primarily a rain- and tributary-fed river, and the Yarlung Tsangpo contributes just 10-15% of the entire volume of the Brahmaputra's water."The Brahmaputra gets fatter and fatter as it moves downstream," says Ghosh.
China contributes only a small portion of the Brahmaputra's total water. As the river flows through India, its volume increases more than six times due to several tributaries joining in. (Image: Arun Uniyal/India Today)
In January this year, Ghosh and fellow researcher, Sayanangshu Modak, published a research paper in the peer-reviewed International Journal of Water Resources Development where they used hydrological data to junk the rhetoric around China being capable of turning the Brahmaputra tap off.Data collated over the years show that the discharge of the Yarlung Tsangpo, measured at Nuxia in Tibet, to be at 31.2 billion cubic meters (BCM) annually, which then swells to an estimated 78.1 BCM as it passes through the Great Bend and exits China.At the measuring station at Pandu in Guwahati, the Brahmaputra's annual discharge is 526 BCM, showing a six-fold volume increase. At Bahadurabad, in Bangladesh, which is just across the border with India, the annual discharge is 606 BCM.This shows that since the river's entry into India, the Brahmaputra has been fed by its tributaries to grow massively.The Brahmaputra has shaped Assam for centuries by carving out banks and creating shape-shifting islands. It has caused flooding woes, but has also left behind life-sustaining fertile soil.advertisementThe Majuli island on the Brahmaputra is the world's biggest riverine island, and has been at the heart of neo-Vaishnavism, spearheaded by Srimanta Sankaradeva. The Vaishnavite satras (monastries) in Majuli have been centres of cultural and art for centuries.Like the one-horned rhino, the twin-leaf tea buds and the xorai and gamusa, the Brahmaputra has become a marker for Assam's civilisational identity."Mahabahu Brahmaputra" is how legendary Assamese singer Bhupen Hazarika refers to the mighty river in one of his ever-popular songs, which tells the story of the land it feeds.WHAT BRAHMAPUTRA FLOODS SUGGESTOriginating in the Angsi Glacier in western Tibet, the Yarlung Tsangpo travels 1,625 km in the China-controlled territory of Tibet and enters India after the Great Bend near the Namcha Barwa peak. Then, as the Brahmaputra, it flows for 918 km within India and another 337 km in Bangladesh, where it is called Jamuna, and empties into the Bay of Bengal.The length of the Tsangpo-Brahmaputra system in Tibet gives the perception that it is a major river with a huge water volume in China.advertisementGhosh agrees with Himanta Biswa Sarma's analysis of the Brahmaputra but calculates the Tsangpo's water contribution to the Brahmaputra at much lower than the 30-35% pegged by the Assam chief minister.The expert says though the river system completes 56% of its run in China, it contributes just 15% of the water in its boundary."That is why some literature suggests the Yarlung Tsangpo to be a tributary of the Brahmaputra," Ghosh tells India Today Digital.It is believed that the Brahmaputra was actually formed at Sadia in eastern Assam after the merger of three rivers -- the Dihang (Siang), Lohit and Dibang."So, I don't think that, given these hydrological facts, there will be any substantial impact on India, even if China blocks the flow of Tsangpo," says Ghosh.
The Brahmaputra in Assam gains significant volume of water as it flows parallel to the Himalayan foothills and is fed by many snowmelt tributaries such as the Subansiri, Kameng, and Kameng rivers.(Image: Arun Uniyal/India Today)
advertisementDerek J Grossman, a national security and Indo-Pacific analyst with Rand Corporation, says Pakistan cannot count on China to turn off the tap as monsoons feed the Brahmaputra."China has little control over the water flow of the Brahmaputra River, according to Indian government officials. One reason is that monsoons are the primary source of water. Another is that Beijing can only halt roughly 30 percent of the flow. Pakistan can't count on China," says Grossman.Tibet, one should remember, is a cold desert with very little precipitation. It is the glaciers that give birth to the rivers there.In India, the Brahmaputra has been linked with devastating annual floods, which are a result of the water drained into it by over two dozen tributaries in the monsoon months.Sadia – the town where experts argue that the Brahmaputra is formed – is the town where Bhupen Hazarika was born, and a good part of it was engulfed by the Brahmaputra as it changed course after the earthquake in 1950.Hazarika rebukes the Brahmaputra, referring to it as Burha Luit, in one of his songs, for flowing silently, deaf to the wails of the numerous people on its banks. "...Burha Luit tumi boa kiyo (Why do you flow)," he asks.CHINA'S BLOCKING OF BRAHMAPUTRA FLOW WON'T HIT SOIL FORMATIONExperts have suggested that the Brahmaputra is an antecedent river that is older than the Himalayas.While the Brahmaputra, in its age-old wisdom, flows silently, taking away land, like in Sadia, the sediment it carries is crucial to soil formation.Even from the perspective of soil formation and fertility, China's blocking of the Yarlung-Tsangpo wouldn't impact India.According to the 2016 book -- River morphodynamics and stream ecology of the Qinghai-Tibet Plateau -- by Chinese experts, the annual suspended sediment load of the Yarlung-Tsangpo near Nuxia in Tibet is around 30 million metric tonnes (mmt), much lower than the 735 mmt of sediment load at Bahadurabad in Bangladesh.The stream-like Yarlung Tsangpo in Tibet cannot carry the sediment load, and it is the powerful Brahmaputra that does the heavy-lifting of the sediment load not just in India but to form the fertile Jamuna floodplain in Bangladesh.The average width of the Brahmaputra is 5.46 km, according to the Assam Water Resources website. In areas where it forms a braided system due to sediment deposition, the width extends to up to 18 km.
Satellite images show the Yarlung Tsangpo (top) in Tibet as a narrow, fast-flowing river cutting through the plateau, while in the Assam plains the Brahmaputra (bottom) spreads out and swells into braided channels, often accommodating islands as large as Majuli and the one with the Dibru-Saikhowa National Park.Note: The scale of the two images is not uniform, and they are presented only for visual comparison, not to exact proportions. (Image: Google Maps)
INDUS WATERS TREATY SUSPENSION AND CHINA'S DAMSThe Indus Waters Treaty (IWT) that India kept in abeyance after the April 22 Pahalgam terror attack is very different from the treaty that India has with China on the Tsangpo-Brahmaputra system.While the IWT is a water-sharing treaty under which India gave the rights to water use of the western rivers of the Indus Rivers System to India, the pact with China on Yarlung-Brahmaputra is just for sharing of information, and not water.What China could do worst is stop sharing hydrological data with India, but even that won't matter much, according to Ghosh."India has an MoU with China for hydrological data from three stations [in China]. Even if China stops sharing data, it won't matter because the information isn't helping much anyway due to the wrong choice of stations [agreed on] by the Indian government at the beginning of the millennia," he tells India Today Digital.Ghosh says no one should draw parallels between the Indus Water System and the Tsangpo-Brahmaputra River System because of the difference in the nature of the two."The Indus System is largely fed by glacial and ice melt. It has around 45% to 55% normalised melting index (NMI). While the contribution of glacial and ice melt of the Brahmaputra is barely 10-12%," says Ghosh.What this means is that the bulk of the water in the Indus River System is added upstream, which isn't true in the case of the Yarlung-Brahmaputra. While India has the advantage of being the upper riparian state in the case of the Indus system, China doesn't enjoy that in the case of the Brahmaputra.While Pakistan, an agrarian economy, is completely dependent on the Indus River System for its agriculture and power generation, India, according to Ghosh, barely taps 25% of the renewable water flow of the Brahmaputra.Therefore, while Pakistan might love to believe that its "all-weather friend" China might be able to turn the tap off on India and hurt it, this isn't true going by the hydrological and meteorological data.The Brahmaputra has historically been associated with Assam's resilience. The Saraighat rail bridge that one uses to travel to Guwahati is a reminder of that.It was the crucial Battle of Saraighat, led by legendary Ahom general Lachit Borphukan, on the Brahmaputra that led to the defeat of the Mughal forces and the end of the siege of Guwahati.Mahabahu Brahmaputra nurtures Assam. It is formed in Sadia and China cannot weaponise its waters against India.