Will China’s mega dam in Tibet bring a water crisis to India? New study gives hint

China’s planned super dam will see water levels rise during dry seasons and control flooding during high-risk periods, data shows

On the Tibetan plateau, a super dam will harness the roaring river of Yarlung Tsangpo, generating triple the electricity of the Three Gorges Dam.

But politicians in India, sitting downstream, have voiced fears the dam could be a “water bomb” exacerbating floods in monsoons, or that it could steal water in dry seasons.

Since Beijing approved the project in December last year, there have been lots of discussions, but little proof.

Now a joint study by Hohai University and China’s Ministry of Water Resources suggested the dam’s impact on the Yarlung Tsangpo could be opposite to India’s fears.

The study draws data from two large dams already working upstream: Zangmu and Jiacha. Measured since 2014 at hydrological downstream, the results are clear: dry seasons get wetter.

Low flows were up more than 50 per cent in February. Water rose significantly throughout the dry season. India feared drought – the dams brought more water instead.

And floods became smaller, with peak flows down by 2 per cent. In August, the riskiest period for flooding, water levels remained moderate.

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The Yarlung Tsangpo River, situated in the southeastern Qinghai-Tibet Plateau, possesses immense hydropower potential – second only to the Yangtze River in China.

But dams came late to Tibet, said the team led by Dr Zhang Jianyun, China’s dam safety chief.

“Harsh climates, technological limitations, economic challenges and political factors have constrained large-scale reservoir construction in this high-altitude region,” wrote Zhang and his colleagues in a peer-reviewed paper published in the Chinese journal Advances in Water Science on May 15.

With the implementation of the West-East Power Transfer strategy, hydropower development is now booming.

And so are the dams’ environmental impacts.

“Research on how reservoir operations in extreme cold environments affect downstream hydrological and thermal regimes remains limited due to scarce long-term observational data,” wrote Zhang, who is also the water ministry’s director of climate change research.

“Yarlung Tsangpo is an ideal natural laboratory for studying river system responses to global climate change and human activities, particularly under cascade hydropower development.

“Quantifying the impacts of large-scale water infrastructure on river hydrology and thermal behaviour in alpine zones is now a critical research frontier.”

https://youtu.be/lDFwYKAmyVc?si=i6BOTxJyaqr9SRew

Glacial melt adds a significant amount of water into the river between June and October, as air warms at a pace of 0.05 degrees Celsius per year in the region.

And water heats oddly. In cold months, the chill goes more deeply while warm months get hotter – fish feel it.

“Against the backdrop of global warming, the joint operation of the Zangmu and Jiacha reservoirs has amplified the hydrothermal lag effect downstream to some extent,” Zhang’s team said.

“Peak flood flows decrease, while dry season flows increase, thereby altering the hydrological rhythm of river ecosystems and disrupting habitats and life cycles of aquatic organisms.”

“Findings from such studies will provide essential references for sustaining river ecosystem health and optimising water resource management in the Yarlung Tsangpo basin,” they added.

Indian Officials have expressed apprehensions that the proposed dam would give Beijing significant power to regulate or even divert the flow of the trans-border river, which enters India through Arunachal Pradesh before flowing into Assam and Bangladesh.

In a recent interview with news agency PTI, Arunachal Pradesh chief minister Pema Khandu warned of the dangers posed by the project, saying, “It is going to cause an existential threat to our tribes and our livelihoods. It is quite serious because China could even use this as a sort of ‘water bomb’.”

Dubbed the Great Bend Dam, the 60,000 MW dam will have a power capacity three times that of the massive Three Gorges Dam, also in China.

Why India is Alarmed by the Chinese dam ?

The Yarlung Tsangpo is not just a Tibetan river; as it crosses into India, it becomes the Siang in Arunachal Pradesh, and further downstream in Assam, it merges with tributaries such as the Dibang and Lohit to become the Brahmaputra—a river lifeline for millions in India and Bangladesh.

Regarding the potential for weaponising water in geopolitical strategy, a 2020 report by the Lowy Institute, an Australian think tank, warned that Chinese control over rivers originating in Tibet could give it a powerful hold over India’s economy and agriculture.

“If the dam is completed, our Siang and Brahmaputra rivers could dry up considerably,” Arunachal CM flagged.

The concern here is not hypothetical. China is not a signatory to international water-sharing treaties. This limits India’s ability to legally restrain Beijing from altering the flow of the transboundary river.

Khandu said if China had been a signatory to such agreements, the project might have been beneficial for India.

“Suppose the dam is built and they suddenly release water, our entire Siang belt would be destroyed. In particular, the Adi tribe and similar groups… would see all their property, land, and especially human life, suffer devastating effects,” he explained.

What is India’s counterplan?

In response, India has initiated steps to secure its own water security through the Siang Upper Multipurpose Project—a proposed 10 GW hydropower plant in Arunachal Pradesh, said Prema Khandu. This dam will act both as a power generator and a strategic buffer.

He added that the decision came after extensive consultations with the central government. “The Arunachal Pradesh government has conceived a project called the Siang Upper Multipurpose Project, which will serve as a defence mechanism and ensure water security,” he said.

Though China has not shared any official updates, Khandu believes construction may already be underway. India’s own project could help regulate water availability and act as a safeguard during potential floods induced by China’s dam. “In the future, if China releases water, there will definitely be flooding, but it can be controlled,” he added.