Brahmaputra could experience increased runoff, heightened flood risks: Chinese researchers as China builds mega dam

Chinese researchers have warned that the Brahmaputra River could experience increased runoff and heightened flood risks over the course of this century, as the country builds the world’s largest planned hydropower project in Tibet at an estimated cost of $168 billion.

Researchers from the Chinese Academy of Sciences and Yunnan University reconstructed the river’s runoff history from 1325 to 2020 using tree-ring width data from the southeastern Tibetan Plateau. Combining the reconstruction with climate data, they developed a model projecting that runoff could increase under future climate scenarios, alongside a possible rise in high-runoff events such as floods.

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The findings were published in the journal China Science Bulletin on October 8, the Hong Kong-based South China Morning Post reported on Monday.

“These results provide a long-term perspective on hydroclimatic variability in the Yarlung Tsangpo River and a scientific basis for assessing future water-resource risks,” the researchers said.

Yarlung Tsangpo is the Tibetan name for the river that flows into India as the Brahmaputra. The researchers said projected changes should be considered when planning water-resource development and storage infrastructure, as well as assessing transboundary water risks.

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The Tibetan Plateau has been warming at about twice the global average rate, affecting its ice cover and hydrological cycle. The researchers said changes in the river system could influence drought and flood patterns across South Asia.

The warning comes amid concerns over the safety of China’s mega dam project in Medog, also known as Motuo, in southeastern Tibet near the disputed border with India. The project is expected to have an installed capacity exceeding 60,000 megawatts, nearly three times that of China’s Three Gorges Dam.

In July, Chinese geologists warned that an active fault line directly beneath the planned dam could threaten its structural stability. They urged engineers to strengthen slope stability and introduce protective measures against landslides and collapses.

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The Himalayan region’s vulnerability to mountain hazards was highlighted by the August 26 flash floods along the China-Nepal border, triggered by an ice-and-rock avalanche and the subsequent collapse of a temporary river blockage. The disaster killed nearly 1,500 people and left more than 5,500 missing in Nepal and China.

China has defended the dam, with its Foreign Ministry previously saying the project would not affect downstream countries and that safety concerns had been addressed through decades of studies and protective measures.