China study warns Brahmaputra flows and flood risk could rise this century

The Brahmaputra River in Tibet could see increased water flow and a greater risk of floods during this century, Chinese researchers have warned, according to news agency Press Trust of India. China is building the world's largest dam on the river at an estimated cost of USD 168 billion.

The researchers said future changes in the river's flow should be considered while planning water projects and storage facilities, as well as while assessing water-related risks across national borders.

Researchers from the Chinese Academy of Sciences and Yunnan University studied tree-ring records from the southeastern Tibetan Plateau to reconstruct the river's runoff history from 1325 to 2020.

They combined the findings with climate data to develop a model. It projected an increase in river runoff under future climate conditions, along with a possible rise in high-runoff events such as floods.

“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 team said in a paper published in the journal China Science Bulletin on October 8, PTI reported, citing the Hong Kong-based South China Morning Post.

Yarlung Tsangpo is the name used in Tibet for the river that enters India as the Brahmaputra. It is known as the Siang in Arunachal Pradesh before being called the Brahmaputra further downstream.

According to the researchers, the Tibetan Plateau has been warming at about twice the global average rate, affecting its ice cover and water cycle. They said changes in the river reflect conditions within the plateau and also affect drought and flood patterns in South Asia.

“In recent years, with the ongoing warming of the climate, the hydrological regime of the Yarlung Tsangpo River basin has been undergoing significant changes,” they said.

In July, Chinese geologists warned that an active fault line directly beneath the planned dam could threaten the project's structural stability. In a paper published in the journal Sedimentary Geology and Tethyan Geology, they urged engineers to strengthen slopes and install protective structures to reduce the risk of landslides and collapses, the South China Morning Post reported.

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

The Brahmaputra originates in Tibet and flows south into India. The planned hydropower project is expected to have a total installed capacity of more than 60,000 megawatts when completed, nearly three times that of China's Three Gorges Dam, the world's largest operating hydropower plant by installed capacity.

The project is being built in Medog, also known as Motuo in Chinese, a county in southeastern Tibet near the disputed border with India. The site is in a deep Himalayan gorge where the Brahmaputra makes a sharp U-turn before flowing into Arunachal Pradesh and then Bangladesh.

China proceeded with the project despite major engineering challenges because the site lies along a tectonic plate boundary where earthquakes are frequent. The Chinese Foreign Ministry has previously defended the project, saying it would not affect downstream countries and that safety concerns had been addressed through decades of studies and protective measures.

The study has therefore raised concerns about rising river flows and flood risks as China builds the massive hydropower project in a region already exposed to earthquakes, landslides and other mountain hazards.

With PTI Inputs

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