Beijing: Chinese researchers have warned that the Brahmaputra River in Tibet, where China is building the world’s largest dam at an estimated cost of USD 168 billion, could experience increased runoff and heightened flood risks over the course of this century.
Researchers from the Chinese Academy of Sciences and Yunnan University used tree-ring width chronologies from the southeastern Tibetan Plateau to reconstruct the river’s runoff history from 1325 to 2020.
They combined the reconstruction with climate data to create a model that projected that river runoff would increase under future climate scenarios, 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, the Hong Kong-based South China Morning Post reported on Monday.
Yarlung Tsangpo is the name used in Tibet for the river that flows into India as the Brahmaputra.
The researchers said future runoff should be considered in planning “water resource development and storage infrastructure” and in assessing transboundary water risks in the region.
The Tibetan Plateau has been warming at about twice the rate of the global average, affecting its ice cover and hydrological cycle, according to the Chinese researchers.
They emphasised that changes in the river not only reflect the hydrological system within the plateau but 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 structural stability of the project.
In a paper published in the Sedimentary Geology and Tethyan Geology journal, the researchers urged engineers to strengthen slope stability and implement retaining protections to mitigate the risk of landslides and collapses, the South China Morning Post reported.
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 highlighted the vulnerability of the Himalayan region to mountain hazards.
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. It is known as the Siang in Arunachal Pradesh before being called the Brahmaputra further downstream.
The river is the site of the world’s largest planned hydropower project, which is expected to have a total installed capacity of more than 60,000 megawatts upon completion nearly three times that of China’s Three Gorges Dam, the world’s largest operating hydropower plant by installed capacity.
The mega project is being built in Medog, also known as Motuo in Chinese, a county in southeastern Tibet close to the disputed border with India.
The dam is being built in a deep gorge in the Himalayan reaches where the Brahmaputra makes a sharp U-turn before flowing into Arunachal Pradesh and then Bangladesh.
China went ahead with the project despite the enormous engineering challenges, as the site is located along a tectonic plate boundary where earthquakes occur frequently.
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 safety measures.
