China is building the world’s largest hydroelectric dam in the lower parts of the Yarlung Tsangpo River in Tibet, about 50 kilometres from the border with India.

New Delhi: China’s under-construction mega hydropower project on the Yarlung Tsangpo River in Tibet has led to concerns in India and Bangladesh over water supply and environmental impacts downstream. Now, a Beijing-backed geological study has flagged its structural safety, the South China Morning Post reported.

An active fault line directly beneath the project could pose a threat to the mega dam and significantly affect the integrity of its infrastructure, according to the findings, published in a study supervised by the state-owned China Geological Survey, added.

The Paizhen Fault runs directly through the reservoir area of the massive hydropower project, the study, published last month in the Chinese-language journal Sedimentary Geology and Tethyan Geology, stated. 

Researchers said the fault has remained active since the Pleistocene (Ice Age) and could significantly affect the structural integrity of dams, bridges, roads, tunnels and other infrastructure built in the region.

The Yarlung Tsangpo flows into India’s Arunachal Pradesh and Assam as the Brahmaputra River before entering Bangladesh as the Jamuna River.

The team noted that the fault has fractured surrounding rocks and changed their mechanical properties, making the foundation bearing capacity and structural stability of nearby engineering projects more vulnerable to damage.

The terrain in the reservoir area has a loose structure and weak cohesion, warning that fault activity, earthquakes and prolonged immersion could easily trigger instability in the slopes on both sides of the reservoir, they added.

The Yarlung Tsangpo downstream hydropower project, construction of which began last year, is expected to generate around 300 billion kilowatt-hours of electricity annually, with a capacity nearly three times that of China’s Three Gorges Dam. 

“Since the Pai village area is located within the construction zone of the Yarlung Tsangpo downstream hydropower project, its records of Quaternary tectonic activity provide an important basis for exploring the structural stability of nearby projects,” the team said.

Researchers said geological records indicate that the Paizhen Fault remained active well into the Holocene period, with evidence showing movement as recently as about 9,500 years ago.

They also cited the magnitude 6.9 Milin earthquake that struck Tibet in 2017 near the northern end of the fault as evidence of the fault line’s modern seismic potential. According to the researchers, future earthquakes could trigger landslides and collapses that may endanger engineering structures and personnel.

The study was conducted by researchers from Chengdu University of Technology, the Civil-Military Integration Centre of the China Geological Survey, and the Middle Yarlung Zangbo River Natural Resources Observation and Research Station.

To reduce these risks, the study recommends strengthening structural stability during construction through measures such as slope reinforcement, retaining barriers to minimise the possibility of landslides and collapse.