Nepal-China border: Why a newly-formed lake is sparking fears of more flooding

Rescue efforts persisted in Nepal's flood-stricken areas on Friday, as authorities remained vigilant following the emergence of a new lake near the Nepal-China border, which has sparked concerns of additional flash floods. This warning follows devastating floods that struck the Himalayan border region two days ago, claiming over 500 lives and leaving more than 1,500 people missing.

Nepal's disaster management authorities revealed that satellite imagery and preliminary evaluations suggested a river had been obstructed upstream, leading to the formation of a growing lake that might overflow and unleash a sudden torrent of water downstream. The rescue operations were further hampered by the newly formed barrier lake, which began overflowing, heightening fears of another flash flood in regions already devastated.

The newly formed lake is situated at an elevation of approximately 2,950 meters, around 1,000 meters above the affected area. Satellite imagery from China's state broadcaster CCTV showed that the lake had formed in the same region where a glacial detachment occurred on Wednesday, setting off a chain of events that resulted in widespread destruction downstream. The lake is positioned roughly 10 kilometers away from Gyirong Port, a vital border crossing with Nepal that was inundated by mud and floodwater.

The lake's formation occurred after debris from a massive glacier collapse obstructed the river near the Nepal-Tibet border, creating a natural barrier and trapping water upstream. Debris and rocks blocked part of the river, forming a temporary dam and causing water to accumulate behind it. The lake is located close to the confluence of the Chhochen Khola and Purepu Tsangpo rivers, both of which originate in Tibet and merge before entering Nepal, where they are known collectively as the Bhote Koshi before eventually flowing into the Trishuli river.

Nepal's National Disaster Risk Reduction and Management Authority (NDRRMA) warned that the lake was still expanding and posed a risk of bursting. "The lake is continuing to grow and there is a risk that it could burst," the NDRRMA stated. Qianggong Zhang, from the International Center for Integrated Mountain Development, informed the Associated Press that the lake contains a few million cubic meters of water and is situated in a valley with limited elevation change towards downstream areas. Zhang estimated that the water volume is roughly equivalent to 1,200 Olympic-sized swimming pools.

Authorities are concerned due to warnings from scientists about the potential for further flooding caused by continuing glacial melt, high temperatures, and debris obstructing river channels. Jakob Steiner, a geoscientist at the University of Graz in Austria, highlighted that continued glacial melting due to high temperatures and an accumulation of debris and rocks along the river's path could lead to more flooding.

Both Zhang and Steiner emphasized the necessity of taking the warnings seriously, particularly as rescue teams continue searching for people missing in the floods. However, they also noted that another flash flood of the same catastrophic scale was unlikely. India is closely monitoring the situation, with 96 Indian nationals stranded in China safely crossing into Nepal on land, and the Ministry of External Affairs (MEA) stating that they are prepared to offer any necessary assistance to Nepal in its rescue operations.