A glacier collapse, flood, now a lake ready to burst: Fresh threat to Nepal

A fresh barrier lake holding around 2 million cubic metres of water has formed on the Nepal side near the confluence of Chhochen Khola and Purepu Tsangpo rivers close to the Nepal-Tibet border. It was already overflowing Thursday.China’s ministry of water resources warned of a high breach risk over the next three days as another 3 million cubic metres was expected to flow into it. Moderate to heavy rain and thunderstorms forecast through Aug 29 have heightened fears of another surge into Bhote Koshi river a day after Wednesday’s flash flood.For perspective, 2 million cubic metres is enough to cover about 280 standard football pitches — each measuring 105m by 68m, with water one metre deep. The additional 3 million cubic metres expected to flow towards the lake was equivalent to about 420 such pitches.Chhochen Khola and Purepu Tsangpo originate in Tibet and merge before crossing into Nepal, where the combined river is known as Bhote Koshi, which then flows into Trishuli river. Any release from the barrier lake could follow the same downstream corridor hit by Wednesday’s flood and threaten settlements farther south as far as the Indian border.Nepal’s national disaster risk reduction and management authority (NDRRMA) issued a warning after receiving information about the blockage from China through the ministry of foreign affairs. “The lake is continuing to grow and there is a risk that it could burst,” NDRRMA said. Flood forecasting division urged people downstream along Bhote Koshi, travellers and rescue workers to stay away from riverbanks.China’s ministry of water resources said it was tracking the lake and running flood simulations to assess the impact of a possible breach. Chinese engineering teams used drones, portable satellite equipment and 3D laser scanners to map the blockage. The footage showed masses of brown water accumulating in a basin with no visible outlet. The weather outlook added to the concern. China’s national meteorological centre forecast rain in Gyirong county through Aug 29, with moderate to heavy spells during some periods. Xinhua quoted chief forecaster Ma Xuekuan as saying afternoon conditions could also bring thunderstorms, strong winds and short spells of intense rainfall.Meanwhile, Basanta Raj Adhikari, director of Centre for Disaster Studies at Tribhuvan University in Nepal’s capital Kathmandu, warned that “second and third waves” of floods could hit if fresh landslides triggered another surge. “We don’t know yet,” he said, adding that he was in touch with colleagues in China monitoring developments. Adhikari said the episode showed how difficult such Himalayan hazards remained to predict. “Climate change is really happening here,” he said.Catch the latest World News and Live updates. Download the TOI app.