Bhotekoshi Flash Floods: Risk of glacial lake outbursts persists in Nepal-China border
At 9:00 AM on August 31, the river flow at the Kerung port was measured at 125 cubic meters per second. The Ministry stated that this data is being utilized for risk monitoring and early warning systems to assist teams deployed downstream for rescue and relief operations.
KATHMANDU:- China’s Ministry of Water Resources has stated that glaciers surrounding the area affected by the devastating landslide and flood on August 26 in Nepal’s Chhochen Khola (known as the Guojian River in Chinese sources) remain at risk of further collapse.
According to a report published by the ‘Global Times’ on Tuesday, citing China’s state broadcaster CCTV, drone imagery captured at 8:00 AM on September 1 shows that most of the water accumulated in the area affected by the landslide along the Chochen River has drained away.
The river flow downstream of the affected area has also returned to normal. However, the ministry has stated that the risk of collapse for nearby glaciers remains high.
China’s Ministry of Water Resources is conducting continuous consultations, monitoring, and comprehensive risk assessments regarding the threat of landslides and debris flows in Gyirong (Kerung) County—located in the Tibet Autonomous Region of southwest China, bordering Nepal. The Ministry has stated that it has also initiated hydrological monitoring to support rescue and relief operations.
An analysis of satellite and radar imagery conducted on August 31 revealed that the surface area of the water accumulated in the impact zone of the Chhochen River was approximately 83,000 square meters. This represented a decrease of 25,000 square meters compared to 11:00 AM on August 30 and 14,000 square meters compared to 7:00 PM on the same day. At that time, the volume of water in the area was estimated to be around 650,000 cubic meters.
Three small areas of still water had been identified approximately 2.5 kilometers downstream from the affected area. The Chinese ministry had reported that some of these water bodies were connected to the river’s main channel and that water was flowing through them.
However, recent drone imagery shows that the bulk of the accumulated water in the affected area has drained away, and the river downstream is flowing normally.
The Chinese side has warned that although the water flow has returned to normal, the risk has not been eliminated. It is reported that if glaciers in the surrounding area collapse, large amounts of debris could once again enter the river, potentially creating a new natural dam or glacial lake.
Previous drone inspections revealed numerous landslide deposits along both banks of the river, approximately three kilometers downstream from the Purepu Changpo glacial lake. Chinese researchers have pointed out that although water is currently flowing through the area, there is a risk that further landslides could obstruct the river’s flow and lead to the formation of a new lake.
According to China’s Ministry of Water Resources, no significant changes have recently been observed in the water levels of the 14 glacial lakes identified in the Gyirong Tsangpo River basin. The Ministry stated that, overall, these glacial lakes remain in a stable condition.
According to an analysis from August 31, 14 moraine-dammed glacial lakes larger than 0.1 square kilometers were identified on the Chinese side. Of these, 11 are located in the Donglin Tsangpo River basin and its tributaries, while three are situated in the Gyirong Tsangpo River basin and its tributaries.
Based on the natural state of the rivers and the settlements and infrastructure located within the flow paths, 10 of these 14 glacial lakes have been classified as high-risk, while four have been categorized as having medium to low risk.
However, the Chinese side has reported that no significant changes in water levels have been observed in any of these glacial lakes over the past month. Meanwhile, satellite analysis indicates that no moraine-dammed glacial lakes larger than 0.1 square kilometers have been found in the area above the Kerung border crossing on the Nepal side.
On August 31, China’s Ministry of Water Resources deployed a 14-member technical team to conduct emergency hydrological monitoring in the river basins of the Pyurepu Tsangpo, Donglin Tsangpo, and Grung Tsangpo. The team also surveyed potential sites for establishing additional monitoring stations.
At 9:00 AM on August 31, the river flow at the Kerung port was measured at 125 cubic meters per second. The Ministry stated that this data is being utilized for risk monitoring and early warning systems to assist teams deployed downstream for rescue and relief operations.
