Major hidden risks remain after Xizang barrier lake drains

A barrier lake in Gyirong county, Xizang autonomous region, has essentially drained, but major hidden risks remain in a scour pit in a Nepalese river that flows into the lake and three waterlogged areas downstream, the Ministry of Water Resources said in a media release on Sunday.

The latest assessment, based on drone footage, panoramic images and reports from a front-line emergency team, showed that the barrier lake in the Purepu Tsangpo River in China has been essentially emptied and that the river channel is flowing normally, the release said.

However, major risks remain in the Chhochen Khola River, which converges with the Purepu Tsangpo River, the ministry emphasized.

A scour pit in the Nepalese river, about 5.6 kilometers upstream from the barrier lake, was still holding about 1.4 million cubic meters of water, it said. The pit is about 800 meters higher in elevation than the barrier lake.

Based on satellite imagery, the ministry said that as of 11:23 am on Saturday, the pit had a water surface area of about 108,000 square meters, down 19,000 square meters from 7 am.

Three waterlogged areas were also identified within 2.5 kilometers downstream of the pit, with a combined surface area of less than 70,000 square meters, the ministry said.

"The scour pit in the Chhochen Khola River in Nepal, and the three downstream waterlogged areas pose significant risks and hidden dangers," the ministry stressed.

The ministry also said a new barrier lake formed 2.8 kilometers downstream of the Purepu Tsangpo barrier lake after a landslide on the Nepal side on Saturday. It has since been breached by upstream inflow and is now in a state of channelized flow.

There remains a risk that new landslides could form fresh barrier lakes along the banks of several rivers in the area, the ministry said.

As of 6 pm Saturday, 16 people had been killed and 546 remained missing after the mudslide struck Gyirong Port along the China-Nepal border on Wednesday, according to Xizang's emergency management department.