Nepal Launches $50m Plan to Drain Four Dangerous Glacial Lakes

Nepal is preparing to lower the water levels of four high-altitude glacial lakes as part of a major effort to reduce the risk of catastrophic flooding in communities downstream.

The planned intervention follows a devastating glacier-related disaster in August that killed more than 1,400 people, while more than 5,000 others remain missing, according to officials cited by Reuters. The disaster unleashed landslides and flash floods through valleys in the Nepal-China border region.

The four lakes targeted under the project are Thulagi in Manang, Lower Barun in Sankhuwasabha, and Lumding Tsho and Hongu II in Solukhumbu. They are located at elevations ranging from about 4,050 metres to 5,483 metres above sea level and have been identified among Nepal’s potentially most dangerous glacial lakes.

Rather than simply emptying the lakes, engineers plan to lower their water levels in a controlled manner. The project is expected to involve gated drainage structures and canals that will allow water to flow gradually into nearby rivers, reducing the pressure on natural moraine dams that hold the lakes in place.

The project is estimated to cost about $50 million and could take up to six years to complete. Funding will come from the Green Climate Fund, the United Nations Development Programme and the Nepalese government.

Authorities also plan to install monitoring sensors and strengthen flood forecasting and early-warning systems, alongside measures to improve preparedness among communities living downstream.

The four lakes were previously identified as high-risk sites in a 2020 assessment by the International Centre for Integrated Mountain Development (ICIMOD) and UNDP. Nepal has more than 2,000 glacial lakes, while 21 have been identified as potentially dangerous within the country.

Nepal has experience in reducing the threat posed by dangerous glacial lakes. Authorities previously lowered the water level of Tsho Rolpa by about three metres in 2000 and reduced the level of Imja Lake near Mount Everest about a decade later.

However, scientists have cautioned that lowering the four lakes alone will not eliminate the danger. The Kathmandu Post reported that experts have called for continued risk assessment, early-warning systems, careful management of lake outlets and restrictions on construction in areas exposed to potential flood paths.

ICIMOD has also documented the vulnerability of Lower Barun Lake, which sits at about 4,500 metres in the Makalu region. The lake is approximately 2.7 kilometres long and is fed by the retreating Barun Glacier. Researchers have warned that avalanches, extreme rainfall and changes around its moraine dam could increase the risk of dangerous water releases.

The latest plan reflects Nepal’s growing concern over the effects of a warming climate on its Himalayan glaciers. As glaciers retreat, meltwater can accumulate behind unstable deposits of rock, soil and ice, creating lakes capable of releasing huge volumes of water in a short period through glacial lake outburst floods (GLOFs).