Nepal explores tapping flood-risk glacial lakes for clean power

View of the landscape at Langtang, Nepal in this undated handout image. Tika Gurung/Handout via REUTERS

View of the landscape at Langtang, Nepal in this undated handout image. Tika Gurung/Handout via REUTERS

What’s the context?

In an effort to turn a risk into a gain, Nepal aims to drain burgeoning glacial lakes and could produce hydropower from the flow

  • As climate change melts glaciers, floods a growing risk
  • Efforts to partially drain high mountain lakes underway
  • Tapping water released could produce clean hydropower

LANGTANG, Nepal - High in the Himalayas, two villages near Nepal's border with Tibet are getting power from an unusual source: a threatening glacial lake.

In this high-altitude region, climate change is accelerating the melting of mountain ice, with villages located below fast-filling glacial lakes facing a rising risk of catastrophic flooding.

But efforts to drain some of the excess water building up in the lakes, to lower surging disaster risk, also present an opportunity to boost clean power production, by installing small hydropower generators in the drainage channels.

Since 2017, 175 households in Langtang and Kyanjin, two villages in the high Kyanjin Valley, have been able to tap clean hydropower from efforts to drain the Kyanjin glacial lake for cooking, lights and other energy needs.

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"We used to go three hours away from here to collect firewood" - something hard to find above the tree line, said 48-year-old Pasang Tamang, who runs a hotel in Kyanjin, a popular stopping point for tourists trekking in the mountains.

"Now we have electricity to cook food and boil water," she said.

The hydropower project, which cost $448,000, was paid for by the Hong Kong-based Kadoorie Charitable Foundation.

But expanding such smart solutions - which unusually cut both disaster risk and climate changing emissions - is proving challenging in Nepal with funding limited and work in high-mountain environments challenging and often costly.

Power from risk

Communities in the Himalayas - and other high mountain regions of the world - face growing risks from fast-filling glacial lakes, which can suddenly burst under pressure and send huge volumes of flash floodwater surging downstream.

More than 150 people were killed and 2,000 houses damaged after Lhonak Lake in the northeastern Indian province of Sikkim burst its banks in October last year. 

Nepal has worked to lower the pressure in several of its most at-risk mountain lakes, including Tsho Rolpa and Imja, using canals to channel some water away.

It also has looked at generating power from glacial lake draining since at least 2016, when Dhananjay Regmi, a glacier expert at Tribhuvan University, recognised the possibility while leading work on efforts to reduce lake levels and cut disaster risk near Mount Everest.

Working with colleagues, he studied four Nepalese glacial lakes - Thulagi, Lower Barun, Lumding Tsho and Hongu-2 - and produced a study showing hydropower generation was possible as part of drainage efforts.

All four lakes were identified in a 2020 report by the International Centre for Integrated Mountain Development as having a high risk of bursting their banks.

"There are two benefits to us: first, the risk of outburst will be reduced, and second, we get energy at the same volume throughout the year," Regmi told Context.

He has focused in particular on Thulagi glacial lake, about 200 km (125 miles) from Kathmandu in Manang district.

The 2.5-km-long (1.55-mile) lake is 73 metres (240 ft) deep and holds 36 million cubic metres (1.27 billion cubic feet) of water, according to Regmi's 2017 report - enough to fill more than 14,400 Olympic swimming pools.

General view at Langtang National Park, Nepal in this undated handout image. Jitendra Raj Bajracharya/ICIMOD/Handout via REUTERS

General view at Langtang National Park, Nepal in this undated handout image. Jitendra Raj Bajracharya/ICIMOD/Handout via REUTERS

General view at Langtang National Park, Nepal in this undated handout image. Jitendra Raj Bajracharya/ICIMOD/Handout via REUTERS

If it were to burst, the resulting floods could directly affect 166,000 people downstream and impact many more, with roads, bridges and larger hydropower projects in the region at risk, according to an unpublished analysis by Narendra Khanal, a geography professor at Tribhuvan University.

Losses could reach $415 million, the research found, if expected flood levels of 35 metres (114 feet) above the riverbed were reached, requiring replacement of the Marsyangdi and Middle Marsyangdi hydropower dams and putting their revenue at risk.

Channelling water out of the lake to hydropower generating equipment, could produce 50 megawatts (MW) of electricity year-round, he said, and lower the lake's water level by five to 10 metres (16.4 to 32.8 feet).

"When the water level is reduced, we don't have to worry about the lake bursting," Regmi said.

Funding dilemma 

But finding money for such double-benefit projects and putting them into operation is not easy.

Nepal, working with the United Nations Development Programme (UNDP) is seeking $50 million from the Green Climate Fund, with co-financing from the government, UNDP and the private sector, to lower water levels and cut the risk of floods from the Thulagi, Lower Barun, Lumding Tsho and Hongu-2 lakes.

But the proposal does not include plans to also generate hydropower.

Chiranjeevi Chataut, the director general of Nepal's Department of Energy Development, said making such generation projects work in the high Himalayas is too challenging, one reason the country is not making plans for them.

Still, "if any private sector (applicants) are interested, we can discuss," he said.

Regmi admitted that working at high altitude could be difficult and costly, but said such generation could be helpful in regularising year-round hydropower supplies.

Nepal, for instance, in recent years has generated about 2,800 MW of hydropower nationally each year during the monsoon season, but only a third of that at other times of year, according to the Nepal Electricity Authority.

Deepak K.C., a climate change and resilience analyst for UNDP in Nepal, said tapping the country's high-mountain hydropower potential in combination with efforts to cut disaster risk would likely require more joined-up funding.

"Only the private sector can invest in that type of (power) project," he said. "Donor agencies don't invest in generating hydropower."

If the government goes ahead with a lake-lowering project at Thulagi, Regmi's team hopes to find private backing to build a demonstration hydropower project, to show generating clean power at high altitude can work.

Installing the project could have other benefits as well, Regmi said. For instance, putting in place a hydropower system would require establishing a cable in the mountains to transport equipment to the site.

That could then be turned into a cable car system to attract tourists, or for local transport, he said.

"The project can be done without environmental or ecosystem loss," he said.

(Reporting by Mukesh Pokhrel; Editing by Laurie Goering and Jonathan Hemming.)

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