Small Glacial Lakes’ Mass Destruction in the Himalayan Community

By Tanka Dhakal
KATHMANDU, Sep 10 2024 – Small glacial lakes can cause destruction, which may impact the livelihoods of entire communities. Now this is the harsh reality that the community of Thame village in the Mt. Everest region of Nepal now faces as they rebuild after the August 16 disaster.

On that day a devastating flood struck Thame, a Sherpa village in the Khumbu region, damaging houses, local businesses, a school, a health facility, and the community’s means of livelihood. 

“Thame is one of the main villages that is important in terms of trekking attraction, and the flood swept away the entire village. That will definitely impact our livelihood,” said Pashang Sherpa, “Even though I am not from that village, I have been working as a trekking guide for the last 15 years, and villages like Thame are crucial to us.”

An assessment of the damage by the local government-Khumbu Pasang Lhamu Rural Municipality in the Solukhumbu district-reports that at least 18 properties have been destroyed, including seven homes, five hotels, one school, and one health post.

“Given the difficult geographical terrain, reconstruction efforts will be costly, and the local government’s budget will not be enough. That’s why we appeal for help from individuals and institutional sectors,” the rural municipality stated in an appeal for assistance.

What Exactly Happened

A view of glacial lake after the flood. Credit: Khumbu Pasang Lhamu Rural Municipality

Initially, the cause was unclear, but now things are becoming clearer: Thame village was hit by a flash flood caused by a glacial lake outburst. Thyanbo glacial lake, located upstream of Thame, burst, sending floodwaters mixed with sediment down to the village.

“It was the result of more than one event—ice/snow melt or an avalanche caused spills from one glacial lake, which then triggered an outburst flood from the lower Thyanbo glacial lake,” said Dr. Arun Bhakta Shrestha, Senior Climate Change Specialist at ICIMOD. “It’s not that both lakes burst, but rather that the overflow or spill of water from one lake caused the other lake to outburst.”

Leading up to the flood, multiple weather-related factors were at play. Recent rainfall and rising temperatures likely contributed to ice/snow melt, which in turn led to the outburst. According to the Department of Hydrology and Meteorology (DHM), the area received relatively high rainfall in the week leading up to the event, and temperatures were also relatively high.

“That may have caused ice/snow melt or an avalanche at the upper lake, and the spilled water caused erosion, which ultimately triggered the lower lake to burst,” DHM said in a statement.

Experts are saying that this flood is the latest example of the causal impact of climate change and the level of impact that can be seen at the local level. Tenzing Chogyal Sherpa, ICIMOD’s Cryosphere Analyst—who also belongs to the mountain Sherpa community and is from the Khumbu region—views this event as both personal and a stark reminder of the climate crisis.

ICIMOD’s Cryosphere Analyst, Tenzing Chogyal Sherpa’s comment on X tells of the ‘heartbreaking reality’ of the flood. Credit: X

“Seeing the ancestral homes of Sherpa families in ruins was just numbing,” he wrote on X (formerly Twitter). “Every disaster tests our resilience, but it also strengthens it. We, the mountain community, will emerge united and determined to protect our homes and way of life. Now, more than ever, we must raise our voices to the global community. Our stories and struggles need to be heard.”

Small Glacial Lakes Are Also Dangerous 

According to satellite image assessments, the lake’s size was approximately 0.05 square kilometers just a few hours before the breach. “This lake was not on the list of potentially dangerous lakes that may cause GLOFs, and it wasn’t that big either. There are thousands of lakes like that,” Shrestha says. “This means even small lakes can cause vast destruction, and our river corridors are not safe.”

There are several lakes upstream of Thame, and satellite images show that these lakes’ sizes are constantly growing. However, they are not listed as potentially dangerous glacial lakes (PDGLs) like the nearby Tsho Rolpa. A glacial lake inventory report published in 2020 identified 47 PDGLs within the Koshi, Gandaki, and Karnali river basins of Nepal (21 in Nepal), the Tibet Autonomous Region of China (25 in China), and India (one in India).

This report identified other small lakes in the region, but they were not listed as PDGLs; there are more than 3,624 lakes in total. The report indicates that there are 2,214 lakes smaller than 0.02 square kilometers in size and 759 lakes ranging from 0.02 to 0.05 square kilometers in size.

“Yes, lakes are getting bigger day by day because of snowmelt and glacier retreat. But these small lakes are also dangerous when it comes to the destruction they may cause to downstream communities,” Shrestha said.

He argues that it’s time to integrate potential danger into development plans and disaster risk reduction (DRR) mechanisms so that disasters like the one in Thame can be avoided. The Thame flood occurred in the afternoon, allowing locals to move to safety, which prevented human casualties. But if it had happened at night, the situation could have been much worse.

“We are getting multiple wake-up calls, but we haven’t woken up yet,” Shrestha said. “We need to consider glacial lake-related events from a watershed perspective, not from the viewpoint of individual lakes. A multi-hazard preparedness approach is needed to avoid larger destruction because there are thousands of lakes above the communities.”

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