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Dammed

  • Successful lowering of water levels at Imja Tsho comes as a relief for locals, but also underscores the challenges that lie ahead
- Sanjeeb Phuyal
Imja Tsho, a glacial lake fed by the melt-off from the Imja Glacier, is one of the 21 glacial lakes in the Nepal’s Himalayas identified as potentially hazardous,

Dec 3, 2016-For Phurwanima Sherpa, a 28-year-old resident of Pangboche—a small settlement in Solukhumbu—a recent successful operation to drain water from the Imja Lake comes as a sigh of relief. Sherpa, like the 90,000 others living downriver on the Dudh Koshi, into which Imja drains, had been living in constant fear of a glacial lake outburst, particularly after the Gorkha earthquakes and its recurring aftershocks.    

“We have had restless nights for the past year,” said Sherpa, who runs a small lodge in Pangboche—a gateway to several trekking destination in the Everest region—“For now, the persistent fear has subsided.” 

Imja Tsho, a glacial lake fed by the melt-off from the Imja Glacier, is one of the 21 glacial lakes in the Nepal’s Himalayas identified as potentially hazardous, and one of the six marked as critically in danger of bursting. Now, with the completion of a project to lower the water levels at Imja by 3.4 metres—marked by a handover ceremony held on November 23, the danger of an outburst and resultant flooding has been averted, even if it is a measure that is ultimately just a stop gap.

When first mapped in 1962, Imja Tsho measured just 0.03 square kilometres. But the accelerated melting of the Imja Glacier and the merging of small glacial lakes over the decades meant that by 2000, Imja measured 0.8 square kilometres; by 2009 it measured 1.055. Most recent data pegs the lake at 1.28 square kilometres and its depth at 149 metres.  

“Imja is one of the fastest growing glacial lakes in Nepal,” said Nawang Thwane Sherpa, of Phakding, Chaurikharka VDC, who is a member of a local taskforce, “but the successful lowering water level has come as a big relief.”

For the past six months, locals have collaborated with the Nepal Army’s engineering department to build a controlled drainage system that is now capable of draining 15 cubic metres of water per second into the Dudh Koshi River. Nepal Army had been contracted by the Department of Hydrology and Meteorology (DHM) in March, 2015 to construct a dam at the lake as part of the water-lowering project. 

According to Senior Technical Advisor at DHM, Pravin Raj Maskey, the project has quadrupled the capacity of water flow during the monsoon from the previous drainage of four cubic metres per second. He added that the project has also installed censors or detection centres in the region.

“We have installed auto sirens at six different places and 18 community-based sirens and hydro metrology stations to alert the locals living in vulnerable areas downstream,” said Maskey. “Now, we have a system in place by which we can track events in real time.” 

As part of the project, four VDCs of Solukhumbu—Khumjung, Chaurikharka, Namche and Jubing—identified as having the most vulnerable settlements to a flooding caused by a glacial lake outburst have been equipped with evacuation centres and early warning systems. Some locals have received training for first aid and search and rescue operations as well. 

The DHM and Nepal Army Engineering Department with support from the United Nations Development Programme (UNDP) and the Global Environment Facility implemented the 7.2 million dollar Community-Based Flood and Glacial Lake Outburst Risk Reduction Project (CFGORRP) in order to avert the possible risk of loss to human lives and infrastructure in case of a outburst-induced flooding in Solukhumbu and the districts in the Churia range and the Tarai further downstream. 

Mingma Sherpa, a member of a taskforce from Dingboche—another settlement in the region said that the water-level reduction has significantly reduced the risk, but questions if more water (as much as 10 metres) should have been drained, given the alarming rate to which the lake is growing. 

But according to Dhananjaya Regmi, a geographer who specialises in mountain geomorphology, oftentimes delicately balanced conditions mean that any attempts at draining glacial lakes must be done with precision. “The decision to reduce the water level by only 3.4 metres was taken in view of the terminal moraine that lies at the depth of 8 metres at the lake,” he said, referring to the unconsolidated soil and mud that dam the glacial outflow, forming the lake, “These are unstable structures held together by ice and can collapse if not dealt with properly.”

In recent years, there have been 14 minor glacial lake outbursts in Nepal. However, till date, the 1985 outburst of the Dig Tsho glacial lake—that caused wide-spread damage to a large number of infrastructures in the same region as Imja—has been the only major catastrophe. 

But experts warn that like Khumbu, settlements throughout the Hindu Kush-Himalayan region are in eminent danger as a result of the accelerated melting of glaciers. A 2013 study, by a team from the University of Milan, found that some glaciers in the Everest region had shrunk by 13 percent in the last 50 years, with the snow line 180 metres higher than it was 50 years ago. The glaciers are disappearing faster every year, the study said, with some smaller glaciers now only half the size they were in the 1960s. And though particular estimates vary, many studies speculate that the Himalayan glaciers—the third largest deposit of ice in the world after the two poles, and headwaters to many rivers that flow into sub-continent—might melt by 2100.   

Highlighted by the alarming rate of growth of Imja (the lake has grown 50 times its size in past five decades), the rapidly receding glaciers from the Himalayas is no longer an abstract concept.  And while the successful lowering of the lake’s water levels comes as a welcome relief, it also underscores the need for a larger, long-term conversations and action. 

Published: 03-12-2016 10:09

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