Lowering Imja alone will not prevent GLOFs, say experts

OM ASTHA RAI

KATHMANDU, Sept 22: A month ago, Keshav Raj Sharma, a hydrologist at the Department of Hydrology and Meteorology (DoHM), was about to sleep. His cell phone started buzzing. It was from an unknown number.

“Sir, are you sleeping?” said the caller, who introduced himself as a Dolakha-based journalist. “Tsho Rolpa Lake has just burst out; thousands of people are going to die. You must do something to save us, sir.”

Petrified by the potential devastation that Tsho Rolpa outburst might cause, Sharma restrained his fears; and just said, “Don´t worry; nothing is going to happen.”

As soon as he hung up the phone, Sharma contacted the field office, which was set up by the DoHM to monitor glacier activities in Tsho Rolpa. The field office dismissed rumors about Tsho Rolpa outburst. “Only then was I relieved,” says Sharma, recalling the night of August 15.

Although the news of Tsho Rolpa outburst proved to be a flash flood in the Tamakoshi River, the risk of Nepal´s most vulnerable glacial lake bursting and causing catastrophic devastation in the downstream valley still looms large. Om Ratna Bajracharya, former Director General of DoHM, believes Tsho Rola is still Nepal´s most dangerous glacial lake. “The risk from Tsho Rolpa is still higher than from any other glacial lake,” says Bajracharya. “It is getting bigger and bigger every year.”

In 2000, in a bid to avert the risk of a Glacial Lake Outburst Flood (GLOF) in the Tamakoshi River basin, the water level in Tsho Rolpa was lowered by three meters through a 70-meter-long canal, which has been channeled into the Rolwaling River.

“That was just a temporary measure,” says Bajracharya. “Unless we lower the water level in Tsho Rolpa by 17 meters, as suggested by a study report in the 1990s, safety of thousands of people living on the banks of the Tamakoshi river basin cannot be ensured.”

According to Kamal Budhathoki, former Deputy Director General (DDG) of DoHM, even if water level in Tsho Rolpa is lowered by just nine meters, the risk of GLOFs in the Tamakoshi River basin can be reduced to a great extent. “There is another report prepared by an American glaciologist in collaboration with DoHM experts. The report says lowering of water level in Tsho Rolpa by about 12 meters is sufficient,” says he.

However, instead of further lowering Tsho Rolpa, government authorities, under a US$ 7.2 million project funded by the Least Developed Countries Fund (LDCF) of Global Environment Facility (GEF), are now working toward reducing the water level in Imja, another dangerous glacial lake in the Khumbu region, some 163 km from Kathmandu.

Some experts argue that Tsho Rolpa is situated at a relatively low altitude, which makes it more vulnerable than other high-altitude glacial lakes, including Imja. “The lower the altitude, the higher the risk of GLOF events,” explains Bajracharya. “Impact of global warming can be felt more in low-altitude glacial lakes.”

Going by what Bajracharya argues, Tsho Rolpa, situated at an altitude of around 4,500 meters, is more vulnerable to the effects of global warming. At an altitude of over 5,000 meters, glaciers that feed Imja are less exposed to rising temperature.

An expert, unwilling to be named, says Imja was chosen just because it caught the attention of national and international mountaineers. “Imja is in close proximity to climbing and trekking routes in the Khumbu region. Therefore, many people see melting glaciers there,” says he. “But, there are other glacial lakes that are more vulnerable. But, very few have noticed them.”

According to a 2009 report by the International Center for Integrated Mountain Development (ICIMOD), apart from Tsho Rolpa and Imja, there are four more glacial lakes which are at the risk of GLOFs. These lakes include Thulagi, Lumding, Lower Barun and West Chamjong. Apart from gradual degradation of moraines, fast receding of glaciers has also rendered these lakes vulnerable.

Since 1964, at least 10 GlOF events have been recorded in Nepal. As the Himalayas face threats from rising temperature, minimizing the risk of GLOFs by lowering water levels, developing early-warning system in the downstream human settlements and empowering local communities to adapt to climate change seems necessary, say experts.

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