Sat, Oct 15, 2011 - Page 9 News List

Glacier lakes are disasters in the making

As high-altitude glaciers in the Himalayas melt because of climate change, the lakes they form can burst through their dams of debris at any time, wiping out villages and swamping farmland

By Suzanne Goldenberg  /  The Guardian, IMJA LAKE, NEPAL

Illustration: Tania

It is strangely calming to watch the Imja glacier lake grow, as chunks of ice part from black cliffs and fall into the gray-green lake below.

However, the lake is a high--altitude disaster in the making — one of dozens of new danger zones emerging across the Himalayas because of glacier melt caused by climate change.

If the lake, situated at an altitude of 5,100m in Nepal’s Everest region, breaks through its walls of glacial debris, known as moraine, it could release a deluge of water, mud and rock as far as 100km. This would swamp homes and fields with a layer of rubble up to 15m thick, leading to the loss of the land for a generation. The question is when, rather than if.

Mountain regions from the Andes to the Himalayas are warming faster than the global average under climate change. Ice turns to water; glaciers are slowly reduced to lakes.

When Sir Edmund Hillary made his successful expedition to the top of Everest in 1953, Imja did not exist. It is now the fastest growing of some 1,600 glacier lakes in Nepal, stretching down from the glacier for 2.5km and spawning three small ponds.

At its center, the lake is about 600m wide, and according to government studies, up to 96.5m deep in some places. It is growing by 47m a year, nearly three times as fast as any other glacier lake in Nepal.

“The expansion of Imja lake is not a casual one,” said Pravin Raj Maskey, a hydrologist with Nepal’s Ministry of Irrigation.

The extent of recent changes to Imja has taken glacier experts by surprise, including Teiji Watanabe, a geographer at Hokkaido University in Japan, who has carried out field research at the lake since the 1990s.

Watanabe returned to Imja last month, making the nine-day trek with 30 other scientists and engineers on a US-funded expedition led by the Mountain Institute. He said he did not expect such rapid changes to the moraine which is holding back the lake.

“We need action, and hopefully within five years,” Watanabe said. “I feel our time is shorter than what I thought before. Ten years might be too late.”

Unlike ordinary flash floods, a glacier lake outburst is a continuing catastrophe.

“It’s not just the one-time devastating effect,” said Sharad Joshi, a glaciologist at Kathmandu’s Tribhuvan University, who has worked on Imja. “Each year for the coming years it triggers landslides and reminds villagers that there could be a devastating impact that year, or every year. Some of the Tibetan lakes that have had outburst floods have flooded more than three times.”

ENGINEERING ANSWERS

However, mobilizing engineering equipment and expertise to a lake 5,100m up and several days’ hard walking away from the nearest transport hub is challenging in Nepal, one of the poorest countries in the world. People living in the small village of Dingboche below the lake say scientists and government officials have been talking about the dangers of Imja for years.

Some years ago one of the visiting experts was so convincing about the dangers of an imminent flood that the villagers packed up all their animals and valuables and moved to the next valley. They came back after a week when the disaster did not materialize, but say it is hard to dismiss the idea that there could be a flood one day.

“When I was 21, I went to the lake and it was black and really small,” said Angnima Sherpa, who heads a local conservation group in Dingboche. “Two years ago I went there and it was really big. I couldn’t believe it could get so big. It was really scary.”

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