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One lake receiving worldwide attention in the last few years is Lake Imja, Nepal. Also known as Imja Tsho, this glacial lake in eastern Nepal lies across the valley that holds the main trekking path to Mount Everest. A product of melting ice, Lake Imja is fed by run-off waters from Lhotse Shar, Imja and Ambulapecha glaciers. From its first appearance as a large puddle in 1960, Lake Imja has grown to about 322 acres and is suspected to have a depth approaching 297 feet. At an elevation of over 16,000 feet, temperature conditions are warm enough for the lake to be relatively ice-free much of the year, except for ice floes calving away from the local glaciers. Lake Imja's liquid water is held in place only by an icy moraine dike which could break unexpectedly, sending thousands of acre-feet of water cascading down into the valley below. The expanding lake has generated many studies designed to find ways to mitigate the damage that could be caused by flooding downstream.
Lake Imja lies in the Solukhumbu region of Nepal and is the home of the largest concentration of Sherpa people in Nepal. Mount Everest is located in the Solukhumbu region as is Sagarmatha National Park, a World Heritage site and environment of endangered species like the snow leopard and red panda. Sagarmatha is home to 3,000 Sherpas, more than 3,000 livestock, and 63 settlements. If the moraine dam were to give way, the resulting flood - called a Glacial Lake Outburst Flood or GLOF by scientists - could result in multiple deaths, destruction of the trekking trails, loss of endangered species and loss of income for the many local people who rely on tourism for their livelihoods.
Visitors to the region come most often to view and climb Mount Everest, the world's highest mountain. At 29,029 feet above sea level, Mount Everest has captured the imaginations of at least 3,100 individuals who have made the ascent; some have climbed more than once. Over 200 people have died in the attempt to scale the mountain - most of their bodies remain on the mountain due to the extreme difficulty of retrieval. Nepal gains considerable income from Mount Everest tourism, as they require each climber to purchase a permit costing as much as $25,000. The threat Lake Imja poses to tourism dollars in the region is enormous, because a possible GLOF could wash away 70% of the trekking route.
Mount Everest lies within the boundaries of 443 square-mile Sagarmatha National Park, designated a Natural World Heritage Site in 1979. Most of the park area is very rugged and steep, with its terrain cut by deep rivers and glaciers. The entire park is at high elevations, with the lowest zone beginning at over 9000 feet. Above 16,000 feet, the land is barren. Below that level, the park is home to a number of rare mammal species, including Himalayan black bear, snow leopard, red panda and musk deer,. Himalayan thars, langur monkeys, martens and Himalayan wolves are also found in the park. A company of the Nepal Army is stationed at the park's visitor center in Namche Bazaar to provide protection to the park.
Because of the popularity of trekking the Mount Everest region, tourism constitutes a large portion of the incomes in the area. The Sherpa people have developed a worldwide reputation as the best guides and cargo bearers on the trails to Mount Everest and other nearby peaks. Without their assistance most visitors would be unable to complete the trek due to the thin atmosphere if they were forced to carry their own packs. Hundreds of small 'lodges' have opened to provide shelter and meals to visitors in the threatened valley. The Sherpa also grow some crops and grazing animals for meat and milk at the lower altitudes. Therefore, even though the local people are very concerned about the warnings they have received of the danger of a GLOF, most cannot simply leave.
Scientists and environmentalists continue to monitor Lake Imja for warning signs that a GLOF is in imminent danger of occurring. Because the water is at a warmer temperature than the nearby glaciers, the continually-enlarging surface of the lake tends to warm surrounding air, causing even more glacial melt. One of the more useful ideas to be tried in the past few years is video surveillance and monitoring sensors connected by WiFi. Because there are no roads or electricity anywhere near the area under study, this remains in the experimental stages. A natural outflow channel at the foot of the lake continues to drain off some of the steadily accumulating water, but there are concerns that the channel appears to be widening, further weakening the moraine dam.
Proposals to siphon off some of the accumulating water for irrigation purposes downstream or to run a hydroelectric plant to provide electricity to this remote region are under discussion. But such projects are costly, requiring enormous sums to move equipment in this roadless region, highlighting the difficulty in finding qualified engineers and labor who can acclimate to work in the thin atmosphere. The government of Nepal is concerned, but they are just as concerned about other possible GLOFs that could occur at any time, and believe some are more pressing than Lake Imja.
The Nepali government ranks Imja among the six most dangerous glacier lakes in the country, largely because it is growing so quickly. More than 12 other such lakes are also seen as high risk. Some in government prefer to focus on Tsho Rolpa, which, they say, might not capture the attention of the international community but is more important locally. For GLOFs are not a new danger in Nepal: some researchers have reported that the Himalaya region has experienced at least 33 such GLOF events in the past. Claims of global warming are common, but scientists studying the region report that the glaciers in the Himalayas, like glaciers around the world, have been in decline since the end of the Little Ice Age in 1850. The reason Lake Imja has received such widespread world attention is because, as center of a well-known and heavily visited tourism area, it is simply more visible to the public. Because of this thriving tourism business, a GLOF at Lake Imja would cause considerable economic damage to Nepal. So the discussions continue, trying to weigh the needs of all against a very small pot of dollars.
Lake Imja is a new lake. Over the years other glacial lakes in Nepal formed, experienced GLOF events, and reformed only to eventually experience a second GLOF. The glacial lakes of Nepal are both a curse and a blessing: the streams and rivers that irrigate the entire eastern portion of Nepal and much of neighboring China originate in glacial melt. The rivers power hydroelectric plants and vastly improve the standard of living for remote villages. If these glaciers were to cease melting, the rivers would dry up. If glacial melt becomes too great, rivers can become torrents, destroying all in their path.
Glacial lakes like Lake Imja add to the uncertainty of such water sources, making them somewhat unreliable. A GLOF in 1985 destroyed 14 bridges and a nearly-completed hydroelectric project. So the struggle continues to find a way to monitor and manage glacial lakes to both benefit from the water flow and avoid catastrophic GLOF events that can cause flood damage downstream as far as 125 miles. The continued attention paid to Lake Imja by the world community has helped to secure the assistance of Andean scientific experts who have experience in controlling glacial lakes in danger of a GLOF. It is hoped that their experience can help Nepal come up with ways to control the dangerous glacial lakes through hydroelectric generation and siphoning away dangerous excess water. Meanwhile, the trek routes to Mount Everest and Sagarmatha National Park are still open.
*All statistics for Lake Imja are tentative as they are changing as the lake grows.
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