Lake Imja, Nepal

Lake Locations:

Nepal -

Also known as:  Imja Tsho

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.

Things to do at Lake Imja

  • Vacation Rentals
  • Hiking
  • Wildlife Viewing
  • National Park

Lake Imja Photo Gallery

Lake Imja Statistics & Helpful Links

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Lake Type: Natural Freshwater Lake, Not Dammed

Surface Area: 322 acres

Shoreline Length: 3 miles

Normal Elevation (Full Pond): 16,417 feet

Average Depth: 136 feet

Maximum Depth: 297 feet

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Trophic State | LakeLubbers

Trophic State measures the level of algae and nutrients in a lake.

An oligotrophic lake is very clear (blue in color) and does not support much plant or fish life. A hyper-oligotrophic lake is the clearest of all lakes, and is nearly devoid of plants and fish.

A mesotrophic lake is slightly green and supports a moderate degree of plant and fish life. A lake's most desired trophic state is generally this mid-point - the mesotrophic state.

A eutrophic lake is somewhat murky and supports a large amount of plant and fish life. A hypereutrophic lake is clouded with algae, plant life, and fish life. A eutrophic or hyper-eutrophic lake can be difficult to navigate by boat - and is often an unpleasant place to swim.

The use of phosphorus-rich and nitrogen-rich fertilizer on lawns and golf courses surrounding a lake can cause it to become eutrophic or hypereutrophic.


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Catchment or Drainage Area | LakeLubbers

This is the surrounding area that drains into a lake, including land, rivers and their tributaries. This is also known as the lake's "catchment basin".

Small lakes at the highest peaks of mountains have small drainage areas. The world's oceans have the largest drainage areas.


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Lake-Area Population | LakeLubbers

This is the estimated number of people who live in a house with a view of a lake, plus those who self-describe the lake as their home, for example: "I live at Smith Mountain Lake."


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Water Residence Time | LakeLubbers

This is the estimated time that it takes for an amount of water equal to the entire volume of a lake to flow out of - or evaporate from - the lake.

Residence Time can be as short as a few days for fast-flowing small lakes, and can exceed 100 years for slow-flowing large lakes.


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Completion Year | LakeLubbers

This is the year that a reservoir was first filled to the reservoir's normal elevation - or the year that a natural lake was first dammed. A large reservoir can take more than a year to fill after its dam is first closed.

The Grand Anicut in southern India is generally considered the world's oldest dam that still operates. Grand Anicut was constructed in the second century BC. It now impounds an irrigation network that includes roughly one million acres.

You can find many of the the world's newest reservoirs on LakeLubbers. Many of the world's oldest reservoirs appear on the last page of that list.


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Water Volume | LakeLubbers

This is the estimated volume of water that a lake contains -- measured at the lake's normal elevation. By this measure, the world's largest freshwater lake is Siberia's Lake Baikal.

You can find many of the the world's largest lakes (by water volume) on LakeLubbers.

Water Volume can be measured in acre-feet, in cubic miles, or in cubic kilometers. One acre-foot is the amount of water needed to cover one acre (43,560 square feet) to a depth of one foot. One cubic mile equals 3,379,200 acre-feet. One cubic kilometer equals 810,713 acre-feet.

1 acre-foot is equal to 325,851 US gallons. Siberia's Lake Baikal contains about 6,276,367,740,000,000 gallons of freshwater - nearly 1 million gallons for every living person on earth.

The other - and more widely used - measure of a lake's size is the lake's surface acreage. By that measure, the world's largest freshwater lake is North America's Lake Superior.


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Maximum Depth | LakeLubbers

This is the estimated greatest depth of the water in a lake -- measured at the lake's normal elevation. The world's deepest lake is Siberia's Lake Baikal; that lake's maximum depth is estimated at 5,314 feet.

You can find many of the the world's deepest lakes on LakeLubbers. If you select the last page of that list, you will find the (maximum depth of) the shallowest lakes in our database.


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Average Depth | LakeLubbers

This is the estimated average depth of the water in a lake -- measured at the lake's normal elevation. If the water volume and surface area of a lake are known, an estimate of the lake's average depth can be calculated:

Water volume ÷ Surface Area = Average Depth

Example: 1,000,000 acre-feet ÷ 20,000 acres = 50 feet average depth


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Maximum Elevation | LakeLubbers

This is a lake's highest water level, measured by the lake's surface distance above sea level, that can occur during flooding. A lake's highest possible maximum elevation is usually the top of the lake's dam or spillway.

At lakes that include residential development, government regulations usually forbid the construction of homes below a lake's maximum elevation.


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Minimum Elevation | LakeLubbers

This is a lake's lowest water level, measured by the lake's surface distance above sea level, that can be reasonably expected to occur. Low lake levels can occur due to deliberate seasonal draw downs for irrigation or impending snow melt, reduced water inflows, drought and evaporation, residential or commercial water demands, and hydropower generation.

Some lakes' minimum and maximum elevations are virtually the same. Lakes that generate hydropower may vary by several feet - according to power demand. Lakes whose primary purpose is to prevent flooding can seasonally vary by 100 feet or more.

When some lakes reach their minimum elevation, their boat ramps may not be long enough to permit boat access - and boats docked on shallow parts of the lake may end up on dry ground. In those cases, kayakers and shore-based anglers may be among the few happy recreational users of the lake.


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Normal Elevation | LakeLubbers

This is a lake's normal water level, measured by the lake's surface distance above sea level. For a reservoir, this water level is also known as "full pond" or "full pool".

You can find many of the world's highest-elevated lakes on LakeLubbers. Lakes with the lowest elevations (known by LakeLubbers) are shown on the final page of that list.


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Shoreline Length | LakeLubbers

This is the length of the exterior shoreline around a lake - measured at the lake's normal elevation. The shoreline length can be considerably shorter or longer when lake water levels are lower or higher than normal.

A lake with many coves has a much longer shoreline than a lake of similar surface area that is nearly circular in shape.

When known, the shoreline miles that we report in our statistics include only the lake's exterior shoreline, and exclude the shorelines of islands located within a lake's boundaries. In lakes with many islands, those islands' combined shorelines may exceed a lake's exterior shoreline.

You can find many of the world's longest-shoreline lakes on Lakelubbers.


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Surface Area | LakeLubbers

This is the area (acreage, square kilometers, etc.) of the top surface area of a lake - measured at a lake's normal elevation. The surface area can be considerably smaller or larger when lake levels are lower or higher than normal. North America's Lake Superior is the world's largest freshwater lake by this measure.

The other measure of a lake's size is the lake's water volume. By that measure, the world's largest freshwater lake is Lake Baikal in Siberia.

You can find many of the world's largest lakes (acres) on Lakelubbers. There is no widely-accepted minimum surface area that defines a lake. What Lakelubbers describes as a lake, you might call a pond. The smallest lake that Lakelubbers currently includes is Hawaii's 2-acre Lake Waiau.


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Water Level Control | LakeLubbers

This is the organization that controls water releases or outflows from the lake or reservoir. In the USA, this is often the US Army Corps of Engineers, a power company, a municipal water system, an irrigation district, or a paper manufacturing company. In the case of private or gated lakes, a homeowners' association may be the lake's controlling authority.

Many lakes cross borders, including North America's Great Lakes. The control of such lakes and their coveted freshwater may be amicably shared - or hotly disputed.

"Water wars" continue at many lakes as growing populations and crop irrigation needs compete for the freshwater that lakes contain.


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Lake Type | LakeLubbers

There are 3 basic types of lakes that are currently included on LakeLubbers. 2 types may be dammed or not dammed, producing 5 classifications.

- A Reservoir is a man-made freshwater lake that is usually created by damming rivers.

- A Natural Freshwater Lake occurs naturally - often by glacial activity - and has a salinity of less than 30 parts per thousand. It may be dammed to produce electricity or for other reasons.

- A Natural Saltwater Lake occurs naturally and has a salinity of more than 30 parts per thousand (ppt). It may be dammed.

"Brackish" water may be categorized as freshwater or saltwater, depending on its salt content (salinity). Oligohaline water has less than 15 ppt of salt. Mesohaline water has 15-29 ppt. Polyhaline has 30-335 ppt.


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