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The glaciers in Bhutan, which covers about 3 percent of the total surface area, are responsible for feeding all rivers of
Bhutan Bhutan, officially the Kingdom of Bhutan, is a landlocked country in South Asia, in the Eastern Himalayas between China to the north and northwest and India to the south and southeast. With a population of over 727,145 and a territory of , ...
except the Amochu and Nyere Amachu. Not much historical information is available on these glacial systems; the first modern survey was conducted by
Augusto Gansser-Biaggi Augusto Gansser-Biaggi (28 October 1910 – 9 January 2012) was a Swiss geologist who specialised in the geology of the Himalayas. He was born in Milan. Career His geological researches were global in scope: * East Greenland (1934), a 4-month e ...
in the 1970s, who developed a chronology of past glaciations, and warned of imminent
glacial lake outburst flood A glacial lake outburst flood (GLOF) is a type of outburst flood caused by the failure of a dam containing a glacial lake. An event similar to a GLOF, where a body of water contained by a glacier melts or overflows the glacier, is called a jà ...
s (GLOF) in Lunana. This prompted the
Geological Survey of India The Geological Survey of India (GSI) is a scientific agency of India. It was founded in 1851, as a Government of India organization under the Ministry of Mines, one of the oldest of such organisations in the world and the second oldest survey ...
(GSI) and Geological Survey of Bhutan (GSB) to carry out joint surveys in the mid-80s, and their report rejected Biaggi's threat-assessment. On 7 October 1994, a GLOF from Luggye lake (part of Lunana glacial system) led to over 20 fatalities in
Punakha Punakha () is the administrative centre of Punakha dzongkhag, one of the 20 districts of Bhutan. Punakha was the capital of Bhutan and the seat of government until 1955, when the capital was moved to Thimphu. It is about 72 km away from Thim ...
. This disaster, the first of its kind in Modern Bhutan, increased the frequency of glacial-system-surveys by manifold. Evaluation of GLOF hazard has since formed a significant component of glacial expeditions. Multiple inventory-lists of glaciers and glacial lakes in Bhutan exist. The precise figures vary to some extent, based on the methodology used.


Inventories


Glaciers

Multiple trans-Himalayan inventories of variable accuracy and area-span have existed for decades. This section concerns with inventories specifically curated for Bhutan. The first inventory was compiled in 1996 by Phuntso Norbu (of the Division of Geology and Mines) using satellite data from 1989 to 1990 and
topographic map In modern mapping, a topographic map or topographic sheet is a type of map characterized by large- scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation), but histori ...
of 1962/63. A revised edition was published in 1999 by GSB. The same year, another inventory was published by
China Science Publishing & Media China Science Publishing & Media (CSPM, traditional Chinese: 科學出版社; simplified Chinese: 科学出版社), also translated into English as Sciences Press, Science Publishing House, or China Science Publishing, is a People's Republic of ...
on the basis of near-infrared Landsat 2 imagery (1975–1978) and some aerial snapshots — 649 glaciers were located, covering an area of 1,304 km2. and a volume of 150 cubic kilometer. A more accurate inventory, prepared from 1993 SPOT Imagery, Landsat data of 90s,
IRS-1D IRS-1D is the seventh satellite in Indian Remote Sensing satellite series of Earth Observation satellites, built, launched and maintained by Indian Space Research Organisation (ISRO). The satellite has similar capabilities as that of ISRO's IR ...
data of 1999, and GSI topographic maps of 1950-60s, was published in 2001 by the International Center for Integrated Mountain Development (ICIMOD). 677 glaciers, covering an area of 1,317 km2 were located and classified per Müllerian (WGMS) nomenclature. In 2011, ICIMOD recompiled its data-set for the entire Hindu Kush, using an automated classification of satellite imagery from 2005 ± 3 years in combination with
digital elevation model A digital elevation model (DEM) or digital surface model (DSM) is a 3D computer graphics representation of elevation data to represent terrain or overlaying objects, commonly of a planet, Natural satellite, moon, or asteroid. A "global DEM" refer ...
— the area was revised to 642 km2 (based on Bhutan's new national boundary). In 2012, data from World Glacier Inventory (WGI), Global Land Ice Measurements from Space (GLIMS), and Natural Earth (NE) were blended and refined to create yet another inventory of glaciers — the area estimates came out to be 1930 km2. (did not take the new boundary into account). The ICIMOD database was updated in 2014 (using Landsat imagery from 2010) — no areal difference existed. In 2018, the National Center for Hydrology and Meteorology published the most recent inventory of glaciers in Bhutan using automatic classification of
Sentinel-2 Sentinel-2 is an Earth observation mission from the Copernicus Programme that acquires optical imagery at high spatial resolution (10 m to 60 m) over land and coastal waters. The mission's Sentinel-2A and Sentinel-2B satellites were joined in or ...
data from 2016 — 700 glaciers were located covering an area of about 629.55 km2.


Glacial Lakes


Glaciers

By convention, glaciers are located in the river basins, they lie — Wang Chhu basin (consisting of Pa Chhu, Ha Chhu and Thim Chhu sub basins), Punatshang Chhu basin (consisting of
Pho Chhu Pho Chhu (Male River) is one of the major rivers of Bhutan, which tracks its source to Gasa District on the borders between Bhutan and Tibet. It joins with the Mo Chhu (Female River) at the confluence below Punakha Dzong, the winter residence of ...
,
Mo Chhu Mo Chhu is a major river in Bhutan. The word "Chhu" means "river" or "water" in Dzongkha, the official national language in Bhutan. The river rises in Gasa Dzongkhag (district) near the border between Bhutan and Tibet. From there, the Mo Chhu flo ...
and
Dang Chhu The Tang Chuu is a tributary of the Mo Chhu in western Bhutan. Course It originates in the Himalayas near Thowadra Gompa. It receives numerous hill streams, including the Yenyer Chhu. It joins the Mo Chhu, which later takes on the name of Sankos ...
sub basins), and Manas Basin (consisting of
Mangde Chhu Mangde Chhu or Tongsa river flows in central Bhutan traversing roughly north–south. The river rises in Wangdue Phodrang district (or dzongkhag in Dzongkha), near Gangkhar Puensum, Bhutan's highest peak at . Bhutan's main east–west highway c ...
, Chamkhar Chhu,
Kuri Chhu The Kuri Chhu, also known as the Lhozhag Xung Qu () or Norbu Lag Qu (), is a major river of eastern Bhutan, that has formed a scenic valley with high peaks and steep hills. Kuri Chhu is a tributary of the Manas River system, which is the largest ...
, and Drangme Chhu sub-basins). Two other river basins exist in Bhutan corresponding to
Amo Chhu The Torsa River (also spelt Torsha and also known as Kambu Maqu, Machu and Amo Chhu) rises from the Chumbi Valley in Tibet, China, where it is known as Machu. Its course continues into Bhutan, India, and Bangladesh before joining the Brahmaputra ...
and Nyere Ama Chhu but is not associated with any glacier. In order of area (or volume), the vast majority are classifiable as "valley glacier", and "mountain glacier". "Ice apron", and "niche glacier" types exist in significant numbers but occupy far less area (or volume). Far rarer are "cirque glaciers", and "ice caps". The "valley glaciers" are located along the southern flanks of the main topographic divide of the Bhutan Himalaya, and are characterized by debris-mantled snouts. They are primarily concentrated in the upper part of the
Pho Chhu Pho Chhu (Male River) is one of the major rivers of Bhutan, which tracks its source to Gasa District on the borders between Bhutan and Tibet. It joins with the Mo Chhu (Female River) at the confluence below Punakha Dzong, the winter residence of ...
basin and Northern Basin. "Mountain glaciers" are common on peaks, and back walls of valley glaciers. "Cirque glaciers", "ice caps", "ice aprons", and "niche glaciers" are common on plateaus and ridges that stretch to the south from the main Himalayan divide; they are virtually debris-free.
Rock glacier Rock glaciers are distinctive geomorphological landforms that consist either of angular rock debris frozen in interstitial ice, former "true" glaciers overlain by a layer of talus, or something in between. Rock glaciers are normally found at hi ...
s exist in many places along the Snowman Trekking Route in northwestern and northern Bhutan. The south flowing glaciers exhibit steeper head-walls, more debris cover, and slower flow rates than their north-flowing counterparts. As of 2016, the Punatsang Chhu basin contained the highest number of glaciers (341) with an area of about 361.07 km2 and the Wang Chhu Basin had the lowest number of glaciers (47) with an area of about 33.38 km2. The largest glacier (2016) is in the Mangde Chhu sub basin, having an area of 45.85 km2. The longest glacier (2001) is the Wachey Glacier in Pho Chhu river-basin, measuring about 20.1 km. The highest elevation (2016) of glacier basins is at about 7,361 m in the
Mangde Chhu Mangde Chhu or Tongsa river flows in central Bhutan traversing roughly north–south. The river rises in Wangdue Phodrang district (or dzongkhag in Dzongkha), near Gangkhar Puensum, Bhutan's highest peak at . Bhutan's main east–west highway c ...
basin. Lowest snout-elevations (2001) are found to be slightly above 4,000 m, for glaciers in the
Kuri Chhu The Kuri Chhu, also known as the Lhozhag Xung Qu () or Norbu Lag Qu (), is a major river of eastern Bhutan, that has formed a scenic valley with high peaks and steep hills. Kuri Chhu is a tributary of the Manas River system, which is the largest ...
basin and
Drangme Chhu The Manas River (pron: ˆmÊŒnÉ™s, known in Bhutan as the Drangme Chhu, is a transboundary river in the Himalayan foothills between southern Bhutan, India, and China. It is the largest of Bhutan's four major river systems, with the other three ...
basin; debris free glaciers exhibit lower snouts.


Retreat

Several programs concerned with monitoring trans-Himalayan glaciers are underway, and a heterogeneous shrinkage is the general rule. Most of the glaciers in Bhutan are summer-accumulation type and hence, even more sensitive to fluctuations in temperature. However,
equilibrium line altitude Glaciology (; ) is the scientific study of glaciers, or, more generally, ice and natural phenomena that involve ice. Glaciology is an interdisciplinary Earth science that integrates geophysics, geology, physical geography, geomorphology, clim ...
(ELA) information is scarce and little rigorous data on glacier changes are available due to issues in accessing higher-altitude glaciers. In general, it is accepted that glaciers are significantly retreating; the precise causes remain unknown but generally, retreats serve as highly sensitive indicators of climate change. Significant evidence about retreat in lower-elevation glaciers exists. A 1999 publication, deriving from satellite images, maps, and survey data, reported the retreat of multiple glaciers in the Bhutan Himalayas. A 2003 digital survey of 103 debris-free glaciers (small, and of similar length) from 1963 to 1993 determined that 90 were retreating, 13 were stationary, and none was advancing. The magnitude of retreat was larger in the south and smaller in the north, probably because of the higher sensitivity of glacier mass balance to relatively warmer temperature and greater precipitation in the south. Excluding the ones with unclear variations, an areal comparison of 66 glaciers exhibited an 8.1% shrinkage. In-situ observations of several glaciers in the 80s and 90s have pointed towards retreat. A 2012 conservative modelling predicted significant retreat (and shrinkage) in the ensuing decades to attain stability with mean climate conditions absent a near-double increase in precipitation or significant regional cooling. A 2.5 C increase in regional temperature over the next century (as predicted by
IPCC The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to "provide governments at all levels with scientific information that they can use to develop climate policies". The World M ...
) will reduce glaciated area by half and bring
meltwater Meltwater (or melt water) is water released by the melting of snow or ice, including glaciers, glacial ice, tabular icebergs and ice shelf, ice shelves over oceans. Meltwater is often found during early spring (season), spring when snow packs a ...
discharges to negligible values. These were however not validated with in-situ observations. In 2016, the first ever in-situ mass-balance record of a glacier (Gangju La; debris free) in Bhutan was published. It recorded a drastic reduction in mass to the extent that no accumulation zone existed at all, and the observations were in agreement with the 2012 model. The authors noted that remote sensing methodologies indeed estimated far lower mass-losses, as hypothesized in the model. A 2014 analysis by ICIMOD on the evolution of Bhutan glaciers (using Landsat imagery) from 1980 to 2010 concluded that the glaciers were rapidly shrinking in recent decades. From 1980 to 2010, net area had roughly shrank by 23%; absence of debris and presence of a glacial lake at snout accentuated these retreat rates. The numbers increased by about 14.8% due to fragmentation of existing glaciers.


Effects and mitigation

The consequences of glacier retreat remain poorly understood. Changes in river runoff, global sea-level rise, and increase in frequency of glacial lake outburst floods are probable. Decrease in meltwater discharge directly affects the viability of hydroelectric power production, which is one of the economic lifelines for Bhutan. Bhutan was the first country to receive climate mitigation fund from the UN's Least Developed Countries fund.


Glacial lakes

Some glacial lakes, such as Thorthormi Lake in
Lunana Gewog Lunana Gewog () is a gewog (village block) of Gasa District, Bhutan. The village Lunana is the administrative center of Lunana Gewog. The gewog lies almost entirely within protected areas, mostly in Jigme Dorji National Park, though eastern sec ...
, are not a single bodies of water but collections supraglacial ponds. Most glacial lakes identified as potentially dangerous feed into the
Manas River The Manas River (pron: ˆmÊŒnÉ™s, known in Bhutan as the Drangme Chhu, is a transboundary river in the Himalayan foothills between southern Bhutan, India, and China. It is the largest of Bhutan's four major river systems, with the other three ...
and Puna Tsang (Sankosh) River water systems of north-central Bhutan. During a GLOF, residents of nearby downstream villages may have as little as twenty minutes to evacuate; floodwaters from one 1994 GLOF at Luggye lake took about seven hours to reach Punakha, some downstream. For public safety, these glaciers and glacial lakes are maintained by the Ministry of Economic Affairs' Department of Geology and Mines, an executive (cabinet) agency of the
Government of Bhutan The government of Bhutan has been a constitutional monarchy since 18 July 2008. The King of Bhutan is the head of state. The executive power is exercised by the Lhengye Zhungtshog, or council of ministers, headed by the Prime Minister. Legisla ...
. The department, as part of its environmental "mitigation projects," aims to lower the levels of glacial lakes and thereby avert GLOF-related disaster. In 2001, for example, scientists identified Lake Thorthormi as one that threatened imminent and catastrophic collapse. The situation was eventually relieved by carving a water channel from the lip of the lake to relieve water pressure. The Department uses silent explosives and other means it considers environmentally friendly in order to minimize the ecological impact of its mitigation projects. These projects, however, remain difficult to conduct because of the weather, terrain, and relative lack of oxygen at the glacial lakes' altitudes. As of September 2010, GLOF early warning systems were slated for installation by mid-2011 in
Punakha Punakha () is the administrative centre of Punakha dzongkhag, one of the 20 districts of Bhutan. Punakha was the capital of Bhutan and the seat of government until 1955, when the capital was moved to Thimphu. It is about 72 km away from Thim ...
and
Wangdue Phodrang Wangdue Phodrang (, Dzongkha 'Wangdi Phodr'a) is a town and capital (dzongkhag thromde) of Wangdue Phodrang District in central Bhutan. It is located in Thedtsho Gewog. Khothang Rinchenling History The town shares its name with the Wangdue Ph ...
districts at a cost of
USD The United States dollar (symbol: $; currency code: USD) is the official currency of the United States and several other countries. The Coinage Act of 1792 introduced the U.S. dollar at par with the Spanish silver dollar, divided it int ...
4.2 million.


GLOF


See also

*
Climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
*
Geography of Bhutan Bhutan is a sovereign country at the crossroads of East Asia and South Asia, located towards the eastern extreme of the Himalayas mountain range. It is fairly evenly sandwiched between the sovereign territory of two nations: first, the Peopl ...
* List of rivers of Bhutan *
Mountains of Bhutan The mountains of Bhutan are some of the most prominent natural geographic features of the kingdom. Overview Located on the southern end of the Eastern Himalaya, Bhutan has one of the most rugged mountain terrains in the world, whose elevation ...
*
Retreat of glaciers since 1850 The retreat of glaciers since 1850 is a well-documented effects of climate change, effect of climate change. The retreat of Mountain glacier, mountain glaciers provides evidence for the Instrumental temperature record, rise in global temperatures ...


References

{{Bhutan topics
Bhutan Bhutan, officially the Kingdom of Bhutan, is a landlocked country in South Asia, in the Eastern Himalayas between China to the north and northwest and India to the south and southeast. With a population of over 727,145 and a territory of , ...
Glaciers A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...