Glaciers of Asia—

GLACIERS OF BHUTAN—An Overview

By Shuji Iwata

SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD

Edited by RICHARD S. WILLIAMS, JR., and JANE G. FERRIGNO

U. S. G EO LO G I C A L SU RV EY P RO F E SSI O N A L PA P E R 1 3 8 6 –F– 7

CONTENTS III

CONTENTS

Introduction----------------------------------------------------------------------------------------321

Glacier Distribution and Types of Glaciers-------------------------------------------------322

Figure 1. Map showing river basins and glacier distribution of the 

 Bhutan Himalaya--------------------------------------------------------------------323

Table 1. Total number, area, volume, and average thickness of each 

 glacier type in Bhutan --------------------------------------------------------------323

Figure 2. Photograph showing small debris-free plateau glacier with glacial

 lakes at the Gangrinchemzoe La in 1998----------------------------------------324

Figure 3. Graph showing distribution of the lowest elevations of debris-free

 glaciers and debris-mantled glaciers in the Bhutan Himalaya ------------325

Glacier Equilibrium Line Altitude (ELA) and Climate ----------------------------------325

Figure 4. Diagram showing variation of annual precipitation along 

 the Himalaya -------------------------------------------------------------------------326

Glacier Variations ---------------------------------------------------------------------------------327

Figure 5. Diagram showing horizontal distance of glacier-front retreat 

 in the Bhutan Himalaya compared with latitude between 

 1963 and 1993 -----------------------------------------------------------------------327

Figure 6. Map of Gangrinchemzoe-Gophu La Plateau area showing 

 debris-free and debris-covered glaciers and small glacial lakes-----------328

Figure 7. Geomorphological map of the area around Thanza village 

 in the eastern part of Lunana, northern Bhutan, showing 

 debris-mantled glaciers, glacial lakes, and moraines------------------------329

Glacial Lakes ---------------------------------------------------------------------------------------330

Figure 8. Photograph of Lugge Tsho lake from the western end -------------------------331

Figure 9. Photograph of Raphsthreng Tsho lake and erosion on the toe 

 of the lateral moraine caused by the 1994 glacier lake outburst 

 flood from Lugge Tsho--------------------------------------------------------------331

Figure 10. Photograph of Chubda Tsho supraglacial lake on the debris-

 mantled ablation area of Chubda Glacier, upstream in the 

 Chamkhar Chhu basin, north-central Bhutan --------------------------------331

Figure 11. Map of the optimum Landsat 1, 2, and 3 MSS images of the glaciers 

 of Bhutan------------------------------------------------------------------------------332

Table 2. Optimum Landsat 1, 2, and 3 MSS images of the glaciers of Bhutan------332

References Cited ----------------------------------------------------------------------------------333

GLACIERS OF ASIA — BHUTAN F321

SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD 

GLACIERS OF ASIA— 

GLACIERS OF BHUTAN—An Overview

By Shuji Iwata1

Introduction

The Kingdom of Bhutan is a little-known mountainous and heavily 

forested country located in the eastern Himalaya. Having a total area of 

46,500  km2, it extends about 300 km east to west, and 170 km north to 

south. The  total area covered by glaciers in Bhutan is 1,317  km2 (Mool and 

others, 2001). 

Officials, explorers, and naturalists who traveled to Bhutan in the past 

provided no descriptions of glaciers in the Bhutan Himalaya; therefore, not 

much historical information is available. The first modern descriptions of the 

glaciers of Bhutan were undertaken in the 1970s by Augusto Gansser, who 

carried out intensive geological surveys and developed a chronology of past 

glaciations in northern Bhutan (Gansser, 1970, 1983). In  addition, Gansser 

(1970) warned of the potential for glacier lake outburst floods [GLOFs (or 

jökulhlaups)] in the Lunana area and documented his report with excellent 

photographs of glaciers and glacial lakes. 

The report by Gansser (1970) prompted interest in the glaciers and glacial 

lakes of Bhutan, and in 1984 and 1986, the Geological Surveys of Bhutan and 

India carried out joint surveys of glaciers and glacial lakes for an assessment 

of the hazard potential in the Lunana area (Sharma and others, 1986). Their 

report concluded that there was no danger of outburst floods from Raphsthreng 

Tsho (called Lunana Lake in the report). Unfortunately, on 7 October 1994, a 

GLOF from Lugge Tsho glacial lake killed more than 20 people in the town of 

Punākha in the lower reaches of the drainage basin (Watanabe and Rothacher, 

1996; Geological Survey of Bhutan, 1999). 

After the GLOF disaster, several field studies focused on glaciers and 

glacial lakes in the Lunana area (Indo-Bhutan Expedition, 1995; Royal 

Government of Bhutan (RGOB) Expedition, 1995; Water and Power Consultancy Services (WAPCOS), 1997; Haeusler and Leber, 1998, Ageta and Iwata, 

1999). At the same time, some of the field teams visited areas outside Lunana 

to observe glaciers and glacial lakes, conducting GLOF-hazard assessments 

(RGOB Expedition, 1995, Ageta and Iwata, 1999; Karma and Tamang, 1999; 

Karma and others, 1999, 2004; Ageta and others, 2000; Iwata, Ageta, and 

others, 2002; Iwata, Narama, and Karma, 2001), and compiling inventories of 

glaciers and glacial lakes (Division of Geology and Mines, 1996; Geological 

Survey of Bhutan, 1999; Mool and others, 2001). Bhutan and Japan initiated 

cooperative glaciological studies of large debris-mantled glaciers and small 

debris-free glaciers (Yamada and Naito, 2003; Ageta and Kohshima, 2004). 

1

Department of Geography, Tokyo Metropolitan University, Minami-Osawa, Hachiochi, Tokyo 192–0397, 

Japan [iwata-s@comp.metro-u.ac.jp]
F322 SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD

Intensive hazard-assessment and mitigation efforts have continued 

in Lunana (Leber and others, 2000, 2002, 2003). Based on the findings of 

these studies, this paper provides brief descriptions of glaciers and related 

phenomena in the Bhutan Himalaya.

Glacier Distribution and Types of Glaciers

Glacier distribution in a region, including exact numbers and areas 

of glaciers, is shown by a glacier inventory. The  first glacier inventory in 

Bhutan was compiled in 1996 by the Geological Survey of Bhutan (Division 

of Geology and Mines, 1996), and was subsequently published in a revised 

form with 83 pages of text and 13  map sheets (Geological Survey of Bhutan, 

1999). A more complete inventory was published by the International Center 

for Integrated Mountain Development (ICIMOD) in Katmandu, Nepal 

(Mool and others, 2001). These inventories were compiled from analysis of 

1993 Satellite Pour l’Observation de la Terre (SPOT) imagery, and 1:50,000-

scale topographic maps made by the Geological Survey of India from vertical 

aerial photographs taken in the 1960s. Mool and others (2001) counted 677 

glaciers in Bhutan covering a total area of 1,317 km2. [Editors’ note: An inventory of glacier resources by Qin (1999), compiled from analysis of 1975–1978 

Landsat  MSS band 7 and false-color infrared images and some aerial photographs, documented 649 glaciers in Bhutan, covering a total area of 1,304 km2

, 

and including a total volume of 150 km3.] 

Glaciers are common on peaks and mountain flanks along the main 

topographic divide of the Bhutan Himalaya, and on plateaus and ridges that 

stretch to the south from the main Himalayan divide (fig. 1). Most glaciers are 

located in river basins, where the rivers flow from north to south. However, 

Bhutan also includes the north flank of the main divide in the northernmost 

part of the country, an area called the Northern Basin,2 where rivers flow from 

Bhutan northward, toward the Autonomous Region of Tibet, China. 

The total number, area, estimated volume, and average thickness of each 

glacier type in Bhutan is listed in table 1. Valley glaciers on the southern side 

of the main divide have narrow and steep upper basins, whereas glaciers in 

the Northern Basin have large, gently sloping accumulation areas. The longest 

glacier in Bhutan is 20.1  km — Wachey Glacier in Pho Chhu (river) basin 

(Mool and others, 2001). The largest single glacier basin, with a total area of 

99.7 km2 , is located on the north slope of Table Mountain in the Northern Basin, 

northeast of Lunana (Mool and others, 2001). The  accumulation areas of 

glaciers in the Northern Basin form an ice field that constitutes the north slopes 

of Table Mountain.

Large glaciers within valleys are characterized by debris-mantled snouts. 

On the south flank of the Bhutan Himalaya, slopes are steeper than those on 

the north slopes because topography on the south is formed by headward 

erosion of the rivers. As a result, rock cliffs occupy the heads of glacierized 

valleys. Headwalls of glacierized basins have ice and/or snow avalanches and 

rockfalls, processes enhanced by high precipitation from the summer monsoon. 

2

U.S. Government publications require that official geographic place-names for foreign countries be 

used to the greatest extent possible. In the Glaciers of Bhutan section, the use of geographic place-names 

is based on the U.S. Board on Geographic Names as listed on the GEOnet Names Server (GNS) website: 

http://earth-info.nga.mil/gns/html/index.html. Names not listed in the BGN website are shown in italics.
GLACIERS OF ASIA — BHUTAN F323

50 MILES

0 50 KILOMETERS

0

N

28°N

Amo

Chhu

Ha

Chhu

27°N

89°E 90°E 91°E 92°E

Pho Chhu

Dang

Chhu

Mangde

Chhu Drangme

Chhu

Pa

Chhu

Thim

Chhu

Mo

Chhu

Northern

Chamkhar

Chhu

Kuri

Chhu

Chhu

Basin

Nyere

BHUTAN Ama

CHINA

INDIA

GLACIER

INTERNATIONAL BOUNDARY

BASIN BOUNDARY

EXPLANATION

Table 1.—Total number, area, volume, and average thickness of each 

glacier type in Bhutan 

[Data sources: Mool and others (2001), and Karma and others (2003). 

Units: km, kilometer; m, meter]

Glacier type1 Number Area 

(km2)

Estimated volume 

(km3)

Average 

thickness 

(m)

Valley glacier 51 691.76 90.222 130

Mountain glacier 453 579.02 35.510 61

Ice apron 94 33.40 1.197 36

Ice cap 16 5.19 0.182 35

Niche glacier 51 5.57 0.105 19

Cirque glacier 12 1.79 0.035 20

 Total 677 1,316.73 127.251 97

1

Glacier types are adapted from Müller and others (1997). Mountain glaciers are the most 

common, and their profile shows a hanging type.

Figure 1.—River basins and glacier distribution of the Bhutan Himalaya. After Mool and others (2001).
F324 SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD

The  large amount of supraglacial debris in accumulation areas produces 

extensive debris-mantles in ablation areas downglacier. Large debris-mantled 

glaciers develop in Lunana, the upper part of the Pho Chhu basin, and in the 

Northern Basin, where there are many steep, high mountains. 

Numerous mountain glaciers, especially small hanging-type glaciers, 

occur on steep slopes of high peaks and on back walls of valley glaciers. Cirque 

glaciers, small ice caps, ice aprons, and niche glaciers are common on plateaus 

and ridges that stretch to the south from the main Himalayan divide (fig.  2). 

These small glaciers are virtually debris-free. 

According to Mool and others (2001), the highest elevation of glacier 

basins is at about 7,500  m, near Gankerphuensum (7,570  m) in the Mangde 

Chhu basin, and the second highest is at about 7,300  m, near Chomo Lhāri 

(7,314  m) in the Pa Chhu basin. Although no measurements were conducted 

for the ICIMOD inventory, glacier basins at higher elevations may exist on 

Kula Kangri (Kunla Khari, 7,538  m). Values in Mool and others (2001) show 

that the lowest elevations of glacier termini are found slightly above 4,000  m. 

Glacier termini between longitudes 90.2°E. and 90.9°E. (the Mangde Chhu and 

Chamkhar Chhu basins) are somewhat higher, above 4,300  m. Glaciers in this 

area cannot flow down to lower elevations because of plateau-like landforms and 

high valley floors. A  group of small mountain glaciers in the Kuri Chhu basin, 

located east of long 90.9°E., and the Drangme Chhu basin farther east, have very 

low maximum (below 5,000 m) and minimum (nearly 4,000 m) elevations. 

Figure 2.—Small debris-free plateau glacier with glacial lakes at the Gangrinchemzoe La (pass is at 5,200 m) in 

1998. The lake started to form around the mid-1980s.
GLACIERS OF ASIA — BHUTAN F325

The Geological Survey of Bhutan inventory (1999) lists a smaller number 

of glaciers than do Mool and others (2001), but glaciers on the list can be classified into debris-mantled and debris-free from the associated maps. Karma 

and others (2003) plotted frontal elevations of both debris-mantled and 

debris-free glaciers (fig. 3). The graph clearly shows that the termini of debrismantled glaciers extend to lower elevations (4,200 m) than those of debris-free 

ones (4,700 m). 

4,000

4,200

4,400

4,600

4,800

5,000

5,200

5,400

5,600

LOWEST ELEVATION,

IN METERS ABOVE SEA LEVEL

89°00’E 89°30’E 90°00’E 90°30’E 91°00’E

LONGITUDE

DEBRIS FREE

DEBRIS COVERED

Figure 3.—Distribution of the lowest elevations (glacier termini) of debris-free 

glaciers (open circles) and debris-mantled glaciers (solid diamonds) in the 

Bhutan Himalaya. Karma and others (2003).

Glacier Equilibrium Line Altitude (ELA) 

and Climate

Bhutan has a monsoonal climate and most precipitation occurs in 

summer. Because monsoonal precipitation is much greater in the eastern and 

southern parts of the Himalaya than in the western and northern parts (Eguchi, 

1991; fig. 4), glaciers have the characteristics of “summer-accumulation types.” 

Glaciers receive most of their annual accumulation in the summer when ablation occurs simultaneously. The  higher summer air temperature provides the 

following negative effects on mass balance of the summer-accumulation type 

glaciers (Ageta and Higuchi, 1984; Ageta and Kadota, 1992): (1)  increased 

percentage of total precipitation in the form of rainfall reduces accumulation by 

snowfall, (2) decreased albedo due to less snowfall enhances ablation by insolation, (3) higher temperatures increase ablation. As a result, the variations of 

monsoon-type glaciers are very sensitive to the summer air temperature.

The equilibrium line altitude (ELA) is the most important parameter 

used to analyze glacier response to climate. Unfortunately, ELA information 

on glaciers in Bhutan is not available from the existing inventories. The  ELA 

obtained from the author’s observation in the field in September and October 

1998 was 5,200–5,300 m on glaciers on the south side of the Himalaya in the 

northwestern and northern parts of Bhutan (Iwata, Naito, and others, 2003). 

This value is the lowest elevation of the ELA throughout the central and 

eastern Himalaya (Matsuoka, 2003). The intensity of the monsoon apparently 

produces the low ELA. 
F326 SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD

Rock glaciers exist in many places along the Snowman Trekking Route

in northwestern and northern Bhutan. Iwata, Gurung, and Komori (2003) 

reported on the lower limit of permafrost based on the distribution of active 

periglacial rock glaciers. The  lower limit of discontinuous permafrost is at 

4,800  m on north-facing slopes and at 5,000  m on south- and east-facing 

slopes. Results of automatic weather-station measurements between 1998 

and 1999 suggest that mean annual air temperatures at the lower limits of the 

permafrost zone are −1.1 °C at 5,000 m and +0.1 °C at 4,800 m. These values 

mean that the relative height difference between the ELA and the lower limit 

of permafrost in the Bhutan Himalaya is the smallest in the Asian Continent 

(Matsuoka, 2003).

Isacks and others (1995) discussed the ELA depression during the Last 

Glacial Maximum (LGM) based on a determination of the maximum extent 

of glaciation using satellite imagery. Although their attempt was noteworthy, 

their conclusions are not supported by any field observations, and no glacial 

landforms have been dated using morphostratigraphic or cosmogenic-isotope 

dating methods.

0

1,000

2,000

3,000

4,000

5,000

70° 80° 90° 100°

EAST LONGITUDE

A

A’

B’

C’

B

C

PRECIPITATION, IN MILLIMETERS

70°E 80°E 90°E

30°N

40°N

20°N

C

C’

A

A’

B

B’

60°E 100°E

HIGH MOUNTAIN AND PLATEAU AREAS – That have

approximate elevations greater than 3,000 meters.

HILLY AREAS – That have approximate elevations

greater than 500 meters.

EXPLANATION

Figure 4.—Variation of annual precipitation along the Himalaya. 

A, North of the Himalaya, B, Southern slopes of the Himalaya, 

C, Indian plain. From Eguchi (1991).
GLACIERS OF ASIA — BHUTAN F327

Glacier Variations

Karma and others (2003) identified termini variations of debris-free 

glaciers in the 30-year period between 1963 and 1993 by analyzing published 

inventories (Geological Survey of Bhutan, 1999; Mool and others, 2001), 

topographic maps (1:50,000 scale, showing the early 1960s positions), and 

satellite images (1993 SPOT images). A total of 103 debris-free glaciers were 

selected for measurement, because these types of glaciers are sensitive to 

climatic change, and most debris-mantled glaciers show no changes of their 

frontal positions. The debris-free glaciers selected for analysis were small and 

had similar lengths. Karma and others (2003) determined that 90 glaciers 

(87.3 percent) are retreating, 13 (12.7 percent) are stationary, and no glacier 

was advancing. The  horizontal distance of the frontal retreat of each glacier 

was plotted versus its latitude (fig.  5). Results indicate that the magnitude of 

glacier retreat is larger in the south and smaller in the north because of the 

higher sensitivity of glacier mass balance to the warmer temperature and 

greater precipitation in the south. Karma and others (2003) concluded that the 

average retreat rates of glacier termini in Bhutan are higher than those in Nepal.

Areal shrinkage of 66 glaciers selected from the 103 debris-free glaciers 

was measured on the maps with a planimeter (Karma and others, 2003). 

The 66 glaciers had a total area of 146.9 km2 in 1963, and the area decreased to 

134.9 km2 in 1993 — an 8.1 percent shrinkage in 30 years. The smaller glaciers 

show higher shrinkage rates than larger glaciers, and three small glaciers with 

areas of 0.1, 0.15, and 0.2  km2 in 1963 had completely disappeared by 1993 

(Karma and others, 2003). 

HORIZONTAL RETREAT, IN METERS

LATITUDE

400 500 600 700 800 900

27°48’

27°54’

28°00’

28°06’

28°12’

27°42’

0 100 200 300

Figure 5.—Horizontal distance of glacier-front 

retreat in the Bhutan Himalaya compared with 

latitude between 1963 and 1993. Dashed line 

shows the linear regression. From Karma and 

others (2003).
F328 SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD

Frontal variations of several debris-free glaciers on GangrinchemzoeGophu La Plateau were observed in the field by Dr. Nozomu Naito in 1999 

and compared with photographs taken in 1983–1984 by the Kyoto University 

Expedition (Yamada and Naito, 2003). Gangrinchemzoe-Gophu La Plateau, 

located to the southeast of Lunana, is 5,000–5,500 m in elevation, with many 

small glaciers and small glacial lakes (fig.  6). Observed glaciers have been 

shrinking markedly in recent decades as Karma and others (2003) reported.

Glacier variations since the late Pleistocene were mapped by Gansser 

(1983). He classified moraines and erosional landforms into six glacial stages 

in the entire area of northwestern and northern Bhutan. Gansser’s glacial 

stages, however, were illustrated on the map but without explanation, and, in 

some cases, landforms with similar morphostratigraphic characteristics were 

assigned to two or more glacial stages.

Loju La

27°55’

28°00’

90°15’

0 2 MILES

0 2 KILOMETERS

1

1

Scale is approximate

Gangrinchemzoe La

Jichu Dramo

Jaze La

Tsochena

Gophu La

GLACIER – With supraglacial debris

MORAINE RIDGE

GLACIER LAKE –

In the Mangde Chhu basin

In the Pho Chhu basin

RIDGE CREST – Dashed where

obscured by snow or ice

DIRECTION OF GLACIER OR

STREAM FLOW

MOUNTAIN PEAK - With elevation in

meters above sea level

LINES OF EQUAL ELEVATION

TRAIL

GLT

GLP

5,919

EXPLANATION

5,919

5,162

5,356

5,776

5,586

GLP17

GLP18

5,240

5,638

5,504

5,710

GLP19

GLT8

GLT9

GLT10

5,324

5,650

5,614

5,587

5,400

Figure 6.—Gangrinchemzoe-Gophu La Plateau area showing debris-free and debris-covered glaciers and small glacial 

lakes. After Yamada and Naito (2003); revised from Ageta and Iwata (1999), based on interpretation of 1993 SPOT image.
GLACIERS OF ASIA — BHUTAN F329

Iwata and his colleagues carried out geomorphological research in the 

Lingshi area, northwestern Bhutan, and Lunana in northern Bhutan (Iwata, 

Narama, and Karma, 2002). Moraines formed by valley glaciers in the Lingshi 

area constitute three distinct stages, with differences in spatial situations, 

volume of moraines, and surface features, such as clasts, soils, and vegetation. 

Moraines in the Thanza village area in Lunana also show three stages (fig. 7), 

with characteristics similar to those in the Lingshi area. Based on morphostratigraphic criteria (Iwata, 1976), these three stages correlate with some glacial 

stages in the Khumbu Himal, eastern Nepal. Dates of moraines in the Khumbu 

Himal (Richards and others, 2000) provide a tentative chronological sequence 

of these three stages. Valley glaciers in Bhutan expanded during the following 

periods: (1) the Takaphu and Raphsthreng Stages that may correlate to the 

“Little Ice Age” and late Holocene Epoch glacial advances, (2) the Jykhuje and 

Tenchey Stages that may represent the late Pleistocene Epoch and/or early 

Holocene glacial advances, and (3) the Lingshi Dzong and Lunana Stages that 

may coincide with the “Late glacial stage” of the Pleistocene Epoch.

90°15’E

28°05’N

Bechung Glacier

Raphsthreng

Glacier

Thorthormi Glacier

Lugge Glacier

Lugge Tsho

Tsho

Raphsthreng

Thanza

4,174

Tenchey

Pho Chhu

4,441

5,087

4,740

4,716

4,600 4,600

Glaciated Plateau

4,695

5,643

5,987

Yaore Gang (Table Mountains)

RAPHSTHRENG STAGE

TENCHEY STAGE

LUNANA STAGE

GLACIER ICE

DEBRIS-MANTLED AREA M O R A I N E S

LAKE

RIDGE

STREAM

HOUSE

ELEVATION – In meters

above sea level

5,643

EXPLANATION

0 2 MILES

0 2 KILOMETERS

1

1

Scale is approximate

Figure 7.—Geomorphological map of the area around Thanza village (4,170 m) in the eastern part of Lunana, northern 

Bhutan, showing debris-mantled glaciers, glacial lakes, and moraines. From Iwata, Narama, and Karma (2002).
F330 SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD

Glacial Lakes

Glacial lake outburst flood (GLOF) events have occurred in the 

high-mountain areas of the Bhutan Himalaya during the past 50 years and 

have increased in recent years. After the 1994 GLOF from Lugge Tsho glacial 

lake (fig. 8), inventories of glacial lakes were compiled based on 1989 and 1990 

SPOT images to identify potentially hazardous lakes (Division of Geology and 

Mines, 1996; revised version: Geological Survey of Bhutan, 1999). A  total of 

62 glacial lakes were listed with information, such as code name, types of lake, 

elevation, dimensions, geographic coordinates, and location. The  remarks 

noted that 37 glacial lakes should be field checked and/or monitored. 

The inventory of glacial lakes made by ICIMOD (Mool and others, 2001) 

was compiled from topographic maps made by the Survey of India (1960s), 

aerial photographs, and Landsat Thematic Mapper (TM) (1993–1999), 

Indian Remote Sensing (IRS) 1D Linear Self Scanning (LIS) S3 (1999), and 

SPOT (1994) satellite images. A total of 2,674 lakes were listed with a total 

area of 106,776 km2. The number of lakes is very large, because it includes all 

lakes in glaciated and glacierized areas, including small tarns in empty cirques. 

Mool and others (2001) identified 24 potentially dangerous glacial lakes 

concentrated in the Pho Chhu (Lunana) and Mangde Chhu basins; lakes in the 

Northern Basin (north of the main divide) were excluded from the assessment. 

Potentially dangerous glacial lakes are mostly located in or adjacent to the ablation areas of large debris-mantled glaciers. Field observations and analyses of 

maps and satellite images indicate that most supraglacial lakes tend to connect 

with each other and can enlarge rapidly. Since the 1970s, some morainedammed lakes formed and have rapidly expanded in area, caused by retreating 

and/or melting of glaciers (Ageta and Iwata, 1999; Ageta and others, 2000; 

Iwata, Ageta, and others, 2002).

After the 1994 GLOF from the Lugge Tsho glacial lake, many research 

groups visited the Lunana area to carry out risk assessments, risk mitigation, and disaster prevention efforts (Indo-Bhutan Expedition, 1995; RGOB 

Expedition, 1995; WAPCOS, 1997; Haeusler and Leber, 1998; Leber and 

others, 2000, 2002, 2003). The  Bhutan Government carried out hydraulicengineering projects, and between 1996 and 1998, they excavated a drainage 

channel at the outlet of Raphsthreng Tsho (figs. 7 and 9) using hand labor. As a 

result, the water level of the lake was lowered by 4 m. [Editors’ note: see figure 

14 (p. I71) and the Glacier Hazards section (p. I68–I71) in Morales Arnao 

(1998) for a discussion of similar hazard-mitigation work in Perú.]

A Bhutan-Japan joint team, which included the author, visited and assessed 

the risk potential of glacial lakes in areas along Snowman Trekking Route through 

northwestern and northern Bhutan (Ageta and Iwata, 1999). Analysis of the 

occurrence of trigger mechanisms, impact on the lakes, and stability of morainedams suggests that there are at least five potentially dangerous glacial lakes of 

the 30 lakes studied in northwestern and northern Bhutan. Three of these in 

eastern Lunana, including Lugge Tsho, Raphsthreng Tsho, and Thorthomi Tsho,

still contain a large volume of water, are connected to each other, and interact 

sensitively through water flux and erosion (Iwata, Ageta, and others, 2002). 

The inventory by Mool and others (2001) identified a large and 

dangerous glacial lake called Chubda Tsho in the upper part of Chamkhar Chhu

basin, Bumthang, central Bhutan. In 2002, this author carried out a short field 

study at the lake. The Chubda Tsho is not a moraine-dammed lake, but a large 

supraglacial lake (fig.  10). No definite terminal moraine dams the lake, but 

at the lower end of the lake there is only a gentle threshold composed of the 

debris-mantled glacier. The  lake tends to expand more toward the upglacier 

end than the downglacier end. However, the expansion rate is not high, most 
GLACIERS OF ASIA — BHUTAN F331

Figure 8.—Lugge Tsho lake from the 

western end. The ice cliff of Lugge 

Glacier is at the eastern end of the lake. 

A large volume of water still remains 

after the 1994 glacier lake outburst flood 

(GLOF) (1998 photograph by S. Iwata).

Figure 9.—Raphsthreng Tsho lake 

and erosion on the toe of the lateral 

moraine caused by the 1994 glacier 

lake outburst flood (GLOF) from Lugge 

Tsho. The excavation made at the outlet 

of Raphsthreng Tsho lowered the water 

level 4 m. To the left is the debris-mantled 

Bechung Glacier (1998 photograph by 

S. Iwata).

Figure 10.—Chubda Tsho supraglacial 

lake on the debris-mantled ablation 

area of Chubda Glacier, upstream in 

the Chamkhar Chhu basin, north-central 

Bhutan (2002 photograph by S. Iwata).

likely because expansion toward the upglacier end may be counter balanced 

by glacier advance. Although this glacial lake does not pose an urgent danger 

of GLOF, the lake threshold itself may fail and so detailed inspections of 

the threshold by glaciologists with knowledge of debris-covered glaciers are 

necessary (Iwata, Gurung, and Komori, 2003; Komori and others, 2004).

The inventories of glacial lakes from satellite images indicate that many 

large and dangerous glacial lakes exist in headwater areas of Kuri Chhu in the 

Autonomous Region of Tibet, China. Kuri Chhu flows from the Autonomous 

Region of Tibet, China, to Bhutan, so that, if a GLOF from these lakes occurs, 

areas in the lower reaches of Kuri Chhu in Bhutan could sustain heavy losses. 
F332 SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD

In analyzing SPOT images, Dr. Jiro Komori found evidence of a recent GLOF 

and warned of the risk of future GLOFs in the region (Ageta and Kohshima, 

2004). The Bhutanese Government is concerned about this danger, but cannot 

take preventative action because the lakes are located in China. 

Constant and regular monitoring of glaciers and glacial lakes is urgently 

required to develop necessary hazard-mitigation strategies (Wangda, 2000). 

Monitoring of satellite imagery is the most effective tool for the purpose. 

Table 2 and figure 11 show optimum Landsat  1, 2, and 3 imagery for 

conducting historic studies of the glaciers of Bhutan.

Table 2.—Optimum Landsat 1, 2, and 3 MSS images of the glaciers of Bhutan

[Code column indicates usability for glacier studies; see figure 11 for explanation]

Path-Row Nominal scene center 

latitude and longitude

Landsat 

identification 

number

Date Code

Cloud 

cover

(percent)

147–41 27°23′N. 91°49′E. 2147040007635190 16 Dec 76 5

148–40 28°49′N. 90°47′E. 2148040007635290 17 Dec 76 5

148–41 27°23′N. 90°23′E. 2148041007635290 17 Dec 76 10

149–40 28°49′N. 89°21′E. 2149040007635390 18 Dec 76 10

149–41 27°23′N. 88°57′E. 2149041007635390 18 Dec 76 15

Figure 11.—Map of the optimum Landsat 1, 2, and 3 MSS images of the glaciers of Bhutan. 

Compare with table 2.

EXCELLENT IMAGE – 0 to 5 percent cloud cover.

GOOD IMAGE – 5 to 10 percent cloud cover.

FAIR TO POOR IMAGE – 10 to 100 percent cloud cover.

NOMINAL SCENE CENTER

≤

> ≤

> <

– For a Landsat image outside the area of glaciers of Bhutan.

EXPLANATION

BHUTAN

CHINA

NEPAL

INDIA

Path

150

Row

40

Row

40

Path

150

88°E 90°E 92°E

28°N

26°N

88°E 90°E 92°E

28°N

26°N

Path

147

Path

147

Row

41

Row

41

0 50 MILES

0 50 KILOMETERS

Scale is approximate
GLACIERS OF ASIA — BHUTAN F333

References Cited

Ageta, Y., and Higuchi, K., 1984, Estimation of mass balance 

components of a summer-accumulation type glacier in the 

Nepal Himalaya: Geografiska Annaler, v. 66A, no. 3, p. 249–255. 

Ageta, Y., and Iwata, S., eds., 1999, Report of Japan-Bhutan joint 

research 1998 on the assessment of glacier lake outburst 

flood (GLOF) in Bhutan: Nagoya University, Institute for 

Hydrospheric-Atmospheric Science (not officially published; 

available for inspection in the Geological Survey of Bhutan, 

Thimphu), 161 p.

Ageta, Y., Iwata, S., Yabuki, H., Naito, N., Sakai, A., and others, 

2000, Expansion of glacier lakes in recent decades in the Bhutan 

Himalayas, in Nakawo, M., Raymond, C.F., and Fountain, A., 

eds., Debris-covered glaciers, Proceedings of a workshop held at 

Seattle, Washington, USA, 13–15 September 2000: IAHS Publ. 

no. 264, p. 165–175.

Ageta, Y., and Kadota, T., 1992, Predictions of changes of glacier 

mass balance in the Nepal Himalaya and Tibetan Plateau — 

A case study of air temperature increase for three glaciers: 

Annals of Glaciology, v. 16, p. 89–94.

Ageta, Y., and Kohshima, S., eds., 2004, Report of Japan-Bhutan 

joint research 2003 on the assessment of glacier lake outburst 

flood (GLOF) in Bhutan: Nagoya University, Graduate School 

of Environmental Studies; Tokyo Institute of Technology, 

Graduate School of Bioscience and Biotechnology; Geological 

Survey of Bhutan, 64  p.  (not officially published; available for 

inspection in the Geological Survey of Bhutan, Thimphu).

Division of Geology and Mines, 1996, Glaciers and glacier lakes 

in the headwaters of major river basins of Bhutan: Thimphu, 

Ministry of Trade and Industry, 55 p. (not officially published; 

available for inspection in the Geological Survey of Bhutan, 

Thimphu).

Eguchi, T., 1991, Regional and temporal variations in precipitation 

in the eastern part of the Himalayas: Kochi, Japan, Kochi 

University, Faculty of Humanities and Economics.

Gansser, A., 1970, Lunana: The peaks, glaciers and lakes of 

northern Bhutan: The Mountain World 1968/69, p. 117–131.

Gansser, A., 1983, Geology of the Bhutan Himalaya: Basel, 

Birkhauser Verlag, 181 p.

Geological Survey of Bhutan, 1999, Glaciers and glacier lakes in 

Bhutan: Thimphu, Ministry of Trade and Industry, Geological 

Survey of Bhutan, 2 vols., 83 p., and 13 map sheets.

Haeusler, H., and Leber, D., 1998, Final report of the Raphstreng 

Tsho outburst flood mitigation project: (Lunana, Northwestern 

Bhutan), Phase I: University of Vienna, Institute of Geology, 

33  p. (not officially published; available for inspection in the 

Geological Survey of Bhutan, Thimphu).

Indo-Bhutan Expedition, 1995, Geology, environmental hazards 

and remedial measures of the Lunana area, Gasa Dzongkha — 

Report of 1995 Indo-Bhutan Expedition: Geological Survey 

of India, 40 p., and maps (not officially published; available for 

inspection in the Geological Survey of Bhutan, Thimphu).

Isacks, B.L., Duncan, C.C., and Klein, A.G., 1995, Modern 

and LGM glacial extents from satellite images and digital 

topography — Implications for LGM climate in the Bhutan 

Himalayas [abs.]: Abstracts-International Himalayan/Tibetan 

Plateau Paleoclimate Workshop, Kathmandu, p. 24.

Iwata, S., 1976, Late Pleistocene and Holocene moraines in the 

Sagarmatha (Everest) region, Khumbu Himal: Seppyō ( Japanese 

Journal of Snow and Ice) v. 38, special iss., p. 109–114.

Iwata, S., Ageta, Y., Naito, N., Sakai, A., Narama, C., and Karma, 

2002, Glacial lakes and their outburst flood assessment in the 

Bhutan Himalaya: Global Environmental Research [Tokyo], 

v. 6, no. 1, p. 3–17. 

Iwata, S., Gurung, Deo Raj, and Komori, J., 2003, Report of 

Chubda Tsho in the head waters of Chamkar Chhu, Bumthang, 

2002, in Yamada, T., and Naito, N., eds., Report of Japanese - 

Bhutan joint research 2002 on the assessment of glacier lake 

outburst flood (GLOF) in Bhutan: Hokkaido University, p. 54–66.

Iwata, S., Naito, N., Narama, C., and Karma, 2003, Rock glaciers and 

the lower limit of mountain permafrost in the Bhutan Himalayas: 

Zeitschrift für Geomorphologie, N.F. Supplementband 130, 

p. 129–143.

Iwata, S., Narama, C., and Karma, 2002, Three Holocene and late 

Pleistocene glacial stages inferred from moraines in the Lingshi 

and Thanza village areas, Bhutan: Quaternary International 

v. 97/98, p. 69–78. 

Karma, Ageta, Y., Naito, N., Iwata, S., and Yabuki, H., 2003, Glacier 

distribution in the Himalayas and glacier shrinkage from 1963 

to 1993 in the Bhutan Himalayas: Bulletin of Glaciological 

Research v. 20, p. 29–40. 

Karma, and Tamang, K.B., 1999, Preliminary report on Tsokar 

Tsho in the head waters of Chamkhar Chhu, Bhumthang: 

Geological Survey of Bhutan, (not officially published; available 

for inspection in the Geological Survey of Bhutan, Thimphu).

Karma, Thapa, T., and Ghalley, K.S., 1999, Preliminary report 

on Chubda Tsho in the headwaters of Chamkhar Chhu, 

Bhumthang: Geological Survey of Bhutan, 11  p., and tables, 

figures, and maps (not officially published; available for 

inspection in the Geological Survey of Bhutan, Thimphu).

Komori, J., Gurung, D.R., Iwata, S., and Yabuki, H., 2004, Variation 

and lake expansion of Chubda Glacier, Bhutan Himalayas, 

during the last 35 years: Bulletin of Glaciological Research, 

v. 21, p. 49–55.

Leber, D., Haeusler, H., Brauner, M., Payer, T., and Wangda, D., 

2003, Final report of the glacier lake outburst flood (GLOF) 

mitigation project (2002–2003) — Pho Chhu-Western branch 

(Tarina and Tang Chhu Watershed), Bhutan: University of 

Vienna, Department of Geological Sciences; Thimpu, Bhutan, 

Ministry of Trade and Industry, Department of Geology and 

Mines, 97  p., and maps (not officially published; available for 

inspection in the Geological Survey of Bhutan, Thimphu).

Leber, D., Haeusler, H., Brauner, M., and Skuk, S., 2000, Technical 

Report — Luggye Mitigation Project, Lunana, Bhutan: 

University of Vienna, Institute of Geology, 71 p. (not officially 

published; available for inspection in the Geological Survey of 

Bhutan, Thimphu).

Leber, D., Haeusler, H., Brauner, M., and Wangda, D., 2002, Final 

report of the glacier lake outburst flood (GLOF) mitigation project 

— Pho Chhu-Eastern branch (Thanza-Lhedi; 2000–2002), 
F334 SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD

Lunana, Bhutan: University of Vienna, Institute of Geology; 

Thimpu, Bhutan, Ministry of Trade and Industry, Department of 

Geology and Mines, 189 p., and maps (not officially published; 

available for inspection in the Geological Survey of Bhutan, 

Thimphu).

Matsuoka, N., 2003, Contemporary permafrost and periglaciation 

in Asian high mountains — An overview: Zeitschrift für 

Geomorphologie, N.F. Supplement Bd. 130, p. 145–166.

Mool, P.K., Wangda, D., Bajracharya, S.R., Kunzang, K., Gurung, 

D.R., and Joshi, S.P., 2001, Inventory of glaciers, glacial lakes 

and glacial lake ouburst floods — Monitoring and early 

warning systems in the Hindu Kush-Himalayan region, Bhutan: 

Kathmandu, International Centre for Integrated Mountain 

Development (ICIMOD), 227 p.

Morales Arnao, B., 1998, Glaciers of Perú (I–4), with a section 

on Quelccaya Ice Cap, by Hasternrath, S., in Williams, R.S., Jr., 

and Ferrigno, J.G., eds, Satellite image atlas of glaciers of the 

world: U.S. Geological Survey Profesional Paper 1386–I (South 

America), p. I51–I79. [http://pubs.usgs.gov/prof/p1386i/]

Müller, F., Caflish, T., and Müller, G., 1977, Instruction for 

compilation and assemblage of data for a World Glacier 

Inventory: Zürich, Temporary Technical Secretariat for World 

Glacier Inventory, Swiss Federal Institute of Technology; 

International Commission on Snow and Ice, International 

Association of Hydrological Sciences, United Nations 

Environment Programme, United Nations Educational, 

Scientific and Cultural Organization, 28 p.

Qin Dahe, chief ed., 1999, Map of glacier resources in the 

Himalayas; 1st ed.: Beijing, Science Press, scale 1:500,000, 

7 sheets. [Compilation of map based on analysis of 1975–

1978 Landsat MSS 7 and false-color images and some aerial 

photographs]

Richards, B.W.M., Benn, D.I., Owen, L.A., Rhodes, E.J., Spencer, 

J.Q., 2000, Timing of late Quaternary glaciations south of Mount 

Everest in the Khumbu Himal, Nepal: Geological Society of 

America, Bulletin, v. 112, no. 10, p. 1621–1632.

Royal Government of Bhutan (RGOB) Expedition, 1995, 

Preliminary report on the investigation of glacial lakes at Pho 

Chhu source and the assessment of flood affected areas in 

Lunana: Royal Government of Bhutan Expedition (not officially 

published; available for inspection in the Geological Survey of 

Bhutan, Thimphu). 

Sharma, A.R., Ghosh, D.K., and Norbu, P., 1986, Report on Lunana 

Lake expedition —1986: Geological Survey of India (not 

officially published; available for inspection in the Geological 

Survey of Bhutan, Thimphu, Bhutan).

Wangda, D., 2000, The need to monitor glaciers and glacier lakes in 

the headwaters of major river basins of Bhutan: Bhutan Geology 

News Letter SL No. 2, p. 17–19.

Watanabe, T., and Rothacher, D., 1996, The 1994 Lugge Tsho glacial 

lake outburst flood, Bhutan Himalaya: Mountain Research and 

Development, v. 16, no. 1, p. 77–81.

Water and Power Consultancy Services (WAPCOS), 1997, 

Raphstreng Lake, Lunana (Bhutan) — Report on flood 

mitigatory measures (Phase 1—1996): Water and Power 

Consultancy Services (India) Limited.

Yamada, T., and Naito, N., eds., 2003, Report of Japan-Bhutan 

joint research 2002 on the assessment of glacier lake outburst 

flood (GLOF) in Bhutan: Hokkaido University, Institute 

of Low Temperature Science; Nagoya University, Graduate 

School of Environmental Studies; Geological Survey of Bhutan, 

106  p. (not officially published; available for inspection in the 

Geological Survey of Bhutan, Thimphu, Bhutan).