The Himalayan range encompasses a very large number of glaciers, notable among which is the Siachen Glacier, the largest in the world outside the polar region. Some of the other more famous glaciers include the Gangotri and Yamunotri (Uttarakhand), Nubra, Biafo and Baltoro (Karakoram region), Zemu (Sikkim) and Khumbu glaciers (Mount Everest region).
The higher regions of the Himalayas are snowbound throughout the year in spite of their proximity to the tropics, and they form the sources for several large perennial rivers.
The western rivers combine into the Indus Basin, of which the Indus River is the largest. The Indus begins in Tibet at the confluence of Sengge and Gar rivers and flows southwest through Pakistan to the Arabian Sea. It is fed by the Jhelum, the Chenab, the Ravi, the Beas, and the Sutlej rivers, among others.
Most of the other Himalayan rivers drain the Ganga-Brahmaputra Basin. Its two main rivers are the Ganges and the Brahmaputra. The Ganga originates as the Bhagirathi from the Gangotri glacier and flows southeast through the plains of northern India, fed by the Alaknanda and the Yamuna among other tributaries. The Brahmaputra originates as the Yarlung Tsangpo River in western Tibet, and flows east through Tibet and west through the plains of Assam. The Ganga and the Brahmaputra meet in Bangladesh, and drain into the Bay of Bengal through the world's largest river delta.
The eastern-most Himalayan rivers feed the Ayeyarwady River, which originates in eastern Tibet and flows south through Myanmar to drain into the Andaman Sea.
The Salween, Mekong, the Yangtze and the Huang He (Yellow River) all originate from parts of the Tibetan plateau that are geologically distinct from the Himalaya mountains, and are therefore not considered true Himalayan rivers. Some geologists refer to all the rivers collectively as the circum-Himalayan rivers.
In recent years scientists have monitored a notable increase in the rate of glacier retreat across the region as a result of global climate change. Although the effect of this won't be known for many years it potentially could mean disaster for the hundreds of thousands of people that rely on the glaciers to feed the rivers of northern India during the dry seasons.
The Himalaya region is dotted with hundreds of lakes. Most lakes are found at altitudes of less than 5,000 m, with the size of the lakes diminishing with altitude. The largest lake is the Pangong Tso, which is spread across the border between India and Tibet. It is situated at an altitude of 4,600 m, and is 8 km wide and nearly 134 km long. A notable high (but not the highest) lake is the Gurudogmar in North Sikkim at an altitude of 5,148 m (16,890 ft). Other major lakes include the Tsongmo Lake, near the Indo-China border in Sikkim (India) and Tilicho Lake, a large lake in an area that was closed to outsiders until recently.
The mountain lakes are known to geographers as tarns if they are caused by glacial activity. Tarns are found mostly in the upper reaches of the Himalaya, above 5,500 metres. In addition to its lofty mountains, Nepal provides beautiful displays of its resplendent flora and fauna.
Many major mountains are located entirely within India, such as Nanda Devi (7,817 meters) in the state of Uttar Pradesh. The snow line averages 4,500 to 6,000 meters on the southern side of the Greater Himalayas and 5,500 to 6,000 on the northern side. Because of climatic conditions, the snow line in the eastern Himalayas averages 4,300 meters, while in the western Himalayas it averages 5,800 meters.
The Lesser Himalayas, located in northwestern India in the states of Himachal Pradesh and Uttar Pradesh, in north-central India in the state of Sikkim, and in northeastern India in the state of Arunachal Pradesh, range from 1,500 to 5,000 meters in height. Located in the Lesser Himalayas are the hill stations of Shimla (Simla) and Darjeeling (Darjeeling).
During the colonial period, these and other hill stations were used by the British as summer retreats to escape the intense heat of the plains. It is in this transitional vegetation zone that the contrasts between the bare southern slopes and the forested northern slopes become most noticeable.
The Outer or Southern Himalayas, averaging 900 to 1,200 meters in elevation, lie between the Lesser Himalayas and the Indo-Gangetic Plain. In Himachal Pradesh and Uttar Pradesh, this southernmost range is often referred to as the Siwalik Hills. It is possible to identify a fourth, and northernmost range, known as the Trans-Himalaya.
This range is located entirely on the Qinghai-Xizang Plateau, north of the great west-to-east trending valley of the Yarlung Zangbo River. Although the Trans-Himalaya Range is divided from the Great Himalayan Range for most of its length, it merges with the Great Himalayan Range in the western section--the Karakoram Range--where India, Pakistan, and China meet.
The southern slopes of each of the Himalayan ranges are too steep to accumulate snow or support much tree life; the northern slopes generally are forested below the snow line. Between the ranges are extensive high plateaus, deep gorges, and fertile valleys, such as the vales of Kashmir and Kulu. The Himalayas serve a very important purpose.
They provide a physical screen within which the monsoon system operates and are the source of the great river systems that water the alluvial plains below (see Climate, this ch.). As a result of erosion, the rivers coming from the mountains carry vast quantities of silt that enrich the plains.
The area of northeastern India adjacent to Burma and Bangladesh consists of numerous hill tracts, averaging between 1,000 and 2,000 meters in elevation, that are not associated with the eastern part of the Himalayas in Arunachal Pradesh. The Naga Hills, rising to heights of more than 3,000 meters, form the watershed between India and Burma.
The Mizo Hills are the southern part of the northeastern ranges in India. The Garo, Khasi, and Jaintia hills are centered in the state of Meghalaya and, isolated from the northeastern ranges, divide the Assam Valley from Bangladesh to the south and west.
The Himalayas are not merely a geographical feature, a range of mountains; they epitomize a people’s civilization identity that goes back to the dawn of history. If these majestic mountains were not there, the rain clouds sweeping up from the Indian Ocean would have passed over the Indian subcontinent into central Asia leaving it a burning desert.
Sacred Mounatin Lakes
The Himalayas is also the home to many lakes that are considered sacred to different religions. Some of such sacred lakes in Nepal are:
Gokyo and Associated Lakes - 4,710 - 4,950 meters
Gokyo and Associated Lakes. 23/09/07; Sagarmatha; 7,770 ha; 27°52'N 080°42'E. Within Sagarmatha National Park, UNESCO World Heritage site.
A system of glacial lakes at 4,710m-4,950m altitude in the high Himalayan region at the base of Cho Oyo (the world's 6th highest mountain), not far from Mt. Everest, at the headwaters of the Dudh Koshi River which is part of the Ganges river system.
The alpine pasture meadow and sloping mountain terrain support IUCN Red listed rare and vulnerable species, such as the kutki plant, the Himalayan tahr or goat, the snow leopard, wood snipe, endemic species like the flowering plant Kobresia fissiglumis, and many important birds.
The system is a vital source of water for downstream communities.
Eight hotels with campgrounds serve ecotourists and religious visitors. Garbage and sewage left by visitors is difficult to dispose of and such pollution pressures represent a potential threat, as does overgrazing and deforestation caused by mountaineering expeditions seeking firewood.
The site is two days' walk from Namche, the nearest town.
Gosaikunda and Associated Lakes - 4,054 - 4,620 meters
Gosaikunda and Associated Lakes. 23/09/07; Bagamti; 1,030 ha; 28°05'N 085°25'E. Within Langtang National Park. A treeless region with shrub land interspersed by rocky slopes and alpine pasture, with a complex of at least 15 lakes and ponds.
IUCN Red listed endangered and vulnerable species of animals and plants are present. The site has religious associations for Hindus and Buddhists and is the locus of the important Gangadashahara and Janaipurnima festivals.
Human uses include grazing during summers, and there are four hotels with campgrounds for trekking groups and pilgrims. Threats to the site include pollution from the huge gathering during the festivals. There is a religious ban on the killing of animals within much of the site.
Phoksundo Lake - 3,611 meters
Phoksundo Lake. 23/09/07; Karnali; 494 ha; 29°12'N 082°57'E. Within Shey-Phoksundo National Park. A glacial lake near Ringmo in the Dolpo region, the deepest lake in the country, that is the centre of endemism in the eastern Himalayan region and a vital source of freshwater for downstream, with the highest waterfall 167 meters in Nepal a short walk from the lake.
The lake, alpine meadows, and bogs provide habitat for a number of rare and vulnerable plants and animals, including the snow leopard, musk deer, and grey or Tibetan wolf.
The site has great cultural and religious importance, with traditional Tibetan culture of the upper Dolpo and both Buddhism and the ancient Tibetan Bon-Po religion of the lower Dolpo both observed in Ringmo village. There is some grazing and cultivation, but tourism, dependent upon the wetland, is the base of the economy.
Overgrazing and pollution from the 42 households of Ringmo village are seen as potential threats to the site.
Rara Lake - 2,900 meters
Rara Lake. 23/09/07; Karnali; 1,583 ha; 29°30'N 082°05'E. National Park. The largest lake in Nepal, lying at about 2,900m altitude and providing water to the important Kamali River.
The area has developed unique floral and faunal assemblages with a number of rare and vulnerable animal and plant species, and the wet alpine pasture, moraines, and damp stream banks along the lake area are the natural habitats for endemic species of plants.
The endemic frog Rara paha is found at only one other location in the Central region, and three endemic species of snow trout are found only here.
Two temples in the area are the venue for a number of religious festivals. Principal threats come from pollution caused by army personnel and tourists and unregulated fuelwood collection, especially during festivals.