Climate of Nepal

Nepal measures about along its Himalayan axis by across. It has an area of .

Nepal is landlocked by China's Tibet Autonomous Region to the north and India on other three sides. West Bengal's narrow ''Siliguri Corridor'' separate Nepal and Bangladesh. To the east are Bhutan and India.

Landform regions

For a country of its size, Nepal has tremendous geographic diversity. It rises from as low as elevation in the tropical Terai—the northern rim of the Gangetic Plain, through beyond the perpetual snow line to 90 peaks over including Earth's highest ( Mount Everest or ''Sagarmatha''). In addition to the continuum from tropical warmth to cold comparable to polar regions, average annual precipitation varies from as little as in its narrow proportion of the rainshadow north of the Himalayas to as much as on windward slopes, the maximum mainly resting on the magnitude of the South Asian monsoon.

Forming south-to-north transects, Nepal can be divided into three belts: Terai, Pahad and Himal. In the other direction, it is divided into three major river systems, east to west: Koshi, Gandaki/Narayani and Karnali (including the Mahakali along the western border), all tributaries of the Ganges river. The Ganges-Yarlung Zangbo/Brahmaputra watershed largely coincides with the Nepal-Tibet border, save for certain tributaries rising beyond it.

Himal

Himal Region is a mountainous region containing snow.
The Mountain Region begins where high ridges (Nepali: लेक; lekh) begin substantially rising above into the subalpine and alpine zone which are mainly used for seasonal pasturage. By geographical view, it covers 15% of the total area of Nepal. A few tens kilometers further north the high Himalaya abruptly rise along the Main Central Thrust fault zone above the snow line at . Some 90 of Nepal's peaks exceed and eight exceed including Mount Everest at and Kanchenjunga at .

There are some 20 subranges including the Kanchenjunga massif along with the Mahalangur Himal around Mount Everest. Langtang north of Kathmandu, Annapurna and Manaslu north of Pokhara, then Dhaulagiri further west with Kanjiroba north of Jumla and finally Gurans Himal in the far west.

Trans-Himalayan

The main watershed between the Brahmaputra (called ''Yarlung Tsangpo'' in Tibet) and the Ganges system (including all of Nepal) actually lies north of the highest ranges. Alpine, often semi-arid valleys—including Humla, Jumla, Dolpo, Mustang, Manang and Khumbu—cut between Himalayan sub ranges or lie north of them.

Some of these valleys historically were more accessible from Tibet than Nepal and are populated by people with Tibetan affinities called ''Bhotiya'' or ''Bhutia'' including the famous Sherpas in Kumbu valley near Mount Everest. With Chinese cultural hegemony in Tibet itself, these valleys have become repositories of traditional ways. Valleys with better access from the hill regions to the south are culturally linked to Nepal as well as Tibet, notably the Kali Gandaki Gorge where Thakali culture shows influences in both directions.

Permanent villages in the mountain region stand as high as with summer encampments even higher. Bhotiyas graze yaks, grow cold-tolerant crops such as potatoes, barley, buckwheat and millet. They traditionally traded across the mountains, e.g., Tibetan salt for rice from lowlands in Nepal and India. Since trade was restricted in the 1950s they have found work as high altitude porters, guides, cooks and other accessories to tourism and alpinism.

Hilly

Hilly Region is a mountain region which does not generally contain snow. It is situated to the south of the Himal Region (the snowy mountain region). This region begins at the Lower Himalayan Range, where a fault system called the ''Main Boundary Thrust'' creates an escarpment high, to a crest between . It covers 68% of the total area of Nepal.

These steep southern slopes are nearly uninhabited, thus an effective buffer between languages and culture in the Terai and Hilly. Paharis mainly populate river and stream bottoms that enable rice cultivation and are warm enough for winter/spring crops of wheat and potato. The increasingly urbanized Kathmandu and Pokhara valleys fall within the Hill region. Newars are an indigenous ethnic group with their own Tibeto-Burman language. The Newar were originally indigenous to the Kathmandu valley but have spread into Pokhara and other towns alongside urbanized Pahari.

Other indigenous Janajati ethnic groups -— natively speaking highly localized Tibeto-Burman languages and dialects -— populate hillsides up to about . This group includes Magar and Kham Magar west of Pokhara, Gurung south of the Annapurnas, Tamang around the periphery of Kathmandu Valley and Rai, Koinch Sunuwar and Limbu further east. Temperate and subtropical fruits are grown as cash crops. Marijuana was grown and processed into ''Charas'' (hashish) until international pressure persuaded the government to outlaw it in 1976. There is increasing reliance on animal husbandry with elevation, using land above for summer grazing and moving herds to lower elevations in winter. Grain production has not kept pace with population growth at elevations above where colder temperatures inhibit double cropping. Food deficits drive emigration out of the Pahad in search of employment.

The Hilly ends where ridges begin substantially rising out of the temperate climate zone into subalpine zone above .

Terai

Terai is a low land region containing some hill ranges. Looking out for its coverage, it covers 17% of the total area of Nepal. The Terai (also spelt Tarai) region begins at the Indian border and includes the southernmost part of the flat, intensively farmed Gangetic Plain called the ''Outer Terai''. By the 19th century, timber and other resources were being exported to India. Industrialization based on agricultural products such as jute began in the 1930s and infrastructure such as roadways, railways and electricity were extended across the border before it reached Nepal's Pahad region.

The Outer Terai is culturally more similar to adjacent parts of India's Bihar and Uttar Pradesh than to the Pahad of Nepal. Nepali is taught in schools and often spoken in government offices, however, the local population mostly uses Maithali, Bhojpuri and Tharu languages.

The Outer Terai ends at the base of the first range of foothills called the ''Siwaliks'' or ''Churia''. This range has a densely forested skirt of coarse alluvium called the '' Bhabhar''. Below the Bhabhar, finer, less permeable sediments force groundwater to the surface in a zone of springs and marshes. In Persian, ''terai'' refers to wet or marshy ground. Before the use of DDT this was dangerously malarial. Nepal's rulers used this for a defensive frontier called the ''char kose jhadi'' (four ''kos'' forest, one kos equaling about three kilometers or two miles).

Above the Bhabhar belt, the Siwaliks rise to about with peaks as high as , steeper on their southern flanks because of faults are known as the Main Frontal Thrust. This range is composed of poorly consolidated, coarse sediments that do not retain water or support soil development so there is virtually no agricultural potential and sparse population.

In several places beyond the Siwaliks, there are dūn valleys called Inner Terai. These valleys have productive soil but were dangerously malarial except to indigenous Tharu people who had genetic resistance. In the mid-1950s DDT came into use to suppress mosquitos and the way was open to settlement from the land-poor hills, to the detriment of the Tharu.

The Terai ends and the Pahad begin at a higher range of foothills called the Lower Himalayan Range.

Climate

Altitudinal belts

Nepal's latitude is about the same as that of the United States state of Florida, however with elevations ranging from less than to over and precipitation from to over the country has eight climate zones from tropical to perpetual snow.

The tropical zone below experiences frost less than once per decade. It can be subdivided into lower tropical (below 300 meters or 1,000 ft.) with 18% of the nation's land area) and upper (18% of land area) tropical zones. The best mangoes and well as papaya and banana are largely confined to the lower zone. Other fruit such as litchee, jackfruit, citrus and mangoes of lower quality grow in the upper tropical zone as well. Winter crops include grains and vegetables typically grown in temperate climates. The Outer Terai is virtually all in the lower tropical zone. Inner Terai valleys span both tropical zones. The Sivalik Hills are mostly upper tropical. Tropical climate zones extend far upriver valleys across the Middle Hills and even into the Mountain regions.

The subtropical climate zone from occupies 22% of Nepal's land area and is the most prevalent climate of the Middle Hills above river valleys. It experiences frost up to 53 days per year, however, this varies greatly with elevation, proximity to high mountains and terrain either draining or ponding cold air drainage. Crops include rice, maize, millet, wheat, potato, stone fruits and citrus.

The great majority of Nepal's population occupies the tropical and subtropical climate zones. In the Middle Hills, "upper-caste" Hindus are concentrated in tropical valleys which are well suited for rice cultivation while Janajati ethnic groups mostly live above in the subtropical zone and grow other grains more than rice.

The Temperate climate zone from occupies 12% of Nepal's land area and has up to 153 annual days of frost. It is encountered in higher parts of the Middle Hills and throughout much of the Mountain region. Crops include cold-tolerant rice, maize, wheat, barley, potato, apple, walnut, peach, various cole, amaranthus and buckwheat.

The Subalpine zone from occupies 9% of Nepal's land area, mainly in the Mountain and Himalayan regions. It has permanent settlements in the Himalaya, but further south it is only seasonally occupied as pasture for sheep, goats, yak and hybrids in warmer months. There are up to 229 annual days of frost here. Crops include barley, potato, cabbage, cauliflower, amaranthus, buckwheat and apple. Medicinal plants are also gathered.

The Alpine zone from occupies 8% of the country's land area. There are a few permanent settlements above 4,000 meters. There is virtually no plant cultivation although medicinal herbs are gathered. Sheep, goats, yaks and hybrids are pastured in warmer months.

Above 5,000 meters the climate becomes Nival and there is no human habitation or even seasonal use.

Arid and semi-arid land in the rainshadow of high ranges have a Transhimalayan climate. Population density is very low. Cultivation and husbandry conform to subalpine and alpine patterns but depend on snowmelt and streams for irrigation.

Precipitation generally decreases from east to west with increasing distance from the Bay of Bengal, source of the summer monsoon. Eastern Nepal gets about annually; the Kathmandu area about and western Nepal about . This pattern is modified by adiabatic effects as rising air masses cool and drop their moisture content on windward slopes, then warm up as they descend so relative humidity drops. Annual precipitation reaches on windward slopes in the Annapurna Himalaya beyond a relatively low stretch of the Lower Himalayan Range. In rainshadows beyond the high mountains, annual precipitation drops as low as .

Seasons

The year is divided into a wet season from June to September—as summer warmth over Inner Asia creates a low-pressure zone that draws in moist air from the Indian Ocean—and a dry season from October to June as cold temperatures in the vast interior create a high-pressure zone causing dry air to flow outward. April and May are months of intense water stress when cumulative effects of the long dry season are exacerbated by temperatures rising over in the tropical climate belt. Seasonal drought further intensifies in the Siwaliks hills consisting of poorly consolidated, coarse, permeable sediments that do not retain water, so hillsides are often covered with drought-tolerant scrub forest. In fact, much of Nepal's native vegetation adapted to withstand drought, but less so at higher elevations where cooler temperatures mean less water stress.

The summer monsoon may be preceded by a buildup of thunderstorm activity that provides water for rice seedbeds. Sustained rain on average arrives in mid-June as rising temperatures over Inner Asia creates a low-pressure zone that draws in moist air from the Indian Ocean, but this can vary up to a month. Significant failure of monsoon rains historically meant drought and famine while above-normal rains still cause flooding and landslides with losses in human lives, farmland and buildings.

The monsoon also complicates transportation with roads and trails washing out while unpaved roads and airstrips may become unusable and cloud cover reduces safety margins for aviation. Rains diminish in September and generally end by mid-October, ushering in generally cool, clear, and dry weather, as well as the most relaxed and jovial period in Nepal. By this time, the harvest is completed and people are in a festive mood. The two largest and most important Hindu festivals—Dashain and Tihar (Dipawali)—arrive during this period, about one month apart. The post-monsoon season lasts until about December.

After the post-monsoon comes the winter monsoon, a strong northeasterly flow marked by occasional, short rainfalls in the lowlands and plains and snowfalls in the high-altitude areas. In this season the Himalayas function as a barrier to cold air masses from Inner Asia, so southern Nepal and northern India have warmer winters than would otherwise be the case. April and May are dry and hot, especially below where afternoon temperatures may exceed .

Environment

The dramatic changes in elevation along this transect result in a variety of biomes, from tropical savannas along the Indian border, to subtropical broadleaf and coniferous forests in the hills, to temperate broadleaf and coniferous forests on the slopes of the Himalaya, to montane grasslands and shrublands, and finally rock and ice at the highest elevations.

This corresponds to the Terai-Duar savanna and grasslands ecoregion.

Subtropical forests dominate the lower elevations of the Hill region. They form a mosaic running east–west across Nepal, with Himalayan subtropical broadleaf forests between and Himalayan subtropical pine forests between . At higher elevations, to , are found temperate broadleaf forests: eastern Himalayan broadleaf forests to the east of the Gandaki River and western Himalayan broadleaf forests to the west.

The native forests of the Mountain region change from east to west as precipitation decreases. They can be broadly classified by their relation to the Gandaki River. From are the eastern and western Himalayan subalpine conifer forests. To are the eastern and western Himalayan alpine shrub and meadows.

Environmental issues

; Natural hazards:
: Earthquakes, severe thunderstorms (tornadoes are rare), flooding and flash flooding, landslides, drought, and famine depending on the timing, intensity, and duration of the summer monsoons
; Environment - current issues:
: Deforestation in Nepal, Deforestation (overuse of wood for fuel and lack of alternatives); contaminated water (with human and animal wastes, agricultural runoff, and industrial effluents); wildlife conservation; vehicular emissions
; Environment - international agreements
:* Party to: Biodiversity, Climate Change, Climate Change-Kyoto Protocol, Desertification, Endangered Species, Hazardous Wastes, Law of the sea, Law of the Sea, Montreal Protocol, Ozone Layer Protection, Tropical Timber 83, Tropical Timber 94, Wetlands
:* Signed, but not ratified: Marine Life Conservation
:* Existing and proposed dams, barrages and canals for flood control, irrigation and hydroelectric generation

River systems

Nepal has three categories of rivers. The largest systems -— from east to west the Koshi, Gandaki/Narayani, Karnali River, Karnali/Goghra and Sarda River, Mahakali—originate in multiple Tributary, tributaries rising in or beyond the high Himalaya that maintain substantial flows from snowmelt through the hot, drought-stricken spring before the summer monsoon. These tributaries cross the highest mountains in deep gorges, flow south through the Middle Hills, then join in candelabra-like configuration before crossing the Lower Himalayan Range and emerging onto the plains where they have deposited alluvial fan, megafans exceeding in area.

The Koshi is also called ''Sapta Koshi'' for its seven Himalayan tributaries in eastern Nepal: Indravati River, Nepal, Indrawati, Sun Kosi, Sun Koshi, Tama Koshi, Dudh Kosi, Dudh Koshi, Liku, Arun River (Nepal), Arun, and Tamor River, Tamor. The Arun rises in Tibet some beyond Nepal's northern border. A tributary of the Sun Koshi, Bhote Koshi also rises in Tibet and is followed by the Arniko Rajmarg, Arniko Highway connecting Kathmandu and Lhasa (prefecture-level city), Lhasa.

The '' Gandaki/Narayani'' has seven Himalayan tributaries in the center of the country: Daraundi River, Daraundi, Seti Gandaki River, Seti Gandaki, Madi, Kali, Marsyandi, Budhi, and Trisuli River, Trisuli also called ''Sapta Gandaki''. The ''Kali Gandaki'' rises on the edge of the Tibetan Plateau and flows through the semi-independent Mustang (kingdom), Kingdom of Mustang, then between the 8,000 meter Dhaulagiri and Annapurna ranges in the Kali Gandaki Gorge, world's deepest valley. The Trisuli rises north of the international border inside Tibet. After the seven upper tributaries join, the river becomes the ''Narayani'' inside Nepal and is joined by the East Rapti from Chitwan Valley. Crossing into India, its name changes to ''Gandak''.

The Ghaghara River, Karnali drains western Nepal, with the Bheri River, Bheri and Seti River, Seti as major tributaries. The upper Bheri drains Dolpo, a remote valley beyond the Dhaulagiri Himalaya with traditional Tibetan cultural affinities. The upper Karnali rises inside Tibet near-sacred Lake Manasarovar and Mount Kailash. The area around these features is the hydrographic nexus of South Asia since it holds the sources of the Indus River, Indus and its major tributary the Sutlej, the Karnali—a Ganges Basin, Ganges tributary—and the Yarlung Tsangpo/Brahmaputra. It is the centre of the universe according to Mount Meru (mythology), traditional cosmography. The Sarda River, Mahakali or ''Kali'' along the Nepal-India border on the west joins the Karnali in India, where the river is known as ''Goghra'' or ''Ghaghara''.

Second category rivers rise in the Middle Hills and Lower Himalayan Range, from east to west the Mechi River, Mechi, Kankai River, Kankai and Kamala River, Kamala south of the Kosi; the Bagmati that drains Kathmandu Valley between the Kosi and Gandaki systems, then the West Rapti River, West Rapti and the Babai between the Gandaki and Karnali systems. Without glacial sources, annual flow regimes in these rivers are more variable although limited flow persists through the dry season.

Third category rivers rise in the outermost Siwalik foothills and are mostly seasonal.

None of these river systems supports significant commercial navigation. Instead, deep gorges create obstacles to establishing transport and communication networks and de-fragmenting the economy. Foot-trails are still the primary transportation routes in many hill districts.

River management

Rivers in all three categories are capable of causing serious floods. Koshi River in the first category caused a major flood in 2008 Bihar flood, August 2008 in Bihar state, India after breaking through a poorly maintained embankment just inside Nepal. The West Rapti in the second category is called "Gorakhpur's Sorrow" for its history of urban flooding. Third category Terai rivers are associated with flash floods.

Since uplift and erosion are more or less in equilibrium in the Himalaya, at least where the climate is humid, rapid uplift must be balanced out by annual increments of millions tonnes of sediments washing down from the mountains; then on the plains settling out of suspension on vast alluvial fans over which rivers meander and change course at least every few decades, causing some experts to question whether manmade embankments can contain the problem of flooding. Traditional ''Mithila (Nepal), Mithila'' culture along the lower Koshi in Nepal and Bihar celebrated the river as the giver of life for its fertile alluvial soil, yet also the taker of life through its catastrophic floods.

Large reservoirs in the Middle Hills may be able to capture peak flows and mitigate downstream flooding, to store surplus monsoon flows for dry season irrigation and to generate hydroelectricity, electricity. Water for irrigation is especially compelling because the Indian Terai is suspected to have entered a food bubble where dry season crops are dependent on water from tube wells that in the aggregate are unsustainably "mining" groundwater.

Depletion of aquifers without building upstream dams as a sustainable alternative water source could precipitate a Malthusian catastrophe in India's Food security, food insecure states Uttar Pradesh and Bihar, with over 300 million combined population. With India already experiencing a Naxalite–Maoist insurgency in Bihar, Jharkhand and Andhra Pradesh, Nepalese reluctance to agree to water projects could even seem an existential threat to India.

As Nepal builds barrages to divert more water for irrigation during the dry season preceding the summer monsoon, there is less for downstream users in Bangladesh and India's Bihar and Uttar Pradesh states. The best solution could be building large upstream reservoirs, to capture and store surplus flows during the summer monsoon as well as providing flood control benefits to Bangladesh and India. Then water-sharing agreements could allocate a portion of the stored water to be left to flow into India during the following dry season.

Nevertheless, building dams in Nepal is controversial for several reasons. First, the region is seismically active. Dam failures caused by earthquakes could cause tremendous death and destruction downstream, particularly on the densely populated Gangetic Plain. Second, global warming has led to the formation of glacial lakes dammed by unstable moraines. Sudden failures of these moraines can cause Glacial lake outburst flood, floods with cascading failures of manmade structures downstream.

Third, sedimentation rates in the Himalaya are extremely high, leading to rapid loss of storage capacity as sediments accumulate behind dams. Fourth, there are complicated questions of cross-border equity in how India and Nepal would share costs and benefits that have proven difficult to resolve in the context of frequent acrimony between the two countries.

Area

:* Total:
:* Land:
:* Water:

; Coastline:
: 0 km (landlocked)
:
; Elevation extremes:
:* Lowest point: Kechana Kawal, jhapa district 59 m
:* Highest point: Sagarmatha (Mount Everest) 8,848 m

Resources and land use

; Natural resources:
:Quartz, water, timber, hydropower, scenic beauty, small deposits of lignite, copper, cobalt, iron ore
; Land use:
:* Arable land: 16.0%
:* Permanent crops: 0.8%
:* Other: 83.2% (2001)
; Irrigated land:
: 11,680 km² (2003) Nearly 50% of arable land
; Total renewable water resources
: 210.2 km³ (2011)

Land cover

International Centre for Integrated Mountain Development, ICIMOD’s first and most complete national land cover database of Nepal prepared using public domain Landsat program, Landsat Thematic Mapper, TM data of 2010 shows that show that forest is the dominant form of land cover in Nepal covering 57,538 km² with a contribution of 39.09% to the total geographical area of the country. Most of this forest cover is broadleaved closed and open forest, which covers 21,200 km² or 14.4% of the geographical area.

Needleleaved open forest is the least common of the forest areas covering 8267 km² (5.62%). Agriculture area is significant extending over 43,910 km² (29.83%). As would be expected, the high mountain area is largely covered by snow and glaciers and barren land.

The Hill region constitutes the largest portion of Nepal, covering 29.5% of the geographical area, and has a large area (19,783 km²) of cultivated or managed lands, natural and semi natural vegetation (22,621 km²) and artificial surfaces (200 km²). The Tarai region has more cultivated or managed land (14,104 km²) and comparatively less natural and semi natural vegetation (4280 km²). The Tarai has only 267 km² of natural water bodies. The High mountain region has 12,062 km² of natural water bodies, snow/glaciers and 13,105 km² barren areas.

Forests

25.4% of Nepal's land area, or about is covered with forest according to FAO figures from 2005. FAO estimates that around 9.6% of Nepal's forest cover consists of ''primary forest'' which is relatively intact. About 12.1% Nepal's forest is classified as ''protected'' while about 21.4% is ''conserved'' according to FAO. About 5.1% Nepal's forests are classified as ''production forest''. Between 2000 and 2005, Nepal lost about of forest. Nepal's 2000–2005 total deforestation rate was about 1.4% per year meaning it lost an average of of forest annually. Nepal's total deforestation rate from 1990 to 2000 was or 2.1% per year. The 2000–2005 true deforestation rate in Nepal, defined as the loss of primary forest, is −0.4% or per year. Forest is not changing in the plan land of Nepal, forest fragmenting on the "Roof of the World".

According to International Centre for Integrated Mountain Development, ICIMOD figures from 2010, forest is the dominant form of land cover in Nepal covering 57,538 km² with a contribution of 39.09% to the total geographical area of the country. Most of this forest cover is broadleaved closed and open forest, which covers 21,200 km² or 14.4% of the geographical area. Needleleaved open forest is the least common of the forest areas covering 8,267 km² (5.62%). At national level 64.8% area is covered by core forests of > 500 ha size and 23.8% forests belong to patch and edge category forests. The patch forest constituted 748 km² at national level, out of which 494 km² of patch forests are present in hill regions. Middle mountains, Siwaliks and Terai regions have more than 70% of the forest area under core forest category > 500 ha size. The edge forests constituted around 30% of forest area of High Mountain and Hill regions.
Forest Resource Assessment (FRA) which was conducted between 2010 and 2014 by the Ministry of Forest and Soil conservation with the financial and technical help of the Government of Finland shows that 40.36% of the land of Nepal is forested. 4.40% of the land has shrubs and bushes.

Deforestation is driven by multiple processes.
Virtually throughout the nation, over-harvest of firewood remains problematic. Despite the availability of liquefied petroleum gas in towns and cities, firewood is sold more at energy-competitive prices because cutting and selling it is a fallback when better employment opportunities aren't forthcoming. Firewood still supplies 80% of Nepal's energy for heating and cooking. Harvesting construction timber and lopping branches for fodder for cattle and other farm animals are also deforestation/degradation drivers in all geographic zones.

Illegal logging is a problem in the Siwaliks, with sawlogs smuggled into India.
Clearing for resettlement and agriculture expansion also causes deforestation as does urban expansion, building infrastructure such as schools, hospitals, electric transmission lines, water tanks, police and army barracks, temples and picnic areas.

In the Middle Hills road construction, reservoirs, transmission lines and extractive manufacturing such as cement factories cause deforestation. In the mountains building hotels, monasteries and trekking trails cause deforestation while timber-smuggling into the Tibet Autonomous Region and over-grazing cause degradation.

Boundaries

:* Total: 2,926 km
:* Border countries: China 1,236 km, India 1,690 km

Border crossings with India

While India and Nepal have an open border with no restrictions on movement of their citizens on either side, there are 23 Border checkpoint, checkpoints for trade purposes. These are listed in clockwise order, east to west. The six in ''italics'' are also used for entry/exit by third country nationals.

Border crossings with China

See also

* Geology of Nepal
* List of mountains in Nepal
* Valleys of Nepal

References

External links

*
*

Atlas of Nepal

Nepal Encyclopedia Geopolitical category


Brief and Concise Geography of Nepal

{{Asia topic, Climate of

Geography of Nepal,
Geography of South Asia, Nepal