Nepal

Nepal is a landlocked federal democratic republic in South Asia, bordered by China to the north and India to the south, east and west. Its territory runs from the flat Gangetic lowlands to the high ranges of the Himalayas, so a short north–south distance produces sharp contrasts in climate, soils, vegetation and land use. The country contains Mount Everest and several other of the world's highest peaks.

Nepal's geography matters well beyond its scenery. Its rivers carry Himalayan water and sediment into the populous plains of northern India, its steep slopes and active faults shape hazard risk, and its glaciers and forests are sensitive to climate change. Terrain has long constrained transport, settlement and economic development, so geographic knowledge is central to infrastructure planning and to the management of biodiversity and erosion.

The entry begins with Nepal's location and physiographic regions, then turns to its tectonic framework, high mountains, river systems and climate. It then covers natural hazards, soils, biodiversity, land use and settlement, water resources, environmental change, administrative and transport geography, the history of mapping, and open research questions.

Location, borders and extent

Nepal occupies the southern flank of the Himalayas, wedged between the Tibetan Plateau to the north and the Gangetic Plain to the south. This position places the country where high-mountain and lowland environments meet, so that its climate, vegetation and settlement patterns change sharply over short distances.

Lacking any coastline, the state has no direct outlet to the sea. Its trade routes, energy supplies and transport links therefore pass through neighbouring territory, and Nepal must rely on its neighbors for trade routes, energy supplies, and connections to the wider world. The northern frontier adjoins the Tibet Autonomous Region of China, while India forms the boundary along the southern, eastern and western sides. Two other countries are close but do not share a frontier with Nepal: it is narrowly separated from Bangladesh by the Siliguri Corridor, and from Bhutan by the Indian state of Sikkim.

Published frontier lengths are not uniform across sources. One compilation gives total land borders of 2,926 km, with China at 1,236 km and India at 1,690 km, whereas another lists India: 1,751 km and China: 1,236 km. The difference lies in the Indian boundary, and it reflects differing measurement sources rather than any change in the border itself.

The country's dimensions are likewise given in slightly different forms. East to west, the territory is commonly put at roughly 800 to 885 kilometers (km) from east to west, while its north–south width is generally stated as about 150 to 250 km from north to south. The total area is also reported in two versions: 147,181 km² (or 147,516 km² in some official documents). The larger figure is the one most widely used in reference works, and it includes water surfaces, which the same Wikipedia-derived data put at Land: 92.94%; Water: 7.06%.

In coordinate terms, the territory covers about four degrees of latitude. Nepal is located in South Asia, between 26 and 30 degrees North Latitude and 80 and 88 degrees East Longitude. The spread across longitude is therefore much wider than the spread across latitude, which accounts for the country's elongated, east–west orientation.

That shape has a direct consequence for travel and for the country's internal geography. The three traditional belts, Terai, Pahad and Himal, are arranged as south-to-north transects, so a single line drawn from the Indian border to the northern peaks crosses each of them in turn. Along such a line the change in elevation is extreme. It hosts the second largest altitude range in the world, beginning in the Terai region at less than 100 m above sea level and ending at the top of Mount Everest at 8,850 m. Within the first stretch from the plains, the ground rises quickly: the land rises 900 m to form the Chure Hills (Siwalik Hills) within a short distance of the lowland edge. At the far north of such a transect, Mount Everest (Sagarmāthā in Nepali) on the border with China marks the highest point of the frontier.

Physiographic regions

Nepal is usually described as a series of east–west belts that cross the whole country, and the schemes used to name them differ. Two main classifications of Nepal into physiographic regions are currently in use: a broad, three zone scheme, and a more refined system of seven regions. The traditional approach counts eight units. Hagen's eight-zone topographic classification recognised the Inner Terai as a separate zone. The regions below follow that finer tradition, and the boundaries between them are approximate.

The southernmost belt is the Terai, which is the northern rim of the Gangetic plain and lies along the border with India. Sources give slightly different elevation bands. One puts the Terai at between 67 and 300 m, while another gives altitudes ranging from 60 m (Dhanusha) to 330 m, with an average ca. 200 m. It is also narrow in places. Its width reaches up to 40 km in a band of flat, fertile alluvial soil.

North of the Terai, the Siwalik (Churia) hills form a steep, young range. Siwalik hills rise abruptly from the Terai plains from about 120 m to almost 1800 m, and their rock is weak. Uplift is estimated at 3–4 mm per year, which makes the belt one of the most tectonically dynamic zones of the Himalaya. The hills are also the main source of sediment for the plains: torrents flowing down the steep gradients erode material from the fragile rock and transport it downstream. Because the porous soils hold little water in the dry season, the zone is comparatively sparsely populated (lack of water in the dry season). The Dun valleys are the long, broad valleys tucked between the Siwalik ridges and the Mahabharat. The Dun (Doon) valleys [also known as the Inner Terai or Vitri Madhesh] are long, broad, gently sloping valleys, and are generally more populated than the rest of the Siwalik Hills region.

The Mahabharat range lies north of the Siwalik hills and forms the core of the middle hills. Its ridges run east to west, are up to 2750 m, and are composed of hard, metamorphosed, sedimentary and igneous rocks. The climate there is cool and humid, and the soils are water-retentive, allowing cultivation on the characteristic terraced steep hillsides. The Midlands share these hill conditions but differ in relief and settlement history, with dense terraced farmland and long-established villages.

The High Himalaya and Great Himalaya occupy the northern third of the country. In the regional scheme used by the British Geological Survey, the country is divided into five major physiographic regions that extend across the length of Nepal, and the northernmost of these, the High Himalayas, carries the highest peaks. These zones have steep slopes, deep valleys and seasonal snow, and the high mountain belt holds only a small share of the population. This is the least inhabited region of Nepal, with less than 8% of the population living there. Most permanent settlements are at less than 4000m altitude, although there are summer settlements as high as 5000m.

North of the Himalayan crest, the Trans-Himalaya forms a separate, arid belt. It lies in the north-westernmost part of the country, north of Dhaulagiri and Annapurna Himals, at 6000-7000 m, and line[s] the southern margin of the Tibetan Plateau. Its peaks are among the oldest features of the Himalayan orogeny, having first formed about 45 million years ago. The high ridges block the monsoon, so the area receives little rain. Average annual precipitation there can fall as little as 160 millimetres in the rain shadow north of the Himalaya, compared with much heavier totals on the southern slopes.

Tectonic and geological structure

The Himalaya is the product of the collision between the Indian and Eurasian plates. The Indian subcontinent moved northward and closed the Tethys Ocean that once separated it from Asia. Estimates for the onset of continental contact cluster around the early Eocene, roughly 55 to 50 million years ago, but the timing differs along the suture, and some reconstructions place the completion of collision near 40 million years ago. Convergence continued afterward, and crustal thickening lifted the range. To the north, the belt is bounded by the Indus–Tsangpo Suture Zone, which marks the junction between the Indian plate and the Tibetan (Eurasian) plate.

Geologists divide Nepal into five latitudinal zones, from south to north: the Gangetic plain (Terai), the Sub-Himalaya (Siwalik or Churia), the Lesser Himalaya, the Greater (Higher) Himalaya, and the Tibetan-Tethys zone. Each zone has its own rock assemblage and structural style. The Siwalik zone consists of younger clastic sediments eroded from the rising mountains. The Lesser Himalaya is built of metamorphosed sedimentary rocks, including quartzite, marble, slate, phyllite, schist and gneiss, with minor volcanic and granitic bodies of Proterozoic to Cambrian age. Its stratigraphic thickness is commonly put at 10 to 20 km. The Greater Himalaya is dominated by high-grade metamorphic gneisses and granites, while the Tibetan-Tethys zone preserves fossiliferous sedimentary sequences from the Cambrian to the Eocene.

The zones are separated by major faults that act as structural boundaries. The Main Boundary Thrust lies between the Lesser Himalaya and the Siwalik zone, and at the surface the Main Frontal Thrust marks the outer front of the belt. The Main Central Thrust (MCT) separates the Lesser and Greater Himalaya. It is generally described as a broad ductile shear zone, several hundred metres to a few kilometres thick, in which the hanging wall has been pushed southward over the Lesser Himalayan rocks. The South Tibetan Detachment System (STDS) lies at the northern edge of the Greater Himalaya. It is a north-dipping normal fault system that separates the high-grade rocks from the overlying Tibetan-Tethys sequence. Its interpretation remains debated, and some workers argue for a thrust component.

These faults are not only boundaries but also controls on the rock record. Movement along them juxtaposed rock units of very different metamorphic grade and age, and in parts of central and eastern Nepal the metamorphic sequence beneath the MCT is inverted, with the grade increasing upward toward the thrust. Structural activity was concentrated in the Miocene. Leucogranites emplaced between about 24 and 17 million years ago along the STDS form the cores or summits of several high peaks, including Manaslu and Annapurna, and the rapid uplift and exhumation of the Greater Himalayan rocks are closely tied to slip on these two faults. The MCT is therefore best understood as a structure whose sense of motion and timing have been reconstructed through a combination of field mapping, metamorphic petrology and geochronology.

The Gangetic plain is the youngest of the zones and is not a mountain-building unit in the same sense. It is a foreland basin that has subsided under the load of the advancing mountain belt and has been filled with sediment carried southward by Himalayan rivers. Fluvial deposition on the plain is still active today, which means that the sediment record of the orogeny continues to accumulate at the mountain front.

High peaks and glaciers

Nepal contains all eight of the world's eight-thousanders that lie within its borders, a set that includes Everest, Kanchenjunga, Lhotse, Makalu, Cho Oyu, Dhaulagiri, Manaslu and Annapurna I. Together these peaks occupy eight of the ten highest places on Earth. Everest (8,848.86 m) stands on the Nepal–China border, Cho Oyu lies on the Tibetan frontier just west of Everest, and Kanchenjunga straddles the boundary with the Indian state of Sikkim. Lhotse is joined to Everest by the South Col, a saddle above 8,000 m, and climbers commonly acclimatise on Lhotse before attempting Everest.

Above 8,000 m, the air pressure is too low for the human body to acclimatise, a zone that mountaineers call the "death zone". The vertical distance between the Terai plains, at roughly 70 to 330 m, and the summit of Everest is close to 8,800 m, and it is covered within a north–south distance of only about 150 to 200 km. Because air temperature falls by about 6.5 °C for every kilometre of height under standard lapse conditions, and precipitation patterns shift with altitude and with the orientation of each valley, this compressed gradient produces very different climates within short distances. The high peaks therefore sit at the top of a sequence of ecological and climatic belts rather than standing alone.

The high mountains hold permanent snow and a large number of glaciers. The Khumbu Glacier, which descends from the Western Cwm between Everest and Lhotse, is the best-documented example. It is heavily covered by rock debris in its lower reaches, and estimates of its length differ considerably depending on how its limits are drawn. Monitoring since the 1970s has shown a retreating terminus: one long-term series records an average retreat of about 18 m per year from 1976 to 2007, with yearly values varying widely with weather. Glacier surveys across the Khumbu region indicate that ice-volume loss accelerated markedly in the early twenty-first century. Debris cover slows melting over much of the glacier surface, but it also creates ice cliffs and supraglacial ponds, and these features melt faster at their edges, so the glacier does not thin evenly.

Glacier meltwater and snowmelt are central to the hydrology of the high valleys. In the Khumbu Valley, one study concluded that up to two-thirds of the water in the dry season comes from snow and glacier melt, which makes downstream communities highly sensitive to any decline in ice. More broadly, rivers in the region receive most of their snowmelt in April to June and glacier melt from June to October, and the ice stores water that is released in the months when rainfall is scarce. Glacier loss is concentrated below about 6,000 m, the zone that most strongly regulates meltwater, so the impacts reach both seasonal supply and long-term river flow.

Changes in the ice also create hazards. Retreating glaciers leave behind moraine-dammed lakes, and when these lakes give way they release large volumes of water downstream. The Dig Tsho outburst discharged an estimated 6 to 10 million cubic metres of water into the valley below, causing damage of more than three million dollars and disrupting the downstream Khumbu community for several months. Assessments of glacial lakes therefore combine hazard mapping with the monitoring of lake growth and surrounding ice.

Across the wider Hindu Kush Himalaya, regional assessments report that glacier losses between 1990 and 2020 reduced glacier area by about 12 percent and estimated ice reserves by about 9 percent, and that the rate of loss is increasing. Projections suggest that glacier contributions to river flow will rise until around 2050 and then fall, a turning point that researchers call "peak water". Within Nepal, the balance between glacier melt and monsoon rainfall therefore shapes both dry-season river flow and the reliability of water for hydropower and irrigation.

Rivers and drainage systems

Nepal's river network is organised into three major systems, which run from east to west: the Koshi, the Gandaki (called the Narayani within Nepal), and the Karnali, known in India as the Ghaghara. The Mahakali forms part of the western border. All of them ultimately feed the Ganges basin. The Koshi is the largest of the three. Its catchment covers about 74,500 km², and it drains both the northern slopes of the Himalaya in Tibet and the southern slopes inside Nepal, so it is a transboundary river shared with China and India. The Gandaki has a catchment of about 46,300 km², with roughly 72 per cent lying in Nepal, and seven major tributaries, several of which rise on glaciers. The Karnali, the longest of the three, is a much larger river once it reaches the plains, where it carries the Ghaghara name.

Many of these rivers are older than the mountains they cross. Where a river existed before the ranges began to rise, it kept its course and cut downward as the land uplifted, producing deep gorges through the Himalaya rather than diverting around them. The best-known example is the Kali Gandaki Gorge, which runs between Dhaulagiri and Annapurna. The riverbed near Lete sits at roughly 2,520 m, while the summit of Annapurna I rises to 8,091 m, giving a vertical relief of more than 5,000 m. Claims about whether this is the world's deepest gorge depend on how depth is measured. Some measurements place it second after the Yarlung Tsangpo Grand Canyon. The gorge has carried traffic for centuries, serving as a salt and trade route between India and Tibet. The Koshi shows a similar pattern: after its tributaries unite inside the mountains, the Sapta Koshi passes through the Chatra Gorge and is then regulated by a barrage before it enters the Gangetic plain.

The rivers that rise in the Siwalik (Churia) hills behave very differently. These are smaller, largely seasonal streams that originate in the outermost foothills and drain into the plains. Their flow is dominated by monsoon rain and snowmelt is absent, so they swell rapidly after heavy storms and shrink to little or nothing during the pre-monsoon and winter months. Where these streams leave the hills, they enter the Bhabar belt, a narrow zone of coarse gravel, boulders and alluvium deposited at the foot of the Siwaliks. Water disappears quickly into this permeable material, so the surface channels often run dry for much of the year. The Bhabar nonetheless plays a critical hydrological role: infiltration here recharges the aquifers of the Terai, which is why the belt is treated as the main recharge area for the lowland groundwater system.

The middle-hill and high-mountain rivers form a distinct group. The Trishuli, Marsyangdi, Kali Gandaki and other tributaries of the Gandaki system are supported by springs, rainfall and, in the higher basins, glacial and snowmelt, which keeps their flow more regular through the dry season. In some basins, melting snow and ice supply a large share of dry-season discharge, so the timing of melt matters as much as the timing of rain. Rivers in the middle hills also carry substantial sediment from steep, cleared slopes, and this load is deposited on the floodplains and in the Terai, where channels shift frequently. Flooding, erosion and sedimentation therefore affect communities far from the mountains that generate them, and cross-border coordination is needed on most of the major basins.

Climate and the monsoon

Nepal's rainfall is dominated by the South Asian monsoon. Moist air moves north from the Bay of Bengal, and roughly 80 percent of the annual precipitation falls between June and September. The season's timing varies from year to year. In 2022 the rains began on 5 June, earlier than usual, and lasted 134 days, the longest season on record, yet total rainfall was not much above average. Western districts were drier than normal, while eastern areas received slightly more.

The Himalayas act as a barrier. When humid air meets the southern slopes, it is forced upward, cools, and releases heavy rain, a process known as orographic precipitation. Rainfall therefore follows terrain closely. Annual totals exceed 3,000 mm around Pokhara, while sheltered valleys receive far less. Slopes facing south generally get more rain than north-facing slopes, and the monsoon's effect weakens from east to west. The monsoon also has a pronounced diurnal cycle: in the 2022 hourly data, about 60 percent of the seasonal rain fell at night, with a peak around 9 p.m.

The rain shadow

North of the High Himalaya, the Trans-Himalaya lies in a rain shadow. Because the high ranges block the monsoon clouds, districts such as Mustang, Dolpo and Manang stay dry. Jomsom, at about 2,650 m, records only about 250 to 300 mm of rain a year. Western disturbances, which carry moisture from the Mediterranean region, contribute more to precipitation in the high Himalaya and Trans-Himalaya than in the south, so these areas receive a small share of winter precipitation. For this reason the Trans-Himalaya stays arid throughout the year, and its valleys remain usable for travel during the monsoon, when southern routes are often cut.

Temperature and seasons

Temperature falls by about 6 °C for every 1,000 m of altitude. This lapse rate, combined with the monsoon, produces three broad thermal regimes. In the Terai, the subtropical lowlands, winter days are mild, while the pre-monsoon period is very hot, with temperatures often above 35 °C and summer highs exceeding 37 °C. The mid-hills have a temperate climate, with cool, drier winters and humid summers. Kathmandu, at about 1,350 m, illustrates this pattern: July is its wettest month and November its driest, and the monsoon supplies nearly 79 percent of its rainfall. Above the tree line, winters are long and snow-bound, and summers remain near freezing at higher elevations.

From October to March the country is generally dry and cold. Winter rain is most noticeable in the western hills, where a small amount of precipitation falls in January and February.

Local variation and classification

Climatic conditions change over short distances. Slope aspect, valley orientation and elevation together create microclimates, so two places a few kilometres apart can receive very different amounts of rain or experience different temperatures. A 2016 classification based on 1981–2010 station records adapted the standard Köppen scheme for Nepal, lowering the coldest-month threshold so that the tropical Terai could be distinguished. Under this system the most extensive type is a temperate, dry-winter, hot-summer climate, covering about 30 percent of the country. These classification choices reflect the central fact of Nepal's climate: it is governed by the interaction of steep altitudinal gradients with a seasonal monsoon, and a single description rarely fits the whole country.

Natural hazards

The Himalayan arc is one of the most seismically active and geologically young mountain belts on Earth, and Nepal occupies much of its length. Earthquakes, steep relief and intense monsoon rain interact so that hazard exposure is high across most of the country. The same tectonic and glacial processes that built the mountains also keep their slopes unstable.

Earthquakes

The Mw 7.8 Gorkha earthquake of 25 April 2015 ruptured the Himalayan thrust system that separates the Indian and Eurasian plates. The rupture ran along the Main Himalayan Thrust, a low-angle fault that absorbs roughly half of the annual convergence between the two plates. Strain builds up on the locked upper section of this fault, which extends roughly 100 km south of the Main Frontal Thrust, and is released in large ruptures at irregular intervals. A magnitude 7.3 aftershock followed on 12 May 2015.

Reported deaths range from about 8,800 to nearly 9,000, depending on the source and on whether aftershocks are counted, and more than 500,000 houses were destroyed. Losses were concentrated in unreinforced masonry buildings, particularly in poorer rural areas where few houses had seismic-resistant features. The shaking also set off rock slides and avalanches; one buried the village of Langtang, leaving few survivors. Of the great Nepali earthquakes, the 1934 Nepal–Bihar event had long been the benchmark for catastrophe, and the 2015 sequence was widely described as the most severe natural disaster in the country since then. The Kathmandu Valley, with its dense population and sediment-filled basin, faces a similar seismic threat in future events.

Monsoon floods and landslides

Steep catchments shed rain quickly, so flash floods arrive with little warning. Between 1983 and 2013, floods and landslides killed about 8,400 people, an average of roughly 269 per year. The northern hills and the Siwalik (Churia) zone are more prone to landslides, while the Terai is more exposed to river flooding. Notable events include the 2008 breach of a Koshi embankment and the 2014 Jure landslide.

The most destructive recent disaster occurred on 26 August 2026. A glacial collapse near the Nepal–China border generated flash floods and mudslides along a stretch of the Bhote Koshi and Trishuli rivers, destroying villages, roads, bridges and power plants. Seismometers registered the event as a tremor of magnitude 5.2, but analysis showed that the seismic signal came from the collapse of rock and ice followed by debris flow rather than from an earthquake. Sources differ on the extent of the downstream impact: one describes a 72-kilometre affected stretch, while another reports debris travelling up to about 100 km. On 11 October 2026, a landslide blocked a tributary of the Budhi Gandaki River near Chumchet in Gorkha district, and the temporary dam later gave way, sending a surge through the valley. Nepal's Department of Hydrology and Meteorology stated that rainfall did not cause the surge.

Glacial lake outburst floods

Glacial lakes dammed by unstable moraines pose a distinct threat. A 2001 study by ICIMOD and UNEP identified 20 potentially dangerous lakes in Nepal. Tsho Rolpa, in the Rolwaling valley, is considered the largest and most dangerous of them. Its end moraine is partly cored by stagnant glacier ice, and a sudden outbreak could release millions of cubic metres of water within a few hours. Around 6,000 households lie downstream. Because the lake continues to expand as the adjoining glacier melts, the hazard is not static.

Mitigation at Tsho Rolpa began in the late 1990s, when an artificially reinforced channel was cut through the moraine to lower the lake level. An early warning system installed in the same period later fell into disuse for lack of maintenance, and a modern replacement has been planned.

Engineering geology and hazard mapping

Engineering geology determines where roads, dams, hydropower tunnels and buildings can be placed with acceptable risk. Slope-stability assessment, mapping of landslide-prone and flood-prone ground, and seismic design standards inform decisions on construction sites and land use. Hazard maps, increasingly built with remote sensing and GIS tools, are used to set building restrictions and zoning rules, although enforcement remains uneven in rapidly growing settlements.

Soils, vegetation and altitudinal zones

Soils

Nepal's soils are young, because they form on rapidly uplifted and actively eroded rock. Their character changes sharply from the plains to the high mountains. In the Himalayan foreland, the Terai's soils are mostly alluvial and fine to medium in texture, laid down by rivers. Fertility depends on the age of the deposit. Newly deposited alluvium along active channels receives fresh sediment during the monsoon and has fair to medium nutrient levels, depending on how long it has been cultivated. Older alluvium on higher ground, away from the river courses, is much poorer, which shapes the choice of crops and the need for inputs.

South of the mountains, the Siwalik (Churia) hills are built of sandstone, shale and conglomerate that weather easily. Their soils are very young and coarse, and they stay dry for most of the year. The same fragile rocks supply much of the silt that reaches the plains, because torrents erode the slopes and deposit their load where they lose gradient. The Bhabar belt, immediately north of the Terai, is floored by pebbles and gravel. Its soil is coarse and porous, and rivers there often sink underground before re-emerging on the plain. Cultivation is therefore confined largely to patches of finer soil.

In the middle hills, soils follow landform. Residual material lies on ridges and hilltops, colluvium covers the slopes, and alluvium fills the valley floors. Valleys such as those around Kathmandu and Pokhara carry sandy and silty alluvial soils that are comparatively fertile, while the Kathmandu Valley also contains lake-derived sediments. Slope soils are generally moderate to low in plant nutrients, and their productivity is limited by moisture and climate. Accounts differ on how well hill soils retain water. Water retention depends on texture and depth, and terracing is one way of holding both soil and moisture on steep ground.

Vegetation by altitude

Natural vegetation in Nepal follows the pattern of climate and altitude, so the country is often described in vertical bands. Stainton's classification, which remains a common reference, lists tropical forests up to about 1,000 m, subtropical forests from 1,000 to 2,000 m, temperate forests from 2,000 to 3,000 m, and subalpine and alpine zones above that. Each band has a characteristic forest type and species mix.

In the tropical zone, sal (Shorea robusta) is the leading tree. In the Terai it forms the largest share of wood volume, while in the hills it is a minor species by volume. Sal can reach about 1,500 m on the outer foothills but is uncommon above that. The Terai also contains tall grasslands, scrub savanna and clay-rich swamps. The Bhabar belt is dominated by sal forest, scrub and grassland, and it is less productive for agriculture because its soils are coarse and surface water is scarce.

The subtropical zone is marked by Schima–Castanopsis forests, which dominate between about 1,000 and 1,700 m on both north- and south-facing slopes in central and eastern Nepal. Pine (Pinus roxburghii) and alder (Alnus nepalensis) are also important in this band. Above it, the temperate zone shifts to mixed broadleaf and coniferous forests, where oak (Quercus semecarpifolia) and blue pine (Pinus wallichiana) dominate in the upper part of the zone. Above about 3,000 m, the subalpine zone has sparser woodland, with juniper, birch and dwarf rhododendron, followed by alpine meadows. Above the tree line, shrub communities and steppe continue to high altitudes. Flowering plants have been recorded near 6,100 m. A protected-area assessment counts eleven bioclimatic zones, from tropical conditions below 500 m to nival conditions above 5,000 m.

Land use and ecological pressure

Because each altitudinal band supports different forests and vegetation, the same band also determines what can be grown and grazed. Lowland soils and warm conditions suit intensive cropping. Hill terraces are cut into slopes that have moderate nutrient levels and seasonal moisture limits. Higher bands are used for forest products, fodder and seasonal grazing. Forest cover in the Terai and hill areas declined by about 1.3% a year between 1978 and 1979, and faster, by about 2.3%, between 1990 and 1991. Overcutting has also depleted accessible sal stands in the Terai. Clearing removes the vegetation that slows runoff, so with deforestation and cultivation spreading, a permeable mix of gravel, boulders and sand develops, and the water table in the plains can sink.

Biodiversity and protected areas

Nepal's elevation range, which runs from roughly 67 m in the south-eastern Terai to the summit of Everest, packs several biogeographic realms into a country of about 147,000 km². The protected areas sit across the lowland Terai, the Siwalik foothills and the high mountains, and they draw on both the Palearctic and Indomalayan realms. Within a short north–south distance the country therefore contains subtropical forests, grasslands, wetlands and alpine habitats. Wildlife records list 208 mammal species, of which 28 occur outside the boundaries of protected areas.

The formal protection system began with the 1957 Wildlife Conservation Act, which was the first Nepali law to stress the value of wildlife. Chitwan National Park, created in 1973, became the first national park. The Department of National Parks and Wildlife Conservation (DNPWC) was set up in 1980 to manage wildlife and biodiversity nationally. Its portfolio now covers 12 national parks, one wildlife reserve, one hunting reserve and six conservation areas, which together account for about 23 per cent of the national territory according to official figures. The system includes four legal classes of protection, from strict national parks to hunting reserves. Conservation areas differ from national parks in that they allow greater local use and management. Two examples are the Api-Nampa and Gaurishankar conservation areas, both established in 2010. Gaurishankar borders Tibet and forms part of the Sacred Himalayan Landscape, which shows that conservation extends into the high Himalaya as well as the lowlands.

Chitwan National Park, in the central Terai, is the best-known example of the lowland network. It covers about 953 km² and has been a UNESCO World Heritage Site since 1984. The park shelters the greater one-horned rhinoceros, the Bengal tiger, the Asian elephant, the gharial and the gaur, and the contiguous habitat of Chitwan and neighbouring Parsa National Park supports the largest population of gaur among vulnerable species in the region. Sagarmatha National Park, which encompasses the high Khumbu country around Everest, represents the alpine end of the gradient and is also inscribed on the World Heritage List. Together these parks show how a single national system must protect species with very different habitat requirements, from tall grassland and riverine forest to snowfields and rocky ridges.

Protected areas do not operate in isolation. Much of their ecological function depends on the surrounding buffer zones, where community forests and local users share resource management with park authorities. Most of the threats recorded for these areas originate outside park boundaries or spread across them. A study of gaur in Chitwan ranked uncontrolled fire, invasive species, human disturbance and climate change as the most prevailing threats. Habitat fragmentation, in which forest is cut into smaller and more isolated patches, reduces the movement of large mammals between protected core areas and undermines the ability of populations to recover after local losses. Corridor management and buffer-zone forestry are therefore central to conservation outside the parks.

Invasive species have become one of the most visible challenges. The plant Mikania micrantha is among the world's 100 worst invasive alien species and is the principal invader of Chitwan National Park. It was first reported inside the park in 1963. A survey found it in about 44 per cent of sampled habitats, with heavy infestation in roughly 15 per cent. Its highest densities occur in riverine forest, tall grassland and wetlands, which are among the most important habitats for rhinoceroses. The plant suppresses fodder grasses and prevents tree regeneration, so it degrades food resources for herbivores and, in turn, for tigers that depend on those prey species. It also damages cropland in the buffer zone, which makes it a livelihood problem as well as an ecological one. Other species, including Parthenium hysterophorus, Lantana camara and Bidens pilosa, are also spreading, and researchers have reported invasive plants moving upslope into the mountains.

Control programmes have so far concentrated on the lowland parks. The government, working with the National Trust for Nature Conservation, has run manual removal of Mikania and biological control of Parthenium using beetles in Chitwan and Shuklaphanta National Park. Biodiversity management in this setting must weigh these measures against the needs of hill and Terai farming communities, who rely on forest products, grazing and cropland in and around the protected areas. Conservation policy therefore depends on local participation, on the protection of livelihoods and on the management of land beyond park boundaries.

Land use and agriculture

Agriculture remains a large part of the Nepali economy, although its weight has fallen. World Bank data show value added from agriculture at about 21.9% of GDP in 2024, down from a peak of roughly 69% in 1975, while agriculture still supports around three in five workers. Land use, however, is limited and uneven. Cultivated land covers only about an eighth of the national land area, and the amount of land suitable for farming depends heavily on altitude.

The middle hills contain much of the country's farmland, but the ground is steep, and the terraces built on it are the main form of cultivation. Hill households have increasingly moved onto slopes as populations grew, and the terraces that resulted hold soil and water in place on land that would otherwise erode quickly. Farm holdings are small: national surveys cited by a 2019 review put the average landholding below 0.68 hectares per family, and that figure has been falling for decades as land is divided among heirs. Fragmentation is especially visible in the Terai, where it reduces the scale at which irrigation and mechanised work can be applied.

The Terai is the most productive agricultural zone. Its flat, alluvial soils are deep and fertile, and the gentle gradient allows canals and tube wells to supply water. A 2019 review based on Central Bureau of Statistics figures estimated that about 56% of the country's arable land lies in the Terai, compared with about 36% in the hills and only a small share in the mountains, where only about 8% of temporary crop area is found. Paddy, maize, wheat, sugarcane and oilseeds dominate. Irrigation is a central constraint: one widely cited figure gives roughly 1.3 million hectares of irrigated land out of about 2.7 million hectares of agricultural land, with most schemes small or medium in scale, though more recent estimates differ in their totals.

Cropping calendars follow altitude and the monsoon. Summer rains govern the main sowing of paddy and maize in the lowlands and the hills, while winter crops such as wheat, barley and mustard are grown after the rains recede, especially where irrigation or residual moisture is available. In the high hills and mountains, the cool climate and short growing season favour buckwheat, potatoes and other hardy crops, while cash crops such as cardamom, ginger, garlic and turmeric are important in suitable hill districts. Each band therefore has its own timing for planting, weeding and harvest, and labour demand peaks at different times in different places. Commercial cultivation has also reshaped some lowland areas: banana cultivation has expanded rapidly in several Terai districts, displacing earlier cropping patterns.

Cultivation has also cost forest cover, particularly in the south. Forest-cover histories from the Chure-Tarai landscape show that Terai forest fell from about 30% of the area in 1954 to roughly 10% by 1994, as clearing for farmland accelerated. Later national mapping, which uses different definitions and includes other wooded land, puts Terai forest and other wooded land at about 20% of the region in 2022, so the figures are not directly comparable. Clearing in the hills has a different pattern: deforested slopes are often terraced or turn into scrub, while in the Terai they are usually converted to farmland. Migration from the hills into the Terai has been a major driver of this conversion, and the associated loss of forest has feedbacks on erosion, groundwater recharge and the biodiversity of the lowland belt.

Settlement patterns and population distribution

Nepal's population has moved toward the lowlands over the past seven decades. In the 1952–54 census, the mountain and hill regions together held 64.8 percent of the population, with the Terai at 35.2 percent. By the 2021 census, the balance had reversed: 53.66 % of the population lived in the Terai, 40.25 % in the hilly region, and 6.09 % in the mountain region. Estimates of the Terai's share of national land differ by source. One puts it at 23% of the total land area, while another states that the Terai covers only 17 percent of the country's total land area. The gap is far larger in population terms: Terai's population density is rising quickly, reaching 461 people/sq km, compared to only 34 people/sq km in the mountains.

Upland settlement is uneven rather than empty. Villages tend to cluster where water, workable slope and access coincide, typically on terraces above river valleys, on ridge spurs near springs, and along trails that once linked valley settlements to markets and mountain passes. This explains why some middle-hill valleys remain densely peopled while the land around them is steep and thinly settled. The pattern is shaped by the same terrain that governs Himalayan land use more broadly, and it has been reinforced by historic trade routes that funnelled people and goods along river corridors.

The Kathmandu Valley is a special case because its floor was once the bed of a large lake. Geologists call this body of water the Paleo-Kathmandu Lake. The level of the lake ebbed and rose between 1,400-1,440m, depending on the prevailing climate, making it about 200m deep in places. Drainage was eventually achieved through a gorge at Chobhar, where the main water body carved its way through the soft limestone. Sources disagree on the timing: one account states that the Paleo-Kathmandu Lake was formed 1 million years ago by the damming of the Bagmati River, and dried 12,000 years ago, while another holds that the shrinkage began 30,000 years ago. The resulting flat, fertile basin now holds the country's principal urban centre, and urban growth in the valley has been rapid. The 2021 census recorded strong growth in valley districts such as Bhaktapur, and it also noted new urban centres in the Terai, including Bharatpur and Butwal.

Labour migration has reshaped rural settlement and household livelihoods. The modern export model began when the introduction of the Foreign Employment Act in 1985 initiated a formal labor export policy and encouraged the private sector to recruit Nepali youths for its foreign employment. Remittances have since become central to household income: Nepal received around $8.3 billion – equivalent to about 30% of GDP – remittance in 2018/19. The share of households receiving remittances also climbed sharply, from 23.4% in 1995/96, which increased to 55.8% in 2010/11. Spending of these transfers has gone partly into education and health; studies have found that remittance spending correlates with a positive effect on education spending, increased years of schooling and greater educational opportunities for girls.

Migration has also changed the composition of rural households and the places where people live. Many hill families have shifted from their ancestral villages to the Terai or to towns in the central region, which has added to pressure on lowland services and land. Households left behind face different constraints. Studies report that migration exacerbates labor shortages, reducing agricultural yields, and remittances rarely improve farm productivity. Gender roles have shifted as well, since with fewer men around, women undertake more responsibility in household and community decisions, including managing limited funds. Figures on the share of remittance-receiving households vary between surveys and years, so comparisons across studies should be made with care.

Water resources and hydropower

Nepal's water wealth depends on steep gradients. Monsoon rain and glacier melt fall through very short horizontal distances, which gives the country a theoretical hydropower potential of about 83,000 MW. The share that can be developed technically and economically is usually put at roughly 40,000 to 43,000 MW. A 2019 study by the Water and Energy Commission Secretariat gave a gross potential of about 72,500 MW, with the Koshi, Gandaki and Karnali basins accounting for most of it. Actual development is far smaller. Installed capacity grew quickly in the 2020s, but reported totals for 2025 and 2026 range from roughly 3,900 to 4,300 MW depending on the source, date and whether small plants are counted. Development was slow for most of the twentieth century. The first plant, the 500 kW Pharping station, dates from 1911, and by 2005 only about 557 MW had been built, a delay attributed to limited private investment, political factors and dependence on external finance. Because hydropower supplies nearly all domestic generation, the sector is central to electricity access, to plans for exports to India and Bangladesh, and to the wider renewable energy agenda. Output drops in the dry season when flows fall, and Nepal has very little reservoir storage to offset this, which the country's limited dam capacity makes clear.

Irrigation in the Terai, the southern lowland that serves as the country's main grain belt, is shaped by the monsoon. About 80 percent of precipitation and river discharge in the western Terai districts falls between July and October, and flows fall sharply soon afterwards, which limits year-round use of canal water. Canal schemes are said to reach around 40 percent of Nepal's cultivated land, but a considerably smaller area actually receives water from them. Many Terai canals draw from small and medium rivers that dry up in winter and early summer. Official figures put the share of Terai cropland with some access to irrigation at close to 60 percent, yet only about 39 percent of cultivated land nationally has year-round irrigation. Estimates of groundwater's role also differ: some studies describe most Terai irrigation as groundwater-based, while others put its contribution at around a quarter of the total. Shallow tubewells, which are cheap to install, have spread widely, and in the 2011–2012 agricultural census about 42 percent of Terai farmers reported access to them. Pumping costs and energy supply, however, limit how many farmers can use them.

Terai groundwater is one of the country's most productive resources. The aquifers consist of alluvial sediments that become finer towards the south. An unconfined layer extends to about 50 metres, and deeper confined aquifers may reach around 200 metres. Recharge comes mainly from the Bhabar zone at the foot of the Siwalik hills, where highly permeable gravels and sands allow rainfall and river water to infiltrate. Annual recharge is estimated at about 8,800 million cubic metres, yet only around 22 percent of this is extracted, which suggests considerable untapped capacity. The aquifers are often transboundary, and pumping in India can affect supply on the Nepali side. Groundwater quality is a constraint, since Terai groundwater has naturally high arsenic levels in some areas. In the hills the situation is different. Groundwater potential declines with elevation, and aquifers there are small and rainfall-dependent. Springs and glacier-fed rivers sustain flows in the main valleys, but many small streams and the rivers of the Siwalik zone run low or dry in winter, so hill settlements often face seasonal water shortages.

Several major rivers cross the border with India or start in neighbouring territory, so their management is a matter for international agreement. The Koshi Agreement was signed in 1954 and the Gandak Agreement in 1959, both focused on barrages, canals, flood control and power sharing. Nepal objected that these terms were unequal, and the two treaties were revised in 1964 and 1966. The Mahakali Treaty of 1996 covers the Sharda and Tanakpur barrages and the Pancheshwar Multipurpose Project. Joint commissions and committees provide a channel for dialogue on flood management and water data. Many smaller cross-border rivers and streams, however, fall outside any treaty. Cooperation with China is less formal. No long-term water-sharing treaty covers the rivers that flow north-south across the border, and the exchange of hydrological data remains limited. Hydropower projects on shared rivers thus raise questions of infrastructure design, benefit sharing and flood risk that extend beyond national planning, linking to wider drainage basin management in the region.

Environmental change and degradation

Forest loss in Nepal has been driven mainly by human demand for fuelwood, fodder and farmland. In the mountains, fuelwood gathering, grazing and the lopping of trees for fodder, combined with shifting cultivation in some places, are considered the main causes of deforestation. Lopping is especially damaging because it strips leaves and branches repeatedly, and in many hill districts the result is scrubby, low-value bush rather than regenerating forest. Fodder scarcity is structural: a 1988 government forestry plan judged most of the mid-hills to be in fodder deficit, and the concentration of livestock near villages has placed much of the remaining forest under strain. Women and children often bear the labour cost, walking long distances for fuel and fodder. Forest cover is also lost to road building, irrigation canals, hydropower reservoirs and the growth of administrative centres, which have accelerated clearance in recent decades. In the Terai, illegal felling of timber for export to India has added a separate pressure. Estimates of the scale of loss vary by method and period. A study based on successive land-cover maps reported that forest area fell from about 76,700 km² in 1930 to about 39,400 km² in 2014, a net loss of roughly half, while national assessments that include shrub and community-managed woodland record a more recent stabilisation or partial recovery, particularly where forest clearance has been checked by community forest management since the 1990s. Local studies in mid-hill and Terai watersheds show both loss and regrowth, so the national trend depends heavily on how forest is defined and over which years it is measured.

Erosion is the most direct consequence of vegetation loss on steep ground. Where forest cover has been cleared, or where slopes have been converted into terraces that are repeatedly disturbed, the soil is exposed to heavy monsoon rain and loses its capacity to hold water and nutrients. The eroded material is carried into rivers, raising sediment loads and filling channels and reservoirs downstream. At the same time, thinner and less fertile soils reduce crop yields, which in turn encourages farmers to clear more land, creating a self-reinforcing cycle that is especially visible in the middle hills. Tourism has added local pressure along popular trekking routes, where lodges and tea shops consume timber and firewood, and the high altitude slows the regrowth of trees.

Kathmandu Valley shows a different form of environmental change, driven by rapid urbanisation. The valley's population has grown quickly, and the city has absorbed an increasing number of vehicles, mostly two-wheelers, on narrow and poorly planned roads. Vehicle exhaust, construction dust, brick kilns, waste burning and seasonal wildfire smoke all contribute to air pollution. The valley's bowl-shaped topography restricts wind movement and traps pollutants, and dry winter months are typically the worst period. Research on the valley has found that PM2.5 concentrations exceed the national guideline on nearly half of all days in a typical year, and that population growth alone can increase health impacts even where pollution levels remain stable. Construction activity, including unpaved roads and haphazard disposal of building materials, adds to the burden. Solid waste is a parallel problem: growing volumes of household and commercial waste have outpaced collection, recycling and disposal systems, and landfill sites remain limited and contested. These issues are addressed in part by the Kathmandu Valley Air Quality Management Action Plan approved in 2020, but implementation depends on coordination across several levels of government and sectors, and on urban planning that anticipates future growth.

Environmental degradation and natural hazards are closely linked. Vegetation intercepts rainfall, binds soil with roots and slows runoff, so when forest and shrub cover is lost, slopes become more prone to landslides and debris flows, and rivers respond to heavy rain with sharper floods. This is most evident on deforested hillsides in the middle hills and in watersheds where terraces are poorly maintained, as the same monsoon storms that would once have been absorbed now produce rapid runoff and mass movement. Degradation also weakens the land's productivity, which can push settlements onto more hazardous ground. Reducing this risk therefore depends on measures that restore vegetation, manage grazing and fuel demand, control erosion on cultivated slopes and limit uncontrolled growth in urban areas, all of which connect to broader goals of sustainable development.

Administrative geography

Since the 2015 constitution, Nepal has been a federal democratic republic with three tiers of government: federal, provincial and local. The Provinces of Nepal were formed on 20 September 2015 in accordance with Schedule 4 of the Constitution of Nepal. The seven provinces are Koshi, Madhesh, Bagmati, Gandaki, Lumbini, Karnali and Sudurpashchim. Before this change, the country was a unitary state divided into 14 zones and 75 districts, a structure that had been in place since the early 1960s. The constitution abolished the zones, while the districts survived as sub-units within the provinces. The country now has 77 districts.

The provinces differ sharply in size and population. Madhesh is the smallest by area, while Karnali is the largest. Bagmati has the largest population. The constitution originally numbered the provinces, and the names were settled later by each provincial assembly, so Koshi received its name only in 2023.

Below the provinces sits the local tier, which is the layer closest to citizens. The local level comprises 753 units: six metropolitan cities, eleven sub-metropolitan cities, 276 municipalities and 460 rural municipalities. These units are divided into 6,743 wards. The first local elections were held in 2017, and a second round followed in 2022, which restored elected local government after a gap of about two decades. Each local unit has its own elected assembly and executive. Article 56 of the constitution defines the local level, and federal legislation determines the number and boundaries of local units.

The distribution of powers is set out in lists. The federal government holds 35 exclusive powers, the provinces hold 21 and the local governments hold 22, and some powers are concurrent among the tiers. Provincial and local governments have directly elected leadership and raise their own revenue, but they depend heavily on transfers from the federal government. Districts have coordinating assemblies and committees that link local units with each other and with the higher tiers of government.

Implementation has been uneven. Analysts have noted unclear jurisdictional boundaries between the tiers, overlapping functions and limited staffing. Early assessments found that many local bodies had only moderate or weak capacity to draft inclusive plans and carry them out, and that the work of preparing local laws and by-laws strained their limited resources. Recent reporting describes administrative decentralisation as the weakest part of the reform, with only 38 percent of approved provincial civil service posts filled at the time of one review. Several analysts also argue that provinces hold less real authority than the constitutional design suggests, because they are squeezed by the federal and local tiers in areas such as education.

Administrative and ethnolinguistic patterns do not map neatly onto one another. Groups and languages are distributed differently across the high mountains, the middle hills and the Terai, so provincial and district boundaries cut across cultural areas in various ways. Many boundaries follow river valleys and ridge lines, which affects how easily services and infrastructure can reach remote communities. Road access, electricity and telecommunications therefore influence how effectively a local unit can deliver services. The same geographic constraints shape the cost and reach of administration, so decisions about boundaries and service delivery are closely tied to the physical landscape described elsewhere in this article.

Transport and connectivity

Nepal's transport network is shaped by the same relief that defines its geography. Steep slopes, fragile rock and deep gorges make road construction expensive, because engineers must cut into unstable hillsides, bridge fast-flowing rivers and protect roadways against landslides. Monsoon rain adds a seasonal layer of disruption: many hill routes close during the wet season, and communities that rely on footpaths and seasonal tracks can be cut off for extended periods. Before the mid-twentieth century the country had almost no motorable roads, and long-distance travel depended on foot trails, mule tracks, river routes and porters. Modern road building began after 1950, largely with foreign assistance.

The main arterial route is the East–West Highway (Mahendra Highway, NH01), which crosses the Terai from Kakarbhitta in the east to Bhim Datta in the west over more than 1,000 km and is the longest highway in the country. For much of its length it carries one lane in each direction, and its construction in the 1960s and 1970s through partnerships with several foreign governments made it the backbone of mobility across the plains. Upgrading to four lanes has been under way for years with loans from the World Bank and the Asian Development Bank, but progress has been slow. Land compensation disputes, unresolved right-of-way boundaries and contractor delays have pushed back completion, and the Narayanghat–Butwal section is among the most significant bottlenecks.

Hill routes are generally narrower and more exposed. The Prithvi Highway (NH17) links Naubise, on the Kathmandu side of the hills, with Pokhara over about 170 km. It was built with Chinese assistance between 1967 and 1974, and it remains one of the country's most important links between the capital and the western hills, although it is prone to landslides and heavy congestion. Its widening includes the Nagdhunga–Naubise tunnel, which is designed to be Nepal's first modern road tunnel. Other hill corridors, such as the Sagarmatha Highway (NH16) linking the Terai at Siraha with Solukhumbu district, connect the southern plains with districts that lie further into the mountains. Many smaller roads serving villages above the main valleys are unpaved or seasonal.

Rail transport is limited. Nepal had only a few short lines, all built in the Terai, and two cross-border services operate today. The Raxaul–Sirsiya line, about 6 km long, links the Indian rail network to a dry port near Birgunj and is used mainly for freight. The Jayanagar–Janakpur line, which opened in 1937 as a narrow-gauge timber and passenger route, was converted to broad gauge and reopened in 2022 with a route of roughly 52 km. Several longer schemes are planned rather than operating, including the Raxaul–Kathmandu link, for which India and Nepal have reviewed survey reports, a broader East–West Railway across the Terai and a proposed line from the Chinese border at Kerung to Kathmandu. Because of the terrain and seismic risk, these projects face high engineering costs and long preparation periods.

The principal road link with China is the Araniko Highway (NH34), which runs about 112 km from Kathmandu to Kodari on the Tibetan border. Chinese assistance financed its construction in the 1960s, and it opened in 1967. The route crosses the border at the Sino-Nepal Friendship Bridge, which connects with China National Highway 318 at Zhangmu and continues towards Lhasa. The earlier bridge, opened in 1964, served as the only official crossing for decades. The 2015 earthquakes triggered landslides that closed the highway, and the replacement bridge opened in 2019. Trade by truck remains constrained: for many Chinese goods, shipping through Indian ports has been cheaper than trucking across the plateau. Further west, the Korala pass near the Gandaki region carries a vehicle crossing at about 4,660 m, although terrain and altitude restrict its use.

Air travel fills gaps that roads and rail cannot cover. Short scheduled flights connect Kathmandu with Pokhara and with airstrips in the mountains, including Lukla, the usual gateway to the Everest region. Air services are essential for emergency evacuation, the movement of officials and tourists, and the delivery of goods to remote districts, although their capacity and cost limit their role for bulk freight.

Exploration and mapping history

Modern measurement of the Himalaya began with the Great Trigonometrical Survey of India, which triangulated across the subcontinent through much of the nineteenth century. The survey ran from 1802 to 1871, and its work on the northern frontier brought the mountains of Nepal into its figures. Peak heights were derived by chaining angular sightings between stations, and before electronic computers this took many months for a team of humans to calculate, analyze and extrapolate the trigonometry involved. The Bengali mathematician Radhanath Sikdar completed the calculations in 1852 that identified a peak then catalogued only as Peak XV as the highest in the world (see the 1852 calculations for Peak XV). The result was published in 1856, when the survey officially gave Peak XV, later named Mount Everest, a height of 29,002 ft (8,840 m). The same publication confirmed Kangchenjunga, previously thought to be the world's highest, at 28,156 ft (8,582 m). The peak was renamed in 1865, when the Royal Geographical Society renamed Peak XV to Mount Everest in his honour.

The 1953 ascent turned the mountain into a global focus. Edmund Hillary and Tenzing Norgay made the first ascent of Everest on 29 May 1953 by the South Col route. That route climbs Everest from the Nepal side, so the summit was reached from Nepali territory. The expedition was led by Colonel John Hunt. After the climb, the Survey of India adjusted the height by 8 m (26.24 ft) in 1955, and the elevation of 8848 m remained Mount Everest's official height until 2020. The shift from the 1856 figure reflected better instruments and observation sites rather than any change in the mountain itself.

Systematic geological exploration of Nepal came later than the survey work. Apart from a few sporadic observations made by foreign geologists, detailed study of the Nepal Himalaya began only after 1950. The most important early figure was the Swiss-trained geologist Toni Hagen, who was appointed as the government geologist by the Nepal government in 1952 and covered at least 14,000 kms during his fieldwork in the 1950s. His results were published in preliminary form, and although a great part of his material, unfortunately also most of his geological maps, remained unpublished, his essential results appeared in several preliminary papers. His 1969 volume, a kind of anticipated summary of the geology of Nepal with emphasis on the structural aspects, became a reference point. His structural interpretation was not uniformly accepted: Hagen's structural concept with its multitude of nappes became highly disputed.

Mapping continued through the following decades. Several further teams worked in the country after Hagen, including Bordet (1961), Geological Survey of India (1968), Le Fort (1969), Fuchs and Frank (1970), Talalov (1972), Hashimoto (1973), Stocklin and Bhattarai (1977). A second phase of regional mapping in the early 1980s checked earlier field data and compiled it for publication, and it established a unified stratigraphic scheme and tectonic structure of the Lesser Himalayas and Siwalik. The resulting tectonostratigraphic zones are characterised by distinctive stratigraphy and physiography.

Measurement techniques have changed again in recent decades. In 1999, an American team used GPS instruments to record Everest's rock height at 8,850m, and an additional ice cap that took the reading to 8,851m. For the most recent determination, Nepal's Survey Department combined traditional methods (trigonometry levelling as done by Survey of India in 1950s) with precise levelling and more accurate modern geoid system with gravity survey, and Global Navigation Satellite System (GNSS) to cross check the results. Today, satellite imagery and geospatial databases underpin hazard mapping, glacier monitoring and land-cover studies, extending the older field-based surveys across the whole country.

Open research questions

Glacier mass balance and retreat

Field data on glacier mass balance are thin for a range this size. In-situ glacier observations are restricted to only 35 glaciers across the Himalaya, so satellite-based estimates (remote sensing and GIS analyses) are hard to check against ground measurements. The overall direction is clear, since glaciers across the Himalaya exhibit a consistent negative mass balance trend, but the rate differs with regional climate and the extent of debris cover. Studies have found that retreat rates contrast between the eastern and western Himalaya, and climatic controls on glacier mass balance are distinct from region to region, so a single basin's results cannot easily be extended to the whole range.

Nepal's own record is incomplete. Glacier thinning is widespread in the Everest region, and all monitored glaciers in Nepal show a clear trend of sustained mass loss, yet a nationwide future glacier projection in Nepal has not yet been conducted. Uncertainty also arises from the way loss is counted. Subaqueous melting at lake-terminating glaciers has been missing from earlier totals; adding it raises the estimated mass loss of greater Himalayan glaciers, with the largest correction in the central Himalaya glacier studies have identified. Sensitivity to precipitation adds further uncertainty: in a Himalaya–Karakoram model, snowfall variability explains ~60% of the MB variability, which indicates that changes in snowfall can outweigh changes in temperature in some settings.

Monsoon behaviour under climate change

Projections of the climatic behaviour of the monsoon are still divided. In CMIP6 simulations, the relative dependence is 5.3 % per kelvin of global warming for the ensemble, but the spread across individual models is large. Most models point to more precipitation over the Himalaya, yet the precipitation signal is hard to pin down regionally. A recent glacier study gives a range for the Himalaya: glacier mass in the Himalaya is projected to shrink by 53 %–70 % due to climate change by 2100 CE, but the authors stress that the impact of changes in precipitation amount and distribution on future glacier change remains uncertain. Regional climate models for the monsoon-influenced Himalaya show particularly poor RCM consensus and high levels of uncertainty in future precipitation trends. The timing of the rainy season, the share of rain versus snow, and the frequency of extreme days all bear on hazards and water supply, and they remain under active study (climate change research).

Sediment budgets and erosion rates

Long-term erosion of the range is only partly quantified. Two independent approaches, gauged sediment fluxes and 10-Be in sediments constrain the Himalayan denudation rate to ca. 0.8 and 1.0 mm/yr, but the uncertainties on both methods remain high, which limits what can be inferred about the sources of the difference. Sediment from the Ganga floodplain samples gives an average Himalayan denudation rate of 1.0–1.1 mm yr^−1, and whether the flux has been steady over centuries is still uncertain, as the large uncertainties associated with each method hamper more precise assessments.

Within Nepal's foothills, short-term deposition is better documented but still local. Rivers draining the Siwalik Hills have relatively small catchments (20–30 km2) but are thought to have high erosion rates and sediment yields. Measurements from radar remote sensing show sediment aggradation in river channels during the wet monsoon, with rates reaching up to approximately 20 mm yr^−1 near the mountain front, while the floodplain in the basin is subsiding at varying rates that average ∼ 15 mm yr^−1. Whether these local rates persist over decades, and how they feed into river avulsion and floodplain flood risk, are questions that longer records would need to answer.

Biodiversity inventories

Species surveys remain uneven. Lowland and mid-hill sites are comparatively well documented, whereas inventories above the main forest belt and in remote valleys are still incomplete. This gap limits knowledge of species ranges, population trends and the responses of alpine habitats to warming, and it complicates the design of conservation measures for biodiversity and ecosystem function at high elevations.

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63. Nepal — Weatheriexplore.com
64. Audit of stored strain energy and extent of future earthquake rupture in central Himalayancbi.nlm.nih.gov
65. Better understanding seismic hazardsnews.asu.edu
66. Nepal: Gorkha Earthquake 2015preventionweb.net
67. Damage Due to Gorkha Nepal Earthquake of 2015 and Its Intensitylink.springer.com
68. Causes of deaths and injuries in the 2015 Gorkha (Nepal) earthquakecentral.scec.org
69. (PDF) The 2015 Gorkha Nepal Earthquake: Insights from Earthquake Damage Surveyresearchgate.net
70. Weather Radar in Nepal: Opportunities and Challenges in Mountainous Regionarxiv.org
71. 2026 Nepal–Tibet floodsen.wikipedia.org
72. Flooding in Nepal: What You Need to Knowinternationalmedicalcorps.org
73. A Landslide, Not Rain, Triggered Nepal's Latest Himalayan Flood. Five Still Missinglatintimes.com
74. Glacial lake outburst flooden.wikipedia.org
75. Reassessing Tsho Rolpa glacial lake - ICIMODicimod.org
76. Full article: People's risk perception of glacial lake outburst flooding: a case of Tsho Rolpa Lake, Nepaltandfonline.com
77. 1 Glacial Lakes and Glacial Lake Outburst Floods in Nepal THE WORLD BANKdocuments1.worldbank.org
78. Tsho Rolpaen.wikipedia.org
79. The Soils of Nepalspringerprofessional.de
80. Glacial Soils - an overviewsciencedirect.com
81. Inner Terai Valleys of Nepalen.wikipedia.org
82. Types of Forest in Nepal - Online Biology Notesonlinebiologynotes.com
83. Nepal - Himalayan, Flora, Faunabritannica.com
84. Flora of Nepal - Country Information - Vegetationfloraofnepal.org
85. Unraveling Elevation-Driven Variations in Forest Structure and Composition in Western Nepaldoi.org
86. List of protected areas of Nepalen.wikipedia.org
87. Bhabar Beltgktoday.in
88. (PDF) Structure and diversity of natural and managed sal (Shorea robusta Gaertn.f.) forest in the Terai of Nepalresearchgate.net
89. DNPWCdnpwc.gov.np
90. Protected Areas in Nepalprotected-areas-in-nepal-uji.hub.arcgis.com
91. Wildlife of Nepalen.wikipedia.org
92. Gaurishankar Conservation Areaen.wikipedia.org
93. Api Nampa Conservation Areaen.wikipedia.org
94. Ecological and anthropogenic factors influencing the Summer habitat use of Bos gaurus and its conservation threats in Chitwan National Park, Nepalncbi.nlm.nih.gov
95. (PDF) Invasive mikania in Chitwan National Park, Nepal: the threat to the greater one-horned rhinoceros Rhinoceros unicornis and factors driving the invasionacademia.edu
96. "Too Much Weed: Invasive Species in Chitwan National Park" by Laura Nelsondigitalcollections.sit.edu
97. Invasive species inch northwards in Nepal, threatening mountain ecosystemsdialogue.earth
98. A new weed is invading Chitwan National parkkathmandupost.com
99. Agriculture in Nepalen.wikipedia.org
100. Nepal GDP share of agriculture - data, charttheglobaleconomy.com
101. Journal of Agriculture and Forestry University (2019), Vol. 3 1 Review Articleold.afu.edu.np
102. Historical Land Covers Change in the Chure-Tarai Landscape in the Last Six Decades: Drivers and Environmental Consequenceslink.springer.com
103. i TERAI FORESTS OF NEPAL 2022 Government of Nepalfrtc.gov.np
104. GEOGRAPHY AND LAND COVER OF NEPAL: HIMALAYAS, RIVERS, FLOWERS, FORESTSfactsanddetails.com
105. AGRICULTURE IN NEPAL: HISTORY, CROPS, LAND TENURE AND FARMING PRACTICESfactsanddetails.com
106. Agriculture Oldfncci.org
107. 1952%E2%88%9254 Nepal censusen.wikipedia.org
108. Key highlights from the Census Report 2021 - Nepal Economic Forumnepaleconomicforum.org
109. Geographic distribution of population in Nepal.researchgate.net
110. New census data creates ripples in Nepalorfonline.org
111. The lake that was once Kathmandu - Nepali Timesarchive.nepalitimes.com
112. Sedimentary facies distribution map of the Kathmandu basin. Drill sites...researchgate.net
113. (PDF) Leveraging Labor Migration and Migrant Remittances in Nepalresearchgate.net
114. Labour Migration from Nepal: Trends and Explanationslink.springer.com
115. Remittances and migration: the case of Nepal - Devpolicy Blog from the Development Policy Centredevpolicy.org
116. ANALYSIS EMIGRATION FROM NEPAL AND ITS IMPACT ON THE ECONOMY Maheshwar Girifreiheit.org
117. Remittances to Nepalen.wikipedia.org
118. Renewable energy in Nepalen.wikipedia.org
119. Can Nepal harness its huge hydropower potential?kathmandupost.com
120. Balanced Hydropower Development in Nepalnbr.org
121. List of power stations in Nepalen.wikipedia.org
122. Nepal and small-scale renewable energyebsco.com
123. Evolution and future prospects of hydropower sector in Nepal: A review - ScienceDirectsciencedirect.com
124. Hydel (Hydropower) Power in Nepal — The Battery of South Asiahydelenergy.com
125. Nepal Electricity Authorityen.wikipedia.org
126. Implementing conjunctive management of water resources for irrigation development: A framework applied to the Southern Plain of Western Nepal - PMCpmc.ncbi.nlm.nih.gov
127. Groundwater Resources of Nepal: An Overviewresearchgate.net
128. Water Access Challenges in the Western Plains of Nepalcsisa.org
129. About the Board - Groundwater Resources Development Boardgwrdb.gov.np
130. Drivers of groundwater utilization in water-limited rice production systems in Nepalncbi.nlm.nih.gov
131. Rich water, poor people: Potential for transboundary flood management between Nepal and India - ScienceDirectsciencedirect.com
132. Conflicting Riparian Rights and Transboundary Water Governance of Small Rivers: A Case Study of Pandai, in Nepal and Indialink.springer.com
133. Shared Rivers, Shared Responsibilities: The Case for Water Treatiesthedailystar.net
134. Full article: International water law and hydropolitics: an enquiry into the water conflict between India and Nepaltandfonline.com
135. underlying causes of deforestation and participatoryiges.or.jp
136. The Impact of Deforestation on Life in Nepalculturalsurvival.org
137. FRA 2000 ANNOTATED BIBLIOGRAPHY FOREST COVER CHANGE: NEPALfao.org
138. Sustainable livestock production in the mountain agro-ecosystem of Nepalfao.org
139. 3. THE STATE OF FORESTRY IN NEPALfao.org
140. (PDF) Forest and other land cover assessment in Nepal using Collect Earthresearchgate.net
141. Forest Cover Change Pattern after the Intervention of Community Forestry Management System in the Mid-Hill of Nepal: A Case Studymdpi.com
142. Forest Cover Changes and Trajectories in a Typical Middle Mountain Watershed of Western Nepalmdpi.com
143. Municipal Actions for Air Quality in the Kathmandu Valleypublications.jsi.com
144. (PDF) Air Quality Management in Kathmanduresearchgate.net
145. Impact of wildfire smoke on air pollution-related premature mortality in rapidly growing Kathmandu Valley - ScienceDirectsciencedirect.com
146. Kathmandu valley’s crisis is a governance test for RSPtheannapurnaexpress.com
147. Making Livable Cities: Tackling Solid Waste in Kathmandu and Beyondspotlightnepal.com
148. Provinces of Nepalen.wikipedia.org
149. Number of Local levels in different provincesresearchgate.net
150. 1 Nepal Institutional Depth and Policy Scopegarymarks.web.unc.edu
151. Federal Nepal: Provinces & Local Levels of Nepal - VIVEK DHAKALdhakalvivek.com.np
152. List of 77 Districts of Nepal: Provinces with Headquarter, Area & Populationnamastesindhupalchowk.com
153. Local Levels of Nepal by District and Provinceamarnepal.com
154. How Many States in Nepal? — All 7 Provinces Listed (2026)geographyworlds.com
155. Local Levels in Nepalnepalog.com
156. Local government in Nepal — Grokipediagrokipedia.com
157. Opinionkathmandupost.com
158. Institutionalising federalism in Nepal: operationalising obstacles, procrastinated progressemerald.com
159. Overcoming hurdles to effective sub-national governance in Nepaleastasiaforum.org
160. Nepal's experience in implementing the federal government system: Assessment of law-making by the local governments of Kaski district, Nepal - ScienceDirectsciencedirect.com
161. Nepal's experience in implementing the federal government system: Assessment of law-making by the local governments of Kaski district, Nepalncbi.nlm.nih.gov
162. Nepal’s federalism at ten: Strong foundations, but unfinished reformsdecentralization.net
163. Policy Note for the Federalism Transition in Nepal AUGUST 2019 Empowered lives.sthaniya.gov.np
164. Self-Determination versus Development: The Evolution of Federalism in Nepalsolconferences.ku.edu.np
165. Intergovernmental Profile: Nepaldecentralization.net
166. Prithvi Highwayen.wikipedia.org
167. Roads in Nepalen.wikipedia.org
168. Mahendra Highwayen.wikipedia.org
169. Nepal’s Road Infrastructure Update: Slow But Steady Progress Nationwide - Bizness News English - English Version of biznessnews.comenglish.biznessnews.com
170. East-West highway expansion in Nepal - Maritime Gatewaymaritimegateway.com
171. Sagarmatha Highwayen.wikipedia.org
172. Transport in Nepalen.wikipedia.org
173. Overview on Development of Railway Line Network in ...ajeg.nseg.org.np
174. What are the Nepal Railway routes? - Curious Expeditionscuriousexpeditions.org
175. Nepal Train: Are There Trains in Nepal and Is There a Tibet Nepal Train?tibettravel.org
176. List of railway lines in Nepalen.wikipedia.org
177. Araniko Highwayen.wikipedia.org
178. Kodarien.wikipedia.org
179. Sino-Nepal Friendship Bridgeen.wikipedia.org
180. China National Highway 318en.wikipedia.org
181. Koralaen.wikipedia.org
182. Gyirong Porten.wikipedia.org
183. Topping Off Everestearthdate.org
184. Andrew Scott Waughen.wikipedia.org
185. How Tall is Mount Everest? Official Height in Feet and Metersmagicalnepal.com
186. 1856en.wikipedia.org
187. George Everesten.wikipedia.org
188. First Ascent of Everest: Hillary & Tenzing, 1953annapurnatrekking.com
189. 1953 British Mount Everest expeditionen.wikipedia.org
190. Department of Mines and Geologydmgnepal.gov.np
191. bibliography-of-selected-works-on-nepal-by-toni-hagen- ...martinchautari.org.np
192. Developments in the geological exploration of Nepalngs.org.np
193. Geology of Nepalen.wikipedia.org
194. Spaces above 8,000 metres: quantitative and qualitative assessments of Mount Everestblog.geographydirections.com
195. Nepal, China re-measure height of Mt Everestnepalitimes.com
196. Kangchenjungaen.wikipedia.org
197. Radhanath Sikdaren.wikipedia.org
198. Toni Hagenen.wikipedia.org
199. Who First Climbed Mount Everest? Hillary & Tenzing in 1953demonsunglasses.com
200. Mass balance of lake terminating Gepang Gath glacier (western Himalaya, India) and the role of glacier–lake interactionscambridge.org
201. Decoding the Fate of Himalayan Glaciers under Climate Change: Impacts, Challenges, Research Gaps, and Policy Pathways - ScienceDirectsciencedirect.com
202. Glacier status, recession and change in Nepal - AntarcticGlaciers.organtarcticglaciers.org
203. Snowfall Variability Dictates Glacier Mass Balance Variability in Himalaya-Karakoramncbi.nlm.nih.gov
204. ESD - Robust increase of Indian monsoon rainfall and its variability under future warming in CMIP6 modelsesd.copernicus.org
205. TC - Increasing precipitation due to climate change could partially offset the impact of warming on glacier loss in the monsoon-influenced Himalaya until 2100 CEtc.copernicus.org
206. himalayan river system: Topics by Science.govscience.gov
207. 10Be-derived Himalayan denudation rates and sediment budgets in the Ganga basin - ScienceDirectsciencedirect.com
208. ESurf - Sediment aggradation rates in Himalayan rivers revealed through the InSAR differential residual topographic phaseesurf.copernicus.org
209. Underestimated mass loss from lake-terminating glaciers in the greater Himalayanature.com