The Kingdom of Nepal covers an area of 147 180 km2 between latitudes 26° 20´ and 30° 10´ N and longitudes 80° 15´ and 88° 15´ E. Almost rectangular in shape, it extends over 850 km in length from east to west and 180 km in width from north to south.
The country is completely landlocked, surrounded by India on three sides, except on the north, where it borders China. The altitude varies from less than 300 m to that of the world´s highest mountain, Mount Everest, at 8 850 m. The country can be divided into three roughly parallel strips, each running east/west:
- The Terai is the southernmost strip, about 25 km wide, covering almost 17 percent of the total area. An extension of the Gangetic plain of northern India, it consists of generally level alluvial terrain blending into forested hills.
The strip runs across the entire length of the country at the foothills with varying width except at Dang and Chitwan where it is intercepted by the Someswar range. As a result, the Terai can be conveniently divided into eastern Terai, located in the east of Chitwan; mid-western Terai, streching between Chitwan and Dang-Deokhuri and far-western Terai, located in the west of Dang-Deokhuri.
The southern parts of the Terai are densely populated and most of the area is under agriculture. The northern part of the Terai, known as the Bhabher, has a lower population density. Lying adjacent to hills, its soils contain a higher proportion of boulders, gravel and sand that have been washed down from the hills and mountains during monsoon rains. Most of this area is forested and is noted for its fine forests of sal, Shorea robusta and its associates, known as Charkoshi-Jhari, "the 8 mile forests";
- The Churia range, or Siwalik Hills, is the southernmost range of mountains of Nepal. It consists of several rugged folds, knife-like ridges and steep, sharply dissected slopes. The Churia range extends east to west at an average height of 760 m and merges into the Indian border through its extension at Dang, in the Dundwa range and at Chitwan, in the Someswar range. Large valleys, called duns, separate it from the Mahabharat range in the north.
Some of the larger inner Terai valleys are associated with the West Rapti and Babai rivers (Dang Deokhuri), Narayani and East Rapti rivers (Chitwan), Marinknola (Sindhuli-Makwanpur), Kamla (Sindhuli-Udayapur).
Although the inner Terai may be considered as part of the hills the vegetation of its valleys is similar to the Terai;
- The Mahabharat range, the areas between the Mahabharat and the Himalayas proper, the Himalayas and the inner Himalayan valleys are all mountainous. The Mahabharat range extends almost over the entire length of the country and most of it is below 3 300 m. The mountains therefore can be divided into the lower hills, reaching less than 1 300 m, and the upper hills or mountains, upper Mahabharat and great Himalayas. The terrain in this region is steep and rugged.
Climatically the entire country lies in the subtropical zone but a wide range of climatic conditions exist due to variation in elevation and topography. The Terai, being low in elevation, is hot and humid during the summer months. Temperatures at low elevations of 40° C are common during May and early June before the monsoon rains start. Average temperature decreases with elevation to a alpine or polar climate in the high mountains.
Most of the rainfall occurs from June to September. A few scattered rains occur during the winter months. Rainfall decreases from about 2 500 mm in the east to about 1 500 mm in the west. In the mountains, each hill area has its own microclimate depending on the elevation, cloud cover, steepness and direction of slope, etc.
Soils in Nepal are generally light and permeable because of the steep
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