Landlocked Bhutan is situated in the eastern Himalayas and is mostly mountainous and heavily forested. It is bordered for 470 kilometers by Tibet (China's Xizang Autonomous Region) to the north and northwest and for 605 kilometers by India's states of Sikkim to the west, West Bengal to the southwest, Assam to the south and southeast, and Arunachal Pradesh (formerly the North-East Frontier Agency) to the east. Sikkim, an eighty-eight-kilometer-wide territory, divides Bhutan from Nepal, while West Bengal separates Bhutan from Bangladesh by only sixty kilometers. At its longest east-west dimension, Bhutan stretches around 300 kilometers; it measures 170 kilometers at its maximum north-south dimension, forming a total of 46,500 square kilometers, an area one-third the size of Nepal. In the mid-1980s, about 70 percent of Bhutan was covered with forests; 10 percent was covered with year-round snow and glaciers; nearly 6 percent was permanently cultivated or used for human habitation; another 3 percent was used for shifting cultivation (tsheri), a practice banned by the government; and 5 percent was used as meadows and pastures. The rest of the land was either barren rocky areas or scrubland.
In the north, the snowcapped Great Himalayan Range reaches heights of over 7,500 meters above sea level and extends along the Bhutan-China border. The northern region consists of an arc of glaciated mountain peaks with an arctic climate at the highest elevations. Watered by snow-fed rivers, alpine valleys in this region provide pasturage for livestock tended by a sparse population of migratory shepherds.
The Inner Himalayas are southward spurs of the Great Himayalan Range. The Black Mountains, in central Bhutan, form a watershed between two major river systems, the Mo Chhu and the Drangme Chhu (chhu means river). Peaks in the Black Mountains range between 1,500 meters and 2,700 meters above sea level, and the fast-flowing rivers have carved out spectacular gorges in the lower mountain areas. The woodlands of the central region provide most of Bhutan's valuable forest production. Eastern Bhutan is divided by another southward spur, the Donga Range. Western Bhutan has fertile, cultivated valleys and terraced river basins.
In the south, the Southern Hills, or Siwalik Hills, the foothills of the Himalayas, are covered with dense deciduous forest, alluvial lowland river valleys, and mountains that reach to around 1,500 meters above sea level. The foothills descend into the subtropical Duars Plain. Most of the Duars Plain proper is located in India, and ten to fifteen kilometers penetrate inside Bhutan. The Bhutan Duars has two parts. The northern Duars, which abuts the Himalayan foothills, has rugged, slopping terrain and dry porous soil with dense vegetation and abundant wildlife. The southern Duars has moderately fertile soil, heavy savanna grass, dense mixed jungle, and freshwater springs. Taken as a whole, the Duars provides the greatest amount of fertile flatlands in Bhutan. Rice and other crops are grown on the plains and mountainsides up to 1,200 meters. Bhutan's most important commercial centers-- Phuntsholing, Geylegphug, and Samdrup Jongkhar--are located in the Duars, reflecting the meaning of the name, which is derived from the Hindi dwar and means gateway. Rhinoceros, tigers, leopards, elephants, and other wildlife inhabit the region.
Climate:Bhutan's climate is as varied as its altitudes and, like most of Asia, is affected by monsoons. Western Bhutan is particularly affected by monsoons that bring between 60 and 90 percent of the region's rainfall. The climate is humid and subtropical in the southern plains and foothills, temperate in the inner Himalayan valleys of the southern and central regions, and cold in the north, with year-round snow on the main Himalayan summits.
Temperatures vary according to elevation. Temperatures in Thimphu, located at 2,200 meters above sea level in west-central Bhutan, range from approximately 15° C to 26° C during the monsoon season of June through September but drop to between about -4° C and 16° C in January (see table 22, Appendix). Most of the central portion of the country experiences a cool, temperate climate yearround . In the south, a hot, humid climate helps maintain a fairly even temperature range of between 15° C and 30° C year-round, although temperatures sometimes reach 40° C in the valleys during the summer.
Annual precipitation ranges widely in various parts of the country. In the severe climate of the north, there is only about forty millimeters of annual precipitation--primarily snow. In the temperate central regions, a yearly average of around 1,000 millimeters is more common, and 7,800 millimeters per year has been registered at some locations in the humid, subtropical south, ensuring the thick tropical forest, or savanna. Thimphu experiences dry winter months (December through February) and almost no precipitation until March, when rainfall averages 20 millimeters a month and increases steadily thereafter to a high of 220 millimeters in August for a total annual rainfall of nearly 650 millimeters.