Tibet, located in central Asia, is a autonomous region of the People's Republic of China. The Tibetan Plateau extends beyond the TAR into neighboring provinces and countries. Tibet is often called the "the roof of the world," comprising table-lands averaging over 4950 m above the sea with peaks at 6000 to 7500 m and includes Mount Everest. It is bounded on the North by and East by Xinjiang, Qinghai, and Sichuan, on the West by the Kashmir Region of India and on the South by Nepal, Bangladesh and Bhutan.
Physically Tibet may be divided into two parts, the lake region in the west and north-west, and the river region, which spreads out on three sides of the former on the east, south, and west.
The lake region extends from the Pangong t’so (t’so = lake) in Ladak, near the source of the Indus, to the sources of the Salween, the Mekong and the Yangtse. This region is called the Chang-t’ang (Byang sang) or 'Northern Plateau' by the people of Tibet. It is some 700 miles broad, and covers an area about equal to that of France. From its great distance from the ocean it is extremely arid, and possesses no river outlet. The mountain ranges are spread out, rounded, disconnected, separated by flat valleys relatively of little depth. The country is dotted over with large and small lakes, generally salt or alkaline, and intersected by streams, and the soil is boggy and covered with tussocks of grass, thus resembling the Siberian tundra. Salt and fresh-water lakes are intermingled. The lakes are generally without outlet, or have only a small effluent. The deposits consist of soda, potash, borax and common salt. The lake region is noted for a vast number of hot springs, which are widely distributed between the Himalayas and 34° N., but are most numerous to the west of Tengri Nor (north-west of Lhasa). So intense is the cold in Tibet that these springs are sometimes represented by columns of ice, the nearly boiling water having frozen in the act of ejection.
The river region comprises the upper courses of the Brahmaputra, the Salween, the Yangtsze, the Mekong, and the Yellow River. Amidst the mountains there are many narrow valleys. The northern portion of Tibet is an arid and wind-swept desert; but in the southern portion the valleys of Lhasa, Shigatse, Gyantse and the Brahmaputra are covered with good soil and groves of trees, well irrigated, and richly cultivated.
The valley of the Brahmaputra is the great arterial valley of southern Tibet. On the south it is bounded by the Himalayas, on the north by a mountain-system still more vast. The system at no point narrows to a single range; generally there are three or four across its breadth. As a whole the system forms the watershed between rivers flowing to the Indian Ocean — the Indus, Brahmaputra and Salween and its tributaries — and the streams flowing into the undrained salt lakes to the north.