TSAIDAM BASIN

Wade-Giles romanization Ch'ai-ta-mu P'en-ti, Pinyin Qaidam Pendi, northeastern section of the Plateau of Tibet, occupying the northern and western parts of Tsinghai province, China. The basin is bounded on the south by the towering Kunlun Mountains, with many peaks in the western part of more than 20,000 feet (6,000 m) above sea level, and in the north and east by the A-erh-chin and Nan mountain systems, across which the Tang-chin Pass is the only practicable pass into Kansu province. The pass opens into the eastern Tsaidam Basin through the area around Koko Nor (Blue Lake). The basin is considerably lower than other sections of the Plateau of Tibet, being at an average elevation of between 8,000 and 10,000 feet (2,400 and 3,000 m). The Tsaidam Basin is almost entirely an area of interior drainage, with rivers discharging either into Koko Nor or into one of the numerous salt lakes and saline swamps in the basin's central area. In the northwest of the basin is an area of true desert. Another area of true desert occurs in the subsidiary basin in the north, around the Su-kan Lake (a salt lake). The Charhan Salt Marsh in the centre of the basin is China's largest surface rock-salt bed, with an area of 618 square miles (1,600 square km) and solid salt deposits up to 50 feet (15 m) thick. The area has a climate marked by long and extremely cold winters, great temperature variations, and minimal rainfallthe total precipitation of the area is less than 4 inches (100 mm) a year. Outside the desert and salt-marsh areas in the centre of the basin, the land is rolling plain covered with poor grass, but the slopes of the surrounding mountains have areas of good grassland, particularly in the north, where the A-erh-chin and Nan mountains have some forested areas, especially near Koko Nor. Until recent times the Tsaidam area was sparsely peopled, and the population was for the most part composed of pastoralists noted for their horse breeding; the region is also renowned for its sheep. Since World War II, however, the mineral riches of the area have attracted attention. These include vast deposits of salt, potash, various borate minerals, and boron. In the 1950s extensive geologic surveys of the area revealed rich reserves of coal, oil, and asbestos. Oil fields are in operation, including several around Mang-ya. A large oil refinery has been constructed at Leng-hu, southeast of the Tang-chin Pass, and another has been built at Mang-ya. Very large iron deposits have also been found at Golmud, which has developed a chemical industry using local materials and which produces fertilizer on a considerable scale. In the late 1970s the railway from Lan-chou in Kansu to Hsi-ning in Tsinghai was extended to Golmud, and a network of highways had been constructed. The area has also been the scene of experiments in agriculture. With intensive irrigation, some of the marginal areas in the north and east are used to grow wheat.