KOKO NOR

Chinese Ch'ing Hai, or Tsing Hai, Pinyin Qinghai, English Blue Lake lake, Tsinghai Province, China. It is the largest drainless mountain lake of Central Asia. It is situated at an elevation of 10,515 ft (3,205 m) in the Nan Shan (Nan Mountain) system of China in a depression at approximately 37 N, 100 E. Mongolians occupy the northern shores and Tibetans occupy the southern shores. There are some sizable settlements (Ch'iang-hsi-k'ou, Ta-la-ma-ho) lying on the Hsi-ning to Lhasa road, close to the southern shore of the lake. On the northern shore lies the small settlement of Kang-ch'a. The length of the lake approaches 65 mi (105 km), the width 40 mi; the surface of the lake is approximately 2,300 sq mi (about 6,000 sq km) in area in years when the water level is high, and about 1,600 sq mi (4,200 sq km) in area when the water level is low. The greatest known depth is 123 feet. The water is azure in colour, the name deriving from the Mongolian term for sky blue. The Koko Nor depression originated between the Pliocene and the Pleistocene epochs (some 2.5 million years ago). The lake that formed in the depression originally drained into the Ma-ch'u Ho, but the rise of the basin's mountainous frame made this impossible. Melting waters from ancient glaciers thus accumulated and formed a big, deep lake in the late Pleistocene (at least 10,000 years ago). At this time the ancient lake was nearly one-third larger than its present size, and its depth extended to almost 160 ft. The subsequent exhaustion of the glaciers brought about a reduction in the level of the Koko Nor to its present position. The depression in which the lake is set is a plain more than 10,500 ft high. A rolling, hilly relief, with many low mountains, prevails in the north. In the south the depression is bordered by the Nan Koko Nor Shan (South Koko Nor Mountains), which form a narrow chain connecting with distinct peaks. These are continually snowcapped and go to the eastern edge of the lake. Further to the east the ridge drops sharply, becoming flat and opening out. The depression is covered with mainly red and gray sandstone and light-gray and claylike limestones. Traces of human activity are present in mountain loesses. The shores of the Koko Nor open out gently; the delta of the Pu-k'o Ho (Pu-k'o River) empties into the western part of the lake. Along the shores woods spread in terraces, the highest of which extends up over the lake to a height of 160 ft. On the eastern shore there are many small, isolated lakes and a rising, wooded shore area. Numerous sandy islands dot the lake; the largest has a length of 5,410 feet and a width of more than 1,000 feet. Bottom deposits are formed mainly by siltsblack, yellow, and pale yellow. In places sand can be found, but close to the shore there are pebbles. The mineral content of the water changes greatly from year to year, but sodium chloride is always present. The water is brackish and unsuitable for drinking. Twenty-three rivers and streams empty into the Koko Nor, the biggest being the Pu-k'o Ho. They flow fastest in summer, raising the lake level. The Koko Nor basin is distinguished by a comparatively dry climate. During the winter, snowstorms rage through the first half of March. The amount of snow that settles, however, is not great. Most precipitation (more than 70 percent) occurs in July and August, partly by thunderstorm, partly by cloudburst. On the southwest shore of the lake and on the slopes of the Nan Koko Nor Shan there is an annual precipitation of 10 to 12 in. (250 to 300 mm); on the northern shore 14 to 16 in. fall annually, and there is an annual precipitation of up to 20 in. in the mountains to the north of the depression. During the summer, water in the lake warms to 6468 F (1820 C). From November to March the lake freezes over, the ice becoming as much as two feet thick. Adjacent to the lake are luxuriant multigrain steppe grasses, providing one of the best grazing areas in the Nan Shan. The principal vegetation is of wormwood (absinthe) and derris. Nettles, hollyhocks, and asters are common, and numerous other plants are found. In the mountains there are fir forests. Fish are found in the lake, mainly of the carp family. There are few large mammals in the neighbouring area because the territory is populated. The kulankiang (wild ass) and the Przhevalsky horse, however, are found there. The oaran-kukuyaman (blue sheep) live in the mountains, as do wolves. The waterfront and the adjacent slopes are inhabited by a large variety of birds, including skylarks, grouse, sandpipers, cormorants, falcons, eagles, gray geese, and a few types of duck and gull. The chief occupation of the local population is nomadic cattle raising and tending of sheep, horses, and camels.