Xigaze

　　Xigaze connects with three countries of Nepal, Bhutan and Sikkim in the south, Ngari in the west, Nagqu in the north and Lhasa and Shannan in the east. It occupies an area of 176,000 square kilometers, the latitude being between 82_E and 92_20_E and longitude between 27_ 23_N and 31_49_N. It is 800 kilometers from east to west and 220 kilometers from north to south, with a border of 1,354 kilometers.

Farmland in Gyangze

　　Historically, Xigaze was called _Tsang,_ which was an important administrative district of Tibet. During the reign of the Tubo Kingdom, the ruling class divided its central part into two divisions of _Wei_ and _Tsang,_ according to geographic conditions. _Tsang,_ with Xigaze as its center, was again divided into _Yeru_ (present-day Nyang Qu River area) and _Rulha_ (present-day upper reaches of the Yarlung Zangbo River). The area extends to Gamba La 　　Mountains in the east and Kangdese Mountains in the west. Because _Tsang_ is located mostly along the upper Yarlung Zangbo River, it was also called _Houtsang,_ a name still used today. In the 13th century, the Yuan Dynasty divided Tibet into thirteen 10,000-household units, and Xigaze had six _ namely, Qoimai, Xalhu, Jigmei, Lhadoiqain, Lhadoilho and Xangba. During the reign of the Pagmo Zhuba Kingdom, this organizational system in Tibet was abolished and replaced with 13 _zongs (counties)._ Xigaze had also set up counties like Rinbung, Xigaze, Bainang and Gyangze. Early the last century, the Tibetan government promoted Xigaze to the level of _gyizong (district),_ which had under its jurisdiction 16 counties and 30 or so independent _shikas (manor)._ After the Peaceful Liberation of Tibet in 1951, two branch Working Committees were established in Xigaze and Gyangze, respectively. In 1956, an administrative office at the district level was established. In 1959, the Prefectural Commissioner_s Office was set up in Xigaze and Gyangze, respectively. In 1964, the two offices merged into one and was named Xigaze Prefectural Commissioner_s Office, and renamed in 1978 as Xigaze Administrative Office.
Under the jurisdiction of Xigaze Administrative Office are the city of Xigaze at the county level, 17 counties of Gyangze, Bainang, Kangma, Yadong, Rinbung, Namling, Xitongmoin, Larze, Sagya, Kamba, Dinggye, Tingri, Nyalam, Gyilung, Ngamring, Saga, Zongba, and Zham port, the largest State trade port in Tibet. In the district are 218 townships (including 12 towns), 1,752 villagers_ committees and 28 urban residents_ committees.
　　Included in a population of 609,228 in 1997 were 554,704, or 91.1 percent farmers and herdsmen. Tibetans formed 97 percent of the population, and the other 3 percent was composed of Han Chinese and other 15 ethnic groups, such as Hui, Monggol, Tu, Manchu, Miao and Zhuang. There were 1,875 Xia_erba people. The population in Xigaze forms one-fourth of the population in the Tibet Autonomous Region, and the density of population is 3.3 people per square kilometer. Most of the people live in the Yarlung Zangbo River area, and the western pastoral area is sparsely inhabited.
　　Xigaze is located mostly between the middle of the Himalayas and the middle of the Kangdese-Nyainqentanglha ranges. The southern and northern terrains are high, while the South Tibet Plateau and the Yarlung Zangbo River constitute the low-lying middle area. Formed basically of high mountains, wide valleys, lakes and basins, this land has a varied topography with an average elevation of more than 4,000 meters.
　　The Himalayas, which stretch across southern Xigaze, is the youngest and highest mountain range in the world, with an average elevation of more than 6,000 meters. In that area, five peaks are more than 8,000 meters high _ namely, Mount Qomolangma (8,848.13 meters), Mount Lhoze (8,516 meters), Mount Kab (8,463 meters), Mount Qowowuyag (8,201 meters) and Mount Xixabangma (8,012 meters). Mount Qomolangma, located on the border between Xigaze and Nepel, is the world_s highest peak, the roof of the world. In addition are 14 peaks that stand more than 7,000 meters above sea level. Besides those mentioned above are high mountains such as Karru La, Gyaco La, Ma La, Zom La, Lhagyi and Mari La. All these mountains are spectacular natural views ideal for sightseeing, exploring and conducting scientific investigations.
　　The upper southern Tibetan basin along the Yarlung Zangbo and Nyang Qu rivers is the largest grain production area in Xigaze. It consists of two parts of the densely populated Larze-Rinbung valley and Gyangze-Xigaze plain. Other plains include the Penqoi River valley on the southern Tibet Plateau at the northern foot of the Himalayas and some sparsely scattered small river valleys. These plains sprawl on gentle slopes, with thick soil, temperate climate and plentiful water. With natural conditions suitable for growing crops, they form the major farming areas in Xigaze.
　　Over 100 rivers in Xigaze have an annual water volume of 35 billion cubic meters and a potential power of 13.6 million kilowatts. The Yarlung Zangbo River, the largest in Tibet, originates in the Gyima Yamzoin Glaciers in Zongba County. It flows from west to east, crossing 10 counties of Zongba, Sagya, Gyilung, Ngamring, Larze, Saga, Xigongmoin, Xigaze, Namling and Rinbung. It flows in Xigaze for about 700 kilometers, with a drainage area of over 100,000 square kilometers. The Nyang Qu River is another significant river in the area. It originates in Kangma County and snakes through Gyangze and Bainang counties before flowing into the Yarlung Zangbo River. Other rivers include the Penqoi, Dorxiong Zangbo, Zongqoi, Rong, Yerru, Kambu and Gyilong. Apart from a few inland rivers, the rest flow to the India Ocean system. Underground water, rain and melted ice and snow provide the sources of the rivers, and the water is cold and of good quality and low silt content. The rivers_ runoffs vary seasonally, but differ only slightly from year to year.
　　About 40 lakes of various sizes are located mostly in Zongba and Ngamring counties in the west. Four of them each covers an area of over 200 square kilometers _ namely Taro Lake (520 square kilometers), Peku Lake (300 square kilometers), Chabyer Caka Lake (235 square kilometers) and Xuru Lake (208 square kilometers). Since most are inland salt or saltwater lakes, which contain mineral erements like salt, boron, calcium and sodium, the lakes_ water is not suitable for drinking or irrigating fields. Glacial lakes and moraine lakes can also be found among the snow-capped peaks and in glacier areas in the Himalayas. Among them is a small lake near the Changchi Glaciers, which is 6,116 meters above sea level, thus winning itself the name of _Hanging Lake._
　　Three different regional climates exist in Xigaze. The area north of the Himalayas and south of the Kangdese-Nyianqentanglha has a warm, semi-dry monsoon highland climate; a small area north of the Kangdese-Nyianqentanglha ranges has a sub-cold, dry or semi-dry monsoon highland climate; and south of the Himalayas has a warm, semi-humid monsoon highland climate.
The general characteristics of the climate in Xigaze can be summarized in the following:
1) Thin air, low barometric pressure and thin oxygen.
2) Strong solar radiation, with 3,300 hours of sunlight a year and intense ultraviolet rays.
3) Relatively low temperatures with large daily difference but small annual difference _ the average yearly temperature in the western cold region being zero while in the eastern warm region being 6.5 degrees centigrade. The average daily temperature differential in the northwest is 16 degrees centigrade while in the east it is 14 degrees.
4) Clearly divided dry and monsoon seasons. From October to April is the dry and windy season with low temperature and less than 10 percent of the yearly rainfall; from May to September, it is rainy, warm and humid, with over 90 percent of the yearly rainfall. Many night storms and hail activity occupy about 70 to 80 percent of the rainfall during this season. Rainfall is irregular, with 200 to 430 mm in the east and less than 200 mm in the northwest. The eastern area rains fall earlier than the western area, and the yearly rainfall of the eastern part differs largely from year to year.
5) A frost-free period of more than 120 days, with snowfalls mainly in the southern part of Pagri in Yadong, Myalam and Tingri.
6) Yadong, Zham, Gyilung, Chengtang and Rongxa counties on the southern slopes of the Himalayas share a sub-tropical, alpine climate. It is warm year round with plenty of rain. The annual rainfall is around 1,000 mm and the average daily temperature in the warmest season is 18 to 22 degrees centigrade.