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Environment
Most of the population of Tibet lives in the southern valleys, including those around Lhasa.[42] The higher regions are used by nomadic drokpa who tend herds of yaks, sheep and goats on the steppe grasslands of the hills and high valleys.[42][31] In the lower parts it is possible to cultivate products that include barley, wheat, black peas, beans, mustard, hemp, potatoes, cabbage, cauliflower, onions, garlic, celery and tomatoes. The traditional staple food is barley flour called tsampa, often combined with buttered tea and made into a paste.[42]A visitor described the valley around Lhasa in 1889 as follows,
The plain over which we are riding is a wonderfully fruitful one. It is skirted on the south by the Kyi[d] river, and is watered, moreover, by another smaller stream from the north, which flows into the Kyi ... some five miles west of Lhasa. All this land is carefully irrigated by means of dikes and cross-channels from both rivers. Fields of buckwheat, barley, pea, rape, and lindseed lie in orderly series everywhere. The meadows near the water display the richest emerald-green pasturage. Groves of poplar and willow, in shapely clumps, combine with the grassy stretches to give in places a parklike appearance to the scene. Several hamlets and villages, such as Cheri, Daru, and Shing Dongkhar, are dotted over these lands. A fertile plain truly for a besieging army![43]Bharal. Snow leopards are one of the main predators of this sheep.[44]The Lhasa region does not have abundant wildlife or great numbers of species, but the Lhasa valley does support wintering populations of hundreds of black-necked cranes.[45] Hutoushan Reservoir lies in Qangka Township, Lhünzhub County. The reservoir is bordered by large swamps and wet meadows, and has abundant plants and shellfish.[46] The reservoir, which lies in the Pengbo valley, is the largest in Tibet, with total storage of 12,000,000 cubic metres (420,000,000 cu ft).[15] Endangered black-necked cranes migrate to the middle and southern part of Tibet every winter, and may be seen on the reservoir and elsewhere in the Lhasa region.[47] Other wildlife includes bharal, pheasants, roe deer, Thorold's deer, Mongolian gazelle, Siberian ibex, otter, brown bear, snow leopard and duck.[33][48][49][39] Medicinal plants include fritillaries (fritillaria), stonecrop (rhodiola), Indian barberry (berberis aristata), Chinese caterpillar fungus (ophiocordyceps sinensis), codonopsis and Lingzhi mushroom (ganoderma).[33][48][49][39]The dams on the Lhasa river built as part of the Three Rivers Development Project are unlikely to affect the flow of the Brahmaputra in India.[50] However, the climate and soil are unsuitable for large-scale irrigation. Where grasslands have been converted into irrigated farms fed by dams the result may damage the environment.[51] Jama wetland in Maizhokunggar County is vulnerable to grazing and climate change.[52] Extensive mining in some mountainous regions have turned areas of what was green pasturage into a grey wasteland. The authorities are reported to have suppressed protests by the local people.[53] Military personnel have been involved in efforts to protect and improve the environment, including replanting programs.[54]A 2015 study reported that during the non-monsoon season the levels of arsenic in the Duilong River, at 205.6 μg/L were higher than the WHO guideline of 10 μg/L for drinking water.[55] The source of the pollution seems to be untreated water from the Yangbajain Geothermal Field power station. It can be detected 90 kilometres (56 mi) downstream from this site.[56]
Geography
Lhasa lies in south-central Tibet, to the north of the Himalayas. The prefecture-level city is 277 kilometres (172 mi) from east to west and 202 kilometres (126 mi) from north to south. It covers an area of 29,518 square kilometres (11,397 sq mi).[2] It is bordered by Nagqu Prefecture to the north, Nyingchi Prefecture to the east, Lhoka (Shannan) Prefecture to the south and Shigatse prefecture-level city to the west.[3] The prefecture-level city roughly corresponds to the basin of the Lhasa River, which is the center of Tibet politically, economically and culturally.[4] Chengguan District is also the center of Tibet in terms of transport, communications, education and religion, as well as being the most developed part of Tibet and a major tourist destination with sights such as the Potala Palace, Jokhang and Ramoche Temple.[5]Lhasa River basin[edit]Lhasa River to the south of LhasaLhasa prefecture-level city roughly corresponds to the basin of the Lhasa River, a major tributary of the Yarlung Tsangpo River. Exceptions are the north of Damxung County, which crosses the watershed of the Nyenchen Tanglha Mountains and includes part of the Namtso lake,[6][b] and Nyêmo County, which covers the basin of the Nimu Maqu River, a direct tributary of the Yarlung Tsangpo.[8] The river basin is separated from the Yarlung Tsangpo valley to the south by the Goikarla Rigyu range.[9] The largest tributary of the Lhasa River, the Reting Tsangpo, originates in the Chenthangula Mountains in Nagqu Prefecture at an elevation of about 5,500 metres (18,000 ft), and flows southwest into Lhasa past Reting Monastery.[10]The Lhasa River drains an area of 32,471 square kilometres (12,537 sq mi), and is the largest tributary of the middle section of the Yarlung Tsangpo. The average altitude of the basin is around 4,500 metres (14,800 ft). The basin has complex geology and is tectonically active. Earthquakes are common.[4] Annual runoff is 10,550,000,000 cubic metres (3.73×1011 cu ft). Water quality is good, with little discharge of sewage and minimal chemical pesticides and fertilizers.[11]The Lhasa River forms where three smaller rivers converge. These are the Phak Chu, the Phongdolha Chu which flows from Damxung County and the Reting Tsangpo, which rises beyond the Reting Monastery.[12] The highest tributary rises at around 5,290 metres (17,360 ft) on the southern slope of the Nyenchen Tanglha Mountains.[13] In its upper reaches the river flows southeast through a deep valley.[14] Lower down the river valley is flatter and changes its direction to the southwest, The river expands to a width of 150 to 200 metres (490 to 660 ft).[14] Major tributaries in the lower reaches include the Pengbo River and the Duilong River.[15] At its mouth the Lhasa Valley is about 3 miles (4.8 km) wide.[16]The bulk of the water is supplied by the summer monsoon rains, which fall from July to September. There are floods in the summer from July to September, with about 17% of the annual runoff flowing in September. In winter the river has low water, and sometimes freezes. Total flow is about 4 cubic kilometres (0.96 cu mi), with average flow about 125 cubic metres per second (4,400 cu ft/s).[14] The total hydropower potential of the river basin is 2,560,000 kW.[11] Zhikong Hydro Power Station in Maizhokunggar County delivers 100 MW.[17] The Pangduo Hydro Power Station in Lhünzhub County has total installed capacity of 160 MW.[18]
Demographics
The demographics of Lhasa prefecture-level city are difficult to define precisely due to the way in which administrative boundaries have been drawn, and the way in which statistics are collected. The population of Lhasa prefectural-level city is about 500,000, of whom about 80% are ethnic Tibetan and most of the others are ethnic Han Chinese. Approximately 250,000 people live in the city and in towns, most of them in or near Chengguan District, and the remainder live in rural areas.EthnicityTibetan woman with prayer wheel in Lhasa steetThe 2000 census give the following breakdown for the population of the prefecture-level city as a whole:
