Geographical Survey of Langxian County in Lin Mang Area

Langxian County is located in the southwest of Linzhi City, with an east longitude of 92 28 ′ and a north latitude of 28 40 ′ ~ 29 29 ′. Located at the northern foot of the Himalayas, in the middle and lower reaches of the Yarlung Zangbo River, it borders Milin County in the east, Bayi District of Linzhi City and Gongbujiangda County in the north, Gacha County in Shannan region in the west and India in the south, with an area of 4,200 square kilometers.

Langxian county belongs to plateau hilly landform type. The terrain is high in the north and low in the south, mostly open valleys, slopes and mountains. The average elevation of the county is 3200 meters, and the average peak elevation is more than 5000 meters, most of which are covered by glaciers.

Langxian County belongs to the valley landform in southeastern Tibet, and the Yarlung Zangbo River crosses the county from west to east, which divides the county into two parts: the southern part belongs to the northern foot of the Himalayas, with the highest elevation of 6 157.9 meters, and the northern part belongs to the southern foot of Nyainqentanglha Mountain, with the highest elevation of 5572.0 meters. The two mountains form a huge ∨-shaped valley with the lowest elevation of 30543.

The mountains in the territory are undulating, and the surface develops into various landform types under the joint action of river cutting and geological structure. The landforms in the county are divided into alpine ice erosion-moraine landform, alpine flowing water cutting structure landform, river terrace accumulation landform and aeolian landform.

Langxian Gorge is located between Zhong Da Town and the west side of Dongga Town. It is along the Yarlung Zangbo River fault zone and belongs to a part of the Jiacha Gorge in Shannan. It is a narrow valley with a length of 56 kilometers, a cutting depth of less than 1 000 meters, a drop of about 1.50 meters, a valley bottom width of 80-200 meters, and a local area (such as the north side of the county) less than 50 meters, belonging to a medium cutting canyon. The west side of the canyon is steep, the slope is generally 30 ~ 50, and the water flow is generally slow.

Lang county belongs to the Qinghai-Tibet Plateau climate, belonging to a warm and semi-humid climate zone. Main climatic characteristics: no heat in summer, no cold in winter, rainy in summer and autumn, windy in spring and summer, complex and changeable vertical climate, frequent natural disasters and very fragile ecological environment. The annual average sunshine hours are 2000 ~ 2500 hours, the sunshine percentage is 70% ~ 80%, and the annual solar radiation is 700 MJ/m2. Langxian has less rainfall and uneven seasons. The average annual precipitation is about 350 ~ 600 mm, mostly concentrated in June ~ September, accounting for more than 90% of the annual precipitation. The annual evaporation is about 200 mm. The dry season lasts for 8 months and the rainy season lasts only 4 months. Annual average temperature 1 1.0℃, annual average maximum temperature 19. 1℃, annual average minimum temperature 5.3℃, annual average temperature range 13.8℃. The annual average frost-free period is 130 ~ 170 days.

Langxian county is rich in water resources, with a total length of 742,000 meters, per square meter 177.3 meters. There are 14 rivers and streams, and the Yarlung Zangbo River winds through the county seat. The tributary takes Yajiang as the skeleton, radiating all over Langxian, almost all over Langxian. The relatively large tributaries are Dengmu River, Laduo River, Jindong River and Gongzi Rong River, forming four ditches, so Langxian County can also be called "one river and four rivers (ditches)".

The lakes include Rado Tibetan Lake and Fire Wolf Snow Mountain Holy Lake. Among them, the Tibetan Lake is 3,700 meters above sea level and covers an area of 6.7 square kilometers. The majestic Langxueshan Holy Lake is 4200 meters above sea level and covers an area of 3.7 square meters.