Geographical environment of Menglian Dai, Lahu and Wa Autonomous County

Menglian County is located in the southwest of Yunnan Province, with an east longitude of 99 9'-99 46' and a north latitude of 22 35'-22 32'. It is connected with Lancang County in the east, Ximeng County in the north, and Shan State Second Special Zone in Myanmar in the west and south. The length of the boundary line is 133.399 km, and the total area is 1893.42 km2. Menglian County is 645 kilometers away from Kunming, the provincial capital, and 230 kilometers away from Simao District, the resident of the municipal government. The geology of Menglian County is dominated by Permian basalt and Triassic rocks, which were alluvial by Quaternary rivers. Basalt formed in Permian is distributed in Banshun, Chahe and Xin Mang in Xin Mang Town. From Meng Ying in Jingxin Township to Menglianba, the upper reaches of Nanlei River Basin are all limestone. There are coarse-grained crystalline granites in Ma Meng Town, south of He 'e, north of Habuk Mountain and along Nanzhu, Nankang and Mi Nan. Le Lang, Menglian, Ma Meng, Meng 'a and other dams are all still water sedimentary basins where Quaternary rivers alluvial, among which Menglian Dam is the most typical.

Menglian county is located in the remnant vein of Nu Mountain, and the landform is mainly mountainous. Mountainous north and south; The east and west are low, and there are many valley basins. Great Black Mountain in the north, 2239 meters above sea level; Mount Habuk in the south is 2 196 meters above sea level; Menglianba in the east, 960 meters above sea level; Mengmaba in the west is 920 meters above sea level. The highest point in the territory is the peak of Anglang in the south, with an altitude of 2603 meters; The lowest point is at the intersection of Nanyong River and Nanka River in the west, with an altitude of 497 meters. The terrain is a compound of mountains, valleys and dams. There are some wide valley basins in mountainous areas, the larger ones are Menglian, Ma Meng and Meng 'a, followed by Le Lang, Jingxin, Mao Jing, Bai Meng, Xin Mang and Mangjie. The rivers in Menglian County belong to Lancang River and Nujiang River, with Daheishan-Habuke Mountain as the watershed, and the rivers in Menglian County are divided into Nanlei River and Nanka River.

Nanlei River originates in Laba Township, Lancang County, and joins the Mekong River in the lower reaches of Lancang River on the eastern border of Myanmar. It is 70 kilometers long in Menglian County. The main tributaries are Nanlang River, Nange River, Nanbai River, Nanya River, Nannian River, Nansui River, Nanji River and Yunyuan River, with a drainage area of 1.293 square kilometers.

Nanka River is located in the western border of Menglian County, and it is a border river between China and Myanmar. After entering the country, it flows from north to south through Yanfu, Gong Xin and Ma Meng, and flows to Myanmar at the foot of Lunwu Mountain, with a total length of 58 kilometers. The main tributaries are Grand Love River, Grand Outer River, Nanxin River, Nanmei River, Nanma River and Nanyong River.