42°17′N 100°37′E / 42.283°N 100.617°E
The Juyan Lake (Chinese: 居延海; Wade–Giles: Chüyen Hai; Mongolian: Gashuun Nuur (shown on Chinese maps as 嘎顺淖尔 Gāshùn nào'ěr or 嘎顺诺尔, Gāshùn nuò'ěr) for western lake, Sogo Nuur for eastern lake) is a former lake in the Gobi desert. It is located in the western part of Inner Mongolia, in Ejin Banner of the Alxa League, near the border with Mongolia. Gashuun Nuur had an area of 267 km2 (103 sq mi) in 1958, of 213 km2 (82 sq mi) in 1960, and dried up in 1961. The eastern lake reappeared in 2005. As of August 2012[update], the area of the lake is 38 km2 (15 sq mi).[1]
The Juyan Lake basin is a rare wetland located in a desert. It covers an area of about 10,000 square kilometres (3,900 sq mi). The Juyan lake is one of three former terminal lakes located at the outer edges of the Heihe River ('Black River') catchment which formed a large inland delta between the Qilian and the Gobi Altay. The Heihe River is also known as the Ruo Shui (Chinese: 弱水; lit. 'weak river'), also Etsin Gol or Ruo He or Ejin River.
The basin's boundary is formed by the Mazong Shan mountains to the west, the Heli Shan and Longshou Shan mountains to the south, the Helan Mountains and Lang Shan ranges to the east and the Gobi Altay range to the north.