The Bohai Sea is the second largest lake in Yunnan after Dianchi Lake, and the seventh in China's freshwater lake. It was formed at the end of the Ice Age, and its main cause was subsidence erosion. It belongs to the plateau tectonic faulted lake, at an altitude of 1972 meters. Bohai has seven main functions of water supply, agriculture and irrigation, power generation, climate adjustment, fisheries, shipping and tourism. The west of Bohai Sea is a bit of Cangshan horizontally lined like a screen, and the east is surrounded by Yu'an Mountain, and the space environment is beautiful. In 1981, the Cangshan and Bohai Nature Reserve was established with the approval of the Yunnan Provincial People's Government, and in 1994 it was promoted to the national level. The main protection objects are freshwater lakes and aquatic animals and plants, natural landscapes and glaciers in the transition zone of north and south flora and fauna. The Bohai Lake is mainly in Dali City, the north shore is connected to the southeast of Wuyuan County, Cangshan East and Yu'an Shanxi. The northern waters of Bohai are originally from Wuyuan County. On January 1, 2004, after the two towns of Shuanglang and Jiangwei were transferred into Dali City, all the waters belong to Dali City. Wuyuan County has become a bordering situation on the north shore. Along the shore of the lake area, there are Shuanglang and Jiangwei towns in the north, Xizhou, Wanqiao, Chengqi, Qiliqiao and other towns in the east, Xiaguan, Fengyi and other towns in the south, and Haidong and other towns in the west. The Wuyuan River at the spillway is located in Xiaguan, Dali City, at the southwest end.