Erhai, ancient name Kunming Pond, Er River, Ye Yu Ze, etc.. Because of its resemblance to a human ear, it is named Erhai, located in Dali City, Dali Bai Autonomous Prefecture, Yunnan Province. The general area of the lake is about 246 square kilometers (one said 251 square kilometers), the water storage capacity of about 2.95 billion cubic meters, is narrow and long, north from the southern end of the Eryuan County, south of the Dali City Shimonoseki, north and south of 40 kilometers, is the second largest lake in Yunnan after Dianchi, China's freshwater lakes in the 7th place. Erhai was formed at the end of the Ice Age, and its cause is mainly subsidence erosion, is a plateau tectonic fracture lake, elevation 1972 meters. The Erhai has seven main functions: water supply, irrigation, power generation, climate control, fisheries, shipping, and tourism. The Erhai is surrounded by the Cang Mountains to the west and the Yuchen Mountains to the east, and has a beautiful spatial environment. In 1981 by the Yunnan Provincial People's Government approved the establishment of Cang Shan Erhai Nature Reserve, promoted to national level in 1994, the main object of protection for the plateau freshwater lakes and aquatic flora and fauna, the natural landscape of the transition zone of flora and fauna from the north to the south, glacial relics, an area of 79,700 hectares.