Southwest. Lu 'an, also known as Gaocheng and Wanxi, is a prefecture-level city under the jurisdiction of Anhui Province, located in the west of Anhui Province. Pi River, also known as Laobaisha River, is located in the southwest. It originates from Yuexi County and the northern foot of Dabie Mountain in Jinzhai County, and runs from Lianghekou to Hengpaitou, and the main canal of Laosha River runs from Hengpaitou to Luoguan Gate. The whole line is a drinking water source protection area above Grade II.