river system the main course of which is a tributary of the Yangtze River (Chang Jiang) in south-central China. Rising near Weining in the hills of western Guizhou (Kweichow) province close to the border with Yunnan province, the main course flows east through narrow gorges between steep cliffs. It turns north at Sinan, enters Chongqing (Chungking) municipality, and flows into the Yangtze at Fuling. The upstream portions of the Wu River are called, successively, the Yachi and Sancha rivers. From its headwaters to Fuling, the river has a total length of some 700 miles (1,100 km). The Wu River system has 15 major tributaries, including the Liuchong, Maotiao, Qingshui, Xiang, Hongdu, Furong, and Tangyan rivers. Dams and hydroelectric power stations have been built along most of these rivers. The largest project, the Wujiangdu Hydroelectric Power Station near the town of Wujiang, north of Guiyang, was completed in 1983; it was built in conjunction with a dam 535 feet (163 metres) high. The system's drainage basin of 31,000 square miles (80,000 square km), including most of Guizhou, is a region of rugged terrain with an ethnically diverse population. Until the mid-20th century the river system was of little use for reducing the region's isolation, as submerged rocks and rapids prevented navigation for all but a few short stretches. Since the 1950s, however, blasting and dredging have opened more than 300 miles (480 km) of the Wu River and its upstream sections to motorized boats.