river in central china. A tributary of the Yangtze River (Chang Jiang), with the largest drainage area of the Yangtze basin, it rises in the rugged western outliers of the Qin (Qin Mountains) (Tsinling) Mountains in southern Gansu province. It flows south and east into far western Shaanxi (Shensi) province, cuts through the Daba Mountains, and flows southward, in an extremely braided course, into the Sichuan Basin, joining the Yangtze at Chongqing (Chungking) after a course of about 740 miles (1,190 km). Its upper valley, roughly paralleled by roads and railroads, is the major communications artery between the Wei River basin of central Shaanxi and the cities of the Sichuan Basin. It is navigable by junks in its lower course.