The Liao River () is the principal river in southern Northeast China, and one of the seven main river systems in China. Its name derived from the Liao region, a historical name for southern Manchuria, from which the Liaoning province, Liaodong Peninsula and Liao dynasty also all have derived their names. The river is also popularly known as the "mother river" in Northeast China. Coursing long, the Liao River system drains a catchment basin of over , but its mean discharge is quite small at only about , about one-twentieth that of the Pearl River. The Liao River has an exceedingly high sediment load because many parts of it flow through powdery loess. The Liao River is also an important geographical landmark, as it divides the modern Liaoning province into two broad regions — Liaodong ("east of Liao River") and Liaoxi ("west of Liao River"). Course The Liao River is formed from the confluence of its two main tributaries, the Xiliao River from the west, and Dongliao River from the east. The western tributary resides entirely in Inner Mongolia, and is formed by the confluence of the Xar Moron River and the Laoha River at approximately 43° 25' N, 120° 45' E, before being reinforced by another tributary called the Xinkai River at its lower section. The eastern tributary arises in western Jilin Province, and goes through an S-shaped course before meeting its counterpart near the junction region of Liaoning, Jilin and Inner Mongolia, approximately 42° 59' N, 123° 33' E. The resultant river, the Liao River proper, then enters Liaoning Province and courses southwards through the Northeast China Plain, receiving numerous tributaries along the way. It makes a westward turn near Pingdingbao Town, Tieling County, and after receiving more tributaries, earns an infrequently used nickname Juliu River (巨流河, "giant stream river"). The Liao River will then course southwest until it reaches near the Liujianfang Hydrological Station (六间房水文站) at Tai'an County, and historically bifurcates into two distributaries, forming the Liao River Delta (辽河三角洲). The western distributary of the delta, originally smaller, was called the Shuangtaizi River (双台子河) until 2011, receives the tributary Raoyang River at Panjin's Panshan County before draining into the Liaodong Bay of the Bohai Sea west of Dawa County. The eastern distributary, originally the larger and the main body of lower Liao River, was called the Wailiao River (外辽河, "Outer Liao River"). The Wailiao River travelled southwards