The Yellow River is the second-longest river in China and the sixth-longest river system on Earth, with an estimated length of 5,464 km (3,395 mi) and a watershed of 795,000 km2 (307,000 sq mi). Beginning in the Bayan Har Mountains, the river flows generally eastwards before entering the 1,500 km (930 mi) long Ordos Loop, which runs northeast at Gansu through the Ordos Plateau and turns east in Inner Mongolia. The river then turns sharply southwards to form the border between Shanxi and Shaanxi, turns eastwards at its confluence with the Wei River, and flows across the North China Plain before emptying into the Bohai Sea. The river is named for the yellow color of its water, which comes from the large amount of sediment discharged into the water as the river flows through the Loess Plateau.