The Sobat River is a river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 in South Sudan

South Sudan

South Sudan , officially the Republic of South Sudan, is a landlocked country located in the Sahel region of northeastern Africa. It is also part of the North Africa UN sub-region. Its current capital is Juba, which is also its largest city; the capital city is planned to be moved to the more...

, Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

. The most southerly of the great eastern tributaries

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the Nile

Nile

The Nile is a major north-flowing river in North Africa, generally regarded as the longest river in the world. It is long. It runs through the ten countries of Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia, Uganda and Egypt.The Nile has two major...

, the Sobat enters the White Nile

White Nile

The White Nile is a river of Africa, one of the two main tributaries of the Nile from Egypt, the other being the Blue Nile. In the strict meaning, "White Nile" refers to the river formed at Lake No at the confluence of the Bahr al Jabal and Bahr el Ghazal rivers...

 at Doleib Hill, near the city of Malakal

Malakal

-Location:The city of Malakal is located in Malakal County, Upper Nile State, in the northeast of South Sudan, close to the International borders with the Republic of Sudan and with Ethiopia...

 in the Upper Nile state of South Sudan. The Sobat River is formed by the confluence of the west-flowing Baro River

Baro River

The Baro River is a river in southwestern Ethiopia, which defines part of Ethiopia's border with South Sudan. From its source in the Ethiopian Highlands it flows west for to join the Pibor River...

 and the north-flowing Pibor River

Pibor River

The Pibor River is a river in eastern South Sudan, which defines part of South Sudan's border with Ethiopia. From its source near Pibor Post it flows north for about , joining the Baro River to form the Sobat River, which is a tributary of the White Nile.The Pibor and its tributaries drain a...

, on the border with Ethiopia

Ethiopia

Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...

.

When in flood the Sobat River produces an enormous discharge carrying a white sediment, which gives the White Nile its name.

The Sobat and its tributaries drain a watershed

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

  approximately 225000 km² (86,873 sq mi) in size. The river's mean annual discharge

Discharge (hydrology)

In hydrology, discharge is the volume rate of water flow, including any suspended solids , dissolved chemical species and/or biologic material , which is transported through a given cross-sectional area...

is 412 m³/s (14,550 ft³/s).