The Machar Marshes are a large area of wetlands in the state of Upper Nile, 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...

. Estimates of their size vary. A 1950 study put the area of swamp at 6,500 sq. km. A 1980 study put the area of permanent swamp at 8,700 sq. km., 60% of which was grass and forest.

The marshes are fed by waters from the Khor Machar (a distributary of the 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...

), the Yabus River

Yabus River

The Yabus River rises in the far west of Ethiopia, in Asosa Zone, flows west into Sudan past the town of Yabus, then enters South Sudan. At the town of Boing it turns south west and enters the Machar Marshes, where it loses its identity....

 and the Daga River

Daga River (South Sudan)

The Daga River is a river in South Sudan. It rises in the mountains of the Mirab Welega Zone in Ethiopia, just east of the South Sudan - Ethiopia border, where it is known as the Deqe Sonka Shet. It flows west past the town of Daga Post and enters the Machar Marshes, where it loses its identity....

. At times of high water they are also fed by spill from the 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...

. The marshes are drained by the Adar River

Adar River

The Adar River , known to the Dinka as the Yal, is a tributary of the White Nile in the state of Upper Nile, South Sudan. It flows north west from the Machar Marshes and enters the White Nile just upstream of the town of Melut....

, a tributary of 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...

.