Mareb

The Mareb river is one of the longest rivers in Sudan. It is sometimes known as the Gash river and originates in central Eritrea. Its primary function is to define part of the Eritrean-Ethiopian border, from the point where the Mai Ambassa enters the river to the junction of the Balasa and the Mareb. The Mareb is dry for most of the year, but like the Takazze, it is prone to flash floods during the rainy season; only the left bank of the Mareb's upper course is Ethiopian territory. On the right bank, is the Obel River, and on the left bank, are the Sarana, Balasa, Mai Shawesh, and Engweya Rivers.

The Mareb was historically significant as the dividing line between two separately ruled regions in the area: the Bahr negash territory to the north of the river and the Tigray country to the south. The Bahr negash controlled territory as far north as the Red Sea coast and as far south as the Shire, with the capital in Debarwa, Eritrea, some 20 miles south of Asmara.

Length: 273 miles (shared with Ethiopia and Eritrea)