The Bahr al-Arab arises from several tributaries that drain the Bongo Massif and Marrah Mountains in Darfur, close to Sudan's border with Chad and the Central African Republic. The Adda and Umbelasha flow east from the Bongo Massif to join the Ibrah (Wadi Ibra), which flows south from the Marrah Mountains. Formed from these tributaries, the Bahr al-Arab flows east along the border of the Darfur and Bahr el Ghazal regions, then through a southern part of the Kurdufan region.