Омо
The Omo River forms through the confluence of the Gibe River, by far the largest total tributary of the Omo River, and the Wabe River, the largest left-bank tributary of the Omo at . Given their sizes, lengths and courses one might consider both the Omo and the Gibe rivers to be one and the same river but with different names. Consequently, the whole river basin is sometimes called the "Omo-Gibe River Basin". This river basin includes part of the western Oromia Region and the middle of the Southern Nations, Nationalities, and People's Region.