Like the Red Nile, Wadi Howar (Yellow Nile) is fed by rainfall and is now an episodic Nile tributary.
Between 8000 BC and 1000 BC, it fed the Nile continuously with waters from the Ouaddaï highlands located in Chad. It was a vital settlement site between central Africa and the Nile Valley and was one of the major tributaries of the Nile from the Sahara area, which was then a grassland.
