The buried waterway may have formed part of the proposed Tamanrasett River that is thought to have flowed across parts of Western Sahara in ancient times from sources in the southern Atlas mountains and Hoggar highlands in what is now Algeria. The French-led team behind the discovery believe the river carried water to the sea during the periodic humid spells that took hold in the region over the past 245,000 years. Water may last have coursed through the channels 5,000 years ago. The river would have helped people, plants and wildlife to thrive in what is now desert land, and would have carried nutrients crucial for marine organisms far into the sea. Were it still flowing today, the river system would rank 12th among the largest on Earth, the researchers write in the journal Nature Communications.