Which underground water reserve supplies Libya’s Great Man-Made River project?

Libya’s Great Man-Made River project draws heavily on the Nubian Sandstone Aquifer System.

The project is a network of pipelines that transports fossil groundwater from deep wells in the Sahara toward Libya’s northern coastal cities and agricultural areas. Construction began in 1984, and the system became one of the world’s largest irrigation and water-supply projects.

The Nubian Sandstone Aquifer System extends beneath parts of Libya, Egypt, Sudan and Chad. Much of its water entered the rocks during wetter prehistoric periods and is therefore described as fossil groundwater. In the arid Sahara, modern rainfall is generally too limited to replenish the deepest reserves quickly.

The aquifer is not an unlimited underground lake. It consists of water-bearing geological formations, and extraction can lower pressure and reduce future availability. The project’s name refers to its engineered pipelines, not to a natural river flowing across the desert.