Nubian Sandstone Aquifer System

The Nubian Sandstone Aquifer System is a transboundary groundwater system beneath Chad, Egypt, Libya, and Sudan. It stores mostly fossil water in sandstone formations and is among the world’s largest known aquifer systems.

Nubian Sandstone: A thick sequence of sedimentary rocks, chiefly sandstone, underlying parts of northeastern Africa. These permeable formations hold and transmit the system’s groundwater.
Great Man-Made River: A Libyan network of pipelines that transports groundwater from southern aquifers to coastal cities. It is the system’s largest and most visible water-transfer project.
Chad: A landlocked country in north-central Africa. The aquifer extends into Chad, one of its four riparian states.
Cretaceous: A geological period lasting from about 145 million to 66 million years ago. Much of the sandstone sequence hosting the aquifer was deposited during the Cretaceous.
Transboundary aquifer: An aquifer that extends across the territory of two or more countries. The system is a major example of groundwater crossing national borders.
Fossil water: Groundwater that entered an aquifer under past climatic conditions and is renewed very slowly today. Much of the system’s water accumulated during wetter periods and is effectively nonrenewable on human timescales.
Al Kufrah: A southeastern Libyan oasis and agricultural region supplied in part by groundwater from the Nubian system. Its irrigated farming illustrates how stored groundwater supports desert agriculture.
Egypt: A country in northeastern Africa whose population and agriculture depend heavily on the Nile and groundwater. Egypt overlies part of the aquifer and draws groundwater from it.
Paleozoic: A geological era lasting from about 541 million to 252 million years ago. Older rocks in the region’s sedimentary succession also contribute to the aquifer system.
Internationally Shared Aquifer Resources Management: A UNESCO-led initiative supporting cooperation and assessment for aquifers shared by countries. Its regional work has supported joint study of the Nubian system.

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