Nubian Sandstone Aquifer System

The Nubian Sandstone Aquifer System is said to be the world's largest known fossil water aquifer system. It is underground the Eastern end of the Sahara Desert. It spans the boundaries of four countries in north-eastern Africa north-western Sudan, north-eastern Chad, south-eastern Libya, and most of Egypt.
The Great Man-made River Project (GMMR) in Libya makes use of the system. It takes water from this aquifer, about 2.4 km3 of fresh water for drinking and agriculture each year. This system is mainly used to supply water to the Kufra oasis.