The Great Man-Made River is a network of pipes that supplies fresh water obtained from the Nubian Sandstone Aquifer System fossil aquifer across Libya. It is the world's largest irrigation project.

The project utilizes a pipeline system that pumps water from the Nubian Sandstone Aquifer System from down south in Libya to cities in the populous Libyan northern Mediterranean coast including Tripoli and Benghazi. 

The water covers a distance of up to 1,600 kilometers and provides 70% of all freshwater used in Libya. 

It is the largest underground network of pipes (2,820 kilometres (1,750 mi)) and aqueducts in the world. 

It consists of more than 1,300 wells, most more than 500 m deep, and supplies 6,500,000 m3 of fresh water per day to the cities of Tripoli, Benghazi, Sirte and elsewhere. 

According to en.wikipedia