The "Great Man-Made River" is a major irrigation and water supply project that appears to defy both logic and geography. Water is pumped from an aquifer deep in the Sahara Desert and moved by four 4-meter pipelines to the Libyan coast. Million Libyans in the north were jubilant when the taps were finally turned on in 1996 because most had suffered from declining supplies and increasing salinity of local water from coastal aquifers. The project has been an engineering success, albeit with certain problems of corrosion in the pipes due to inadequate cathodic protection.

The economic test of the project is the cost of that water supply as compared with the alternatives available to Libya. There are only two alternatives: desalination or, in theory, the importation of water from Turkey by tanker ships. Water desalination in Libya is expensive. Available gas in Libya can be sold profitably to Europe, in contrast to the situation in Saudi Arabia or Abu Dhabi where high‑value markets for their abundant gas do not exist. The cost of capital in Libya is also rather high because it has no surplus oil revenues to invest.

Thus the costs of lifting and shipping water from the southern Sahara are about one-half of the costs of desalinating the same volume of water. This would be the case even if all possible joint economies were exploited in the co-production of power and water (co-generation). The project provides a compelling economical source of municipal and industrial water. The distribution of water for agriculture, however, is at best marginal, just as is the case for much of irrigated agriculture in Jordan, Israel, and Saudi Arabia.