For a long time water was considered, together with air, as a free good. It is only in recent decades that all elements necessary to human survival or to the quality of life have been given an economic value. Water is becoming the limiting factor not only for agriculture but also for industrial development. This is, particularly acute in areas where rainfall is inadequate or is unevenly distributed throughout the year or where capturing and utilising available water supplies is extremely costly. These phenomena are present in practically all Mediterranean countries. The economics of water, embracing all the possible sources and all the possible utilisations, has to become a major element of public policy in all Mediterranean countries.