This paper presents the economic analysis of the Ebro River transfer (a total amount of 1.050 hm(3)/y) presented for the Spanish Government in his project for the National Hydrologic Plan and its alternative: drinking water obtained from desalination plants. In this paper is proved that the cost of the desalted water is similar to the transferred one, by using conventional reverse osmosis (RO) methods or hybrid methods combining thermal and membrane desalination processes. The sensitivity analysis of the desalting alternative is mainly restricted to the plant size and the energy prices (natural gas or electricity). The new concepts of the global cycle of non-conventional water resources (desalt, use and recycle) is also introduced in order to decrease the water cost for urban supply.