Desalination plants are increasingly regarded as a tool to preserve natural water resources and therefore as a means to protect the environment. Furthermore desalination plants are performing a public service which (for social reasons) take precedence over any other kind of industrial activity. Nevertheless few specific studies have been carried out so far in order to establish the environmental impact of a desalination plant compared with other technologies. Few studies have also been carried out in order to compare the environmental impact of each desalination technology and to describe means to further develop the design in order to smooth further the environmental impact. The environmental impact of power and desalination plant to intrinsically related to the efficiency of the system. This paper aims at describing these specific means and providing a tool and a guideline for the design of new desalination plants.