The problem of the water supply for the town of Constantine is very important, since it must include the domestic, commercial, industrial needs etc.... In this point of view, we were interested at the current evaluation of water consumption, also with the prevision of the demand for water because it is an essential factor of planning and development. This study has two principal objectives represented in one part, by the development of a total method known as "use of scenarios of evolution" by considering the most significant variables and on the second part, by the prevision of the demand for water for the year 2020.