Water scarcity causes food insecurity and will hamper the energy supply, which are the two main factors of social stability. Water in the countries of the Mediterranean basin is rare and spreads irregularly in time and space. It is therefore under growing pressure, linked to population growth, development, and increased irrigation demand. Unconventional water resource mobilization and use will be essential to meet growing needs. The objective of the present study is to identify potential sites to reuse treated wastewater (TWW) for irrigation in the El Fahs region after using an innovative water treatment technology. An analytic hierarchy process (AHP) coupled with a geographic information system (GIS) is used as a decision support tool. We used a relatively simple pairwise comparison method in analytical prioritization. 12 constraints and 5 factors were determined for the selection of sites. The combination of all constraints by the intersection operator resulted in a Boolean map in which the areas were coded; we assumed 0 to be unsuitable for irrigation and we coded the rest as 1. The factors, normalized by fuzzy logic and weighted according to the prioritization process, were used to identify favorable sites. Finally, a sensitivity analysis is applied to check the reliability of the results, based on several potential scenarios, using a weighted linear combination (WLC). The results show that the total suitable area covers 4808.44 ha, which corresponds to 53% of the total study area. The sensitivity analysis confirms the selection of sites suitable for irrigation using fuzzy-AHP based on GIS.