Geospatial and AHP-multicriteria analyses to locate and rank suitable sites for groundwater recharge with reclaimed water

The reuse of reclaimed water in arid and semi-arid regions to recharge aquifers contribute to reduce pressure on conventional water. An appropriate site selection preceding the construction of the basins is required to insure the success of the process. The aim of this research is to develop a methodology to locate and rank suitable sites for groundwater recharge with reclaimed water based on a combination of geospatial and multicriteria analyses. Seven constraints were chosen to identify the suitable areas for aquifer recharge with reclaimed water. A vector spatial layer of each was obtained and the feasible areas were delineated by an intersection operator. To rank these areas three main criteria were identified having technical, economical and environmental aspects, from which twelve sub-criteria were derived. All of them were organized in a decision hierarchy structure and weighted using Saaty pair-wise comparison matrixes. A raster spatial layer of each sub-criterion was obtained and their values were standardized using fuzzy logic functions. A weighted linear combination was carried out to get the decisional index layer from which the suitable sites were ranked. Finally a sensitivity analysis was carried out in order to quantify the influence of the criteria weights on the resulting decision spatial layer. The study area selected to develop the methodology is the Nabeul–Hammamet shallow aquifer. The feasible area for aquifer recharge with reclaimed water is about 5160ha. This area exceeds by far the needed 39ha to absorb the total effluents of the SE3 and SE4 wastewater treatment plants present in the case study. The best 39ha are located in the north west of the city of Nabeul for SE3 and in the northern west and the south west of the city of Nabeul for SE4. For best management and cost reduction it is preferable to gather these sites in a unique area located in the north west of the city of Nabeul in an agricultural region and far from the urban zones.