GIS-based multi-criteria analysis for potential wastewater aquifer recharge sites

GIS and expert knowledge are used as a decision support system to determine adequate potential soil aquifer treatment (SAT) sites for groundwater recharge of Hammamet-Nabeul aquifer located in 'Cap Bon' peninsula in North East of Tunisia. These sites are identified using a single-objective multi-criteria analysis. All criteria selected are assumed to be constraints. The acceptable range of each criterion is determined by a critical threshold value, corresponding to standards or normative statements. Based on these acceptable ranges, all criteria are expressed in a Boolean map: excluded areas are coded 0 and those open for consideration are coded 1. Multi-criteria evaluation were performed combining all Boolean maps by means of intersect operator in order to select sites meeting all the criteria. The selection of criteria and acceptable ranges is based on national expert consulting and international published guidelines and technical documents. The resulting map of this GIS-based multi-criteria analysis shows extended potential sites for SAT, exceeding 1000 ha, which indicates a possible use of treated wastewater for groundwater recharge; 8 ha could be supplied by Hammamet Sud plant, 764 ha by SE3 and 347 ha by SE4. 109 ha of these areas could be supplied by both SE3 and SE4. These potential sites are mostly located at rivers banks, around Grand-Nabeul urban area and in some agricultural domains and coastal dunes.