Identification of groundwater potential recharge zones in a Tunisian anthropogenic coastal region: Insights from multi-criteria decision-making techniques

In coastal areas, increasing population and expanding urbanization are triggering remarkable pressure on groundwater (GW) resources, consequently posing a threat to their long-term sustainability. This is the case for the Chiba coastal region (northeast of Tunisia) where excessive extraction of GW has led to decreasing GW levels and an acceleration of seawater intrusion. Artificial recharge can serve as a prevention and control method to address these challenges and preserve the regional GW reserves. In this paper, favorable GW recharge zones (GWRZs) in the Chiba region are identified using the Analytical Hierarchy Process (AHP) and the Multi Influencing Factors (MIF) approaches; two widely acknowledged multi-criteria decision-making (MCDM) techniques. Within a Geographic Information System (GIS) environment, the field and remote sensing data are used to prepare, classify, and assign weightage to thematic layers of lithology, land use/land cover, slope, topography, lineament density, rainfall, drainage density, and soil texture. Furthermore, GWRZ maps were elaborated using overlay weighted sum method to the eight different layers. Using AHP, 18.6%, 72% and 9.4% of the study zone was classified into poor, moderate and good potential GWRZ. While using MIF, the classification of the study area into poor, moderate and good potential GWRZ was 27.3%, 56.5% and 16.2% respectively. The GWRZ maps were validated using the average GW level and field yield data of 32 wells distributed across the study area. They achieved accuracy rates of 78.12% and 87.5% using the AHP and MIF methods, respectively. The GW recharge estimated using AHP method yielded a mean value of 67.09 mm/year (15.25%), closely aligned with the 68.28 mm/year (15.51%) derived through the MIF technique. The findings from this study provide valuable insights for devising strategies aimed at ensuring the long-term sustainable management of GW resources underneath this environmentally sensitive coastal area.