Abstract
Mapping groundwater recharge zones (GWRZs) is essential for planning artificial recharge programs to mitigate groundwater decline and saltwater intrusion into coastal aquifers. We applied two multi-criteria decision-making approaches, namely the analytical hierarchy process (AHP) and the multi-influencing factors (MIF), to map GWRZs in the Korba aquifer in northeastern Tunisia. GWRZ results from the AHP indicate that the majority (69%) of the area can be classified as very good and good for groundwater recharge. The MIF results suggest larger (80.7%) very good and good GWRZs. The GWRZ maps improve groundwater balance calculations by providing estimates of recharge-precipitation ratios to quantify percolation. Lithology, land use/cover and slope were the most sensitive parameters followed by geomorphology, lineament density, rainfall, drainage density and soil type. The AHP approach produced relatively more accurate results than the MIF technique based on correlation of the obtained GWRZs with groundwater well discharge data from 20 wells across the study area. The accuracy of the approaches ultimately depends on the classification criteria, mean rating score and weights assigned to the thematic layers. Nonetheless, the GWRZ maps suggest that there is ample opportunity to implement aquifer recharge programs to reduce groundwater stress in the Korba aquifer.
Highlights
Excessive groundwater pumping is a global problem, which affects arid/semi-arid regions where surface water is scarce [1,2,3,4]
We identified suitable sites lineament for groundwater recharge through a knowledge-based analysis ofcover, of eight factors, namely rainfall, density, slope, drainage density, land use/land eight factors, namely rainfall, lineament density, slope, drainage density, land use/land cover, for lithology, geomorphology and soil type layers [41,42,43,44]
Lithology (LI): LI governs the porosity and permeability of aquifer rocks [18], which in turn influences the occurrence and distribution of groundwater recharge through physio-mechanical properties that control the ability of the aquifer materials to transmit water and the rate at which groundwater flows [27]
Summary
Excessive groundwater pumping is a global problem, which affects arid/semi-arid regions where surface water is scarce [1,2,3,4]. The Korba coastal area in northeastern Tunisia is faced with groundwater over-pumping, causing seawater intrusion and degradation of groundwater quality. In this region, groundwater is the primary water source for domestic and agricultural purposes for about 90% of the rural population [2,5,6,7,8,9] and. Groundwater levels have continued to decline and seawater intrusion is steadily progressing in most of the coastal areas with the expansion of agricultural lands despite efforts to implement water conservation policies, build recharge dams, transfer water from the north, stop drilling new wells and encourage the re-use of treated wastewater [4,8]. Most of the deficit is observed in the central part of the Korba area where 53% of croplands are irrigated [2,5,6,7,11]
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