Numerical Modeling of the Future Climate Change Impacts on the Ghis-Nekkor Aquifer Under RCP4.5 and RCP8.5 (Al Hoceima, North of Morocco)

The study area covers the Ghis-Nekkor plain on the Mediterranean coast located in the north of Morocco. This groundwater aquifer is a typical example of a coastal aquifer whose water resources are exposed to severe overexploitation combined with increasingly low water supplies. The Ghis-Nekkor aquifer is an area highly vulnerable to seawater intrusion (SWI), firstly, because of less natural recharge, mean sea level rise due to climate change combined to groundwater overexploitation. The Regional Climate Models (RCMs) indicate a decrease in precipitation (18%) and an increase of average temperature (0.5 °C) in the Ghis-Nekkor area by 2050 under the RCP4.5 scenarios. These changes would have a direct impact on groundwater recharge of the aquifer. The results of the predicted groundwater recharge show a reduction of the mean annual recharge of 14% for (2021–2050) following the RCP4.5 scenario. Moreover, predicted values of future groundwater recharge under the RCP8.5 scenario would decrease more and would reach 30% less for the period (2055–2084). In view of the limited fresh water resources and degradation of water quality by sea water intrusion, effective management of ground water resources in this aquifer is necessary and can be made by developing a groundwater flow model taking into account seawater intrusion. Indeed, the outputs of RCMs for precipitation and SLR were used to assess the impact of pumping and climate change on the Ghis-Nekkor aquifer under the RCP4.5 and RCP 8.5 scenarios (2020–2040). The results show that the N-W sector of the coastal area would be more vulnerable to SWI. By 2040, the length of inland encroachment would reach 1 km, with a significant salinity (25 g/l) and a significant drop in hydraulic head (−15 m) following the RCP4.5 scenario. The extreme case of groundwater recharge and SLR under the RCP8.5 scenario will cause more severe impacts. By 2040, the length of inland encroachment would be around 1.23 km in the N-W part, at a distance of 0.55 km from the nearest ONEE well field. The salinity would reach 33 g/l and the SWI volume would increase by 48% (1.78Mm3/year) compared to the results under the RCP4.5 scenario.