Hydrogeological characterization and seawater intrusion inference in the coastal aquifer, using groundwater chemistry and remote sensing data.

In coastal lands groundwater is a vital water resource for supporting ecosystems. However, seawater intrusion is a dramatic global environmental problem threatening sustainable development in these lands. Thus, the coastal aquifers are vulnerable to seawater rise and increased groundwater salinity causing a set of nested groundwater management problems. Therefore, identifying the seawater front's dynamic progression and delineating the aquifer zones of optimized exploitation have significant importance in adapting to the negative effects of saltwater intrusion and ensuring sustainable development. In the present research, the approach involves an integration of remote sensing data, groundwater hydrochemical data, aquifer hydraulic parameters and subsurface well logs to clarify the hydrogeological factors that motivate the saltwater intrusion, and the geochemical evolution of groundwater that determine the seawater-freshwater limit interface in the Lower Miocene Moghra coastal aquifer, northwestern desert of Egypt. The research findings reported that: (1) The Moghra aquifer is characterized by a low to moderate relief and mild topography range from 0 to 90 m with low drainage density (>2) and high lineament density of west and northwards throws in the middle zone, regulating the aquifer transmissivity values to increase in this zone (4000-6000 m(2)/day). (2) NE-SW, N-S and NW-SE subsurface faults enhance the hydraulic connection and recharge from the underlying aquifers. (3) The Normalized Difference Salinity Index shows a gradual increase with time from the index value of 0.2 in 1984 reaching the maximum value of unity in 2021 assuring the progression of saltwater intrusion (4) The hydrochemical investigation revealed significant evidence of saltwater infringing, and fresh to the brackish water of TDS 1000-3000 mg/l at the middle zone of the aquifer due to mixing with the water of the underlying aquifers (5) hydrochemical priority map for five quality zones to assess groundwater continuity and address sea level rise's impact on sustainable development projects.