Seawater intrusion (SWI) is one of the most challenging and widespread environmental problems that threaten the quality and sustainability of fresh groundwater resources in coastal aquifers. The excessive pumping of groundwater, associated with the lack of natural recharge, has exacerbated the SWI problem in arid and semi-arid regions. Therefore, appropriate management strategies should be implemented in coastal aquifers to control the impacts of SWI problems, considering acceptable limits of economic and environmental costs. The management of coastal aquifers involves the identification of an acceptable ultimate landward extent of the saline water body and the calculation of the amount of seaward discharge of freshwater that is necessary to keep the saline–freshwater interface in a seacoast position. This paper presents a comprehensive review of available hydraulic and physical management strategies that can be used to reduce and control SWI in coastal aquifers. Advantages and disadvantages of the different approaches are presented and discussed.

Coastal areas are increasingly endangered by climate change and associated sea level rise, which could have serious consequences, such as shoreline erosion and coastal city submergence. The current study aims to conduct a historical trend analysis (HTA) and predict the shoreline changes of the Nile Delta coasts. The Digital Shoreline Analysis System (DSAS) software, with the GIS environment, is used for monitoring the shoreline changes using a number of statistical methods (SCE, NSM, EPR, WLR and LRR). Satellite images from 1974 to 2022 were collected and geometrically corrected using supervised classification to detect the shoreline change of the Nile Delta. The GIS was used for detecting and monitoring changes in the shoreline, as well as forecasting future changes in the shoreline for the next 10 and 20 years (2033–2043). The critical sections of the Nile Delta were identified, and a time series analysis of shoreline changes was conducted. For each section, linear equations were established to predict probable changes in the shoreline. Between 1974 and 2022, the shoreline of the Nile Delta moved inland in different directions due to coastal erosion, and predictions indicate that this erosion will continue until both 2033 and 2043, particularly affecting the Rosetta and Damietta sections. The erosion rate ranged between 30–60 and 10–25 m/year at Rosetta and Damietta, respectively, but at Manzala, it ranged between 8–15 m/year. Continued erosion of the Nile Delta shoreline could have severe consequences that could affect the inhabitants, economy, buildings, roads, railways, and ports. These areas need an integrated coastal management strategy which incorporates increasing consciousness, urban development, and the implementation of rules and adaptation plans. The results of the current study and forecasting the shoreline change could help in protecting such areas.

The problem of seawater intrusion is encountered in almost all coastal aquifers. Because of its higher density, the seawater migrates inland into freshwater aquifers even without any pumping activities. Excessive pumping of groundwater would accelerate seawater intrusion. Climate change and sea level rise represent critical parameters affecting the rate and degree of seawater intrusion. In this paper, a coupled transient finite element model for simulation of fluid flow and solute transport in saturated and unsaturated soils (2D-FEST) is employed to study the seawater intrusion in the Nile Delta aquifer. The results of the current model are compared to results of SEAWAT for model verification. The (2D-FEST) model is used to investigate seawater intrusion considering the impacts of climate change. Three scenarios are studied: (a) rise in sea level, (b) decline of the piezometric head at the land side due to excessive pumping, and (c) combination of sea level rise and decline of the piezometric head. The results show that the rise in the sea level has a significant effect on the position of the transition zone. The third scenario represents the worst case under which the groundwater quality would deteriorate in large areas of the Nile Delta aquifer.