Exploring methodology for characterization of a complex multi-aquifer coastal system case study: Northeast Nile Delta region

This paper investigates the complex, multi-layered coastal aquifer system in the Northeastern Nile Delta region, addressing critical challenges such as water scarcity, overexploitation of groundwater, deteriorating water quality, and the growing dependence on coastal aquifers to support national development projects. These issues are exacerbated by increasing water demand and the impacts of climate change in this semi-arid region. To address these challenges, the study presents a comprehensive and systematic methodology for characterizing the Nile Delta’s coastal aquifer system. The approach integrates literature review, structured data collection, geophysical surveys, the establishment of exploratory monitoring wells, long-term groundwater level monitoring, step-drawdown and constant-rate pumping tests, hydrogeological mapping using remote sensing (RS) and GIS techniques, and numerical groundwater modeling. This methodology is applied to evaluate the technical feasibility of developing a productive well field to supply raw water for a desalination plant currently under construction in the study area. The applied methodology successfully identified a three-layer aquifer system separated by confining clay layers. Through a combination of geophysical surveys and lithological analysis of exploratory wells, the study delineated the Coastal Holocene aquifer A, the Late Pleistocene Nile Delta aquifer B, and the Early Pleistocene Nile Delta aquifer C, confirming the effectiveness of the integrated characterization approach. As part of the integrated methodology, a calibrated numerical groundwater model was developed to simulate aquifer response under various extraction scenarios. The model was used to evaluate the long-term sustainability of different pumping rates from the middle aquifer B to supply raw water to the planned desalination plant. By testing daily extraction rates of 50,000, 75,000, and 100,000 m3 over a 50-year period, the model demonstrated the technical feasibility of moderate extraction scenarios while identifying the risks of excessive drawdown associated with higher rates. The model also accounted for potential drawdown interference from multiple production wells and supported the optimization of well field design for sustainable long-term groundwater use. The study demonstrates how an integrated methodological framework can refine the hydrogeological conceptualization of complex coastal aquifer systems, such as the Nile Delta. It highlights the value of combining field investigations, geospatial analysis, and numerical modeling to inform sustainable groundwater development. The approach presented here provides a replicable foundation for future research and for guiding effective water resource management strategies in other coastal regions facing similar environmental and anthropogenic pressures, particularly across the Mediterranean.