Impacts of Sea Level Rise and Groundwater Extraction Scenarios on Fresh Groundwater Resources in the Nile Delta Governorates, Egypt

Abstract

As Egypt’s population increases, the demand for fresh groundwater extraction will intensify. Consequently, the groundwater quality will deteriorate, including an increase in salinization. On the other hand, salinization caused by saltwater intrusion in the coastal Nile Delta Aquifer (NDA) is also threatening the groundwater resources. The aim of this article is to assess the situation in 2010 (since this is when most data is sufficiently available) regarding the available fresh groundwater resources and to evaluate future salinization in the NDA using a 3D variable-density groundwater flow model coupled with salt transport that was developed with SEAWAT. This is achieved by examining six future scenarios that combine two driving forces: increased extraction and sea level rise (SLR). Given the prognosis of the intergovernmental panel on climate change (IPCC), the scenarios are used to assess the impact of groundwater extraction versus SLR on the seawater intrusion in the Delta and evaluate their contributions to increased groundwater salinization. The results show that groundwater extraction has a greater impact on salinization of the NDA than SLR, while the two factors combined cause the largest reduction of available fresh groundwater resources. The significant findings of this research are the determination of the groundwater volumes of fresh water, brackish, light brackish and saline water in the NDA as a whole and in each governorate and the identification of the governorates that are most vulnerable to salinization. It is highly recommended that the results of this analysis are considered in future mitigation and/or adaptation plans.

Non-renewable groundwater use and groundwater depletion: a review

“…This is further supported by a sensitivity study by Ferguson and Gleeson (2012), who find that the impact of groundwater withdrawal on coastal aquifers is more significant than the impact of sealevel rise for a wide range of hydrogeologic conditions and withdrawal intensities. Despite the global importance of salinization by groundwater withdrawal and reported cases of imminent salinization (Custodio andBruggeman 1987, Post et al 2018), there are hardly any regional-scale projections of aquifer salinization under future developments of groundwater withdrawal, with Mabrouk et al (2018) as a recent exception.…”

A three-dimensional palaeohydrogeological reconstruction of the groundwater salinity distribution in the Nile Delta Aquifer

“…Hydrogeological research dealing with this area generally assumed that the connection between aquifer and sea is completely open (e.g. Kashef, 1983;Mabrouk et al, 2018;Sefelnasr and Sherif, 2014;Sherif et al, 1988), but there exists ample evidence against this assumption from both seismics (Abdel-Fattah, 2014;Abdel Aal et al, 2000;Samuel et al, 2003) as well as from the fact that offshore borelogs contain more clay than sands (Salem et al, 2016). These observations can be explained by the fact that the fraction of marine clays in deltas generally increases seawards (Nichols, 2009).…”

“…The other, former dune areas ( Fig. 3) were either eroded naturally or removed by humans (El Banna, 2004;Malm and Esmailian, 2013;Stanley and Clemente, 2014) and have high soil salinities, presumably causing former freshwater lenses to salinize. Given this bias in our dataset towards fresh groundwater, the extent of the saline groundwater problem is likely underexpressed in…”

“…Sefelnasr and Sherif (2014) showed the sensitivity of the area to sea-level rise with a 3-D numerical model, as the low topography of the Nile Delta allowed for a far-reaching land surface inundation that can be detrimental to freshwater volumes (Ketabchi et al, 2016;Kooi et al, 2000). Mabrouk et al (2018) showed that groundwater extraction is a larger threat to freshwater volumes than sea-level rise, under the assumption that land surface inundation with seawater is prevented. Van Engelen et al (2018) investigated the origins of hypersaline groundwater that is found starting from 400 m depth, which was overlooked in previous studies.…”

Geological Heterogeneity of Coastal Unconsolidated Groundwater Systems Worldwide and Its Influence on Offshore Fresh Groundwater Occurrence

“…In past decades, an increased pressure is observed on both shallow and deep (modern and fossil) inland fresh groundwater resources which results in depletion and quality deterioration (e.g., due to rising salinity), especially in arid regions (Custodio, 2002;Gleeson et al, 2017). These fragile fresh water sources are also threatened by natural hazards such as seawater-overwash events (Yang et al, 2013(Yang et al, , 2018Cardenas et al, 2015;Chui and Terry, 2015;Yu et al, 2016;Gingerich et al, 2017) and sealevel rise (Carretero et al, 2013;Rasmussen et al, 2013;Sefelnasr and Sherif, 2014;Mabrouk et al, 2018), further stressing the need to adjust water management strategies and find potential additional sources of fresh water. According to the latest IPCC report (Masson-Delmotte et al, 2018), the past decade has seen a record-breaking number of such natural disasters (seawater overwash events such as storm surges) while sea-level rise predictions are increasingly alarming (e.g., Pollard and Deconto, 2016).…”