An Integrated Approach for Deciphering Hydrogeochemical Processes during Seawater Intrusion in Coastal Aquifers

Abstract

For managing the freshwater in the worldwide coastal aquifers, it is imperative to understand the hydrogeochemical processes and flow patterns in the mixing freshwater/saltwater zone. The Egyptian Nile Delta aquifer is a typical example. The management of seawater intrusion (SWI) requires detailed investigations of the intrusion wedge and the dynamic processes in the mixing zone. Thus, a multidisciplinary approach was applied based on holistic hydrogeochemical, statistical analysis, and DC resistivity measurements to investigate the lateral and vertical changes in groundwater characteristics undergoing salinization stressor. The results of cross plots and ionic deviations of major ions, hydrochemical facies evolution diagram (HFE-D), and seawater mixing index (SMI) were integrated with the resistivity results to show the status of the SWI where the intrusion phase predominates in ~2/3 of the study are (~70 km radius) and the compositional thresholds of Na, Mg, Cl, and SO4 are 600, 145, 1200, and 600 mg/L, respectively, indicating that the wells with higher concentrations than these thresholds are affected by SWI. Moreover, the results demonstrate the efficiency of combining hydrogeochemical facies from heatmap and resistivity investigations to provide a large-scale characterization of natural and anthropogenic activities controlling aquifer salinization to support decision-makers for the long-term management of coastal groundwater.

Integrated Hydrogeological, Hydrochemical, and Isotopic Assessment of Seawater Intrusion into Coastal Aquifers in Al-Qatif Area, Eastern Saudi Arabia

“…The spatial distribution pattern of the main hydrochemical parameters (EC, TDS, Cl − , and Br − ) was used by researchers to assess the impact of SWI on GW salinization in coastal regions [ 40 ]. In general, the EC and TDS are a measure of salinity, while Cl − and Br − are conservative ions and are used by researchers to quantify the seawater contribution to GW resources [ 40 , 41 , 42 ]. Therefore, correlating the spatial pattern of EC, TDS, Cl − , and Br − helped define the source of elevated salinity of the analyzed GW in the current study.…”

An integrated seawater intrusion assessment in the Moroccan Ghiss-Nekor coastal aquifer using hydrogeochemical and geospatial techniques

“…The relative level of seawater and freshwater mixing is measured using the seawater mixing index (SMI) (Boumaiza et al 2020;Khan et al 2021;Aladejana et al 2021;Abu Salem et al 2022), in which the major elements of seawater namely Cl − , SO4 2− , Na + , and Mg 2+ were employed to compute this index using the equation ( 5):…”

A geochemical approach in assessing seawater intrusion by integrating geospatial techniques: a case study of Ghiss-Nekor coastal aquifer, Central Rif of Morocco

“…The relative level of seawater and freshwater mixing is measured using the seawater mixing index (SMI) (Abu Salem et al, 2022;Aladejana et al, 2021;Boumaiza et al, 2020;Khan et al, 2021), in which the major elements of seawater namely Cl − , SO4 2− , Na + , and Mg 2+ were employed to compute this index using the equation ( 5):…”

“…13). The water is assumed to be impacted by saltwater mixing if the SMI is greater than 1, while freshwater is indicated by SMI values less than 1 (Abu Salem et al, 2022;Aladejana et al, 2021;Edet, 2017). The calculations revealed twelve places (W05, W19, W26, W27, W28, W31, W35, W38, W39, W50, and W52) had SMI values greater than one.…”