article · Water Cycle
Seawater intrusion presents a critical challenge to coastal groundwater management, particularly in semi-arid regions subjected to heavy pumping and climate shifts. An assessment of the unconfined Ghiss-Nekor coastal aquifer tracked changes between 2015 and 2022 using a range of geochemical diagrams, spatial mapping, and seawater fraction metrics. The evaluation revealed that between 29% and 38% of surveyed wells exhibited a sodium-chloride water profile characteristic of seawater. Salinity levels rose significantly across the observation period, particularly near the shoreline. In addition, hydrochemical facies analysis indicated that the zone affected by seawater intrusion expanded from 14% to 20%, whilst the maximum seawater fraction climbed from 14.84% to 25.77%. These geochemical and mapping approaches effectively quantified the ongoing degradation of the aquifer, establishing a baseline to inform future resource management strategies.
Coastal aquifers provide essential freshwater in dry regions, but excessive pumping and climate pressures can draw in ocean water. Contamination by seawater threatens drinking supplies and agricultural sustainability. Demonstrating reliable methods to measure the spatial and temporal spread of salinisation helps water authorities pinpoint vulnerable zones, evaluate aquifer health, and design interventions to protect vital groundwater reserves from irreversible damage.
The workflow provides an applied assessment framework suitable for water basin authorities, environmental consultancies, and municipal planners managing vulnerable coastal reserves. As an applied analytical study using existing geochemical and mapping tools, it is not a standalone commercial product. However, the diagnostic approach can be readily adopted by technical services to monitor salinity risks, guide extraction limits, and support infrastructure planning for coastal groundwater schemes.
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The impact of seawater intrusion on coastal aquifers is a major concern in managing groundwater resources. The unconfined coastal aquifer of Ghiss-Nekor, located in a semi-arid area, is particularly vulnerable to seawater intrusion (SWI) because of excessive groundwater pumping and climate change impacts. Therefore, the main goal of the present work is to track the spatiotemporal evolution of SWI in the Ghiss-Nekor aquifer by analyzing data from the years 2015 and 2022 using appropriate geochemical approaches. Accordingly, a range of geochemical techniques were employed, including the Piper diagram, Chadha's diagram, Gibbs diagram, Stiff diagram, major ions variation maps, Hydrochemical Facies Evolution Diagrams (HFE-D), and seawater fraction (fsea). As a result, Gibbs diagram clearly indicates the contribution of seawater to the salinization of the Ghiss-Nekor aquifer. Further information is provided by the Piper, Chadha, and Stiff diagrams, which reveal that 29%–38% of the wells studied display Na–Cl water type, a characteristic feature of seawater facies. Additionally, statistical analysis shows a significant increase in salinity levels between 2015 and 2022. Furthermore, the spatiotemporal analysis using the differential mapping technique (DMT) confirmed the increase of salinity, particularly near the shoreline. Additionally, the HFE-D showed that the region impacted by SWI increased from 14% to 20% between 2015 and 2022, and the maximum fsea value rose from 14.84% to 25.77% over the same time frame. Our findings reinforce the assumption that SWI is worsening over time in the Ghiss-Nekor aquifer. In summary, the techniques used in this study were effective in tracking the spatiotemporal evolution of SWI in the aquifer and in quantifying it. The results of this study can inform the development of effective strategies for managing SWI in coastal aquifers.
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DOI: 10.1016/j.watcyc.2023.05.002
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