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Salinity intrusion is one of the most pressing threats to unconfined coastal aquifers, and its simulation is of great importance for groundwater research and management. This study compared the performances of two computational fluid dynamics (CFD) software applications, ANSYS Fluent 2022 R2 and COMSOL Multiphysics 5.6, in simulating the transport of saltwater in a pilot-scale experimental setup, which was built to recreate two boundary conditions of unconfined aquifers with homogeneous stratigraphy. The experiments were performed until the saline wedge reached a quasi-steady-state condition. Sequential photographs and image analysis were required to record the movement of the saline toe and the saline wedge location. The maximum toe length was achieved under the head-controlled boundary condition, with a toe length of 1.6 m after 7 h of the experiment, and 1.65 m and 1.79 m for the COMSOL and ANSYS Fluent simulations, respectively. The findings evidence that the flux-controlled condition produced a better representation of the saline wedge than the head-controlled condition, indicating good agreement between the CFD simulations and the experimental data. Recommendations for future research include CFD simulations of real coastal aquifers and coupling fluid dynamics with other processes such as land subsidence. [ABSTRACT FROM AUTHOR]

Hydrochemical analysis is crucial for understanding soil and water composition dynamics in coastal aquifers. This study presents a novel framework for the comprehensive assessment of groundwater quality, integrating multivariate analysis and hydrochemical techniques. It comprises seven stages aimed at characterizing physicochemical properties, identifying water constituents, elucidating dominant mechanisms in water composition, evaluating ion exchange processes, analyzing spatial distribution of components, identifying impacting processes, and assessing drinking water quality. The framework was applied to the coastal unconfined Arroyo Grande aquifer in Cartagena, Colombia. Fifteen points were sampled, assessing physicochemical parameters such as total hardness, alkalinity, pH, temperature, electrical conductivity, anions, cations, among others. Findings reveal the presence of dominant anions including bicarbonate, chloride, and sulfate, with relevant variations observed between the dry and wet season, with manganese and iron surpassing WHO drinking water standards. The prevalence of these constituents has been attributed to mineral dissolution, ion exchange, salinization due to seawater intrusion, and anthropogenic contamination. Over 50% of samples in both seasons fail to meet freshwater drinking standards due to elevated dissolved mineral concentrations in groundwater. These findings provide insights for sustainable management and mitigation strategies, and the systematic approach enables researchers to identify key factors influencing water composition. [ABSTRACT FROM AUTHOR]

Land subsidence is a global challenge that enhances the vulnerability of aquifers where climate change and driving forces are occurring simultaneously. To comprehensively analyze this issue, integrated modeling tools are essential. This study advances the simulation of subsidence using Computational Fluid Dynamics (CFD); it assessed the effects of exploitation and recharge of groundwater on the vertical displacement of coarse and fine sands in a laboratory-scale aquifer. A model was developed by integrating the Navier–Stokes equations to study the groundwater flow and Terzaghi's law for the vertical displacement of sands. The boundary conditions used were Dirichlet based on the changes in the hydraulic head over time. The specific storage coefficient was used to calibrate the model. The findings confirmed that subsidence occurs at slower rates in soil with fine sands with average particle diameters of 0.39 mm than in coarse sands with average particle diameters of 0.67 mm. The maximum discrepancy between the experimental and the numerical reaffirms that CFD platforms can be used to simulate subsidence dynamics and potentially allow the simultaneous simulation of other dynamics. Concluding remarks and recommendations are highlighted considering the up-to-date advances and future work to improve the research on subsidence in unconfined aquifers. [ABSTRACT FROM AUTHOR]