Advances on the Dynamics of Groundwater Salinization

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydrogeology".

Deadline for manuscript submissions: closed (28 December 2023) | Viewed by 5918

Special Issue Editors

Hellenic Agricultural Organisation, Soil and Water Resources Institute, Thessaloniki, Greece
Interests: hydrogeochemistry; groundwater quality; groundwater salinization; environmental monitoring; hydrogeology; environmental isotopes
Special Issues, Collections and Topics in MDPI journals
Dept. of Geological Eng., Mersin University, Mersin, Turkey
Interests: hydrogeology; hydrogeochemistry; geochemical modeling; environmental pollution; environmental impact assessment; water quality; salinization; geographic information systems (GIS); multivariate statistics; remote sensing; geostatistics
Hochschule Lübeck, Architecture & Civil Engineering, Laboratory for Hydrology and International Water Management, Lübeck, Germany
Interests: environemntal isotopes; groundwater salinization; hydrogeochemistry; modelling; hydrogeology

Special Issue Information

Dear Colleagues,

Groundwater salinization (GWS) is a global phenomenon of increasing interest due to its adverse effects on the socioeconomic structure and the physical environment. Being a complex phenomenon, it includes several inter-linked aspects of spatiotemporal resolution that are yet not fully understood or identified.

We invite contributions that address scientific advances in temporal variations across all time scales and spatial coverages or even combined spatial-temporal dynamics. Experimental data, projections, and reconstructions are needed to show variations of salinization at short time scales to years, decades, or even at historical or paleo-hydrological scope by using residence time analysis combined with salinization indicators or modelling techniques. Paradigms of receding salinization trends due to remediation or management actions can also be highlighted to show the dynamics of salinization reversal.

Contributions may also include various methodological approaches, such as geophysics, geochemistry, environmental isotopes, multivariate statistics, geostatistics, artificial intelligence, remote sensing, and in situ multi-parameter monitoring. Papers on high-resolution temporal variations of salinization in response to tidal effects, pumping, or changing external driving forces are welcome in order to improve our understanding around salinization dynamics. Contributions on spatial dynamics are also welcome and may include the extent and changes of transition zones between salt and fresh water or the detailed mapping of the extent and spatial-temporal evolution of groundwater salinization zones.

Dr. Evangelos Tziritis
Prof. Dr. Cüneyt Güler
Prof. Dr. Christoph Külls
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • groundwater
  • salinization
  • hydrogeology
  • hydrogeochemistry
  • environmental isotopes
  • modelling
  • geostatistics
  • artificial intelligence
  • groundwater monitoring

Published Papers (3 papers)

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Research

18 pages, 17634 KiB  
Article
Spatial or Random Cross-Validation? The Effect of Resampling Methods in Predicting Groundwater Salinity with Machine Learning in Mediterranean Region
by Panagiotis Tziachris, Melpomeni Nikou, Vassilis Aschonitis, Andreas Kallioras, Katerina Sachsamanoglou, Maria Dolores Fidelibus and Evangelos Tziritis
Water 2023, 15(12), 2278; https://doi.org/10.3390/w15122278 - 18 Jun 2023
Cited by 2 | Viewed by 1669
Abstract
Machine learning (ML) algorithms are extensively used with outstanding prediction accuracy. However, in some cases, their overfitting capabilities, along with inadvertent biases, might produce overly optimistic results. Spatial data are a special kind of data that could introduce biases to ML due to [...] Read more.
Machine learning (ML) algorithms are extensively used with outstanding prediction accuracy. However, in some cases, their overfitting capabilities, along with inadvertent biases, might produce overly optimistic results. Spatial data are a special kind of data that could introduce biases to ML due to their intrinsic spatial autocorrelation. To address this issue, a special resampling method has emerged called spatial cross-validation (SCV). The purpose of this study was to evaluate the performance of SCV compared with conventional random cross-validation (CCV) used in most ML studies. Multiple ML models were created with CCV and SCV to predict groundwater electrical conductivity (EC) with data (A) from Rhodope, Greece, in the summer of 2020; (B) from the same area but at a different time (summer 2019); and (C) from a new area (the Salento peninsula, Italy). The results showed that the SCV provides ML models with superior generalization capabilities and, hence, better prediction results in new unknown data. The SCV seems to be able to capture the spatial patterns in the data while also reducing the over-optimism bias that is often associated with CCV methods. Based on the results, SCV could be applied with ML in studies that use spatial data. Full article
(This article belongs to the Special Issue Advances on the Dynamics of Groundwater Salinization)
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18 pages, 9406 KiB  
Article
Investigating Seawater Intrusion in Republic of South Africa’s Heuningnes, Cape Agulhas Using Hydrogeochemistry and Seawater Fraction Techniques
by Abongile Xaza, Harold Wilson Tumwitike Mapoma, Tamiru A. Abiye, Sumaya Clarke and Thokozani Kanyerere
Water 2023, 15(11), 2141; https://doi.org/10.3390/w15112141 - 05 Jun 2023
Cited by 1 | Viewed by 1740
Abstract
The Heuningnes Catchment in the Republic of South Africa was used as a case study in this research to describe the application of saltwater fraction/quantification and hydrogeochemistry methods to evaluate the extent of saline intrusion in the coastal aquifers. The argument of the [...] Read more.
The Heuningnes Catchment in the Republic of South Africa was used as a case study in this research to describe the application of saltwater fraction/quantification and hydrogeochemistry methods to evaluate the extent of saline intrusion in the coastal aquifers. The argument of the research is that the presence of seawater incursion may be conclusively determined by combining the examination of the major ions, seawater fraction, stable isotopes of water, bromide, and geochemical modeling. Using stable isotopes of oxygen (18O) and deuterium (2H), major ions chemistry, seawater composition, and geochemical modeling, the genesis of salinity and mixing of different water masses were examined. Twenty-nine (29) samples of groundwater were examined. All samples showed water facies of the Na-Cl type, indicating a seawater-related origin. The significance of mixing in coastal aquifers under natural conditions was shown by the hydrogeochemical characteristics of key ions derived from ionic ratios, which demonstrated substantial adherence to mixing lines among endmembers for freshwater as well as saltwater (seawater). The quantification of seawater contribution in groundwater percentages varied from 0.01 to 43%, with three samples having concentrations of seawater above 50%. It was clear from the hydrogeochemical analysis and determination of the proportion of saltwater that the seawater intrusion impacted the coastal fresh groundwater. In addition, the chloride concentration in the groundwater ranged from 81.5 to 26,557.5 mg/L, with the corresponding δ18O values ranging from −5.5‰ to −0.9‰, which suggested that freshwater and saltwater were mixing. The Br/Cl ratios showed that evaporation had played a part in elevating groundwater salinity as well. Since saturation indices were below zero, the mineral dissolution could also contribute to the salinization of groundwater. Further proof of seawater incursion in the investigated catchment was supplied by geochemical modeling and bromide. Even though such tools were not verified in multiple coastal aquifers for widespread generalization, the study offered a scientifically significant understanding of the application of such tools on seawater intrusion in coastal aquifers and has useful recommendations for the aquifer setting of similar environments. Full article
(This article belongs to the Special Issue Advances on the Dynamics of Groundwater Salinization)
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16 pages, 4939 KiB  
Article
Origin of Groundwater Salinity in the Draa Sfar Polymetallic Mine Area Using Conservative Elements (Morocco)
by Anasse Ait Lemkademe, Jean-Luc Michelot, Abdelfattah Benkaddour, Lahoucine Hanich and Ouissal Heddoun
Water 2023, 15(1), 82; https://doi.org/10.3390/w15010082 - 26 Dec 2022
Cited by 7 | Viewed by 1794
Abstract
In the Marrakech region of Morocco, where water resources are particularly limited, excessive salinity has been measured in the water from some wells intended for human consumption and irrigation. Moreover, the start-up of a mine for the exploitation of a polymetallic sulfide deposit [...] Read more.
In the Marrakech region of Morocco, where water resources are particularly limited, excessive salinity has been measured in the water from some wells intended for human consumption and irrigation. Moreover, the start-up of a mine for the exploitation of a polymetallic sulfide deposit and the progress of the exploitation work have revealed the existence of very saline deep groundwater with a total mineralization of over 80 g/L. The hydrogeochemical study using conservative elements has helped to understand the origin of the groundwater salinity in the Draa Sfar mine and to assess the contribution of the deep salinity source to the high salinities observed in the mine. The groundwater of the shallow aquifer shows almost constant Br/Cl and Na+/Cl ratios, independent of the chloride content. The constant ratios of these conservative elements indicate a single autochthonous origin of Cl, Br and Na+, and groundwater salinity is diluted by recharge water containing low concentrations of these elements. Regarding the mine groundwater, the high Li+/Cl ratio and Br/Cl ratios in the range measured on the leachates of the rocks extracted from the mine indicate that the pore water is the reservoir for dissolved chloride and the salinity of the mine’s groundwater results from a mixture between these pore waters and fresh meteoric water that seeps in from the surface and recharges the entire aquifer. This porewater would be a remnant of the hydrothermal fluids that formed the sulfide deposit. Full article
(This article belongs to the Special Issue Advances on the Dynamics of Groundwater Salinization)
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