Special Issue "Seawater Intrusion into Coastal Aquifers"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Oceans and Coastal Zones".

Deadline for manuscript submissions: closed (10 May 2021).

Special Issue Editor

Dr. Eyal Shalev
E-Mail Website
Guest Editor
Geological Survey of Israel, Jerusalem, Israel
Interests: groundwater hydrology, coastal aquifers, damage deformation, solute and heat transport

Special Issue Information

Dear Colleagues,

Coastal aquifers are one of the most important water resources in the world. In addition, the natural discharge of freshwater to the sea as submarine groundwater discharge (SGD) has an important role in the ecology of marine environments. The dynamics of seawater and freshwater within coastal aquifers are highly sensitive to disturbances, and their inappropriate management may lead to the deterioration of water quality. In many coastal aquifers, seawater intrusion has become the major constraint imposed on groundwater utilization. Groundwater exploitation and climate variations create dynamic conditions, which can significantly increase the intrusion of seawater into the aquifer and may result in the salinization of wells. They may also reduce SGD and affect the water budget of marine systems.

This Special Issue welcomes original research work dedicated to seawater intrusion and related subjects. Potential topics include but are not limited to the following:

  • Monitoring groundwater salinization
  • Numerical modeling of density-driven solute transport
  • Laboratory fresh–saline water interface experiments
  • Effects of pumping fresh and saline water onto the fresh–saline water interface and SGD

Dr. Eyal Shalev
Guest Editor

Manuscript Submission Information

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Keywords

  • Coastal aquifers
  • Fresh–saline water interface
  • Seawater intrusion
  • Submarine groundwater discharge
  • Density-driven flow

Published Papers (6 papers)

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Research

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Open AccessArticle
Towards a Correlation between Long-Term Seawater Intrusion Response and Water Level Fluctuations
Water 2021, 13(5), 719; https://doi.org/10.3390/w13050719 - 06 Mar 2021
Viewed by 474
Abstract
Laboratory and numerical experiments were conducted to provide a quantitative steady-state analysis of the effect of incremental variations of water level on saltwater intrusion. The purpose was to seek mathematical correlations relating both the wedge toe length and the height along the coastline [...] Read more.
Laboratory and numerical experiments were conducted to provide a quantitative steady-state analysis of the effect of incremental variations of water level on saltwater intrusion. The purpose was to seek mathematical correlations relating both the wedge toe length and the height along the coastline to the boundary head difference. The laboratory experiments were completed in a 2D sand tank where both freshwater and seawater levels were varied. The experiments were conducted for two bead sizes having different hydraulic conductivities. The numerical model SEAWAT was used to validate the results and then to perform sensitivity analysis. The experimental results show that at steady-state conditions, the logarithmic toe length could be expressed as a linear function of the boundary head difference. The linear relationship was recorded in both advancing and receding wedge phases. The linearity of the correlation was also well demonstrated with analytical solutions. Similar relationships were also derived in the scenarios where the sea level fluctuated while the freshwater boundary head was constant. The height of the saltwater wedge along the coastline was also found to be a linear function of the boundary head difference. The sensitivity analysis shows that the regression coefficients were sensitive to the hydraulic conductivity, the dispersivity, and the saltwater density, while the porosity and the rate of boundary head change induced negligible effects. The existence of a linear relationship between the logarithmic toe length and the boundary head difference was also well evidenced in a field-scale aquifer model for all the different hydrogeological aquifer conditions tested. This study is the first attempt in identifying the underlying correlation between the boundary water level variations and the main seawater intrusion (SWI) external metrics under controlled laboratory conditions, which is of great relevance from a water resources management perspective. Full article
(This article belongs to the Special Issue Seawater Intrusion into Coastal Aquifers)
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Open AccessArticle
Industry-Driven versus Natural Groundwater Flow Regime at the Dead Sea Coastal Aquifer
Water 2021, 13(4), 498; https://doi.org/10.3390/w13040498 - 15 Feb 2021
Viewed by 438
Abstract
The coexistence of nature and anthropogenic development requires continuous monitoring and research to address and respond to unforeseen threatening processes that occur with time. This is particularly relevant to the groundwater flow regime in the coastal aquifer adjacent to the Dead Sea, the [...] Read more.
The coexistence of nature and anthropogenic development requires continuous monitoring and research to address and respond to unforeseen threatening processes that occur with time. This is particularly relevant to the groundwater flow regime in the coastal aquifer adjacent to the Dead Sea, the level of which is dropping, and the industrial evaporation ponds, whose levels are rising. The increasing hydraulic gradient between the two water bodies has produced severe leakage through the pond embankments. To prevent this leakage, a vertical deep sealing wall was built along the embankment. In this study, the overall leakage is calculated by mass balance, and the subsurface leakage component is numerically simulated, based on the mass balance and hydrological observations. Some of the leakage discharges into surface canals and some at the Dead Sea. The leakage volume increased from 20 mcm/year in the 1980s to 100 mcm/year before the sealing wall was built (in 2012), and from 60 mcm/year once the wall was established to 80 mcm/year today. Using the calibrated model, the leakage volume is predicted to increase in the next few decades, mainly through the Ye’elim alluvial fan. Further research effort is needed to come up with new preventive measures. Full article
(This article belongs to the Special Issue Seawater Intrusion into Coastal Aquifers)
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Open AccessArticle
Geophysical Assessment of Seawater Intrusion into Coastal Aquifers of Bela Plain, Pakistan
Water 2020, 12(12), 3408; https://doi.org/10.3390/w12123408 - 04 Dec 2020
Cited by 3 | Viewed by 489
Abstract
Seawater intrusion is a major challenge in many coastal areas all around the world, mainly caused by over-exploitation of freshwater resources, climate change, and sea-level rise. Consequently, seawater intrusion reaches several kilometers inland, thus making the freshwater resources polluted and unsuitable for human [...] Read more.
Seawater intrusion is a major challenge in many coastal areas all around the world, mainly caused by over-exploitation of freshwater resources, climate change, and sea-level rise. Consequently, seawater intrusion reaches several kilometers inland, thus making the freshwater resources polluted and unsuitable for human use. Conventionally, the fresh-saline water interface is delineated by the number of laboratory tests obtained from boreholes. However, such tests suffer from efficiency in terms of data coverage, time, and cost. Hence, this work introduces Dar-Zarrouk (D-Z) parameters, namely transverse resistance (Tr), longitudinal conductance (Sc), and longitudinal resistivity (ρL) computed from non-invasive vertical electrical sounding (VES). Two-dimensional (2D) imaging of D-Z parameters provides a clear distinction of fresh-saline aquifers. Such techniques remove ambiguities in the resistivity interpretation caused by overlapping of fresh and saline aquifers during the process of suppression and equivalence. This study was carried out by 45 VES along five profiles in the coastal area of Bela Plain, Pakistan. D-Z parameters delineate fresh, brackish, and saline aquifers with a wide range of values such as freshwater with Tr > 2000 Ωm2, Sc < 3 mho, and ρL > 20 Ωm; saline water with Tr < 1000 Ωm2, Sc > 25 mho, and ρL < 5 Ωm; and brackish water with Tr between 1000–2000 Ωm2, Sc from 3 to 25 mho, and ρL between 5–20 Ωm. The D-Z results were validated by the physicochemical analysis using 13 water samples and local hydrogeological setting. The obtained results propose that D-Z parameters can be used as a powerful tool to demarcate the fresh-saline aquifer interface with more confidence than other traditional techniques. This geophysical approach can reduce the expensive number of borehole tests, and hence contributes to the future planning and development of freshwater resources in the coastal areas. Full article
(This article belongs to the Special Issue Seawater Intrusion into Coastal Aquifers)
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Open AccessArticle
Optimizing Laboratory Investigations of Saline Intrusion by Incorporating Machine Learning Techniques
Water 2020, 12(11), 2996; https://doi.org/10.3390/w12112996 - 26 Oct 2020
Cited by 2 | Viewed by 749
Abstract
Deriving saltwater concentrations from the light intensity values of dyed saline solutions is a long-established image processing practice in laboratory scale investigations of saline intrusion. The current paper presents a novel methodology that employs the predictive ability of machine learning algorithms in order [...] Read more.
Deriving saltwater concentrations from the light intensity values of dyed saline solutions is a long-established image processing practice in laboratory scale investigations of saline intrusion. The current paper presents a novel methodology that employs the predictive ability of machine learning algorithms in order to determine saltwater concentration fields. The proposed approach consists of three distinct parts, image pre-processing, porous medium classification (glass bead structure recognition) and saltwater field generation (regression). It minimizes the need for aquifer-specific calibrations, significantly shortening the experimental procedure by up to 50% of the time required. A series of typical saline intrusion experiments were conducted in homogeneous and heterogeneous aquifers, consisting of glass beads of varying sizes, to recreate the necessary laboratory data. An innovative method of distinguishing and filtering out the common experimental error introduced by both backlighting and the optical irregularities of the glass bead medium was formulated. This enabled the acquisition of quality predictions by classical, easy-to-use machine learning techniques, such as feedforward Artificial Neural Networks, using a limited amount of training data, proving the applicability of the procedure. The new process was benchmarked against a traditional regression algorithm. A series of variables were utilized to quantify the variance between the results generated by the two procedures. No compromise was found to the quality of the derived concentration fields and it was established that the proposed image processing technique is robust when applied to homogeneous and heterogeneous domains alike, outperforming the classical approach in all test cases. Moreover, the method minimized the impact of experimental errors introduced by small movements of the camera and the presence air bubbles trapped in the porous medium. Full article
(This article belongs to the Special Issue Seawater Intrusion into Coastal Aquifers)
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Open AccessArticle
Evaluation of the Groundwater Quality Using the Water Quality Index and Geostatistical Analysis in the Dier al-Balah Governorate, Gaza Strip, Palestine
Water 2020, 12(1), 262; https://doi.org/10.3390/w12010262 - 16 Jan 2020
Cited by 11 | Viewed by 2422
Abstract
Groundwater contamination is a major problem in the Gaza Strip. In this study we investigate the groundwater quality in the Dier al-Balah Governorate. Water samples were collected from 19 municipal wells in April 2009 and April 2014 and analyzed for physio-chemical parameters (pH, [...] Read more.
Groundwater contamination is a major problem in the Gaza Strip. In this study we investigate the groundwater quality in the Dier al-Balah Governorate. Water samples were collected from 19 municipal wells in April 2009 and April 2014 and analyzed for physio-chemical parameters (pH, TDS, Ca2+, Mg2+, Na+, K+, Cl, SO42–, HCO3 and NO3). The aim of the research is to determine the groundwater quality and to produce groundwater quality maps using the water quality index (WQI) method and geostatistical analysis. The results show that all water samples are very saline due to the intrusion of Mediterranean seawater in the coastal aquifer. Differences in chemical composition between 2009 and 2014 indicate that about 1% more seawater was mixed with the groundwater in this period. The majority of the observed chemical parameters of all wells are well above the WHO water quality standards and all WQI values indicate that the water quality is problematic. The spatial variation of the WQI scores is modelled by a deterministic component expressing a linear dependence on the distance to the coastline and a stochastic residual described by an exponential variogram with a practical range of 3000 m. The mapping of the WQI scores and derived water quality classes is achieved through regression-kriging. The results indicate that the groundwater in a large area along the coastline is unsuitable for human consumption and comparison of the maps of 2009 and 2014 shows that this region further expanded by about 700 m inland in a period of 5 years. The results of this study are worrying, but they also contribute to a better understanding of the factors that determine the groundwater quality and can help authorities and stakeholders with sustainable development. Full article
(This article belongs to the Special Issue Seawater Intrusion into Coastal Aquifers)
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Review

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Open AccessReview
Review of Seawater Intrusion in Western Coastal Regions of South Korea
Water 2021, 13(6), 761; https://doi.org/10.3390/w13060761 - 11 Mar 2021
Viewed by 315
Abstract
Groundwater salinization in coastal aquifers because of seawater intrusion has raised serious concerns worldwide since it deteriorates the quality of drinking water and thereby threatens sustainable economic development. In particular, this problem has been a cause of growing concern in the western coastal [...] Read more.
Groundwater salinization in coastal aquifers because of seawater intrusion has raised serious concerns worldwide since it deteriorates the quality of drinking water and thereby threatens sustainable economic development. In particular, this problem has been a cause of growing concern in the western coastal regions of South Korea. In this paper, we review studies of seawater intrusion in western coastal regions of South Korea conducted over the past 20 years, particularly focusing on studies reported in international journals. We summarize the study locations, methods used, and major findings from individual and regional-scale studies. General methods used to identify and interpret seawater intrusion and subsequent geochemical processes are also presented. On the basis of insights gleaned from the previous studies, future research needs are discussed. Full article
(This article belongs to the Special Issue Seawater Intrusion into Coastal Aquifers)
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