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Special Issue "Seawater Intrusion: Simulation and Control"

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

Deadline for manuscript submissions: closed (22 January 2018)

Special Issue Editor

Guest Editor
Prof. Carole Rosier

LMPA Centre Universitaire de la Mi-Voix 50 rue F. Buisson CS80699 62228 Calais
Website | E-Mail
Phone: 03 21 46 55 83
Interests: seawater intrusion; numerical simulations

Special Issue Information

Dear Colleagues,

Groundwater is a major source of water supply. In coastal zones there exist hydraulic exchanges between fresh groundwater and seawater. They are slow in ''natural conditions'' and thus are often forgotten and replaced by a quasi-equilibrium between two fluid layers (Ghyben--Herzberg assumptions). The picture fails in case of more drastic conditions due for instance to meteorological events or to human interventions. Intensive extraction of freshwater leads for instance to local water table depression causing problems of saltwater intrusion in the aquifer. We thus need efficient and accurate models to simulate the displacement of salt water front in coastal aquifer for the optimal exploitation of fresh groundwater. The existing models for seawater intrusion may be classified in three categories: The first one corresponds to the diffuse interface approach. This is the physically correct approach. Fresh and salt water are two miscible fluids. Due to density contrast they tend to separate into two layers with a transition zone characterized by the variations of the salt concentration. This approach is heavy from theoretical and numerical point of view. The second approach, called 'Sharp interface approach', is based on the hypothesis that the two fluids are immiscible. Moreover the domains occupied by each fluid are assumed to be separated by a smooth interface, no mass transfert occurs between the fresh and the salt area and capillary pressure's type effects are neglected. This approximation is often reasonable. Of course, this type of model does not describe the behavior of the real transition zone but give informations concerning the movement of the saltwater front. The other price to pay for this simplified approach is the numerical handling of free interfaces. In the third approach, this abrupt interface approach is mixed with a phase field approach, thus reinjecting in a new way the realism of diffuse interfaces models. It thus combines the advantage of respecting the physics of the problem and that of the computational efficiency. The mathematical difficulty of the analysis of the free interfaces is compensated by an upscaling procedure which allows to model the three-dimensional problem by a system of partial differential equations set in a two-dimensional domain. The aim and scope of this Special Issue is to provide relevant numerical studies derived from above approaches to provide efficient and accurate modeling of the evolution of the saltwater front in coastal aquifers in realistic situations.

Prof. Carole Rosier
Guest Editor

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Keywords

  • seawater intrusion problem
  • numerical modeling
  • mathematical modeling
  • simulations

Published Papers (4 papers)

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Research

Open AccessArticle Assessing the Contribution of Demographic Growth, Climate Change, and the Refugee Crisis on Seawater Intrusion in the Tripoli Aquifer
Water 2018, 10(8), 973; https://doi.org/10.3390/w10080973
Received: 5 June 2018 / Revised: 13 July 2018 / Accepted: 19 July 2018 / Published: 25 July 2018
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Abstract
As a major hotspot of climate change, Lebanon suffers from a water resources crisis enhanced by the increase of anthropogenic activities. In this paper, the impacts of climate change and of the Syrian refugee crisis are combined with the impact of demographic growth
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As a major hotspot of climate change, Lebanon suffers from a water resources crisis enhanced by the increase of anthropogenic activities. In this paper, the impacts of climate change and of the Syrian refugee crisis are combined with the impact of demographic growth to assess their aggregated impact on seawater intrusion in the Tripoli aquifer. A hydrogeological model is used to assess the seawater intrusion evolution for the next 25 years with respect to three phenomena: seawater rise, variation of incoming freshwater flux, and the change of the extraction rate of the pumping wells. Our study shows that the freshwater/seawater interface will move forward inland about 103 m in the next 25 years, leading to the salinization of the aquifer at the position of the pumping wells. Only about 1% of the advancement of the interface is associated with seawater rise; the remaining contributions are 79% from climate change and 20% from demographic growth. Adding the impact of migration reduces the contribution of climate change from 79% to 52%. The results suggest that the remediation solutions and recommendations should take into account the long-term impacts of climate change and the impact of population migration. Full article
(This article belongs to the Special Issue Seawater Intrusion: Simulation and Control)
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Open AccessArticle A Simulation-Optimization Model for Seawater Intrusion Management at Pingtung Coastal Area, Taiwan
Water 2018, 10(3), 251; https://doi.org/10.3390/w10030251
Received: 24 November 2017 / Revised: 22 February 2018 / Accepted: 26 February 2018 / Published: 28 February 2018
Cited by 1 | PDF Full-text (39646 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The coastal regions of Pingtung Plain in southern Taiwan rely on groundwater as their main source of fresh water for aquaculture, agriculture, domestic, and industrial sectors. The availability of fresh groundwater is threatened by unsustainable groundwater extraction and the over-pumpage leads to the
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The coastal regions of Pingtung Plain in southern Taiwan rely on groundwater as their main source of fresh water for aquaculture, agriculture, domestic, and industrial sectors. The availability of fresh groundwater is threatened by unsustainable groundwater extraction and the over-pumpage leads to the serious problem of seawater intrusion. It is desired to find appropriate management strategies to control groundwater salinity and mitigate seawater intrusion. In this study, a simulation–optimization model has been presented to solve the problem of seawater intrusion along the coastal aquifers in Pingtung Plain and the objective is using injection well barriers and minimizing the total injection rate based on the pre-determined locations of injection barriers. The SEAWAT code is used to simulate the process of seawater intrusion and the surrogate model of artificial neural networks (ANNs) is used to approximate the seawater intrusion (SWI) numerical model to increase the computational efficiency during the optimization process. The heuristic optimization scheme of differential evolution (DE) algorithm is selected to identify the global optimal management solution. Two different management scenarios, one is the injection barriers located along the coast and the other is the injection barrier located at the inland, are considered and the optimized results show that the deployment of injection barriers at the inland is more effective to reduce total dissolved solids (TDS) concentrations and mitigate seawater intrusion than that along the coast. The computational time can be reduced by more than 98% when using ANNs to replace the numerical model and the DE algorithm has been confirmed as a robust optimization scheme to solve groundwater management problems. The proposed framework can identify the most reliable management strategies and provide a reference tool for decision making with regard to seawater intrusion remediation. Full article
(This article belongs to the Special Issue Seawater Intrusion: Simulation and Control)
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Open AccessFeature PaperArticle A Generalized Semi-Analytical Solution for the Dispersive Henry Problem: Effect of Stratification and Anisotropy on Seawater Intrusion
Water 2018, 10(2), 230; https://doi.org/10.3390/w10020230
Received: 11 January 2018 / Revised: 15 February 2018 / Accepted: 17 February 2018 / Published: 23 February 2018
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Abstract
The Henry problem (HP) continues to play a useful role in theoretical and practical studies related to seawater intrusion (SWI) into coastal aquifers. The popularity of this problem is attributed to its simplicity and precision to the existence of semi-analytical (SA) solutions. The
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The Henry problem (HP) continues to play a useful role in theoretical and practical studies related to seawater intrusion (SWI) into coastal aquifers. The popularity of this problem is attributed to its simplicity and precision to the existence of semi-analytical (SA) solutions. The first SA solution has been developed for a high uniform diffusion coefficient. Several further studies have contributed more realistic solutions with lower diffusion coefficients or velocity-dependent dispersion. All the existing SA solutions are limited to homogenous and isotropic domains. This work attempts to improve the realism of the SA solution of the dispersive HP by extending it to heterogeneous and anisotropic coastal aquifers. The solution is obtained using the Fourier series method. A special hydraulic conductivity–depth model describing stratified heterogeneity is used for mathematical convenience. An efficient technique is developed to solve the flow and transport equations in the spectral space. With this technique, we show that the HP can be solved in the spectral space with the salt concentration as primary unknown. Several examples are generated, and the SA solutions are compared against an in-house finite element code. The results provide high-quality data assessed by quantitative indicators that can be effectively used for code verification in realistic configurations of heterogeneity and anisotropy. The SA solution is used to explain contradictory results stated in the previous works about the effect of anisotropy on the saltwater wedge. It is also used to investigate the combined influence of stratification and anisotropy on relevant metrics characterizing SWI. At a constant gravity number, anisotropy leads to landward migration of the saltwater wedge, more intense saltwater flux, a wider mixing zone and shallower groundwater discharge zone to the sea. The influence of stratified heterogeneity is more pronounced in highly anisotropic aquifers. The stratification rate and anisotropy have complementary effects on all SWI metrics, except for the depth of the discharge zone. Full article
(This article belongs to the Special Issue Seawater Intrusion: Simulation and Control)
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Open AccessArticle Well Salinization Risk and Effects of Baltic Sea Level Rise on the Groundwater-Dependent Island of Öland, Sweden
Water 2018, 10(2), 141; https://doi.org/10.3390/w10020141
Received: 16 December 2017 / Revised: 22 January 2018 / Accepted: 25 January 2018 / Published: 1 February 2018
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Abstract
In this study, we estimate baseline conditions in terms of the current risk of well salinization on the Baltic Sea island of Öland, Sweden, and assess the effects of future sea level rise on the land area, infrastructure and cultural values. We use
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In this study, we estimate baseline conditions in terms of the current risk of well salinization on the Baltic Sea island of Öland, Sweden, and assess the effects of future sea level rise on the land area, infrastructure and cultural values. We use a multicriterion geographical information systems (GIS) approach. Geomorphological and physical parameters affect the risk of saltwater intrusion into freshwater aquifers, including their hydrology, geomorphology, and climatology; the spatial distribution of the current risk of salinization is mapped in this study. In the event of a future 2 m sea level rise, a total land area of 67 km2 will be inundated on Öland, corresponding to approximately 5% of the island’s land surface. Inundation includes urban areas, nature reserves, and animal protection areas, implying the loss of environmental and socioeconomic values. A future 2 m sea level rise will also cause direct inundation of 3% of all wells on the island. Currently, 17.5% of all wells are at a high risk of becoming saltwater contaminated. More generally, the present results add evidence showing a relatively high vulnerability of major Baltic Sea islands and their infrastructure to future sea level rise. The approach used here and related results, including salinization risk maps, may prove useful for decision-makers in the planning of infrastructure. Drilling of new wells could for instance preferably be done in areas with identified lower risk-index values, which would facilitate an overall higher freshwater withdrawal in the interest of the entire island. Full article
(This article belongs to the Special Issue Seawater Intrusion: Simulation and Control)
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