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Characterization and Monitoring of Coastal Hydrological Environment for Assessing the Impact of Seawater Intrusion on Coastal Aquifers

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A special issue of Hydrology (ISSN 2306-5338). This special issue belongs to the section "Surface Waters and Groundwaters".

Deadline for manuscript submissions: closed (30 April 2026) | Viewed by 9978

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Editors

Dr. Francesco Ronchetti

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Guest Editor

Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia, Via Giuseppe Campi, 103-41125 Modena, Italy
Interests: hydrogeology; water isotopes; aquifer recharge; coastal aquifer; spring; hydrochemistry; slope hydrology; groundwater monitoring; water tracers; groundwater modelling
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Dr. Marco Doveri

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Guest Editor

Department of Earth Sciences, University of Pisa, 56126 Pisa, Italy
Interests: aquifer systems; isotopes hydrology; groundwater and sustainability; foot hill aquifers; coastal aquifers; mountain aquifers; arctic hydrology; hydrogeological conceptual model; groundwater and streamwater monitoring

Dr. Marco Pola

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Guest Editor

Croatian Geological Survey, Ulica Milana Sachsa 2, 10000 Zagreb, Croatia
Interests: hydrogeology; coastal aquifer, fractured aquifer; thermal water; groundwater modeling

Special Issue Information

Dear Colleagues,

Climate change and environmental and anthropic modifications impact the hydrological cycle, water resources, and ecosystems, posing great challenges for global water and ecosystem management, especially where the ecological equilibria are strongly dependent on groundwater–surface water interactions. In coastal aquifers, seawater intrusion is a worldwide problem that greatly restricts the social and economic development of coastal areas. It is caused by natural processes but significantly worsened by aquifer overexploitation for irrigation and drinking water supply, land subsidence, sea level rise, and climate changes, which contribute to the reduction in groundwater natural recharge.

This Special Issue calls for any contributions on the characterization and monitoring of surface water and groundwater resources and the connected ecosystems in coastal areas, with a focus on the impact of seawater intrusion on the quantitative and qualitative statuses of these resources.

A list of desired contributions includes tools, equipment, methods, modeling, and/or experiences in the following areas:

Hydrological, hydrogeological, geophysical, and geochemical mapping and characterization of the subsurface, involving the distribution of freshwater and saltwater;
Assessment of climate change impact on surface/groundwater resources in coastal areas in terms of the quantity and quality, and ecosystem status;
Risk and vulnerability assessment methods;
Management approaches;
Monitoring experiences.

We therefore welcome original papers from researchers, practitioners, and decisionmakers on their findings on seawater/saltwater intrusion from different perspectives. Full research articles, reviews, and short commentaries/communications from practitioners are welcome.

Dr. Francesco Ronchetti
Dr. Marco Doveri
Dr. Marco Pola
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-anonymized peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Hydrology is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 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

seawater/saltwater intrusion
coastal aquifer
environment
hydrogeology
climate change
monitoring
coast

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Published Papers (5 papers)

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Research

31 pages, 9506 KB

Open AccessArticle

Spatio-Temporal Vulnerability Assessment of Coastal Aquifers Using DRASTIC and GALDIT Models with Different Weighting Methods: A Case Study from Iran

by Ali Barzkar, Mohammad Reza Goodarzi and Majid Niazkar

Hydrology 2026, 13(6), 141; https://doi.org/10.3390/hydrology13060141 - 25 May 2026

Cited by 1 | Viewed by 606

Abstract

Coastal aquifers are more exposed to pollution and salinity than other hydrogeological systems due to their proximity to the sea, increasing groundwater withdrawals, and climate change. The aim of this study is not only to evaluate and compare the vulnerability of coastal aquifers using the DRASTIC and GALDIT models but also to investigate effects of different weighting methods on the results of vulnerability zoning. The spatio-temporal vulnerability assessment was conducted for coastal aquifers in Hormozgan Province in Iran over a 15-year period (2010–2024). After collecting information layers required for both models, vulnerability maps were calculated for three consecutive five-year periods using three weighting methods: (a) normal weighting, (b) Shannon entropy, and (c) particle swarm optimization (PSO) algorithm. The results indicate that the coastal areas of the western part of the province have the highest vulnerability in both models, and the intensity and extent of high-risk zones have increased in recent periods. Comparison of weighting methods revealed that normal weighting provided a conservative and uniform distribution, while the entropy method, due to its reliance on statistical dispersion of data in some areas, led to a hyperbole of the risk. In contrast, the PSO algorithm provided the most accurate and realistic results compared to classical fixed-weight and entropy-based vulnerability maps, as it was able to identify critical areas with higher spatial concentration and hydrogeological coherence. The combined results of DRASTIC and GALDIT demonstrated that parts of the coastal aquifers of Hormozgan are simultaneously in a critical state in terms of inherent vulnerability and salinity potential. The findings of this study can be used as a scientific basis for sustainable management of groundwater resources, withdrawal control, and protection climate adaptation planning in coastal areas. Full article

(This article belongs to the Special Issue Characterization and Monitoring of Coastal Hydrological Environment for Assessing the Impact of Seawater Intrusion on Coastal Aquifers)

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20 pages, 17549 KB

Open AccessArticle

Divergent Compositions and Biogeochemical Pathways of Dissolved Organic Matter in a Monsoon-Affected Coastal Aquifer: Insights from Molecular Characterization

by Ashen Randika, Samadhi Athauda, Ruizhe Wang, Zhineng Hao, Yuansong Wei, Yawei Wang, Hui Zhong, Madhubhashini Makehelwala, Sujithra K. Weragoda and Rohan Weerasooriya

Hydrology 2026, 13(5), 120; https://doi.org/10.3390/hydrology13050120 - 28 Apr 2026

Viewed by 1042

Abstract

Coastal groundwater in monsoon-dominated regions faces compounding threats from seasonal hydrological extremes and seawater intrusion (SWI), yet the molecular-scale response of dissolved organic matter (DOM) remains poorly understood. We conducted a two-season investigation in Mannar District, Sri Lanka, integrating hydrochemistry, fluorescence spectroscopy, and Fourier-transform ion cyclotron resonance mass spectrometry to characterize DOM dynamics across shallow and deep groundwater. Dry-season chloride averaged 302 mg/L (shallow—5 to 12 m) and 505 mg/L (tube wells—20 to 30 m), then declined by 60–80% during monsoon recharge. Despite this freshening, DOM dynamics were decoupled from salinity: shallow wells showed dry-season DOC peaks (6.64 mg/L) driven by soil concentration, while tube wells exhibited wet-season enrichment (5.02 mg/L). Shallow aquifers maintained consistently high humification indices (around 0.70) and aromatic-rich DOM, indicating sustained buffering by soil-derived inputs. In contrast, wet-season recharge in tube wells appeared to stimulate microbial processing, as indicated by elevated protein-like fluorescence (C2: 26% to 36%) and a higher contribution of nitrogen-bearing formulas (CHONs: 31.4% to 37.1%). Tube wells also accumulated reduced, energy-rich DOM with correspondingly high molecular lability indices. Paradoxically, correlation networks suggested that these saturated aliphatic and halogenated structures persist due to kinetic protection under low oxygen, high-salinity conditions. These findings indicate that aquifer structure and redox conditions control DOM biogeochemistry in coastal groundwater systems. At the molecular level, DOM dynamics are influenced by aquifer depth and seasonal recharge, leading to a decoupling between salinity and organic matter transformation. Full article

(This article belongs to the Special Issue Characterization and Monitoring of Coastal Hydrological Environment for Assessing the Impact of Seawater Intrusion on Coastal Aquifers)

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16 pages, 13612 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Integrated Multi-Scale Hydrogeophysical Characterisation of a Coastal Phreatic Dune Aquifer: The Belvedere–San Marco Case Study (NE Italy)

by Benedetta Surian, Emanuele Forte and Luca Zini

Hydrology 2025, 12(11), 304; https://doi.org/10.3390/hydrology12110304 - 15 Nov 2025

Cited by 1 | Viewed by 2335

Abstract

Low-lying coastal plains are increasingly threatened by saltwater intrusion, yet the extent of the phenomenon and the role of coastal dune systems remain unevenly assessed. In the northern Adriatic Sea (NE Italy), salinisation has been documented, but systematic, spatially resolved studies are lacking. This work investigates the Belvedere–San Marco relict dune system to assess its hydrogeological function and vulnerability to seawater intrusion. An integrated methodology combining borehole and core stratigraphy, in situ water electrical conductivity (EC) measurements, and multi-method geophysical surveys (FDEM, ERT, GPR, active seismics) was tested. Results reveal a consistent stratigraphy of permeable aeolian sands overlying clay-rich units, with groundwater EC values in the dune sector always remaining well below thresholds for brackish or saline conditions. Geophysical imaging reveals that the dunes are low-conductive bodies contrasting sharply with the conductive surrounding lowlands, thus indicating the persistence of a freshwater lens sustained by local recharge within the dunes. The Belvedere–San Marco dunes therefore act as both freshwater reservoirs and natural hydraulic barriers, buffering shallow aquifers against salinisation. This study demonstrated the applicability of integrated geophysical methods to extensively investigate shallow phreatic aquifers lying a few metres below the surface, and establishes a baseline for monitoring future changes under rising sea levels, subsidence, and increased groundwater exploitation. Full article

(This article belongs to the Special Issue Characterization and Monitoring of Coastal Hydrological Environment for Assessing the Impact of Seawater Intrusion on Coastal Aquifers)

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23 pages, 8881 KB

Open AccessFeature PaperArticle

Stable Water Isotopes and Machine Learning Approaches to Investigate Seawater Intrusion in the Magra River Estuary (Italy)

by Marco Sabattini, Francesco Ronchetti, Gianpiero Brozzo and Diego Arosio

Hydrology 2025, 12(10), 262; https://doi.org/10.3390/hydrology12100262 - 3 Oct 2025

Viewed by 2325

Abstract

Seawater intrusion into coastal river systems poses increasing challenges for freshwater availability and estuarine ecosystem integrity, especially under evolving climatic and anthropogenic pressures. This study presents a multidisciplinary investigation of marine intrusion dynamics within the Magra River estuary (Northwest Italy), integrating field monitoring, isotopic tracing (δ¹⁸O; δD), and multivariate statistical modeling. Over an 18-month period, 11 fixed stations were monitored across six seasonal campaigns, yielding a comprehensive dataset of water electrical conductivity (EC) and stable isotope measurements from fresh water to salty water. EC and oxygen isotopic ratios displayed strong spatial and temporal coherence (R² = 0.99), confirming their combined effectiveness in identifying intrusion patterns. The mass-balance model based on δ¹⁸O revealed that marine water fractions exceeded 50% in the lower estuary for up to eight months annually, reaching as far as 8.5 km inland during dry periods. Complementary δD measurements provided additional insight into water origin and fractionation processes, revealing a slight excess relative to the local meteoric water line (LMWL), indicative of evaporative enrichment during anomalously warm periods. Multivariate regression models (PLS, Ridge, LASSO, and Elastic Net) identified river discharge as the primary limiting factor of intrusion, while wind intensity emerged as a key promoting variable, particularly when aligned with the valley axis. Tidal effects were marginal under standard conditions, except during anomalous events such as tidal surges. The results demonstrate that marine intrusion is governed by complex and interacting environmental drivers. Combined isotopic and machine learning approaches can offer high-resolution insights for environmental monitoring, early-warning systems, and adaptive resource management under climate-change scenarios. Full article

(This article belongs to the Special Issue Characterization and Monitoring of Coastal Hydrological Environment for Assessing the Impact of Seawater Intrusion on Coastal Aquifers)

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29 pages, 8155 KB

Open AccessEditor’s ChoiceArticle

Time-Series Analysis of Monitoring Data from Springs to Assess the Hydrodynamic Characteristics of a Coastal Discharge Zone: Example of Jurjevska Žrnovnica Springs in Croatia

by Andrej Stroj, Jasmina Lukač Reberski, Louise D. Maurice and Ben P. Marchant

Hydrology 2025, 12(5), 118; https://doi.org/10.3390/hydrology12050118 - 13 May 2025

Cited by 1 | Viewed by 2328

Abstract

This study assesses the functioning of the karst aquifer system located on the Croatian coast of the Adriatic Sea, where saltwater intrusion often presents a major problem for freshwater supply. We use two years of sensor data collected from two coastal springs to conduct a range of time-invariant and time-variant statistical analyses over various timescales. We perform separate analyses of the within-day and longer-term variation in the data as well as the interactions between the spring levels, salinity, rainfall, and sea levels. Such comprehensive analyses provide a greater understanding into the inner functioning of the intricate, heavily karstified aquifers. Time-invariant time-series analyses of the hourly data indicate that the spring levels and salinity are strongly controlled by sea levels. Furthermore, time-variant wavelet analyses demonstrate that the variation in spring levels in both springs has two modes defined by flow regime. Increases in the delay of the spring response to sea level indicate that aquifer diffusivity decreases in low flow conditions. Analyses facilitated the development of a conceptual model of the karst subsurface in the discharge zone. Using daily data, we constructed a linear mixed model of the spring levels. This model identified long-term sea level changes, rainfall from previous weeks, and seasonal recharge patterns as the primary factors influencing longer-term spring dynamics. Full article

(This article belongs to the Special Issue Characterization and Monitoring of Coastal Hydrological Environment for Assessing the Impact of Seawater Intrusion on Coastal Aquifers)

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