Assessment of groundwater vulnerability and contamination risk using multi-criteria analysis in a coastal aquifer system

Project Abstract

This study presents a comprehensive assessment of groundwater vulnerability and contamination risk in a coastal aquifer system by integrating multi-criteria analysis (MCA) with hydrogeological and spatial data to support sustainable groundwater management under rising anthropogenic pressures and climate variability. The methodology combines aquifer vulnerability indicators such as intrinsic vulnerability (porosity, hydraulic conductivity, and recharge rates), hydraulic gradient, aquifer thickness, and soil/soil-water interactions with contamination indicators including nitrate and heavy metal concentrations, salinity intrusion metrics, microbial indicators, land-use pressure, proximity to potential pollution sources, and waste management practices. Spatially explicit weighting schemes are developed using analytic hierarchy process (AHP) and entropy balancing to reflect local hydrogeochemical conditions and stakeholder priorities. A geographic information system (GIS)-based framework is constructed to standardize data integration, normalize heterogeneous datasets, and generate a composite vulnerability index (CVI) and a contamination risk index (CRI) across the study domain. Groundwater samples collected from a stratified network of observation wells are analyzed for major ions, trace elements, stable isotopes, and groundwater age (tritium/3H and 14C) to characterize baseline water quality, recharge dynamics, and mixing processes. The CVI emphasizes hydrogeological susceptibility, while the CRI emphasizes actual contamination signals and exposure pathways. The two indices are integrated through a fusion model to produce a final risk map that identifies high-risk zones requiring prioritized management actions such as land-use zoning adjustments, enhanced wastewater treatment, artificial recharge optimization, and monitoring network improvements. Sensitivity analyses test the robustness of risk rankings against changes in indicator weights and data uncertainty. Results indicate spatial heterogeneity in vulnerability and contamination risk, with coastal margins showing elevated salinity intrusion potential and nitrate loading near agricultural and urban interfaces, while deeper aquifers display moderate vulnerability but elevated long-term salinity risks due to sea-level rise. The study also demonstrates how MCA-based risk assessment can reveal critical thresholds where incremental anthropogenic inputs lead to disproportionate increases in groundwater risk, highlighting the importance of proactive governance, stakeholder engagement, and integrated water resource management. The outcomes include actionable maps and decision-support tools designed to assist local authorities, water utilities, and communities in prioritizing protection measures, allocating monitoring resources, and evaluating the effectiveness of policy interventions over time. The research contributes to methodological advancements by validating a transferable MCA-GIS framework for coastal aquifer systems and by providing a data-driven approach to quantify the coupling between vulnerability and actual contamination exposure under complex hydrogeological settings.

Project Overview

What This Project Is About

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A straightforward look at how groundwater in a coastal area can be at risk from pollution and processes that change the water chemistry. The project uses a simple framework called multi-criteria analysis to combine different clues about vulnerability and contamination, such as soil and rock properties, land use, and water quality data, to identify where the water is most at risk and why.

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The Problem It Addresses

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Coastal groundwater often faces pollution from nearby activities like farming, industry, and waste disposal, and saltwater intrusion can push seawater into freshwater layers. However, it is hard to tell which places are most at risk because many factors influence vulnerability. This project helps prioritize areas for protection and monitoring.

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Objectives of the Project

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1. Identify key factors that influence groundwater vulnerability in a coastal aquifer.
2. Combine these factors into a simple scoring framework to map risk areas.
3. Produce a clear vulnerability map that can guide local decision makers.
4. Explain how land use and human activity affect contamination risk.
5. Suggest practical actions to reduce risk in high-priority zones.

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What You Will Do Step by Step

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1. Review basic concepts of groundwater and contamination in coastal zones.
2. Gather data on geology, aquifer properties, land use, and water quality.
3. Explain what multi-criteria analysis means in simple terms.
4. Create a simple scoring model and combine factors into a risk map.
5. Validate the map with available observations or expert input.
6. Interpret results and identify hot spots for action.
7. Discuss limitations and possible improvements.

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Expected Outcome

A practical vulnerability map showing high, medium, and low risk zones, a short explanation of why each area is risky, and recommended steps for monitoring and protection to reduce groundwater contamination in the coastal aquifer.