Vulnerability indicators of seawater intrusion in offshore aquifers

Zayed Mohammed Asiri, Anthony D. Miller, Adrian D. Werner, Cristina Solórzano-Rivas, Sergiy Shelyag

Research output: Contribution to journalArticlepeer-review

7 Downloads (Pure)

Abstract

This study represents the first attempt to define vulnerability indicators for offshore fresh groundwater, extending prior analyses of the key threats to onshore coastal aquifers. The method applies an existing steady-state sharp-interface coastal aquifer model with semi-confined offshore extension to characterise the sensitivities of the tip and toe locations (top and bottom of the freshwater–seawater interface, respectively) and the freshwater and seawater volumes to environmental changes that threaten offshore freshwater resources. Sensitivity analysis applied to seven case studies quantifies their vulnerability to seawater intrusion from sea level rise, recharge change and a regional change in the onshore groundwater heads. The analysis demonstrates that the tip-to-toe distance in offshore aquifers is constant for different fresh groundwater discharge rates (under certain conditions). Otherwise, the interface is usually longer (flatter slope) in offshore aquifers than in onshore aquifers, except where the offshore limit of the aquifer is reached. The offshore extension of the aquifer leads to more seaward toe positions, increases the interface length and reduces the onshore seawater volume. As the freshwater discharge increases, the offshore freshwater volume becomes more vulnerable to impacts from changes in the freshwater discharge until the tip reaches the offshore limit or the toe crosses the coastline. For high values of freshwater discharge, the volume of freshwater stored offshore is more vulnerable to losses from changes in the freshwater discharge rate than is the onshore freshwater storage. For lower values of freshwater discharge, however, offshore freshwater storage is generally less vulnerable than onshore freshwater storage. Contrasts in the behaviour of onshore and offshore freshwater require that both need to be considered in coastal aquifer vulnerability assessments.

Original languageEnglish
Article number132004
Number of pages13
JournalJournal of Hydrology
Volume643
DOIs
Publication statusPublished - Nov 2024

Keywords

  • Analytical solution
  • Freshwater–saltwater interface
  • Offshore fresh groundwater
  • Sea level rise
  • Subsea aquifer

Fingerprint

Dive into the research topics of 'Vulnerability indicators of seawater intrusion in offshore aquifers'. Together they form a unique fingerprint.

Cite this