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Abstract Coastal deltaic aquifers are vulnerable to degradation from seawater intrusion, geogenic and anthropogenic contamination, and groundwater abstraction. The distribution and transport of contaminants are highly dependent on the subsurface sedimentary architecture, such as the presence of channelized features that preferentially conduct flow. Surface deposition changes in response to sea‐level rise (SLR) and sediment supply, but it remains unclear how these surface changes affect the distribution and transport of groundwater solutes in aquifers. Here, we explore the influence of SLR and sediment supply on aquifer heterogeneity and resulting effects on contaminant transport. We use realizations of subsurface heterogeneity generated by a process‐based numerical model, DeltaRCM, which simulates the evolution of a deltaic aquifer with different input sand fractions and rates of SLR. We simulate groundwater flow and solute transport through these deposits in three contamination scenarios: (a) vertical transport from widespread contamination at the land surface, (b) vertical transport from river water infiltration, and (c) lateral seawater intrusion. The simulations show that the vulnerability of deltaic aquifers to seawater intrusion correlates to sand fraction, while vertical transport of contaminants, such as widespread shallow contamination and river water infiltration, is influenced by channel stacking patterns. This analysis provides new insights into the connection between the depositional system properties and vulnerability to different modes of groundwater contamination. It also illustrates how vulnerability may vary locally within a delta due to depositional differences. Results suggest that groundwater management strategies may be improved by considering surface features, location within the delta, and the external forcings during aquifer deposition.
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This content will become publicly available on September 22, 2026
Fluid Stretching at Facies Interfaces Governs Solute Transport
This study provides a kinematic explanation for why facies interfaces dominate solute transport in heterogeneous aquifers. Using flow and transport simulations, we apply kinematic metrics to quantify deformation processes that control plume evolution. Results show that strong conductivity contrasts generate preferential flow corridors, while transitional zones at facies interfaces act as persistent mixing fronts where stretching and folding intensify mixing. These cross-facies transitions emerge as the primary controls on transport observables such as dispersion and dilution, with within-facies variability exerting secondary effects. By linking sedimentary architecture to flow deformation, this work provides the mechanistic justification for earlier findings that cross-transition probabilities govern solute spreading. The results highlight the need to resolve geologic interfaces in both field characterization and remediation design. Flow topology offers a unifying framework for predicting transport in aquifers and points to opportunities for geophysical methods to target the key architectural features that regulate mixing and dilution.
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- Award ID(s):
- 2048452
- PAR ID:
- 10640611
- Publisher / Repository:
- ESS Open Archive
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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