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Title: Impact of Hydrostratigraphic Continuity on Brine‐to‐Freshwater Interface Dynamics: Implications From a Two‐Dimensional Parametric Study in an Arid and Endorheic Basin

Despite the prevalence of density‐dependent flow systems in the brine‐rich aquifers of arid climates and coastal aquifers, the impact of realistic geologic conditions on interface geometry and density‐dependent time‐sensitive dynamics remains poorly constrained. Salar de Atacama provides an analog for exploring interface dynamics in arid regions. A site‐specific two‐dimensional hydrostratigraphic interpretation is used to examine the dynamics of the brine‐to‐freshwater interface. With the same simulation framework and core data, a separate parametric series of hydraulic conductivity distributions with varying horizontal continuity provides a mechanistic explanation for observed dynamics. Comparing modeled interfaces and their sensitivity to perturbations in recharge in each realization yields insight into interface dynamics coupled with horizontal continuity in subsurface heterogeneity. Recharge fluctuation is introduced to each distribution following the interface reaching a dynamic steady state. Metrics for results evaluation include interface slope geometry, interface width, migration length, and response rate. Analyses suggest that the average slope of the modeled interface shallows by 0.01 and 0.05 m ⋅ m−1for an increase in continuity of highly permeable pathways by a factor of two and three, respectively. Increasing continuity also increases the overall response times and the variability in response. Results indicate that accurate representations of transient dynamics in modeling density‐dependent brine‐to‐freshwater interface dynamics requires the consideration of heterogeneity, as saline intrusion in the highest continuity group extends over twice as far on average and the modeled interface takes over 43% more time on average to reach a new dynamic steady state when compared to their homogeneous counterparts.

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Author(s) / Creator(s):
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DOI PREFIX: 10.1029
Date Published:
Journal Name:
Water Resources Research
Medium: X
Sponsoring Org:
National Science Foundation
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