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

Abstract

Numerical simulations of density-dependent flow assess the risk of saline groundwater intrusion in coastal areas (Heiss & Michael, 2014;Meng et al., 2002;Trabelsi et al., 2013), and in arid and often endorheic basins where evaporation outpaces recharge and concentrates solutes in groundwater (Stein et al., 2019). The discrepancy in fluid density develops an interface where the denser brine underlies the less dense fluid to create a freshwater lens, which is commonly known as a brine-to-freshwater interface (Duffy & Hassan, 1988;

Multifidelity Surrogate Models for Efficient Uncertainty Propagation Analysis in Salars Systems

“…Given that the Salar de Atacama has been exploited for a number of decades, it has been widely studied and recently various aspects of flow and brine transport processes for this salar have been simulated using VDST models based on a vertical slice conceptualization (Marazuela et al, 2018(Marazuela et al, , 2020McKnight et al, 2021). Such an approach is a practical approximation of the inherent 3D dimensionality of the physical flow system, given the formidable computational cost of a large-scale 3D VDST model and the spatial and time resolution requirements to simulate high-density differences between freshwater and brine (Marazuela et al, 2018).…”

“…Such an approach is a practical approximation of the inherent 3D dimensionality of the physical flow system, given the formidable computational cost of a large-scale 3D VDST model and the spatial and time resolution requirements to simulate high-density differences between freshwater and brine (Marazuela et al, 2018). Therefore, the VDST numerical model of the present work is based on an idealized 2D vertical slice, conceptually similar to the numerical model instance presented in Marazuela et al (2018) and McKnight et al (2021). The horizontal extent of the model begins from the end of the salt flat nucleus, includes a mixing zone of 5 km and continues for another 10 km in the recharge area (Figure 2).…”

“…This conceptualization ignores the simulation of the early forced convection and fingering phase (Hamann et al, 2015) as it is not the focus of the present study. Thus, the left constant concentration boundary represents the brine plume entering the mixing zone assuming it has been already fully developed into the salt flat nucleus, which is also the approach followed by McKnight et al (2021). The system is simulated until head and brine distribution reach steady state conditions, after a long simulation period of 10,000 years.…”

“…While the above past studies mostly developed small-scale numerical models focusing on the mixing area of salars, only recently large-scale VDST numerical models have been employed to study groundwater flow and brine transport (e.g., Marazuela et al, 2018). McKnight et al (2021) studied the impact of hydraulic conductivity heterogeneity on the interface between freshwater and brine in salars while Marazuela et al (2020) used a thermohaline flow model to describe the process of Lithium enrichment in the Salar de Atacama.…”

Relic Groundwater and Prolonged Drought Confound Interpretations of Water Sustainability and Lithium Extraction in Arid Lands

“…The intense evaporation that far outpaces precipitation on the basin floor has created a massive evaporite deposit (Corenthal et al., 2016) and brine body. The high‐density brine interacts with inflowing freshwater to create density‐driven groundwater flow conditions and fresh groundwater upwelling, which in turn results in freshwater discharge from the low elevation springs (McKnight et al., 2021). The halite‐rich brine aquifer, within the nucleus, is currently being exploited for its lithium resource (Munk et al., 2016).…”