Hydrodynamics of salt flat basins: The Salar de Atacama example

Area of Science:

• Hydrogeology
• Environmental Science
• Geochemistry

Background:

• The Salar de Atacama, a major lithium reserve, hosts sensitive ecosystems within a saline endorheic basin.
• Understanding its hydrodynamics is crucial before extensive brine extraction impacts the region.

Purpose of the Study:

• To characterize the hydrodynamics of the Salar de Atacama.
• To quantify its complex water balance in its natural state.

Main Methods:

• A three-dimensional groundwater flow model was developed and calibrated using numerous hydraulic head measurements.
• The model simulates vertical water flux through a saline interface due to density contrasts.

Main Results:

• The salt flat nucleus acts as a hydrodynamically quasi-isolated area due to low hydraulic gradients and a density-driven mixing zone.
• The quantified natural groundwater balance shows an inflow/outflow of 14.9 m³·s⁻¹.
• High infiltration rates (up to 85% of rainfall) were observed, contrary to typical hyperarid basin assumptions, due to rock fracturing and sparse vegetation.

Conclusions:

• The study reveals unexpected high infiltration rates in the Salar de Atacama, driven by geological and ecological factors.
• The findings suggest the basin functions as a closed endorheic system with no significant external inflows.
• The hydrogeological characterization provides a baseline for assessing the impact of future brine extraction.