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

Demand for lithium batteries is growing rapidly with the global push to decarbonize energy systems. The Salar de Atacama, Chile holds ∼42% of planet's reserves in form brine hosted massive evaporite aquifers. mining these brines and associated freshwater use has raised concerns over environmental responsibility extraction, yet large uncertainties remain regarding fundamental aspects governing hydrological processes environments. This incomplete understanding led perpetuation misconceptions about what constitutes sustainable or renewable water therefore justifies responsible allocation. We present an integrated assessment using tritium stable oxygen, hydrogen isotopes paired remotely sensed terrestrial hydroclimate data define unique sources distinguished by residence time, physical characteristics, connectivity modern climate. Our results describe impacts prolonged drought on surface groundwaters demonstrate that nearly all inflow basin composed recharged >65 years ago. Still, precipitation critical sustaining important wetlands around salar. Recent rain events have increased vegetation extents storage while mining-related withdrawals continued. As we show, poor conceptualizations complex systems perpetuated misallocation misattribution impacts. These issues apply arid regions globally. new framework basins moves beyond calculating gross inputs-outputs at a steady state include compartmentalized stores constitute “modern” budgets.