Groundwater Modeling and Impact Assessment for Large-Scale Lithium Brine Operations in Northwestern Argentina

OUR CHALLENGE

A combination of surface and groundwater resources undergo treatment before use in a selective adsorption process to extract lithium from brine in a high-altitude desert region of northwestern Argentina. To improve sustainability of existing water withdrawals and to support several proposed mine expansions, an additional, larger aquifer was identified as a potential source of raw (untreated) groundwater. Short-term aquifer testing suggested the required supply could successfully be achieved. However, the long-term impacts of groundwater extraction on streamflow in a nearby stream, on groundwater elevations, and on upwelling of deep saline water required evaluation before initiating full-scale production.

OUR APPROACH

We compiled publicly available third-party borehole logs, geophysical survey data, water levels, and assay data, and combined them with our client’s characterization data to develop sub watershed-scale 3-dimensional geologic and conceptual models. These provided the foundation for a numerical flow and transport groundwater model developed using MODFLOW-USG and capable of simulating the complex interactions between groundwater pumping, surface water flow, and dissolved solute migration. The groundwater model was iteratively calibrated to steady–state water levels and streamflow, and transient pumping during short-term aquifer tests, resulting in robust conceptual and groundwater models.

OUR IMPACT

The calibrated groundwater model was used to evaluate the long-term impacts of groundwater withdrawals under a variety of likely operation plans and production scenarios assuming 38 years of pumping followed by 20 years of recovery. Model predictions suggested all the scenarios tested were sustainable and acceptable with respect to impacts on surface water flow, groundwater levels, and groundwater quality. Results also suggested all process water could be sustainably sourced from the aquifer and Integral recommended that its client request to increase the permitted pumping capacity to meet the maximum predicted demand.