Density Constrains Environmental Impacts of Fluid Abstraction in Closed‐Basin Lithium Brines

The unprecedented expansion of lithium mining in closed‐basin brines is sparking concerns that mine‐related brine abstraction will stress freshwater resources and harm sensitive wetland ecosystems. These fears stoke preexisting conflicts between indigenous communities, governments, and mining interests. However, until now there has not been a comprehensive evaluation of how groundwater flux to wetlands in these systems responds to brine and freshwater abstraction to support these concerns. This study characterizes the hydrogeologic relationship between both brine and freshwater abstraction and groundwater discharge to wetlands in closed‐basin brine systems utilizing groundwater‐flow models representing three closed‐basin brine system endmembers. The models show that regardless of hydrogeologic conditions, fresh groundwater abstraction has a 200%–2,300% larger impact than halite brine abstraction on groundwater‐dependent wetlands over a 200‐year period. The primary control mechanisms for groundwater discharge response to abstraction are proximity to the abstraction point and density‐driven storage flux, which magnifies the impacts of freshwater abstraction and buffers the impacts of brine abstraction. Observations of changes in wetland vegetation near existing lithium brine mines show a 90% reduction in vegetated wetland area in response to freshwater abstraction but no observable change in response to brine abstraction, in agreement with the results of the modeling study. These findings demonstrate that minimizing freshwater use is more effective at protecting groundwater‐dependent wetlands than limiting brine drawdowns in closed‐basin brine systems.