This dataset accompanies the manuscript "Impacts of lithium brine mining on groundwater-dependent ecosystems in a multi-producer basin". Global lithium demand under the electromobility transition is driving the rapid expansion of lithium mining. Most new exploration will occur in closed-basin lithium brine deposits, where lithium mining consumes both lithium-rich brine and fresh water. However, closed-basin lithium brines primarily occur in water-scarce, endorheic basins, where new groundwater abstraction could strain water resources. Environmental impact assessments of mining operations in these basins typically evaluate only a single producer and overlook the cumulative impacts of multiple water users. Furthermore, simple water footprint calculations do not capture the complex dynamics between dense brine and fresh water, requiring variable-density modelling[sm1.1][DC1.2] to reasonably predict and evaluate the impacts of groundwater abstraction in these basins. This study is the first to utilize a three-dimensional, variable-density groundwater-flow model to simulate the effects of groundwater abstraction by multiple lithium producers on groundwater-dependent ecosystems, providing a framework for basin-scale environmental impact assessments of groundwater abstraction that is transferable to over 100 lithium brine resources identified globally. This model of the Salar del Hombre Muerto eastern subbasin simulates the individual and combined effects of three producers on surface and groundwater flows to groundwater-dependent ecosystems. The simulations demonstrate that distribution of abstraction within the subbasin and well placement control environmental flow reductions and that conversion from evaporative techniques to direct lithium extraction technology with brine reinjection may have the potential to mitigate environmental flow impacts. These results indicate that direct lithium extraction may be more effective than evaporative techniques at reducing abstraction impacts beneath groundwater-dependent ecosystems.