The University of the Western Cape approached Umvoto to update and calibrate a numerical groundwater model for the Windhoek Aquifer MAR scheme near Namibia’s capital city of Windhoek. The model was constructed using the MODFLOW code as utilized in the numerical modelling software, Groundwater Vistas. The model grid was refined along areas of importance and split into 7 layers based on the hydrostratigraphic understanding of the Windhoek Aquifer. Various sources of information were incorporated into the model, including data from newly drilled deep boreholes, updated recharge calculations and improved understanding of the complex geological and hydrogeological setting. The model was initially constructed in steady-state and calibrated to water levels observed in the 1950s, before large scale abstraction was implemented. Following successful calibration of the steady-state model, the model was converted into transient state, incorporating water level and rainfall measurements over the last 70 years. Different scenarios have been run related to the envisaged increased emergency abstraction from the aquifer and potential impact thereof, and assess the long-term sustainable and optimal utilisation of the aquifer.