Zambezi river basin aquifer systems: opportunities and challenges in using freely available data sources and groundwater flow modelling for spatial exploratory analysis

A groundwater flow model was implemented over the Zambezi River Basin using the state-of-the-art DHI-WASY finite element code Feflow. The analysis was based upon different freely available datasets that include a hydrologically consistent digital elevation model from HYDROSHEDS, the BGS (British Geological Survey) quantitative hydrogeological maps, and the regional hydrogeological SADC-GMI database. The model implementation was aimed at: (i) to identify and analyse challenges and limitations (data scarcity, accuracy of regional datasets, impact of geological, tectonic and hydrogeological complexity on model reliability) in applying groundwater flow modelling at basin scale; (ii) to perform an exploratory spatial analysis with reference to the magnitude and spatial distribution of effective recharge, aquifers’ properties and interlinks between surface water and aquifer systems (surface water – groundwater interactions). High uncertainty is generally associated with the estimation of hydrological and hydrogeological parameters, whose high spatial variability is not necessarily captured by the regional data products. This study evaluates how integrating freely available datasets (such as the DEM, BGS maps) influences model accuracy and uncertainty, particularly in terms of parameter estimation. The findings illustrates that, despite the limitations, freely available datasets can still effectively be used to develop a groundwater model that captures regional piezometric trends and provides insights into spatial variability. This demonstrates the potential for using such models in similar data-scarce regions. The modeling approach is expected to provide valuable quantitative insights into groundwater trends and variability, helping to identify key areas of uncertainty and guiding future data collection and model refinement efforts.