Alluvial channel sands in active ephemeral streams are potentially highly productive aquifers that are normally fully recharged annually. The groundwater resource is constrained by the limited three-dimensional extent of these aquifers. Concepts are developed that propose an increase in alluvial aquifer dimensions at geological boundaries. Multi-electrode resistivity and ground penetrating radar are used to investigate the dimensions of an alluvial channel at a geological boundary with the more resistant lithology upstream. These investigations reveal that alluvial channel fill dimensions are increased in the overlying less-resistant lithology downstream of the boundary. Groundwater flow modelling has been used to determine aquifer potential and identify key fluxes, indicating that significant irrigation potential exists from these aquifers
