An investigation into structural discretisation as a first-order and pilot framework to understand groundwater–stream water connectivity at a reach scale

This study undertook a structural discretisation as a first-order and pilot framework to understand groundwater–stream connectivity at a local to reach scale. Structural discretisation was used as the categorisation of hydrogeological landscapes, where areas having relatively uniform geology and hydrogeological characteristics were conceived of as a single-hydrologic landscape. The results of the study led to the development of reach-scale groundwater–stream typologies, a new paradigm recommended as a first-order and pilot tool to establish a groundwater–surface water interaction framework in similar settings. The typology on the southeastern side reach of the study area is the lateral contact type where groundwater enters the riparian area aquifer from the terrestrial area aquifer through the laterally continuous alluvial gravel sequence. Therefore, over-abstraction from the terrestrial and/or riparian area aquifer may result in the loss of baseflow into the river. The confined contact-type typology operates on the northern reach where the groundwater–surface exchange primarily takes place between the stream and the riparian area aquifer because, due to low-hydraulic conductivities, the terrestrial area aquifer only permits little groundwater to enter or leave the terrestrial area aquifer. In this case, progressive over-abstractions from the riparian area will primarily draw water originating from the stream through transmission losses, resulting in progressively induced stream infiltration. Consequently, groundwater–surface water interaction typologies can also play a key role in the formulation of conjunctive water resource management for greater water supply security and stability.