Investigating the impact of morphology on spatial patterns of groundwater exchange in the Wairau River

Abstract

Braided rivers are common to many regions of New Zealand. Often, they are major drivers of groundwater recharge in the coastal regions. Understanding of the processes of water exchange between rivers and regional aquifers is mandatory for sustainable management of these aquifers. Recent research has proposed the concept of a braidplain aquifer (BPA), a shallow reservoir within the active braidplain channel of the rivers, in hyporheic and parafluvial exchange with the river and simultaneously with the regional aquifer (Wilson et al. 2024). the shallow nature of the braidplan aquifer suggests that morphological changes of braided rivers, that are frequently caused by flood events, highly impact these systems and their interaction with regional aquifers. this work aims to investigate and visualize the morphological effects on river - groundwater exchange in a section of the Wairau River by a detailed physics-based modelling of the coupled system.