Groundwater systems of the upper Darling-Baaka River floodplain, New South Wales

Output Type: Exploring for the Future Extended Abstract

Short Abstract: Communities and ecosystems along the Darling-Baaka River have been impacted by critical water shortages and water quality issues including high salinity, algal blooms, and fish kills due to declining surface water flows. The river is characterised by naturally highly variable flows and is the primary water source for the region, but extraction and a meteorological drying trend associated with climate change have caused declines in discharge of 53–73% since the advent of post-settlement agriculture and industry. Understanding of the spatial extent, quality, and useability of lower salinity groundwater within the surrounding Darling Alluvium, which could provide an alternative and potentially more sustainable water source, was previously limited. Here we present the findings of an integrated study combining modelled ground and airborne geophysical data, groundwater and surface water levels, hydrochemistry, lithology, and remote sensing data to delineate groundwater systems and understand the geological and hydrological controls on their occurrence. The resolution and breadth of datasets acquired and collated permit mapping of the key factors controlling occurrence and quality of groundwater aquifers, namely basement topography and hydrostratigraphy, groundwater-surface water dynamics, and inter-aquifer connectivity. On this basis the study area can be sub-divided into regions with distinctive aquifer distribution and quality, recharge mechanisms, and pressure gradients between aquifers. We also showed that the groundwater levels in the unconfined aquifer have declined, an expected outcome of the decline in discharge in the Darling-Baaka River which forms the primary recharge mechanism for the alluvial aquifers. These outputs have direct implications for key management questions including location and quantity of potentially useable groundwater, risk of saline groundwater up-coning or discharging to the river, and likelihood of groundwater extraction impacting river flows and groundwater dependent ecosystems. 

Citation: Buckerfield, S., McPherson, A., Tan, K.P., Walsh, C., Buchanan, S., Kilgour, P., Suckow, A., Raiber, M., Symington, N. & Pincus, J., 2024. Groundwater systems of the Upper Darling-Baaka River Floodplain. In: Czarnota, K. (ed.) Exploring for the Future: Extended Abstracts. Geoscience Australia, Canberra. https://doi.org/10.26186/149718