Groundwater Sensitivity to Climate Variations Across Australia

Groundwater response to climate variations is often pivotal to managing groundwater sustainably. However, this relationship is rarely explicitly examined because of the complexity of surface to subsurface processes and the diverse impacts of multiple drivers, such as groundwater pumping and land use changes. In this paper, we address this challenge by proposing methods to quantify the sensitivity of groundwater level and recharge to temporal climate variability across Australia. Using the HydroSight groundwater hydrograph toolbox we first identify 1,143 out of a total of 4,350 bores as climate‐driven, where historically, head was primarily driven by climate variations. Streamflow elasticity measures are then adapted to groundwater to quantify the long‐term head and recharge sensitivity. We find that the national median sensitivity of head and recharge to precipitation change are 42 and 0.43 mm mm−1, respectively (interquartiles: 20–77 and 0.30–0.55 mm mm−1); both of which are ∼8 times that of potential evapotranspiration. Nationally, the results are spatially correlated, suggestive of large‐scale effects. The responses of head and recharge appear to be primarily related to climate type and hydrogeology. The more arid the climate, the higher the head sensitivity but the lower the recharge sensitivity. Porous media generally show higher head sensitivity than fractured media due to smaller aquifer specific yield, and again contrarily for that of recharge. These findings contribute to understanding the long‐term impact of climate change on groundwater and thus provide valuable insights for sustainable groundwater management. Plain Language Summary In this study, we assess the response of groundwater to meteorological variations by using long‐term groundwater level records across Australia. We first identify the sites where the groundwater level has been primarily impacted by climate variations alone. The changes in groundwater level and replenishment rate (also called “recharge”) at the natural sites are simulated under a range of precipitation and evapotranspiration shifts and their relationships are statistically quantified. Results show that the national median groundwater level changes by 42 mm and the recharge changes by 0.43 mm per 1 mm change in precipitation. The response of groundwater level and recharge are found to be primarily governed by the inherent properties of the sites, such as climate type and hydrogeology. This study provides valuable insig