Groundwater response to historic climate variability and change

<p>Climate change is projected to impact water resources in many countries around the world, but the projections are highly uncertain due to numerous assumptions of the hydrological stationarity, model structures, and complex hydrodynamics in the surface and subsurface. Quantifying the historic impact of climate variability and change on water resources allows for an improved understanding of the hydrological and climate processes which is necessary for accurate projections. Due to the long memory in groundwater systems of the impacts of climate variability and change, there is an opportunity to investigate the historic impact of long-term changes on water resources. Analysing groundwater hydrographs over multiple decades potentially allows for the quantification of the response of groundwater head to climatic changes. However, there are challenges in using this long-term information to quantify historic climate impacts. One of the challenges is to separate the impact of climatic change on groundwater from other influential drivers, such as pumping for agricultural irrigation, land use and land cover changes, and natural climate variability. In addition, the often short and interrupted nature of groundwater records limits the investigation of long-term impacts. In this study, we establish and test methods to quantify the response of groundwater to climate variability and change at natural sites (not affected by anthropogenic activities) identified across Australia, overcoming the aforementioned challenges. Results show that location, climate, and aquifer hydraulic property play a role in controlling the response of groundwater head and recharge to climate variations, compared with land use changes. This implies that future climate change may significantly impact groundwater availability by altering the response of groundwater. Quantifying the response of groundwater to climatic changes is needed to understand the future of groundwater systems globally. With this improved understanding we can work towards effective adaptive water management strategies for both human and natural systems.</p>