Focused groundwater recharge is controlled by landscape and climate

Focused groundwater recharge, the concentrated infiltration of water through surface features such as streams, depressions, or fractures to the water table, is widely accepted as the dominant recharge mechanism in arid climates. As climates become increasingly arid, groundwater recharge is expected to shift towards focused mechanisms. Yet the magnitude of focused recharge, its spatial distribution and controls across different climate zones remain poorly characterised at the continental scale. Here, we compare historical rainfall tritium with >1,700 groundwater tritium measurements to assess the likelihood of focused groundwater recharge across the Australian continent, providing important context for water resources management in Australia, with global implications. 46% of bores assessed show evidence of focused recharge, suggesting that conventional recharge estimates based solely on diffuse mechanisms may substantially underestimate total recharge. We show that in Australia, fractured rock and perennial watercourses are the main landscape features that strongly influence the likelihood of focused recharge. While focused recharge is most common in arid regions, it also occurs in wetter climates where fractured rock enhances subsurface connectivity. As aridity and climate variability intensify, understanding the landscape-climate interactions that enable focused recharge, and how shifts in energy and water availability alter the role of groundwater in the water cycle, will be critical to sustaining groundwater resources.
If you use the datasets or Python script, we would appreciate it if you could cite this resource as well as the research article submitted to Communications Earth and Environment that is yet to be accepted/published. Details of the journal article will be made available upon final publication. For any further information, please do not hesitate to contact Stephen Lee on [e-mail].