CAREER: Subsurface critical zone architecture controls on hydrologic partitioning across spatial scales

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The global water cycle is accelerating in the face of climate change, however improving our predictions requires that we refine our understanding of how Earth’s subsurface regulates water movement and storage. Currently, we do not fully understand what controls how precipitation is allocated to soil water and groundwater recharge, streamflow, or plant water use. This research and education program will quantify how key hydrologic processes are controlled by the dynamic interactions between subsurface structure (e.g. depth to bedrock, porosity) and hydrologic forcings (e.g. precipitation amount and intensity). This field and modelling effort will be based in a semi-arid oak woodland in central coastal California and project outcomes will inform current water resource management efforts by regional water managers. This program will remove barriers for undergraduate participation in earth science research and showcase real-world applications through stakeholder-based undergraduate research experiences. Through development of online high school and undergraduate curriculum at the intersection of hydrologic sciences and environmental justice, the project will contribute to the development of a strong and diverse workforce in the earth sciences. This program will reach beyond traditional catchment hydrology boundaries to transform our understanding of how the vertical extent of the subsurface, from shallow soil down to unweathered bedrock, controls ecosystem water availability for plant water use, groundwater recharge, and downstream surface water resources. To meet this goal, this work will empirically test a conceptual model that relates differences in within-hillslope subsurface structure across contrasting aspects (south and north facing slopes) to dominant drivers of key hydrological processes. Specifically, project outcomes will be the identification of how differences in depth to fresh bedrock and gradients in material properties within hillslopes modulate subsurface water storage, and how this in turn regulates streamflow and evapotranspiration. This internal hydrologic regulation will help us better understand what controls plant water use, solute export, and water residence times from the hillslope to watershed scale.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.