Surface water-groundwater interactions during extreme floods : hydrologic and biogeochemical controls on water quality
- In both natural and human-impacted ecosystems, floods play a pivotal role in shaping our environment. In natural systems, floods replenish groundwater and support riparian habitats. In intensively managed environments, engineered floods have become a valuable tool for mitigating the effects of global change. During flood managed aquifer recharge (flood-MAR), for example, water managers intentionally inundate working landscapes in order to replenish depleted aquifers. Both natural and engineered floods deliver an influx of water and reactive species into the subsurface, triggering a complex web of hydrologic and biogeochemical processes that can mobilize nutrients and contaminants, impacting water quality. Through a combination of modeling and data science approaches, my research sifts through this complexity and seeks to understand the fundamental drivers of surface and groundwater quality during extreme floods. In my first chapter, I examine the impact of seasonal floods on redox cycling in heterogeneous floodplain aquifers. Through stochastic reactive transport simulations, I show that the hydrogeologic properties of a floodplain often exert a stronger control on redox conditions than do biogeochemical reaction rates. In subsequent chapters, I identify controls on the movement of water and solutes through the subsurface during flood-MAR. Using high-resolution hydrogeophysical data and hydrologic simulations, I find that tension-driven flow within the vadose zone draws recharge water away from coarse-grained flow paths and traps it in lenses of fine-grained sediment. These fine-grained sediments can take years to drain following inundation, limiting recharge efficiency. In my final chapter, I pair hydrologic simulations with Lagrangian particle tracking to investigate contaminant transport during flood-MAR. Results reveal that recharge water applied at the surface takes decades to reach the water table, during which time some contaminants may be removed through biogeochemical reactions. Overall, my work deepens our understanding of subsurface hydrologic and biogeochemical processes during inundation and provides actionable insights for sustainable water resource management in a changing climate.
|Type of resource
|electronic resource; remote; computer; online resource
|1 online resource.
|Perzan, Zachary Michael
|Degree committee member
|Degree committee member
|Stanford Doerr School of Sustainability
|Stanford University, Department of Earth System Science
|Statement of responsibility
|Submitted to the Department of Earth System Science.
|Thesis Ph.D. Stanford University 2023.
- © 2023 by Zachary Michael Perzan
- This work is licensed under a Creative Commons Attribution 3.0 Unported license (CC BY).
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