CAREER: Hydrodynamic Controls on Fluid and Solute Exchanges Across the Aquifer-Estuary Interface

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Surface water and dissolved chemicals cycle through sediments that underlie rivers and the ocean due to tides, waves, currents, and other hydrological processes. Within the sediments, dissolved chemicals, such as organic carbon and nitrate, undergo chemical transformations before re-entering surface water. This cycling affects river and ocean water quality, ecosystem health, and coastal groundwater resources. This project will quantify and map water and chemical exchanges and saltwater intrusion along the land-sea transition zone in three types of estuaries using surface water, groundwater flow, and biogeochemical computer models. The research will be integrated into a multi-step educational pipeline for high school students from underrepresented communities in the hydrologic sciences though field-based learning, and professional development courses on groundwater-surface water interactions that will be offered through partnership with a regional interstate compact. There is limited understanding of the scales of groundwater-surface water and associated chemical exchanges between river and ocean systems. The project will fill this knowledge gap by addressing fundamental questions on the connectedness of rivers and oceans through groundwater-surface water exchanges in estuaries. The research will develop new coupled surface water, groundwater, and reactive transport modeling approaches to understand the role of estuary hydrodynamics and heterogeneity in surface water chemistry on driving fluid and chemical exchanges across aquifer-estuary interfaces. Knowledge of river to seabed exchanges will allow for more accurate estimates of nutrient, metal, contaminant, and carbon fluxes to the ocean, thus bridging understanding of subsea exchanges to exchanges in terrestrial river corridors. Insights into hydrodynamic controls on groundwater-surface water exchanges will 1) aid in predicting the impacts of sea level rise on chemical transformations in estuarine pore water, 2) improve coastal surface water quality models, 3) guide coastal groundwater resource management, and 4) strengthen long-standing restoration efforts in the study estuaries.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.