Collaborative Research: Groundwater Dynamics of a Barrier Island

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Coastal groundwater is a crucial resource for potable water supply and the functioning of ecosystems on both sides of the land/ocean interface. In spite of the global importance of this resource, controls on groundwater dynamics and biogeochemical cycling in coastal settings are poorly understood. Multiple processes drive fresh and saline groundwater flow and mixing at the coastline; the relative roles of these processes are unclear. This project is designed to quantify groundwater flow and chemical exchange at the coastal interface under varying weather and tide conditions. Our primary hypothesis is that brief, high-energy storm events have a major impact on chemical exchange between permeable subterranean sediments and the coastal ocean. A barrier island will serve as a field site because the same complex, transient flow processes operate in a barrier island as on the mainland coast, but at a greatly reduced scale. Barrier islands also stand alone as important and increasingly developed components of the coastline. Piezometers will be installed on Sapelo Island, Georgia, to monitor groundwater hydraulic head, temperature, salinity, radium isotope tracers, and associated biogeochemistry. Numerical models of variable-density fluid flow, heat transport, and solute transport will be developed to aid interpretation of thermal and geochemical data and to quantify fluid flow patterns and rates associated with competing flow processes. This work has immediate implications for contaminant transport in developed settings, saltwater intrusion into coastal aquifers, and ecosystem functions in settings such as salt marshes and coastal fisheries. Knowledge of coastal groundwater dynamics is also critical for understanding the impact of sea level rise and changes in storm frequency associated with climate change. This work complements ongoing work at the Sapelo Island LTER. The project will train at least two graduate students and three undergraduates in fieldwork and scientific research, and the project will coordinate with such programs as the South Carolina Alliance for Minority Participation (SCAMP) and the Center for Ocean Sciences Education Excellence for the southeast (COSEE-SE).