The Hydro Lab is willing to study transient, variable-density fluid flow in almost any setting, from coastal ecohydrology to brine migration in the Alberta Basin. Check the projects below for a sampling of current and recent work, and please contact Dr. Wilson if you are interested in joining the lab!
Fluid and Chemical Fluxes across the Seafloor
Radium isotope activities in the Atlantic Ocean suggest that brackish and saline porewaters discharge to the ocean in volumes that exceed river discharge – but there is very little evidence to support such large fluxes near the coastline, where the vast majority of studies have focused. It is much easier to explain the Ra isotopes if saline groundwater discharges across the broad continental shelf (Moore 2010). In a collaborative project with Drs. Scott White and Billy Moore, Ph.D. student Camaron George has used heat as a tracer to show that groundwater discharges from the continental shelf in pulses as sites located 10-15 km from shore. The pulses relate to wind-driven variations in sea level. There has to be much more flow than just the pulses we have detected so far, so Ph.D. student Jacob Vincent has taken up the project, improving instrumentation and working with Drs. Jay Pinckney, Susan Lang, and Angie Knapp to link this nutrient-rich groundwater discharge to primary productivity on the continental shelf.
Hydrogeology and Ecological Transitions in Salt Marshes
The landward boundary of a salt marsh marks a major ecological transition. This boundary is also where rising sea levels and changing precipitation patterns are most likely to cause significant changes in vegetation. Sophia Sanders (not in the photo!) and I are working with Dr. Steve Pennings and other collaborators at the Georgia Coastal Ecosystems LTER to link changes in hydrology with observed changes in vegetation and ecological productivity.
Does Development Affect Groundwater Composition in Tidal Creek Basins?
We know that surface water quality differs between developed and undeveloped basins, so what about groundwater? It turns out that it is complicated. But M.S. student Meghan Shanahan and a team of outstanding field assistants (thanks to Baker Stevens, Allison Davis, and Parker Whitley!) collected hundreds of samples from 15 tidal creeks in South Carolina. We found evidence that development affects the composition of groundwater in tidal creek watersheds, but that salt marshes probably act as buffers for development.
Hydrogeology, Ecology and Radium Tracers in a Salt Marsh Island
How could drought affect a salt marsh on an island that is flooded by the tide twice a day? Andrea Hughes did her Ph.D. research on a salt marsh island in North Inlet, SC, that was affected by salt marsh dieback during the 2001-2002 drought. She found that more rainfall infiltrates the marsh than you would think. Dieback at this site was probably caused by a rapid increase in salinity during the drought (Hughes et al., 2012).
This island is also an excellent place to investigate controls on Ra activities in coastal groundwater. Ra is an excellent tracer for monitoring submarine groundwater discharge (SGD), but the groundwater endmember is hard to define in many systems because it varies significantly in time and space. Sediment heterogeneity contributes to spatial variation in Ra activities in the porewater, and groundwater exchange causes significant additional temporal and spatial variability (Hughes et al., 2015).
Hydrogeology of a Barrier Island
Cabretta Island is a Holocene barrier island with a salt marsh, freshwater upland, and beach. Groundwater studies of Cabretta Beach led Ph.D. student Tyler Evans to wonder how common “upper saline plumes” are in different types of beaches (Evans and Wilson, 2016, 2017). Work in the salt marsh on the landward side of the island shows that storm surge can drive significant volumes of creek water into salt marsh systems (Wilson et al. 2011). Groundwater exchange between the marsh and the estuary is strongly dependent on tidal amplitude and seasonal variations in mean water level (Wilson et al. 2015a). Spatial variations in groundwater flow patterns within the marsh also coincide with ecological zonation (Wilson et al. 2015b).