Current research: groundwater-surface water interactions in coastal and alluvial aquifers, estimating past sea-level change, interannual and interdecadal controls on water resources in North Carolina
My research involves a variety of collaborations. Most recently, Dr. Chuanhui Gu, a colleague in the Department of Geology at ASU, and I have been using a variety of methods to study the interactions between groundwater and streams. Our work primarily involves field data collected at the ASU Educational and Research Wellfield, but it has also involved data collected in Boone Creek in Boone and on the ASU campus. During the spring and summer 2011, I spent seven months as a Visiting Fellow at the University of Plymouth, UK, where I worked with a graduate school colleague of mine, Dr. Roland Gehrels, on a project looking at new methods of reconstructing past changes in sea level. This work is on-going. A former departmental colleague, Dr. Ryan Emanuel, now at NC State, and I have collaborated on studies of climate influences on groundwater resources in North Carolina. This work is also on-going.
Coastal aquifers: Hatteras Island field site
The majority of my coastal aquifer research has been performed in the barrier-island aquifers of the Outer Banks. I have been working on this problem since 1994, when I was hired by the State of North Carolina to evaluate the surficial aquifer in the Cape Hatteras region. My coastal-related work on Hatteras Island involves using groundwater modeling techniques to evaluate variations in the mixing zone between fresh and saline water, which is commonly referred to as the subterranean estuary. There are many influences on the mixing zone. It is not static at any temporal scale, from wave run-up to diurnal tidal oscillations to monthly tidal variations to seasonal variations in aquifer discharge driven by recharge differences. Of early interest to me was the response of the mixing zone to the large storm events that frequently strike the Outer Banks. My studies demonstrate that it may take the mixing zone a decade or more to recover from a single storm event, calling the whole notion of a static boundary into question. The picture below shows the beach at Hatteras Island near the relocated lighthouse.
Coastal aquifers: Hallsands, UK, field site
I have spent the past three years developing a research program at a 'shingle' beach field site in Hallsands, UK. For this research, I am collaborating with Roland Gehrels, a professor at the University of Plymouth in Plymouth, England. I went to this field site for initial data collection in August 2009. I spent seven months as a Visiting Fellow of the University of Plymouth's Marine Institute in 2011. The ultimate goal of our study is to develop a new method of measuring past changes in sea level using freshwater reed samples rather than the traditional salt marsh samples. This research has also given me the opportunity to study a coastal barrier with a completely different hydrogeology than the barrier islands of North Carolina. The 'shingle' beaches of southwest England comprise high-permeability gravels overlying low-permeability peat. In addition, the macrotidal field site experiences maximum tidal variations of nearly five meters. The picture below shows the 'shingle' beach at Hallsands abutting the English Channel with the freshwater marsh to the right of the beach.
Alluvial aquifers: Boone Creek field site
A significant portion of my research time since my arrival at ASU has been the study the alluvial aquifers adjoining mountain streams. The alluvial aquifer research, although located in a completely different hydrogeologic environment, is similar to the research that I have conducted in coastal aquifers. It also is a study of an aquifer system, from recharge to discharge, with modeling techniques, and involving a component of groundwater-surface water interaction―in this case baseflow rather than SGD. This research also involves a component of transport, but instead of studying a transition zone between fresh and saline water, this work involves the study of stream and streambed temperatures and heat transport modeling. The picture below shows a portion of Boone Creek on the ASU campus.