Groundwater wells Dr. Carolyn D. Ruppel United States Geological Survey

United States Geological Survey Woods Hole Science Center 384 Woods Hole Road Woods Hole Massachusetts 02543-1598 USA

cruppel@usgs.gov Dr. Samantha B. Joye University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

mjoye@uga.edu http://www.marsci.uga.edu/directory/samantha-b-joye Georgia Coastal Ecosystems LTER Project

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

gcelter@uga.edu https://gce-lter.marsci.uga.edu/ Dr. Carolyn D. Ruppel United States Geological Survey

United States Geological Survey Woods Hole Science Center 384 Woods Hole Road Woods Hole Massachusetts 02543-1598 USA

cruppel@usgs.gov Principal investigator 2000-01-01 2002-12-31 Dr. Samantha B. Joye University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

mjoye@uga.edu http://www.marsci.uga.edu/directory/samantha-b-joye Principal investigator 2000-01-01 2026

Groundwater enters the GCE domain via sub-marsh flow, at seepage fronts, and as baseflow to tidal creeks. We have well fields at two sites (GCE 4 and 10) that are sampled regularly for nutrients and water level (wells previously installed at GCE 3 are no longer flowing). We also have instrumented wells located on two marsh hammocks that were set up as part of our efforts to evaluate controls of upland/intertidal gradients lateral gradients (Q4). Time series of well water level fluctuations can be used to identify the predominant flow paths at each site. Analyses of these time series during GCE I by C. Ruppel identified an asymmetric tidally-induced groundwater signal at site 10, which indicates that the hammock’s surficial aquifer responds like a confined aquifer to fluctuations in the Duplin River. Thus, we infer relatively low discharge rate or material exchange between the hammock and the tidal creek. At site 3, Ruppel documented a high degree of hydraulic connectivity between marsh monitoring wells proximal to the upland and the tidal creek, implying the presence of a high permeability pathway between the two and leading us to conclude that submarsh groundwater flow was a reasonable flow pathway along this salinity gradient. At site 4, on the landward side of the GCE, there is a "normal" signal in which the marsh acts as a low-pass filter for the tidal fluctuations, and there is relatively little evidence of submarsh flow. This site is heavily dominated by the influence of surface water flow.

Question 2: How do the spatial and temporal patterns of biogeochemical processes, primary production, community dynamics, decomposition, and disturbance vary across the estuarine landscape, and how do they relate to environmental gradients? (more information)

salinity LTER NSF Georgia GCE groundwater hammock marsh sub-marsh wells Overall geographic extent of the research project -81.370752 -81.195661 31.546868 31.448419 2000-01-01 2002-12-31

National Science Foundation grant number OCE-9982133

estuary marsh complex Hunt Camp - Barrier island/marsh site on western Sapelo Island. This site is located at the upper reaches of the Duplin River, and is within the Sapelo Island National Estuarine Research Reserve. Existing well fields border small marsh area to northwest, some wells have been installed to south end of hammock where marsh is more extensive and permanent plots are located. Two existing hydrographic sondes and weather stations within this site are operated by SINERR (Hunt Camp dock) and UGAMI (flume dock). -81.295506 -81.258908 31.497026 31.462320 North Sapelo - High salinity marsh/Sapelo Sound site. Few or no small creeks, but one large creek is easily accessed. Further upstream upland drainage is affected by culvert at Reynolds' duck pond. Upland is heavily forested. Hydrographic sonde is deployed adjacent to this site attached to a channel marker (under U.S. Coast Guard permit). A huge mud flat is present at the northern tip of Sapelo Island. -81.233249 -81.195661 31.546868 31.515188 Meridian - Inland marsh and tidal creek site near Meridian, Georgia. The primary marsh site is to the south of the dock in front of the Sapelo Island Visitor Center. Some small creeks and one large creek (Hudson Creek) are present. Upland is heavily forested. Marsh to the north of the dock can be used for additional studies if larger areas are required. Upland to the North is being developed for residential use, so future access is uncertain. The USGS super station site (weather station plus multiple-sensor sonde) is deployed off the ferry dock. Salinity is similar to seawater because there is little freshwater input from the upland. -81.370752 -81.357256 31.463533 31.448419 Moore, W.S., Krest, J., Taylor, G., Roggenstein, E., Joye, S.B. and Lee, R.Y. 2002. Thermal evidence of water exchange through a coastal aquifer: implications for nutrient fluxes. Geophysical Research Letters. 29(14):1704. (DOI: 10.1029/2002GL014923) http://onlinelibrary.wiley.com/doi/10.1029/2002GL014923/abstract HYD-GCES-1401b - Groundwater well pressure, temperature, conductance, salinity and oxygen measurements for GCE-LTER study hammock PC_i_29 from 15-Aug-2008 to 13-Dec-2013 https://gce-lter.marsci.uga.edu/public/app/dataset_details.asp?id=567 HYD-GCES-1401a - Groundwater well pressure, temperature, conductance, salinity and oxygen measurements for GCE-LTER study hammock HN_i_1 from 30-Oct-2008 to 03-Dec-2013 https://gce-lter.marsci.uga.edu/public/app/dataset_details.asp?id=566