Paper No. 3
Presentation Time: 2:15 PM
USING END-MEMBER MIXING ANALYSIS TO UNDERSTAND STORM-EVENT STREAM FLOW IN THREE SMALL CATCHMENTS OF COASTAL SOUTH CAROLINA
GRIFFIN, Michael P.1, CALLAHAN, Timothy J.
2, VULAVA, Vijay M.
2, GARRETT, C. Guinn
3, HITCHCOCK, Dan
4, AMATYA, Devendra M.
5 and WILLIAMS, Thomas M.
6, (1)Environmental Studies Graduate Program, College of Charleston, 66 George Street, Charleston, SC 29424, (2)Geology and Environmental Geosciences, College of Charleston, 66 George Street, Charleston, SC 29424, (3)Master of Science in Environmental Studies, College of Charleston, 66 George St, Charleston, SC 29424, (4)Biosystems Engineering Department, Belle W. Baruch Institute of Coastal Ecology and Forest Science Clemson University, P.O. Box 596, Georgetown, SC 29442, (5)Center for Forested Wetlands Research, USDA Forest Service, 3734 Highway 402, Cordesville, SC 29434, (6)Baruch Institute of Coastal Ecology and Forest Science, Clemson University, Georgetown, SC 29442, mpgriffi@g.cofc.edu
Forested lowland catchments of the southeastern coastal plain of the USA are affected by many change agents: climatic and meteorological shifts, land-use and land-cover modifications, and recently sea-level rise and saltwater intrusion of groundwater. To better understand the effects of these interrelated changes on coastal-plain hydrology, it is critical to understand current baseline groundwater and surface-water interactions in minimally disturbed, forested catchments. The objectives of this study were to: 1) develop a mixing model using end-member mixing analysis (EMMA, a multiple-hydrogeochemical-tracer approach) for three small forested catchments in coastal South Carolina of varying soil type and 2) use EMMA-based chemical hydrograph separation to compare storm-event runoff among the catchments.
Two catchment sites are within or near the USDA Forest Service’s Santee Experimental Forest, near Charleston, SC, and a third site is near Georgetown, SC. Stream water and potential end-member samples were analyzed for major ions, and results were used to construct EMMA-based chemical hydrograph separation models for each study site during moderate and large storms and for various antecedent soil moisture conditions.
Preliminary findings indicate that rainwater and soil porewater are among the dominant sources of stream flow at all sites. Groundwater contribution varied for each site. Upland shallow groundwater is limited at one site perhaps due to the large percentage of wetland area within the catchment. Streambed groundwater is limited at another site likely due to the presence of a clayey argillic horizon; at this site, stream flow occurs rapidly and the storm water chemistry is dominated by rainwater. In general, sites dominated by loam and sandy-loam soils appear to have a larger degree of mixing of riparian groundwater and runoff. With the likelihood of increasing urbanization and extreme weather events (such as tropical storms and flooding), increased surface runoff may diminish the role of groundwater contribution to stream flow and enhance rainwater contribution.
