Management of geohydrologic data using a geographic information system for a three-dimensional ground-water flow model of the Savannah River site area, South Carolina and Georgia

Possible migration of ground-water contaminants beneath the Savannah River from South Carolina near the US Department of Energy (DOE), Savannah River Site (SRS), a nuclear processing and disposal facility, into Georgia is a source of recent environmental concern. SRS is adjacent to the Savannah River and is underlain by 650 to more than 1,000 feet of permeable, unconsolidated to poorly consolidated fluvial, deltaic, and marine Coastal Plain deposits of Cretaceous and Tertiary age, which locally have been modified by faulting. The US Geological Survey, in cooperation with the US Department of Energy and the Georgia Department of natural Resources, is evaluating ground-water flow through six regional aquifers in these Coastal Plain sediments within a 3,000-square-mile study area using a modular, three-dimensional, finite-difference ground-water flow model (MODFLOW). ARC/INFO Geographic Information System (GIS) was used to manage and prepare data for input into the flow model. Temporally and areally spaced water-quality and ground-water level data are available for more than 2,800 wells on the 300-square-mile area of the SRS and in the surrounding rural area. Data related to topography, geology, elevations of aquifer tops, well construction characteristics, water levels, and aquifer characteristics were compiled into GIS files or coverages within the system.more » A menu-driven program was developed to derive hydrogeologic surfaces from point and contoured data over the study area; assign wells to aquifers based on well-construction data; discretize aquifer property data into model input arrays; graphically display geologic, hydrologic, and ground-water flow model output data; check for data errors; and alter and refine input arrays.« less