HR: 14:30h
AN: H13C-05    [Abstracts]
TI: Using Electromagnetic Soundings to Determine Fresh and Saline Water Relationships on Barbados, Antigua, and Socorro Islands
AU: * Sandberg, S K
EM: ssandber@chuma1.cas.usf.edu
AF: University of South Florida, Department of Geology 4202 East Fowler Ave., SCA528, Tampa, FL 33620 United States
AU: Farrell, D
EM: dfarrell@cnwra.swri.edu
AF: Southwest Research Institute, CNWRA , San Antonio, TX 78238 United States
AU: Varley, N
EM: nick@ucol.mx
AF: Universidad de Colima, Facultad de Ciencias Av. 25 de Julio #965, Colima, Col CP 28045 Mexico
AU: Mayers, B
AF: APUA, Antigua Public Utilities Authority, St John's, Antigua and Barbuda
AU: Barnes, H
AF: Barbados Water Authority, Barbados Water Authority, St. Michael, Barbados
AU: Wooller, L
AF: The Open University, Department of Earth Sciences Walton Hall, Milton Keynes, MK7 6AA United Kingdom
AU: MacNeil, R
AF: University of South Florida, Department of Geology 4202 East Fowler Ave., SCA528, Tampa, FL 33620 United States
AB: Seawater intrusion can significantly limit the amount of potable groundwater available to coastal communities. Management of the water resources available to such communities is increasingly being studied using an interdisciplinary scientific approach that includes geophysical methods, existing and new well information, and conceptual hydrogeological models as input for complex groundwater modeling. Calibration and validation of groundwater flow models depend on an accurate knowledge of water table elevations, the nature of the fresh - saline water interface at depth, and the spatial variation of hydrologic parameters and variables (including permeability, porosity, storativity, and concentration). Determining the spatial variability of hydrologic variables and parameters sufficient to support detailed hydrologic modeling (including conceptual model development, calibration, and validation) can be achieved though non-invasive geophysical methods at a fraction of the cost associated with more traditional methods, such as drilling. In this study, electromagnetic soundings are used to provide basic information to support an analysis of the density-driven interaction between fresh and saline porewaters on the Caribbean islands of Barbados and Antigua, and Socorro Island in the Pacific. Studies in Barbados and Antigua represent coastal aquifers affected by pumping, and hence modification of the location and widths of the fresh/seawater interface. Data from Socorro Island represents a natural interface, unaffected by anthropogenic modification. Electromagnetic sounding-derived data are shown to provide significant basic information that supports some or all of the following (i) choice of conceptual models of flow, (ii) characterization of the geologic and hydrolgeologic environments, and (iii) model calibration and validation. For example, on Barbados, data from the soundings demonstrated the existance of a diffused freshwater/seawater interface and the presence of karst conduits. On Antigua, the soundings demonstrated that seawater intrusion was focused along stream valleys and was more than likely exacerbated by pumping inland and adjacent to the valleys.
DE: 0684 Transient and time domain
DE: 1803 Anthropogenic effects
DE: 1829 Groundwater hydrology
DE: 1884 Water supply
SC: Hydrology [H]
MN: 2005 Joint Assembly