HR: 0800h
AN: H51F-02    [Abstracts]
TI: Integrated Hydrogeochemical and Geophysical Interpretation of Groundwater Salinization in an Uplifted Pleistocene Carbonate Aquifer of Barbados
AU: * Mayers, B
EM: barry.mayers@gmail.com
AF: Barry L Mayers, Faculty of Pure and Applied Sciences, University of the West Indies, Cave Hill, Barbados
AU: Farrell, D
EM: dfarrell615@earthlink.net
AF: David Farrell, Caribbean Institute for Meterology and Hydrology, Husbands, St James, Barbados
AU: Coffey, R
EM: rucoffey@ic.sunysb.edu
AF: Ruth Coffey, Marine Sciences Research Center, Stony Brook University, Stony Brook, NY 11794, United States
AU: Thompson, G
EM: gregory.o.t@gmail.com
AF: Gregory Thompson, Barbados Water Authority, Spring Garden, St. Michael, Barbados
AB: Understanding the processes that influence spatial and temporal distributions of aquifer salinity are essential to the development of a groundwater salinity management plan. In this paper, we integrate geophysical, hydrogeochemical and submarine seepage measurements to develop a conceptual hydrogeological model of groundwater salinization of a Pleistocene carbonate aquifer that has experienced Quaternary glacio-eustatic sea- level changes and tectonic uplift. The Pleistocene carbonate rock mantles moderately folded and faulted Tertiary marine sedimentary rocks of early Eocene to middle Miocene age. The main issues to be addressed are (1) an understanding of the hydrogeological regime of the karst aquifer, (2) the origin and extent of aquifer salinization, and (3) groundwater provenance. Non-invasive Time Domain and Resistivity soundings were used to map the subsurface electrical resistivity structure to infer the distribution of aquifer salinity and geologic structure. An analysis of the major and minor ions was used to evaluate groundwater chemistry patterns and the main mineralization processes. Submarine seepage measurements were taken from random locations in the near- shore region including a region of spring discharge. The results suggest (1) a heterogeneous distribution of fresh and saline groundwater that deviates from the idealized freshwater/saltwater transition zone on the decimeter scale, (2) a transition from Ca- HCO3 to Na-Cl type waters towards the coast indicating mixing with saline groundwater, (3) an Mg/Ca ratio that suggest aquitard-influenced saline groundwater (4) seepage of recirculated saline groundwater at locations where seepage springs are absent, and (5) an aquifer that has not been adequately flushed. In order to support these concepts, further work will utilize stable and environmental isotopes to age-date both fresh and saline groundwater and to evaluate the effects of water-rock and aquifer- aquitard interactions on the spatial and temporal distribution of aquifer salinity.
DE: 1099 General or miscellaneous
DE: 1835 Hydrogeophysics
DE: 6334 Regional planning (1880)
SC: Hydrology [H]
MN: 2007 Joint Assembly