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Title: A radioisotope tracer study of estuarine goundwater movement of the Eastern Australian coast
Authors: Hughes, CE
Stone, DJM
Acworth, RI
Keywords: Acquatic ecosystems
Chemical composition
Ground water
Groundwater recharge
Isotope applications
NAI detectors
Oxygen 18
Tracer techniques
Issue Date: 19-May-2003
Publisher: International Atomic Energy Agency
Citation: Hughes, C. E., Stone, D, J. M., & Acworth, R. I. (2003). A radioisotope tracer study of estuarine goundwater movement of the Eastern Australian coast. Paper presented at the 11th International symposium on isotope hydrology and integrated water resources management, Vienna, 19-23 May 2003. (pp. 183-187). In unedited proceedings, International synposium held in Viena 19-23 May 2003 organized by the International Atomic Energy Agency and the International Association of Hydrogeologists in cooperation with the International Association of Hydrological Sciences, "Integrated hydrology and integrated water management". Vienna: International Atomic Energy Agency.
Series/Report no.: IAEA-CN;104
Abstract: Groundwater discharge to coastal waters, and the associated transport of nutrients and contaminants, is believed to have a significant impact on coastal ecosystems. However, complex boundary conditions and rapidly changing short-term fluxes make net flows resulting from local or regional groundwater discharge difficult to quantify. Such boundary conditions include beach face wave runup and storm setup, sub-surface tidal forcing, frequent surface inundation and tidally driven surface/groundwater interactions in estuarine and coastal areas. Tracer techniques can complement hydrological and geochemical studies of such systems and help distinguish longer-term net fluxes from the highly variable short-term fluxes. At Hat Head, NSW, on the eastern Australian coast, a comprehensive study of hydrogeology and hydrogeochemistry has being conducted in an estuarine/coastal sand dune aquifer. A scheme currently under construction will dispose of treated sewage effluent from the small coastal community by injection into the sand dune aquifer. Geochemical and isotopic data from the site indicate a high degree of complexity showing evidence of regional groundwater flow occurring at depth and more localised and highly dynamic conditions in the top 10 m of the aquifer. Tritium data indicate that regional groundwater is modern and stable isotope ratios have been used to distinguish between salt flat and sand dune dominated systems where evaporative and seawater mixing processes are observed. Storm wave setup and beach wave runup have been shown to elevate the water table near the coast leading to flow reversal and potential discharge of effluent to the estuarine zone. A radioisotope tracer study of groundwater flow in response to tidal forcing was conducted adjacent to a tidal creek at Hat Head. Using the short-lived radioisotope conservative tracer, bromine-82, groundwater movement was tracked in-situ over a period of ∼5 days on two occasions encompassing both neap and spring tide conditions. The tracer was injected into a screened borehole and gross gamma counts monitored from an adjacent borehole using a variety of collimated NaI detectors as well as down-hole gamma spectrometry. This technique maps the path of the slow moving tracer without sampling and allows the net groundwater movement to be distinguished from short term tidally driven fluxes. Results from the environmental isotope and radiotracer studies will be presented. © The authors.
Gov't Doc #: 9588
ISBN: 9201086040
ISSN: 1563-0153
Appears in Collections:Conference Publications

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