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Wednesday, January 13, 2010 - 14:00
Heriot-Watt University


Water Quality Modelling in a Tropical Macro-Tidal Creek
Buffalo Creek is a macro-tidal estuary located adjacent to the main body of DarwinHarbour in tropical northern Australia. Treated sewage effluent is discharged into the creek which then flows into ShoalBay. The location is complex in hydraulic terms as the 8 metre tidal range means that the two-dimensional hydrodynamic model must consider all parts of the intertidal and coastal zone which floods at high tide. This includes mudflats adjacent to the creek, areas of mangrove forest, upper and lower reaches of the creek and the coastal waters of ShoalBay.
Survey data have been gathered from a combination of available remote sensing, ground and marine surveys. The mangrove areas of the creek have been a particular challenge due to access difficulties and the presence of saltwater crocodiles. The model uses RMA10 and RMA11 which are, respectively, solutions of the Navier-Stokes and the advection-diffusion equations implemented in finite element form. Validation depends on existing tidal and water quality data from previous studies.
The research has initially focused on the dispersion of conservative and non-conservative constituents. The effect of nutrient and pathogen inputs from sewage is also being examined. This work will be informed by a study of the effects of point and diffuse pollution sources on processes, habitats and biota in DarwinHarbour which is concentrating on the least studied habitat, the mudflats.  The main future threats to the health of DarwinHarbour come from urban development.  This project will provide critical information for predicting the effect of future urban development on tropical estuarine ecosystems. Ultimately, the effect of changes to river flow, sediment and nutrient inputs to the estuary will be assessed.  The study will provide the scientific basis for informed policy decisions for future development in DarwinHarbour and the need to ameliorate anthropogenic inputs.

Professor Eric Valentine is a civil engineer with over 30 years experience in hydraulic modelling and coastal and environmental engineering in New Zealand, the UK and Australia.
He currently leads a small research group in the School of Engineering and Information Technology of Charles Darwin University, Darwin, Australia which focuses on hydrodynamic and water quality modelling for harbour, estuary and river issues in the Northern Territory.


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