Abstract
We use a high resolution, three dimensional, calibrated and coupled hydrodynamic, sediment and biogeochemical model to demonstrate and quantify the nutrient dynamics of an estuary. Observations alone cannot be used to understand estuarine dynamics and the impact of various management scenarios. Calibrated models and model scenarios are useful to provide additional understanding of estuarine systems and can be used to explore and quantify alternative management scenarios. Using the biogeochemical model we identified several management scenarios to demonstrate a range of water quality impacts associated with variation in river flow, sewage and aquaculture nutrient loads and marine flushing. The model was used to inform strategic management of waterways and also gives insight into the biogeochemical and physical dynamics of a temperate salt wedge estuary in South Eastern Australia. A low river flow simulation with high anthropogenic nutrient loads resulted in extension of the estuarine salt wedge upstream due to lower river input. The higher levels of denitrification in this scenario helped to offset increased nutrient fluxes across the marine boundary and the increases in sewage treatment plant and industry loads. However the simulation suggested there would be higher concentrations of nutrients and chlorophyll in the surface layers and lower relative levels of dissolved oxygen in the bottom waters and sediment. The simulation with the lowest loads and with no anthropogenic input resulted in low nutrient concentrations indicating that under these conditions the nutrients are retained and recycled in the estuary. The use of our 3D model allowed greater detail of understanding of the estuary dynamics and loads which is essential for testing the realistic state of future management possibilities when running scenarios.
Published Version
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