# Numerical modelling of Macquarie Harbour

Terry, CT (1998) Numerical modelling of Macquarie Harbour. PhD thesis, University of Tasmania.

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## Abstract

Tiris thesis is about the creation of a numerical model and its application to Macquarie
Harbour (Tasmania, Australia). With the aim being to better understand the harbour and aid
the management of its environment and industry. A numerical model was developed through
the combination of an original two-dimensional laterally averaged river model and an
existing three-dimensional ocean model. The existing three-dimensional model used is the
Princeton Oceanographic Model (POM) by Blumberg and Mellor (1987), which is used for
modelling the harbour. The author's river model is used for the two main rivers flowing into
Macquarie Harbour, and part of the ocean surrounding the harbour.
The river model is based on non-Boussinesq primitive equations, which include the density
terms neglected in the commonly used Boussinesq approximation. These density terms are
important where there are large salinity stratifications, which occur in the rivers flowing into
Macquarie Harbour. The primitive equations for the model are derived in a rectangular
Cartesian co-ordinate system and then transformed to a a co-ordinate system. The a coordinate
system transformation, also used by POM, non-dimensionalises depth - resulting in a
more accurate and efficient method for handling a varying bathymetry.
The river model is solved with a finite difference implicit scheme, which is numerically
centred in space and time. As the models' bathymetries vaiy from 1 to 90m, to get the
required resolution in the deeper sections with the a co-ordinates, the resulting vertical
spacing in the shallow sections is small. Hence, the finite difference equations are solved
vertically, which avoids a restrictive Courant, Friedrichs and Lewy (CFL) time restraint with
the explicit finite difference operators.
The model successfully predicts the general circulation and pollution distribution in the
harbour, agreeing to within 36% of peak velocities measured using a broad-band acoustic
doppler current profiler (Koehnken, 1996). It also gives a reasonable representation of the
salinity profile in the Gordon River compared to measurements taken by the Hydro-Electric
Corporation (HEC), during the Lower Gordon River Scientific Survey (HEC, 1979). With
an average depth of 25m, the harbour is sensitive to wind stresses and the large inflow from
the Gordon River. fu the northern harbour, the polluted King River water is mixed by the
tide and action of the Gordon River water.
With no previously published numerical models of Macquarie Harbour, the model from this
thesis has and will continue to be a useful management tool for the environmental
instrumentalities and industry.

Item Type: Thesis (PhD) The Author Copyright 1998 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s). Thesis (Ph.D.)--University of Tasmania, 1999. Includes bibliographical references 04 Feb 2015 23:38 13 Jul 2016 00:21 View statistics for this item