2 CSIEM Model Overview

CSIEM is a spatially resolved 3-dimensional (3D) model able to simulate the environmental conditions within Cockburn Sound and adjacent areas within Perth Waters, spanning between Quinns Rocks and Mandurah. The depth gradient spans from the shallow littoral waters to approximately 20 meters at the centre of the Sound, and in the context of the interactions with ocean dynamics, catchment inputs, and variable climate forcing, this creates a spectrum of water quality conditions and habitat distributions. To capture the spatio-temporal dynamics of the system, CSIEM has been designed to bring together a system of environmental models able to sequentially “downscale” from global to regional to local, and “vertically integrate” between physical, chemical and biological processes (Figure 2.1).

At its core, the model platform consists of the hydrodynamic model TUFLOW-FV and the water quality model AED. Different model domain resolutions can be selected and/or time-periods of interest simulated. Different levels of model complexity are also configurable by the user (e.g., by enabling various biogeochemical or ecological components or modules), with common input files and output analysis workflows.

The model platform has been setup to allow for a variety of stakeholder needs and use-cases by providing a allows a common approach to setup, configuration and visualisation; for example, a long-term low-resolution habitat restoration simulation can be run alongside a high-resolution dredging scenario, with simulations sharing common model settings, parameters, and parameterisations. The intent is to provide decision-makers a single trusted tool that can be used to answer a diversity of questions that span from day-to-day management to long-term policy settings (e.g, restoration and climate change adaptation strategies).

In general, the models are configured to resolve hydrodynamics and flushing, water temperature and salinity, and numerous water quality attributes including oxygen, nutrients (organic and inorganic), planktonic organisms, seagrass and benthic communities, and suspended sediment. CSIEM also links a large volume of data from historical surveys, real-time data streams and recent experimental work. Complex integration workflows are implemented to process data for model inputs (e.g., boundary conditions) or model assessment (e.g., calibration or validation).