Source provides a variety of catchment constituent generation and filtering options. Channel routing, Reservoir Sedimentation and simple decay are included in the core model, with in-stream processing via specialised plugins.

Catchment modelling is an ideal tool to investigate constituent budgets and the potential impact of management strategies and it follows that the better a catchment model performs spatially and temporally the greater the confidence in targeted management actions.¹

Constituents refer to materials that are generated, transported and transformed within a catchment and affect water quality. Common examples include sediments, nutrients and contaminants, such as salt or dissolved solids.

Processes that act on these constituents to generate, transport and transform them can be modelled in Source. A constituent can enter or exit the modelled network in several different contexts:

as water travels over a surface
as a concentration at a point
laterally along a link.

Constituent generation models describe how constituents are generated within a functional unit and the resulting concentrations or loads delivered to the sub-catchment link. Point concentrations and lateral infiltration are configured within the node or link feature editor.

Once the constituent is in the system, other processes can act to move or otherwise transform it.

Constituent filtering models represent any transformation of constituents between generation by a constituent generation model and arrival at the sub-catchment link.
Constituent routing models describe the movement of constituents along a river channel network, including exchange of constituent fluxes between floodplains, wetlands, irrigation areas and groundwater. Constituent routing models are conservative, meaning that they do not alter the total mass of constituent stored in the system;
Constituent processing models describe processes that can alter the mass of a constituent in a storage or river reach (link), such as via a decay process.

Model elements that have constituent functionality include:

Links
Inflow nodes
Splitter nodes (Regulated and unregulated)
Confluence node
Minimum flow nodes (used to generate orders for dilution flows)
Storage nodes (These model reservoirs, wetlands and re-regulating weirs. Flows are routed through weirs using the same methodology as links)
Supply point nodes
Water user nodes and associated demand models
Loss Nodes
Gauge Nodes
Wetland Hydraulic Connector Nodes

¹ C. Dougall a and C. Carroll (2013), Great Barrier Reef Source Catchment’s modelling: Enhanced simulation and water quality targeting through event based assessment. Anderssen, R.S. and Boland J. (eds) MODSIM2013, 20th International Congress on Modelling and Simulation. Modelling and Simulation Society of Australia and New Zealand, December 2013. ISBN: 978-0-9872143-3-1.

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