Source requires functionality to model the movement of conservative constituents (eg. salt) along a river channel network, including exchange of constituent fluxes between floodplains, wetlands, irrigation areas and groundwater.
This functionality is required in Source to satisfy legislative requirements that exist in the Murray-Darling Basin. The MDBA’s Basin Salinity Management Strategy (BSMS) requires that the MDBA, state governments and the federal government contribute to reducing dryland and river salinity through land-use measures, salt interception schemes etc. To evaluate the impacts of these activities a reliable salinity modelling framework is required.
Model elements that require conservative constituent functionality include:
- Link
- Inflow node
- Splitter node (Regulated and unregulated)
- Confluence node
- Minimum flow node (used to generate orders for dilution flows)
- Storage node (These model reservoirs, wetlands and re-regulating weirs. Flows are routed through weirs using the same methodology as links)
- Supply point node
- Water user node and associated demand models
- Loss Node
- Gauge Node
- Wetland Hydraulic Connector Node
This section describes the generic model for routing conservative constituents through links available in Source. It is based on a marker tracking method (Close, 1996).
"Markers" are established at the upstream end of the model and their movement downstream is modelled. The marker travels at the average speed of water in the river reach, thus is dependent on the routing of flow (inflow, outflow, storage, losses and gains for each division). The impact of inflows, evaporation and losses on the solute concentration of the marker is also described.
The method is appropriate for modelling the transport of most conservative constituents within stream channels. The method is inherently stable and is not affected by sudden changes in either concentration or flow.
The model will maintain a conservative constituent balance, even when a reach division ceases to flow and the dead storage evaporates, by allowing the modeller to maintain a small nominal storage volume in the division at all times.
Scale
Conservative constituent routing operates at the same spatial scale as link routing and operates at every model time-step when it is activated.
Principal developer
eWater CRC
Scientific provenance
The principles of the marker tracking method are described by Close (1996). Marker tracking has previously been implemented in BigMod.
Version
Source version 2.19
Dependencies
Each link where conservative constituent routing is activated requires a node at its upstream end to define constituent inputs, and a node at the downstream end to process constituent outputs as appropriate. It is also dependent on the routing of flow (inflow, outflow, storage, losses and gains for each division).
Assumptions and constraints
The parameters for particle tracking are summarised in to Table 1. Definitions of variables used in equations in following sections are listed in Table 2.
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