| Table of Contents | ||
|---|---|---|
|
...
Processes that act on these constituents to generate and transport them can be modelled in Source and are broadly categorised as Catchment Water Quality Quality models and Storage and Link Water Quality models.
Catchment water quality models include:
- Constituent generation models - describe how constituents are generated within a functional unit (and any associated constituent sources) and the resulting concentrations or loads are delivered to the sub-catchment link
- Constituent filtering models - represent any reduction in constituents between generation within the FU and arrival at the link upstream of the sub-catchment link.
Storage and link water quality models include:
- 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.
...
| Info | ||
|---|---|---|
| ||
Note:
|
...
Figure 2. Configure constituents
| Anchor | ||||
|---|---|---|---|---|
|
There are two types of constituent routing available, Lumped and Marker routing. (Figure 2) and the choice made here will affect how constituents are routed at a link. Both of these are conservative routing models, which means that they do not change the total mass of constituent in the system.
Lumped routing (default) is the simplest and most common approach applied in Source. Constituents are routed within a link based on kinematic wave theory. Assuming fully-mixed conditions within a link, the constituent flux and concentration simply move from the top of a link to the downstream end of a link within a time step, preserving the mass balance. Constituent concentrations in a link can be altered by the addition of constituents generated from sub-catchments, external inflows, and losses defined within a reach; and
- Marker routing considers constituents as particles and tracks their movement within a link, which can be divided into divisions for hydrologic routing purposes. While available to all users this method is less commonly used. Initially, the model will start with a marker at the end of each division in every link. At every time step, a new marker for each constituent will be created for each division, and the distance a marker moves is driven by the velocity in the division over the current time step. While the flow rate is assumed constant over the timestep, the velocity within the division will change as a result of a change in reach storage. Markers will travel through the river network until they are either merged with adjoining markers or leave the river network (iei.e. via extractions, decay within the reach, evaporation, groundwater inflows/losses and rainfall). Although available to all users, this method is less commonly used. Refer to Marker routing (Particle tracking) - SRG for more information about Marker routing.
For marker routing, you must specify two additional parameters:- Minimum Marker Gap – defines the spacing between markers as either a fraction of the model time-step or fraction of the reach division. This parameter can improve model efficiency by reducing the number of markers that require processing at each model time step. The allowable range is from 0 to 1, with 0 not deleting any markers, while a value of 1 will ensure that at the end of each time-step, there is only one marker defined for each reach division; and
- Minimum volume – minimum volume required to maintain constituent mass balance within the links.
...
Before using this dialog, you need to define constituents and constituent sources (as described in Defining constituents) and also either set up your catchment area using the Geographic Wizard for catchments and assigned FU areas and/or add constituents to nodes or links Then, you can use the tree menu on the left to view the filter and generation models for each sub-catchment/FU combination, the instream processing model for each storage routing link, and the storage processing model for each storage node.
...
- Change the assigned model,
- Change the parameter values or input data for the assigned model,
- Filter columns based on their contents
- Sort columns in ascending or descending order; and
- For filter and generation models you can also change, add or remove constituent sources, see Configuring constituent sources.
Refer to Working with rainfall-runoff modelswith rainfall-runoff models for more details on assigning a constituent model, adding input data and changing parameters. For more information on using filters see Working with filters in the Feature Table. There is also a sub-catchment filter to help you find sub-catchments either by name or by using the sub-catchment map, see Sub-catchment filter.
...
Figure 3. Constituent Model Configuration
| Anchor | ||||
|---|---|---|---|---|
|
...
Along with flows, constituents are also transferred when using a Scenario Transfer node.
Constituents and Ownership
...
Linking constituent generation or filter models
| Info |
|---|
Note: This functionality is currently under development and not all models can be linked. The description that follows is an illustration of what can be undertaken in Source. |
Constituent generation and filter models may require one or more of their parameters to originate from another generation or filter model. Source allows a constituent NDR filter model to contain parameters which depend on a parameter from another generation / filter model. The concept is similar to that of functions whereby a parameter can be set from elsewhere in the system. Functions cannot be used here because the function manager is unable to influence the running order of models in a functional unit. So instead the design has a simple parameter linking tool which allows a user to connect one parameter on one constituent model to another parameter on another. The model parameter which is to be written to must have been compiled with metadata indicating that its value should come from another constituent model’s parameter. The function described above is termed as “Define Constituent Model Linkage” in Source.
Not all models can be linked. The description that follows is an illustration of what can be undertaken in the current version of Source, where nutrient delivery to the NDR filter model can be configured to depend on, for example, available sediment derived from another filter model (typically the SDR filter model) or one of the configured constituent generation models for a particular FU/sub-catchment combination
To configure constituent model linking between models for a given sub-catchment/FU combination and an optional constituent source, assign an NDR model to the “receiving” constituent, as shown in Figure 15. In this example TN is considered the “receiving” constituent. Although other filter models have been applied, only the NDR model has an active button where a link to another modelled constituent can be defined. The link is defined in the quickflowSedimentIn column. TSS, in this example, is the “contributing” constituent. Constituents derived through a Generation model and a Filter model are available for TSS. The user selects a contributing model and associated parameter which will provide the “contributing” constituent. In this example a linkage is defined between the SDR quickflowConstistuentIn parameter and the quickflowSedimentIn parameters of the NDR model (Figure 16). Once the linkage is created, the “contributing” model (in this case an SDR model) is run before the NDR (“receiving”) model, allowing the correct flow of data at the right point in time.
...
Once a constituent source has been defined, every sub-catchment/FU combination is automatically assigned the default constituent source for both constituent generation and constituent filtering. You can change the constituent source from the default or add or remove additional constituent sources in the Constituent Models table by right-clicking on the constituent source cell and using the dropdown to select an alternative source (Figure 19).
...