Page Comparison

Figure 4. Storage node (Constituents)

Inlet channel mixing allows you to introduce mixing of constituents at a conveyance link (Figure 5). You specify a percentage of the wetland/storage volume that is conceptually represented by the conveyance link, and the remaining volume represents the main body of the storage/wetland. When exchange  Whenexchange of water occurs between the wetland/river or the wetland/wetland, mixing of constituents is assumed to occur in the inlet channel. If the exchange of water is large enough to flush out the inlet channel, then the constituents will mix with the main body of the wetland, or the river depending on the direction of water exchange.

Figure 5. Storage node (Inlet channel mixing)

Additionally, for each constituent, you can configure various aspects of its concentration (Figure 6):

• Additional Inflow Load – specify the amount of constituent to be added to the storage per time-step. It is not specific where this constituent mass comes from;
• Groundwater – concentration of constituents entering the node via groundwater flow; and
• Gauged Concentration – the recorded concentration at that storage node over time. This can be used to compare against modelled results.

Figure 6. Storage node, Constituent concentration

Anchor
Links Links

Configuring constituents

along links

Constituents can be configured for storage routing links in the feature editor (Figure 7). In this screen, you can specify the link’s constituent concentration when the simulation begins. This parameter assigns a concentration for each modelled constituent in the scenario for the markers created in that link during the model initialisation. You can also specify the instream processing model, the parameters of which can then be configured by selecting Configure….

For each constituent, you can specify an increase in concentration from different sources, similar to constituents in the storage node (Figure 6). The parameters are:

• Additional Inflow Load – specify the amount of constituent to be added to the storage routing link per time-step. It is not specific where this constituent mass comes from;
• Groundwater – concentration of the constituent entering the link via groundwater flow; and
• Timeseries Flux  – concentration of the constituent entering the storage routing link via Timeseries viaTimeseries Flux.

Figure 7. Storage Link Routing (Constituents) 

Image Added

Configuring constituent in catchment models

Configuring constituent sources

The first step when configuring constituent sources is to add sources to the Constituents Configuration dialog (as described in Configuring constituents). By default, a single constituent source is added to the scenario when constituents are enabled. This can be changed by using the Set as Default contextual menu on the desired constituent source. The default source cannot be deleted and is the one that is automatically assigned to a FU/sub-catchment combination in the Constituent Model Configuration dialog (Figure 1).

By default, for a specified constituent, every sub-catchment/FU combination is assigned the default constituent source. To change the constituent source:

• Select the constituent you wish to change the source for (the tree view on the left) and the corresponding row in the table. Note that you can choose either the filter OR generation model, as any changes are automatically applied to both; and
• Right-click and choose Add Constituent Source » Current Constituent » <source name>. This will add a new row to the table, allowing you to assign and parameterise a new constituent generation or filter model for the selected constituent/FU.

You can also undertake the following actions using the same contextual menu:

• The process to remove a constituent source from a FU is identical to adding one. Choose Remove Constituent Source » Current Constituent » <source name>. Note that at least one constituent source must exist at all times. If all sources have been removed, a new row with the default source will be automatically added;
• Bulk assignments can be made to the table in one of two ways:
  • Using the All Constituents item; or
  • Selecting multiple rows, then right clicking and choosing the desired menu item. This becomes increasingly difficult as the scenario grows in size.

Figure 1. Constituent Model Configuration dialog

Image Modified

Constituent filter models

Filter models represent any transformation of constituents between generation within the FU and arrival at the link upstream of the sub-catchment node. Filter models process constituents within the FU and as with constituent generation models, are applied to FUs. In the Constituent Model Configuration dialog, click on any of the defined constituents under Filter Models (in the tree menu). Note that in Source, only one filter model can be applied to a sub-catchment/FU combination.

Assign and parameterise filtering models as follows:

1. First, assign a model to the sub-catchment/FU combination. To do this, change the model from the default (Pass through) to your required model:
   • Click on the cell in the Model column that you want to change; and
   • Click on the drop-down arrow that appears and choose the required model from the menu;
2. Then, assign input data (if relevant) to the model in the PET and Rainfall columns (if relevant); and
3. Finally, parameterise the filter model - depending on the chosen model, the right-side of the table will populate with the associated default parameters. Click on the cell and edit these values.

Constituent generation models

These describe how constituents (eg. sediments or nutrients) are generated within a functional unit and the resulting concentrations or loads delivered to the sub-catchment node. Click on any constituent to view the associated FU and generation model for each sub-catchment. Follow the same steps outlined for filter models to assign, add input data and parameterise constituent generation models. The available constituent generation models are:

• EMC/DWC - the Event Mean Concentration (EMC) Dry Weather Concentration (DWC) model applies two fixed constituent concentrations (EMC & DWC) to a FU to calculate total constituent load.
• Export rate - this model applies a fixed constituent generation rate to a functional unit (FU) to calculate total constituent load. It requires only a single parameter so is quick to use and therefore useful for exploring sensitivity.
• Nil Constituent - this model is used as a substitute constituent generation model where no constituent load needs to be modelled for a given constituent from a given FU
• Observed concentration - this option allows you to assign observed quick flow and slow flow concentrations. 
• Power Function - this model fits a rating curve describing the relationship between constituent concentration or load and discharges. It is a straight power curve, where flow in ML/d has been used to generate a relationship with the solute concentration (mg/L), 
• Power Function (flow in mm) - this model is the same as the Power Function model, but uses a normalised power curve, where flow in mm/d has been used to generate a relationship with the solute concentration (mg/L).

 In this case, the default constituent generation model is Nil Constituent.

Linking constituent generation and filter models

Constituent generation and filter models may require one or more of their parameters to originate from another one, for each time-step. That is, a model's input may depend on the output of another model. 

Consider the Nutrient Delivery Ratio (NDR) and Sediment Delivery Ratio (SDR) models. The output of a NDR model depends on the input of the SDR filter model. To configure constituent model linking between these two models for a given FU and constituent source, assign one SDR to the sediment constituent, and one NDR to each other appropriate constituent. A link is then created between the quick flow in parameter on the SDR and the quick flow sediment in parameter on the NDRs. The link system would ensure that the SDR has run before the NDRs, ensuring the correct flow of data at the right time. 

Constituent Model Configurations

You can assign and manage the constituent generation, filter, instream processing and storage processing models for all constituents in the scenario using the Constituent Model Configuration dialog (Figure 1), which is opened by navigating to Edit » Constituent Models.... Before using this dialog, you need to define constituents and constituent sources (as described in Configuring constituents) and also either set up your catchment area using the Geographic Wizard for catchments and assigned FU areas 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. 

The following operations can be undertaken:

• 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 below).

Refer to Working with rainfall runoff models for more details onasssigning a model, adding input data and changing parameters.