Merge two catchment scenarios

Source allows users to merge two catchment scenarios of a project file together, the project file should have at least two scenarios (Figure 1). This way, two merged scenarios can be run as a single scenario. This functionality has been included in the Source software tool since version 5.16.

Figure 1- Scenario A and B of a catchment project in Source

To use this functionality, the user must decide which of these two scenarios (scenario A or scenario B) is the target scenario and which one is the source scenario. It is important to know this because after merging two scenarios all components of the source scenario are transferred to the target scenario to generate a modified target scenario.

Transferred components can include:

• Sub-catchments: boundaries and geo-regions,
• Network elements: nodes and links and their defined configuration,
• Functional Units: all classes and the areas (source and target scenarios can have different classes of FUs, in which case the modified target scenario will have FU classes consisting of both scenario classes)
• Data sources and functions (assigned to network elements)
• Rainfall-runoff models: assigned inputs and the model parameters values,
• Constituent generation and filter models: assigned inputs and the model parameters values.

It should be mentioned that after merging two scenarios, the change of the modified target scenario is unable to reverse and return it to its initial set-up

In this example, scenarios A and B are considered as the source and target scenarios, respectively (Figure 1). To merge these two scenarios, first select the source scenario (scenario A), and then select, “Merge Catchments…” from the Tools menu (Figure 2). The “Merge Catchments” window will open (Figure 3).

Figure 2- "Merge Catchments..." option from the Tools menu

In the “Merge Catchment” window, the name of the source scenario is specified, and it is possible to select the target scenario from the drop-down menu. Also, in this window, it is possible to choose a prefix for the name of all the sub-catchments, nodes, and links that are going to be transferred from the source scenario to the target scenario, the default prefix is “copied”. If two merged scenarios have nodes or links with the same name, this prefix helps to identify which one is related to the source scenario (name with the prefix “copied”) and which one is related to the target scenario. Finally, by clicking on the “Merge Catchments” option, the merging process is initiated (Figure 3). A list of all transferred elements with their previous and new names, including the names of nodes, links, sub-catchments, elements related to the constituent model, and functional units which are added to the target scenario, will be presented in this window. Finally, the message “Merge Complete” indicates the end of the process and the window can be closed (Figure 3).

Figure 3- Merge Catchments Window

By activating the target scenario from the Project Hierarchy, the changes made to this scenario will be visible (Figure 4). Also, in the Project Hierarchy section, the transferred nodes, links, and sub-catchments are shown with the selected prefix (in this example “copied”).

Figure 4- Target scenario after the merging process

Connecting merged scenarios: so far, only the transfer process has taken place and these two scenarios have not yet been connected in terms of the link network. If this merged scenario needs to be run in a connected manner, the user must create a link between them manually. To do so, the user must decide where to connect these two network structures together. For instance, in Figure 5, we want to connect Gauge 1 to the specified confluence.

Figure 5- Connecting the links network of the merged scenario

To do this, right-click on the Geographic Editor Window and select the “Add Link” option. Then, along the flow direction, click on the Gauge node and then on the Confluence node, respectively (Figure 6). According to Figure 6, a new link is added to the flow network to connect the network structures upstream and downstream of the gauge. In this way, the source and target scenarios are not only merged but also connected. In the case of running this scenario (for rainfall-runoff modelling or constituent modelling), all sub-catchments and their related stream networks are run-connected.

Figure 6- Adding a link between two parts of a merged catchment model