Source allows the user to create the catchment model though Geographic Wizard conveniently. However, before Source version 4.10.0 - Beta Release (August 2019), the user cannot change the created sub-catchment boundary such as merge sub-catchment after Geographic Wizard creates the scenario. The new function was developed to merging sub-catchments and reset relevant model elements (such as network/link) and attributes (such as rainfall runoff model parameters) in an existing catchment catchment model. The developed function has been included in the Source software tool after the version 4.10.0 – Beta Release.
There are two methods developed for combining sub-catchments: (a) at selected node boundaries and (b) from selected catchments. Both methods are described below in this page.
First of all, the user needs a Source project with any geographic scenario and open the project.
Combine Catchments At Selected Node Boundaries:
This method allows the user to combine all catchments upstream of the selected node such as a confluence in a catchment model.
The procedure to combine catchments at selected node boundaries is illustrated as follows:
- Click on a single node from the interface to select this node, such as the confluence orange cycled on Figure 1 ( Node on catchment SC#10 in this example)
Figure 1. Selected the node to start combine sub-catchments function
- Right click on the interface’s empty space (that can keep the node selected) to pop up the Geographic Editor.
- Click on Combine Catchments >> At selected node boundaries to display the windows of Combine Catchments as Figure 2. At the beginning, the contests under Catchment Group is empty.
Figure 2. Combine Catchments Windows Interface
- Click on the button of Find catchment groups at boundaries to display all sub-catchments upstream of the selected node (i.e. Node on catchment SC#10 in this example) in Catchment Groups (shown as Figure 3).
Figure 3. Combine Catchments at selected node with all found upstream sub-catchments
Some functions on Figure 3 are given below:
- To Primary catchment: The property of this sub-catchment will be retained for the combined catchment such as the property: the parameters of rainfall runoff and other models. In this example, primary catchment is SC#13. This node is single outlet of the combined catchment.
- Absorbing Catchments: Sub-catchment listed under Catchment (i.e. SC #21, SC #12, SC #20 in this example) will be merged with SC #13 and their properties will be discarded.
- Assign primary: This button allows the user to change the primary catchment if the user wants to use the property from another sub-catchment for the combined catchment. The user can click on any sub-catchments listed under Catchment, then click on Assign primary The selected sub-catchment (SC #12 in this example) will be displayed into Primary catchment, and previous primary catchment will be moved to the absorbing catchments.
- Network Restructure:
Collapse to primary catchment node – Ticking this function will lead a network with one link from the primary catchment to the outlet. Otherwise, the networks and nodes from all absorbed catchments will be kept as it is.
Absorb upstream boundary nodes- This function allows to remove all nodes in absorb catchments and it is enabled only when Collapse to primary catchment is ticked.
- Combine button will close Combine Catchments Interface; combine the upstream catchments and reset the network and nodes accordingly.
- Cancel button will close Combine Catchments Interface without any combination action.
Combine catchment from selected catchments:
This method allows the user manually to select the sub-catchments to combine.
The procedure to combine catchments from manually selected sub-catchments is shown below:
- Manually select the sub-catchments to combine (use the Zoom option to Zoom in to the sub-catchments, and keep Selected Catchment in Layer Manager ticked) as Figure 4
Figure 4. Manually select sub-catchments for combining catchments
- The first catchment selected is deemed to be the Primary Catchment.
- Right click on the interface to pop up the Geographic Editor as Figure 5
Figure 5. start combine sub-catchments function from manually select sub-catchments
- Click on Combine Catchments >> From selected catchments to pop up the Windows of Combine Catchments as Figure 6.
Figure 6. Combine Catchments Windows Interface for manually select sub-catchments
- The elements’ functions on Figure 6 can refer to those on Figure 3 and explained before
- Click on the Combine button on Figure 6 will lead a catchment combined from 4 catchments shown in Figure 7
Figure 7. The results catchment combined from manually selected sub-catchments
- Save the Source project to keep the combined results
Note that
- The change of combined sub-catchments is unable to reverse
- At the moment, the use needs to have a single outlet for all of the sub-catchments you are combining. The Source will relax this restriction in future versions.