The Geographic Wizard is the first in a series of steps required to create a catchments scenario. It consists of a structured sequence of windows (described below) that guides you through the process of defining the catchment area. On completion of the wizard, you will be presented with a node-link network. This figure outlines the sequence of steps in the wizard, with a more detailed explanation provided below.
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| Note: After a scenario has been created using the wizard, you cannot change the network, ie. you cannot merge or remove sub-catchcments. |
On completion of a step, you can move to the next step by clicking Next and backwards by selecting Back. Note that you cannot go back to the network definition step once you have completed it and moved on to the next step. Cancel allows you to quit the wizard at any time. Note that you will lose all the data entered so far. Once you have completed all steps, click Finish to close the wizard and view the catchment in the Geographic Editor. This figure also shows the action buttons that are visible at the bottom of every screen in the wizard.
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- To add a new catchment outlet, choose Select Cell from the contextual menu, and select another point on the catchment map;
- Pan allows you to move the map up, down, left or right;
- To zoom in, right-click, and choose Zoom In. Drag the mouse to form a zoom box (top right to lower left). To zoom out, double-click anywhere on the map or click Undo Zoom;
- To remove a catchment outlet point, choose Remove Cell;
- Choose Properties to change the attributes of various elements, such as the colour or symbol of nodes; or
- Save allows you to save the map as a .asc file.
Figure 1. Geographic Wizard, Network definition via a DEM
Adding nodes
Ordinarily, nodes are placed at stream confluences identified in a DEM analysis. It is possible to supplement these nodes and place additional nodes at different locations, typically to identify some point of interest, such as a gauging station of a dam wall. This will also cause additional sub-catchments to be created.
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If you need to delete a link, right-click on the map and choose Select Link/Node from the contextual menu. Click on the link you wish to delete; it will turn red. Press the Delete key on the keyboard or click Delete Selected elements on the right of the map. Ensure that you delete any unattached nodes that were connected to the deleted link. To re-draw links, right-click on the map and choose Draw Network. Continue drawing links as before.
Figure 3. Geographic Wizard, Network definition by drawing
The other options in the list (Pan, Zoom, Copy graph and Properties) have the same function as that described for using the DEM based network generation method.
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| Note: If all the sub-catchments have not been connected, they will be shaded in blue. All sub-catchments must be connected by links before you can click Next (Figure 4). |
Figure 4. Geographic Wizard, Incomplete connection of sub-catchments
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You must specify all possible functional units present in the area of interest, or that you want to represent in the scenario. There are three ways of defining FUs: manually, from a text file, or from a shape file (Figure 5). This is synonymous to the menu item Edit » Functional Units » List.
Figure 5.
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Geographic Wizard, Adding FUs manually
By default, FUs are defined manually. Once added, they appear on the right under Functional Units.
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| Note: In the shapefile, there should be no empty records in the column which is chosen to describe the FU classes. |
Figure 6. Geographic Wizard, Adding FUs via a shapefile
Using a text file
You can import FU names from a text file by choosing Import from a text file from the Available Methods drop-down menu. The format of the text file is shown in Figure 7.
Figure 7. Geographic Wizard, Adding
functional unitsFUs via a text file
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- Choose Manual Area Allocation from the Available Methods drop-down menu;
- For each sub-catchment, enter the area that is allocated to each FU. You can specify this as an absolute value in the Area (ha) column, or as a percentage in the Area (%) column; and
- You may enter the areas individually, or use the Apply-to options to fill multiple cells at once. This is explained in detail in the Using the Apply-to options section. You can also copy values from one cell and paste into other cells. Right-click on the source cell (the one you want to copy) and choose Copy. Then, right-click on the target cell, and choose Paste. The resulting table is shown in Figure 8.
Figure 8.
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Geographic Wizard, Assigning FU areas
When assigning FU areas manually using the Map tab, you can view the entire catchment and its outlines. FU areas can be assigned as follows:
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For each sub-catchment, the FU areas MUST add to 100% (+/- 0.1%). If areas do not sum to 100%, cells in the Area column will be shaded pale red. An exclamation mark will also appear on the left side of the first column.
Figure 11. Geographic Wizards, Assigning FU areas using a land use raster
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| Note: You can edit the FUs on completion of the wixard using the menu items. If the FU list is modified, you will have to update the units areas to reflect this modification. |
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