Functional units (FUs) refer to areas of particular hydrological response. In Source, Functional Unit classes are initially defined in the Geographic Wizard (Specify functional units). This page explains how to manipulate FU areas outside the Geographic Wizard.
...
- Manually using Edit » Functional Units » Assign Area Manually (Figure 1); or
- From a raster such as a land use map (Figure 2).
Areas can also be imported into the Functional Unit table from a .csv file.
| Info | ||
|---|---|---|
| ||
Note: Areal percentages per sub-catchment must sum to 100%. An error message is shown if Functional Unit areas do not add up to 100%:
A 'Normalize Area Ratios' Button has been introduced in versions of Source after version 4.2.6. This button can be used to manage small errors resulting from decimal rounding. It will automatically fixed the sum of FU areas to equal the sub-catchment area. This is especially useful when areas are calculated from a shapefile or raster, where resolution differences between sub-catchments and FUs can result in small area differences.
|
| Anchor | ||||
|---|---|---|---|---|
|
...
| Info | ||
|---|---|---|
| ||
Note: Using filters in the Functional Unit Area Configuraiton dialog is similar to using them in the Feature Table (see Working with filters in the Feature Table). However, there is also a subcatchment filter to help you find subcatchments either by name or by using the subcatchment map, see Subcatchment filter. |
| Anchor | ||||
|---|---|---|---|---|
|
- Choose Edit » Functional Units » Assign Area Via Raster to open the FU raster dialog (Figure 2);
- Click Load to upload a raster file;
- Selecting the Save spatial FU data option will save the loaded Raster in the Source project file. This can be useful if you are wanting to keep a copy of the original data, but, since raster files are often very large, be aware that this can have an unwanted impact on the size of the Source project file.
- If the loaded land use map layer does not include a mapping of grid code to land use, click Assign Mapping. Multiple grid codes can be assigned to a single FU class;
- In the resulting dialog (Figure 3), assign a FU to each grid code using the drop-down menu in the FU column. Hover over the map to view the grid code which corresponds to each sub-catchmentthe raster cells; and
- Click OK to close the window.
Figure 2. Assigning FU areas using a land use raster
