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.
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- 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
