Now we're going to delineate the streams. For that we need as an input the filled DEM from the previous step and a Strahler order threshold that you can calibrate. We'll add that as an integer input to the model.
1. Go back to the Input panel by clicking the Input tab.
2. Double click on Number.
3. In the Number Parameter Definition type Strahler order threshold as Description. The Number type is Integer. Strahler orders always have a minimum of 1. The maximimum depends on the area, but we can limit it to 20. We can define a default value of 8. Keep the Mandatory box checked.
4. Click OK.
5. Go back to the Algorithms tab and double click the SAGA Channel network and drainage basins algorithm.
6. In the Channel network and drainage basins dialogue change the Description to Delineate streams. Choose for Elevation the Filled DEM algorithm output. Choose for Threshold the Strahler order threshold input value. Save Channels to Streams.
7. Click OK.
You can rearrange the boxes a bit. Your model should now be similar to the one in the figure below.