In the demo example, the Catchment is a schematic catchment, i.e. the catchment is represented by a default shape. To create a schematic catchment, see Creating a catchment (p. 75).
When the catchment has been created, the catchment properties must be specified in the Catchments Tabular view or the Property view (see7.1 Catchment definitions (p. 77)). A runoff time series must be provided. All runoff from the catchment is added to the River network in the Catchment node.