5.10 Routing
Last updated
Last updated
Settings in the Routing tab affect the way streamflow routing is performed and how streamflow routing is reported as model output. An overview of the Routing tab is shown in Figure 43.
5.10.1 Recession coefficient and flow direction
The recession coefficient affects the velocity in which water is transported downstream through the delineated river network. Values for the recession coefficient range between zero and one, and the default value is set to 0.40. You can opt to choose either a spatially distributed recession coefficient map or single value that is applicable to the entire basin. A recession coefficient map can be selected and added to the map canvas by clicking the Select map button.
For the flow direction you need to select a map by clicking the Select map button. After selecting a flow direction map this map will be added to the map canvas. An example of a flow direction map is shown in Figure 44. A flow direction map needs to be prepared by the user, and is based on the DEM. The flow direction map contains for each cell a number that defines the direction of streamflow. The numbers and their corresponding directions are shown in Figure 45.
5.10.2 Initial values
The initial values that need to be set are:
Routed total runoff [m3/s]
Routed rainfall runoff [m3/s]
Routed baseflow runoff [m3/s]
Routed snow runoff [m3/s]
Routed glacier runoff [m3/s]
Routed total runoff is the sum of the individual routing components, which are the last four items shown above. The default values for all routing components are set to zero. However, it may be that you are interested in using results from a previous model as starting point for a new model run. In that case you may provide the routed runoff of the last time-step of your previous model run as initial value for routed runoff of the current model run.
For each of the routed runoff components you may choose to either provide a single value that is applicable to the entire basin, or to provide a spatially distributed map with routed runoff. Maps are selected and added to the map canvas by clicking the Select map buttons.
Routing of the individual streamflow components (rainfall runoff, baseflow runoff, snow runoff, and glacier runoff) is more time-consuming than only routing the total runoff. If you are only interested in routing the total runoff, then it is possible to not compute the routing of the individual routing components. This can be achieved selecting the spatial map option for the routing component that you do not want to be calculated, and leave the corresponding field blank. This is also illustrated in Figure 43, where all routed runoff components will be calculated, except for the routed rainfall runoff.
After completion of all the settings in the Routing tab you are finished with setting all the model input maps and parameters. The next step involves setting the model output options in the Report options tab.
