Once the system elements have been created in the system plan, the calculation method for individual system elements is selected and appropriate parameters are inserted. This is done in the data sheet for each respective system element.
The determination of parameters can vary greatly. Some are known (e.g. diameter of a circular pipe), others require extensive preliminary work in a GIS (e.g. the division of a subcatchment using soil maps, land use maps, determining gradients from a DTM in areas reacting hydrologically similar and finally elementary areas).
Even if parameters are not known and they are the objective of a calibration, a first estimate must be appointed as an inital value for the calibration.