On the Source and Sink (HD) dialog you also specify Evaporation and Precipitation rates (in mm/day). These can be given as constant values, from type 0 data files or from type 2 data files (covering the main area only).
When precipitation or evaporation data are provided in a type 0 data file, values are always considered as instantaneous values. The TS-type specified in this data file for the precipitation and evaporation data should therefore be Instantaneous.
The default numerical scheme in MIKE 21 Flow Model, HD handles evaporation and rainfall/precipitation only at wet computational cells. To activate calculations in dried cells (i.e. over the whole model domain) you need to enable 'Precipitation on dry land'.
Note that when including rainfall, the user assumes 100% runoff, which may or may not be appropriate if significant infiltration and storage can occur in the soil or ground material.