A zone configuration will be applied to the HEC-HMS model based on subbasin locations. Generally, parameters are adjusted for all subbasins within a zone. The user can set each parameter to a specific number for a zone, or multiply/divide the parameter for each subbasin within a zone by a constant, or add/subtract a constant to each parameter for each subbasin, or set the parameter for individual subbasins to specific values. Refer to the HEC-HMS user's manual for a description of setting up zones and configuring a forecast alternative.
For future precipitation, the amount of precipitation is set for the entire zone, and can be specified as a temporal distribution for each zone. The user can also multiply observed precipitation by a percentage for each zone.