The commands in the Tree menu are used in defining any of the hydrologic models supported by WMS. The default model is controlled using the drop-down combo box in the Edit Window. The only model menu that appears as its own menu is the default model, however the other model menus can be reached through the Models menu. Whenever you select a command for another model, the default model will be updated to specify that model.
The default model determines which model should be chosen whenever an operation that requires a choice between one of the hydrologic model is executed. For example double-clicking on a basin or outlet causes the Edit Parameters dialog of the default model to come up. The default model is automatically set whenever a file of the given type is read, or if its Edit Parameters dialog is accessed from the Models menu commands.
Related Topics:
Topologic Trees
HEC-1
TR-20
TR-55
Rational Method
HSPF
NFF