Forebay head loss can be used to model places where there is constriction upstream of the dam, resulting in the forebay being lower then the reservoir "pool." The forebay will determine the outlet capacities while the pool determines the zones. You can add Forebay Head Loss to Dams, Outlets, Diverted Outlets, and Outlet Groups.
To add Forebay Head Loss:
Right-click on the dam, outlet, or group to which you want to add Forebay Head Loss.
Figure: Forebay Headloss Node and Forebay Head Loss Edit Pane
Use the Define button to the right of the Function Of: field to specify the independent variable of the Forebay Head Loss function. Options include: Model Variable, External Variable, State Variable, or Two Variables.