A reservoir is a downstream boundary condition. The reservoir element represents the part of the channel immediately upstream of the (usually vast) reservoir. Since the backwater curve may change substantially in the neighborhood of the reservoir it is advisable to choose the length of the reservoir element to be small compared to the length of the channel branch it is part of. The following constants have to be specified on the line beneath the *FLUID SECTION,TYPE=CHANNEL RESERVOIR card:

The water depth in the downstream node of a reservoir element must be defined by the user by means of a *BOUNDARY card (degree of freedom 2).

Example files: channel1, chanson1.