Rating Curves

Another generic control structure can be a rating curve in which a tabular relationship of discharge and head (or elevation) for the structure is prepared offline in advance by the user, then assigned to a weir or orifice by simply specifying that a rating curve is used. In this case, the model uses this rating curve to calculate the discharge at any time base on the dynamic head.

In general, a rating curve table can be used for any internal control structure to represent its flow-head relationship if there are no anticipated backwater effects. A single-valued-rating-curve can not be used in cases where there are backwater effects since the rating curves assumes no such backwater effects.