The Fraction Return Flow Input category is dependent on the user selecting the Fraction Return Flow method in the Return Flow category. Three methods allow the user to specify how the Fractional Return Flow (series slot) is provided data: Input Fraction, Zero Fraction, and Periodic Fraction.

The methods in this category will be called at the beginning of the run to set the Fractional Return Flow slot at each timestep.

This default method requires that the Fractional Return Flow slot be specified (input or set by a rule) at each timestep. RiverWare terminates with an error if the Fractional Return Flow is not specified.

At the beginning of the run, this method sets the Fractional Return Flow to 0.0 for each timestep. Hence the Return Flow will always be zero. No slots are specific to this method. RiverWare terminates with an error if the Fractional Return Flow is input.

This method allows the user to specify the return flow fraction using the Periodic Fraction slot. The user can input a value of 1.0 to simulate the case where all water is returned. At the beginning of the run, each timestep is used to look-up or interpolate (depending on slot configuration) the value from the Periodic Fraction and set it on the Fractional Return Flow slot. If this value is not between 0.0 and 1.0 on a given timestep, RiverWare terminates with an error. RiverWare terminates with an error if the Fractional Return Flow is input.