Routing

Of the available methods, only No Routing, Time Lag and Impulse Response are supported in RPL optimization; selection of any other method will result in an error during begin run.

See Routing in Objects and Methods for details on the Simulation methods.

No Routing

This method provides no routing functionality but adds consideration of Return Flow to the mass balance.

Slots Specific to This Method

Return Flow

Type: Multi Slot

Units: flow

Description: Return flow into the reach

Information: Enters at the bottom of the reach and so is not lagged by the reach nor is it subject to gains or losses. Return Flow must be defined, either by input, a link or a constraint. It will not default to 0 if undefined.

Defined by: Explicit Optimization variable in the mass balance constraint:

where Inflow Expression depends on model configuration and may include Inflow, Local Inflow, and GainLoss consideration. Inflow may be linked to a slot on another object.

Time Lag

In RPL Optimization, Time Lag routing results in a modified mass balance constraint that includes the lagging effect. Selection of this method excludes usage of Return Flow and Diversion values in the optimization problem. Routing occurs prior to any gain and loss consideration.

where:

– lagINT refers to the timestep on or after the point in time equal to the current timestep minus LagTime.

– lagINT – 1 refers to the timestep prior to LagINT.

– flowFraction1 equals the fraction of a timestep used to weigh the inflow associated with lagINT – 1; flowFraction1 equals the fractional remainder of the LagTime / timestep (for example, 0.7 if LagTime = 1.7 timesteps and 0 if LagTime is a multiple of the timestep).

– flowFraction2 equals the fraction of a timestep used to weigh the inflow associated with lagINT; flowFraction2 equals 1 – flowFraction1. (for example, 0.3, if LagTime = 1.7 timesteps and 1 if LagTime is a multiple of the timestep).

Slots Specific to This Method

LagTime

Type: Table Slot

Units: Time

Description: lag time or travel time of flow through the reach

Information: a single value

Defined by: User input

Impulse Response

Impulse Response routing results in a modified mass balance constraint where the reach Outflow is the weighted sum of the current and previous timesteps’ Inflows. Selection of this method excludes usage of Return Flow and Diversion values in the optimization problem. Any gains or losses are added to or subtracted from the routed flow.

Slots Specific to This Method

Lag Coeff

Type: Table Slot

Units: No Units

Description: impulse response coefficients

Information: There must be the same number of values in the Lag Coeff table as the value given in Num of Coeff

Defined by: User input

Num. of Coeff

Type: Scalar Slot

Units: No Units

Description: number of impulse response coefficients

Information: There must be the same number of values in the Lag Coeff table as the value given in Num of Coeff

Defined by: User input

Revised: 08/02/2021