Dispatch Methods

Water Quality : Distribution Canal Water Quality : Dispatch Methods

Dispatch Methods

Note: If the Flow Routing method is Storage Time or Variable Storage Time, an error is issued as these are not supported.

Solve No Routing Salt

This method is available when the Flow Routing method is No Routing. This method computes the Outflow salt given the Inflow Salt Concentration.

Required Known Slots

• Inflow

• Outflow

• Inflow Salt Concentration

Required Unknown Slots

• Outflow Salt Concentration

Method Details

Inflow Salt Mass is set at the current timestep by multiplying the Inflow volume by the Inflow Salt Concentration.

If Delivered Flow Salt Concentration is not input or set by a rule, then it is set to the Inflow Salt Concentration.

When a non-default Seepage method is selected and the water quality approach is Propagate Salt (on the aggregate), Seepage Salt Concentration and Seepage Salt Mass slots are available. If Seepage is positive, the Seepage Salt Concentration is set to the Inflow Salt Concentration. If Seepage is negative, the Seepage Salt Concentration must be specified possibly by a link to a slot on another object. If Seepage Salt Concentration is linked but not valid, the reach exits the dispatch method and waits until the seepage Salt Concentration is available from that object. Seepage Salt Mass is computed from the Seepage Salt Concentration and the Seepage.

Note: Although there are Seepage Routing methods, these only serve to compute the Seepage at the current timestep. In general, Outflow = Inflow - Seepage. Thus, the Seepage Salt concentration does not need to be routed; it is just the value at that timestep.

Then, for each constituent, if the concentration and the flow is valid, the mass is computed. Otherwise the mass is considered zero, but not set.

Finally:

(9.1)

Finally, Outflow Salt Concentration is computed from the Outflow and Outflow Salt Mass.

Solve TimeLag Salt

This method is available when the Flow Routing method is Time Lag.

This method computes the outflow salt at the current timestep based on inflow salt from previous timesteps and diversion and return flow salt at the current timestep. Lagging on this object is required to be an integer number of timesteps.

Required Known Slots

• Inflow

• Outflow

• Inflow Salt Concentration

Required Unknown Slots

• Outflow Salt Concentration

Method Details

Inflow Salt Mass is set at the current timestep by multiplying the Inflow volume by the Inflow Salt Concentration.

Next, the inflow at the previous timesteps is checked. If either the Inflow(-Lag) or the Inflow Salt Concentration(-Lag) are not valid, the method is exited to wait until they become valid. If they are both valid, then the routedSaltMass is computed using the Inflow(-Lag) and Inflow Salt Concentration(-Lag).

If Diversion Salt Concentration is not input or set by a rule, Diversion Salt Concentration is set equal to the lagged Inflow Salt Concentration, i.e. Inflow Salt Concentration(-Lag)

Then, for each constituent, if the concentration and the flow is valid, the mass is computed. Otherwise the mass is considered zero, but not set.

Finally:

(9.2)

Finally, Outflow Salt Concentration is computed from the Outflow and Outflow Salt Mass.

Note: No Seepage Salt is modeled for the Time Lag method.

Revised: 07/09/2023