Control Point Variable Routing Coefficients
This category is used to compute a set of control point Routing Coefficients based on the previous flows in the system. The category is dependent on having the Operating Level Balancing selected in the Flood Control category.
NoneThis method is the default for the Control Point Variable Routing Coefficients category and should be selected when a calculation of routing coefficients is not desired.
There are no slots specific to this method.
Compute Aggregate Coefficients The Compute Aggregate Coefficients method allows the user to recalculate the Control Point routing coefficients based on flow in the reaches between the Control Point and its associated Reservoirs.
There are no slots specific to this method.
Method Details
This method executes at the beginning of the timestep to recalculate routing coefficients for member Control Points based on the existing flows throughout the subbasin. It does the following:
ForEach Control Point in the computational subbasin:
ForEach Reservoir in the Upstream Reservoir list slot:
ForEach Reach between the current CP and the upstream reservoir, get the
previous timestep’s Inflow.
On the Reach.Variable Lag Coefficients slot, look-up the previous
Inflow on the column map to select the appropriate column of
coefficients to use. Store the column number for use below.
EndFor
When the “Compute Aggregate Coefficient” control point method is selected, if
the looked-up column for the Inflow on each Reach is the 0th column
On the CP, copy the values from the Routing Coefficients to the
Computed Routing Coefficients. The standard values will be used.
Else, recalculate the coefficients as follows (This is used for each timestep
when the “Compute Aggregate Coeffs every Timestep” control point method is
selected):
Starting at the upper most reach, route a unit Inflow (i.e. 1.0 cms)
through the reaches. Each reach must use the set of coefficients
determined from the inflow. Any unknown inflows are assumed to be 0.0.
The set of outflows at the lowest reach represents the coefficients.
Set the Computed Routing Coefficients table slot for the
appropriate reservoir
EndFor, Move on to next Reservoir in upstream list and repeat
EndFor, Move on to next Control Point in the subbasin and repeat
In this algorithm, the Inflow represents the flow for the previous timestep including previous surcharge forecasts, previous Flood Control releases, previous hydropower and any local flows.
See “Compute Aggregate Coefficients” for details on the required Control Point methods. See “Variable Step Response” and “Variable Step Coefficients” for details on the required reach methods. See “Alternative Routing Coefficients Methods” in USACE‑SWD Modeling Techniques for details on using this method for USACE-SWD models.
Revised: 11/11/2019