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Objects and Methods : Control Point : User Methods : Generate Forecast Inflows
Generate Forecast Inflows
* None
This method is the default for this category which does nothing.
* Geometric Recession
On each timestep in the forecast period, this method will adjust the inflow hydrographs. If the Compute Forecast Period Incremental Local Inflows method is selected the Cumulative Local Inflow is used to forecast and set the Forecasted Cumulative Local Inflow. If the Compute Forecast Period Incremental Local Inflows methods is not selected, the input Deterministic Incremental Local Inflow slot is used to forecast and set the Local Inflow series slot.
Slots Specific to This Method
 Deterministic Incremental Local Inflow
Type: SeriesSlot
Units: FLOW
Description: This slots holds a timeseries of the actual Local Inflows to the control point. These values are then adjusted by the forecast method and set on the Local Inflow slot.
Information: At the end of the run, the Local Inflow slot will be identical to this slot. If the Compute Full Run Incremental Local Inflows method is selected, values from the Incremental Local Inflow slot will be copied into this slot prior to the forecast. If the Compute Forecast Period Incremental Inflows method is selected, this slot is not used (that is, inputs are ignored).
Information:  
I/O: Input only
 Local Inflow
Type: SeriesSlot
Units: FLOW
Description: The incremental local inflow to the control point
Information: If a disaggregation method is selected, the local inflow will be set to the result of the last stage of these methods.
I/O: Output
 Period of Perfect Knowledge
Type: ScalarSlot
Units: NONE
Description: Number of timesteps for which the forecast will equal the Deterministic Incremental Local Inflow; that is, the forecast is known with complete certainty.
Information: Minimum value of 1; maximum value equal to the number of timesteps in the forecast period.
I/O: Input only
Type: Not linkable
 Recession Factor
Type: ScalarSlot
Units: NONE
Description: A decimal value that is multiplied by the previous Local Inflow to determine the current value after the Period of Perfect Knowledge.
Information:  
I/O: Input only
Method Details  
This method uses different slots and sets different slots if the Compute Forecast Period Incremental Local Inflows is selected. But, there is always a Source slot and a Target slot where the Source slot is input and used to forecasted and set the Target slot. If the Compute Forecast Period Incremental Local Inflows is selected, the computational subbasin calls this method and uses the Cumulative Local Inflow (Source) to forecast and set the Forecasted Cumulative Local Inflow (Target). If it is not selected, the reservoir calls this method at the beginning of the timestep and uses the Deterministic Incremental Local Inflow (Source) slot to forecast and set the Local Inflow slot (Target). The following uses the Source/Target terminology to describe the methods.
The Source slot values are required inputs for each timestep. At the beginning of each controller timestep, the Geometric Recession method is executed. For each forecast timestep within the period of perfect knowledge, the Target is set to the Source value. For each forecast timestep after the period of perfect knowledge, the Target is set by multiplying the value of the Target from the previous timestep by the constant recession factor.
A value for the Source slot must be known at every timestep during the run. If Target values are desired past the end of the run, there must also be values in the Source slot at timesteps past the end of the run. If values for Source slot are not entered past the end of the run, the Target values for these timesteps are assumed to be zero.
* Exponential Recession
On each timestep in the forecast period, this method will adjust the inflow hydrographs. If the Compute Forecast Period Incremental Local Inflows method is selected the Cumulative Local Inflow is used to forecast and set the Forecasted Cumulative Local Inflow. If the Compute Forecast Period Incremental Local Inflows methods is not selected, the input Deterministic Incremental Local Inflow slot is used to forecast and set the Local Inflow series slot.
Slots Specific to This Method
 Deterministic Incremental Local Inflow
Type: SeriesSlot
Units: FLOW
Description: This slots holds a timeseries of the actual Local Inflows to the control point. These values are then adjusted by the forecast method and set on the Local Inflow slot.
Information: At the end of the run, the Local Inflow slot will be identical to this slot. If the Compute Full Run Incremental Local Inflows method is selected, values from the Incremental Local Inflow slot will be copied into this slot prior to the forecast. If the Compute Forecast Period Incremental Inflows method is selected, this slot is not used (that is, inputs are ignored).
I/O: Input only
 Local Inflow
Type: SeriesSlot
Units: FLOW
Description: The incremental local inflow to the control point
Information: If a disaggregation method is selected, the local inflow will be set to the result of the last stage of these methods.
I/O: Output
 Period of Perfect Knowledge
Type: ScalarSlot
Units: NONE
Description: Number of timesteps for which the forecast will equal the Deterministic Incremental Local Inflow; that is, the forecast is known with complete certainty.
Information: Minimum value of 1; maximum value equal to the number of timesteps in the forecast period.
I/O: Input only
 Minimum Forecasted Flow
Type: SeriesSlot
Units: FLOW
Description: The minimum forecasted flow.
Information: If the computed value for Local Inflow is less than the Minimum Forecasted Flow, it is set to the Minimum Forecasted Flow.
I/O: Input only
 Low Flow Threshold
Type: ScalarSlot
Units: FLOW
Description: The flow rate that dictates whether to use the Low Flow Recession Coefficient or the High Flow Recession Coefficient.
Information:  
I/O: Input only
 Low Flow Recession Coefficient
Type: ScalarSlot
Units: NONE
Description: The recession coefficient used when the Deterministic Incremental Local Inflow (at the end of the Period of Perfect Knowledge) is below or equal to the Low Flow Threshold.
Information:  
I/O: Input only
 High Flow Recession Coefficient
Type: ScalarSlot
Units: NONE
Description: The recession coefficient used when the Deterministic Incremental Local Inflow (at the end of the Period of Perfect Knowledge) is above the Low Flow Threshold.
Information:  
I/O: Input only
Method Details  
This method uses different slots and sets different slots if the Compute Forecast Period Incremental Local Inflows is selected. But, there is always a Source slot and a Target slot where the Source slot is input and used to forecasted and set the Target slot. If the Compute Forecast Period Incremental Local Inflows is selected, the computational subbasin calls this method and uses the Cumulative Local Inflow (Source) to forecast and set the Forecasted Cumulative Local Inflow (Target). If it is not selected, the reservoir calls this method at the beginning of the timestep and uses the Deterministic Incremental Local Inflow (Source) slot to forecast and set the Local Inflow slot (Target). The following uses the Source/Target terminology to describe the methods.
The Source slot values are input for each timestep. At the beginning of each controller timestep, the Exponential Recession method is executed. For each forecast timestep within the period of perfect knowledge, the Target is set to the Source value. For each forecast timestep after the period of perfect knowledge, the Target slot is set as described below.
    
where Source is the value in the Source slot at the end of the period of perfect knowledge, C is the recession coefficient, t is the elapsed time of the forecast period, and T is the total time from the end of the period of perfect knowledge to the end of the forecast period.
If the Source at the end of the period of perfect knowledge is negative, the Target at that timestep is exactly equal to the Source. However, the Source used in the recession equation, is the last positive value for Source. In the event that there is not a positive value for the Source, RiverWare issues a warning, and all values for Local Inflow within the forecast period will be set to the Minimum Forecasted Flow.
A value for the Source slot must be known at every timestep during the run. If the Target values are desired past the end of the run, there must also be values in the Source slot at timesteps past the end of the run. If values for Source are not entered past the end of the run, the Target values for these timesteps are assumed to be zero.
Revised: 01/10/2022