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Diversion Editor: Diversion Tab
The Diversion Editor's Diversion tab ("Figure: Diversion Editor - Diversion Tab") is where you will specify the diversion demand—the quantity of flow that the diversion will try to withdraw from its source (upstream) junction. This tab has two data entry fields: Method and Computed during UnReg, and an edit panel in between them.
Method—The Method selector offers seven options for specifying the diversion quantity:
- Constant
- Monthly Varying
- Seasonal
- Function of Flow
- Function of Pool Elevation
- Time Series
- Flexible Diversion Rule
Select the diversion method from the Method list. The edit panel below the Method selector will fill with the appropriate fields to enable you to specify the parameters for the diversion method you have selected. The default method is Constant. The diversion methods are described in the following sections.
Computed during UnReg—Activate the Computed during UnReg checkbox if you want the diversion to be reflected in the unregulated flow computations. If checked, the diversion will operate during the unregulated flow calculations; if unchecked, the unregulated flow will reflect flow conditions without the diversion.
Diversion Method: Constant
Use the Constant diversion method ("Figure: Constant Diversion Method") when the desired withdrawal from the river system is always the same amount. The only parameter for this method is the flow rate of the diversion. This constant value will apply to each period of your simulation.
Diversion Method: Monthly Varying
Use the Monthly Varying diversion method ("Figure: Monthly Varying Diversion Method") when the withdrawal from the river varies on a monthly basis. For this method, you will need to enter the diversion flow value corresponding to each month of the year. These monthly values will apply to each year in your simulation.
Diversion Method: Seasonal
Use the Seasonal method ("Figure: Seasonal Diversion Method") when the withdrawal pattern varies as a function of date but not on a monthly basis. For each season, you will need to enter:
- a Date, in the format ddMMM (e.g., 01Jan), for the beginning of the season
- an associated Diversion flow value.
The seasonal table always starts on the first of January (01Jan), so if you have a season that spans across the calendar year boundary, be sure to specify the start of that season as the last entry in your table (as well as the first). Like the monthly varying diversion, the seasonal diversion is a pattern that repeats for each year of your simulation and each season's desired value applies until the start of the next season (i.e., step interpolation will be used between values in the table).
Diversion Method: Function of Flow
Use the Function of Flow diversion method ("Figure: Function of Flow Diversion Method") to describe the diversion demand as a function of flow in the river. Although for most function-of-flow diversions the location of the flow is usually the diversion's source junction, you can identify any junction in the network as the flow location for the function.
When specifying the data for this method, first select the Flow Location from the list of junctions in your network. Then, define the diversion function—the relationship between the Flow Location's Flow and the Diversion flow. Linear interpolation will be used between values in the table.
Diversion Method: Function of Pool Elevation
Use the Function of Pool Elevation diversion method ("Figure: Function of Pool Elevation Diversion Method") to describe a diversion demand that varies with the pool elevation of a reservoir in your network. For this method, you will need to select the reservoir from the Reservoir list and then specify the relationship between that reservoir's pool Elevation and the Diversion flow. Linear interpolation will be used between values in the table.
Diversion Method: Time-Series
Use the Time-Series diversion method ("Figure: Time-Series Diversion Method") for a diversion whose demand varies through time without a repeating pattern and without any relationship to flow or pool elevation.
The edit panel for the Time-Series method has no data entry fields; instead you will be required to identify a time-series for this diversion when you setup your alternatives; an entry for this diversion will appear in the Time-Series mapping table when you create an Alternative ("Alternative Editor"). The time-series you provide must be in standard units of flow (cfs or cms).
You can also use the Time-Series diversion method when you want to change the diversion demand per alternative without having to change the network.
Diversion Method: Flexible Diversion Rule
The Flexible Diversion Rule diversion method ("Figure: Flexible Diversion Rule Method") was added to allow the diversion demand to be specified as a function of any model variable or state variable and thus, make specification of the diversion demand as "flexible" as a reservoir release rule (see "Release Function Rules"). Although virtually every other diversion method could be replaced by this method, the older methods with their simpler interfaces are easy to understand and use.
The data required to specify a "flexible diversion rule" depends on how you define the function. The common options for defining the rule are described below.
Function of
The first step in specifying a Flexible Diversion Rule is to identify the independent variable of the "function" (the diversion quantity is the dependent variable). To do so, select the Define button to the right of the Function of: field. The Independent Variable Definition editor will open ("Figure: Select Independent Variable"); use this editor to select the type of variable your "Release is a function of". Options include: Date, Date and Time, Model Variable, External Variable, and State Variable. See "Commonly Used Editors and Dialogs" for a description the Independent Variable Definition editor and of each of the variable types.
Types of "Function of" functions:
Date
If the diversion demand varies seasonally (as a function of date), select Date from the Release is a Function of: list in the Independent Variable Definition editor for your Flexible Diversion Rule's function. A seasonal function table will appear in the diversion's edit panel as illustrated in "Figure: Flexible Diversion - Function of Date". All seasonal tables in ResSim start on 01Jan. You can enter a single demand value for 01 Jan to describe a constant diversion amount throughout the year or enter the appropriate dates and diversion flows to specify the relationship between time of year and the desired diversion flow (release). Be sure to specify the Interpolation type to indicate how to determine the value to be returned when the value of the independent variable is between values in the table.
You can use the Flexible Function of Date diversion method to represent a Constant ("Diversion Method: Constant"), Monthly Varying ("Diversion Method: Monthly Varying") and Seasonal ("Diversion Method: Seasonal") diversion methods by selecting Step for the Interpolation method. However, by using Linear interpolation and/or Hour of Day and Day of Week Multipliers, your flexible diversion function can be defined in ways the original methods could not.
All seasonal tables in ResSim treat each date entered as the beginning of the day, i.e., as applying at 0000 hours. If you would prefer that it applied at the end of the day, use the next day or use a table that allows you specify Time as well as Date.
Date and Time
The Flexible Function of Date and Time diversion function is almost exactly the same as the Flexible Function of Date diversion function — with one difference—the addition of a Time column in the function table — see "Figure: Flexible Diversion - Function of Date & Time". Use this function type when the demand varies with both date and time. When entering time values, use a 24-hour clock, e.g. 6 pm is 1800.
Model Variable
If the diversion demand varies as a function of a standard variable computed by ResSim, you can use the Model Variable form of the Flexible Diversion rule. To set up:
- Select Model Variable from the Release is a Function of: selector in the Independent Variable Definition dialog. The features of this dialog are described in detail in Commonly Used Editors and Dialogs.
The edit panel of the Independent Variable Definition dialog ("Figure: Flexible Diversion - Function of Model Variable") will fill with three Filter fields above a table containing all the model variable time-series computed by ResSim for the current network. To the right of the model variables table is a section labeled Time Series Options.
Note: double-clicking on the variable you want will NOT perform the selection; you must use the Select button.
Find and highlight the appropriate model variable time-series for your function in the table, then click the Select button ("Figure: Flexible Diversion - Function of Model Variable"). Your selection will appear in the Selected Model Time-Series field at the bottom.
Figure: Flexible Diversion - Function of Model Variable- Next, specify the Time Series Options to indicate which value to use from the selected time series at each timestep of the simulation.
Click OK when you have selected the Model Variable and Time Series Options for your function. The Flexible Diversion Rule edit panel will now contain a table for you to enter the relationship between the specified External Variable and the diversion demand.
Be sure that the model variable time-series you selected appears in the Selected Model Time-Series field at the bottom of Independent Variable Definition dialog before clicking the OK button in the to apply your settings, close the dialog, and return to the Diversion Editor. The Flexible Diversion Rule edit panel will now contain a table for you to enter the relationship between the model variable and the diversion demand.
External Variable
When the diversion demand varies as function of an external time-series, select External Variable from the Release is a Function of: list in the Independent Variable Definition dialog ("Figure: Flexible Diversion - Function of External Variable").
When External Variable is selected, the edit panel of the Independent Variable Definition dialog will fill with a Variable Name text field and the Time Series Options. The name you provide will appear in the Alternative Editor's Time Series tab where you will be expected to associate an HEC-DSS time-series dataset with this variable. Enter an appropriately descriptive variable name so that you know what time-series to use for each External Variable to specify in your model.
The Time Series Options apply to the External Variable time-series in exactly the same way as they do for a Model Variable time-series. See "Commonly Used Editors and Dialogs" for details on these options.
Click the OK button in the Independent Variable Definition dialog to apply your settings, close the dialog, and return to the Diversion Editor. The Flexible Diversion Rule edit panel will now contain a table for you to enter the relationship between the specified External Variable and the diversion demand.
State Variable
When the diversion demand varies as a function of a user-defined (scripted) State Variable, select State Variable from the Release is a Function of: list in the Independent Variable Definition dialog ("Figure: Flexible Diversion - Function of State Variable").
When State Variable is selected, the edit panel of the Independent Variable Definition dialog will fill with a selection list showing all the state variables defined in the current network and the Time Series Options. Select the appropriate state variable from the selection list. Note: the state variable must be defined prior to creating a flexible diversion function that uses it (see how to create State Variables.
The Time Series Options apply to the External Variable time-series in exactly the same way as they do for a Model Variable time-series. See "Flexible Diversion - Function of: Model Variable" for details on these options.
Click the OK button in the Independent Variable Definition dialog to apply your settings, close the dialog, and return to the Diversion Editor. The Flexible Diversion Rule edit panel will now contain a table for you to enter the relationship between the specified State Variable and the diversion demand.
Interp
Select an interpolation method to be used between values in the function table. Options include Linear, Step, and Cubic.
Hour of Day Multiplier—The primary purpose of the Hour of Day Multiplier is to turn the diversion on and off at specific times of the day, but it can also be used to vary the diversion demand throughout the day.
To specify a set of hourly multipliers to be applied to the diversion demand, select the Hour of Day Multiplier Edit button. The Hour of Day Multiplier dialog will appear ("Figure: Hour of Day Multiplier with Example Pattern"); this dialog has a table listing each hour of the day and an associated multiplier. The default multiplier is 1.0.
For example, if you have a diversion that only requires flow from 6 a.m. to 4 p.m., but the morning hours require twice as much flow as the afternoon hours, you could modify the multipliers as shown in "Figure: Hour of Day Multiplier with Example Pattern". The multiplier is 0.0 for the hours from 0000 to 0600 and from 1600 to 2400 (to turn off the diversion during those hours) and 0.5 for the hours from 1200 to 1600. Alternatively, you could enter 2 for the hours from 0600 to 1200 —the choice between applying 0.5 for the afternoon or 2 for the morning is dependent on the values you specified in the diversion function that the multiplier will be applied to.
Click OK to apply your entries and close the Hour of Day Multiplier dialog. A checkmark will appear in the checkbox in front of the Hour of Day Multiplier label in the diversion edit panel when the default set of multipliers is modified.
Time Interval
A selector for Time Interval is available in the Hour of Day Multiplier dialog. This selector defaults to 1 hour, but options for intervals of 1, 2, 3, 4, 6, and12 hours are available; if you pick another interval, the Hour of Day Multiplier table will change to reflect your interval selection. For example, if you chose 12 hours, the Multiplier table would have only two rows, 0000-1200 and 1200-2400. If you placed 0.0 in the first row and 1.0 in the second, your diversion would divert flow only between noon and midnight.
Day of Week Multiplier
The purpose of the Day of Week Multiplier is to turn the diversion on or off on specific days of the week, but it can also be used to vary the diversion demand throughout the week.
Select the Day of Week Multiplier Edit button to specify a set of daily multipliers to be applied to the diversion demand. The Day of Week Multiplier dialog will appear ("Figure: Day of Week Multiplier"). This dialog contains a table where you can specify a multiplier for each day of the week. The default value is 1.0.
So, if you have a diversion that diverts only on weekdays, you can set the multiplier for Saturday and Sunday to 0.0 and leave all other days set to 1.0.
Click OK to close the Day of Week Multiplier dialog. If the table contains any non-default values, a checkmark will appear in the Day of Week Multiplier check box in the diversion edit panel
Seasonal Variation
The Seasonal Variation option allows you to add Date (or Season) as a second independent variable to your Function of relationship, but it is only active when your first independent variable is Model Variable, External Variable, or State Variable (i.e., a time-series).
So, if your diversion demand varies as a function of a time-series variable and seasonally, select the Seasonal Variation Edit button to specify the seasons. The Seasonal Variation dialog ("Figure: Seasonal Variation") will appear. This dialog contains a seasonal table in which you can enter dates that represent the start of each "season". Seasonal tables always start on 01Jan. If you have a season that crosses the calendar year boundary, it will be entered as two seasons, one at the beginning of the year and one at the end of the year (the first and last seasons in the table).
The Seasonal Variation dialog also provides an option for Interpolation Type. You can select from: Linear, Cubic, and Step. This interpolation selection applies to the seasonal variation of your function (the columns of your table).
Click OK to close the Seasonal Variation dialog. If you created more than one season, a checkmark will appear in the Seasonal Variation check box in the diversion edit panel and a column will be added to the function table for each season specified in the Seasonal Variation dialog.