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Some features are not available in Source (public version). |
Introduction
Operations forecasting allows you to create alternate forecasts for inflows, water demands, stream flow losses and gains (unaccounted differences) and constituents within a single overall project scenario. In other words, it forecasts the input data for a model.
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This is not available in Source (public version).
The Operations simulation in Source is split into two phases - the historic 'warm-up' and the forecast period. The former is designed to warm-up the network's physical models by playing all known historic data into the system and overriding modelled values where applicable. In the latter, the Operations forecast models extend historic data into the future, effectively providing an estimate of the effect to the modelled system.
To create a default operations scenario in Source:
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- First, create a
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- schematic scenario;
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- Choose Tools » River Operations to open the River Operations dialog (Figure 1); and
- Click on the slider below Operations Mode to ON.
Once you have created forecast models, you can disable operations, but retain these models or overrides using the buttons under Operations Data. The first two buttons in this dialog deal with removing input data, whereas the third one deletes all output data that was created for the forecast models. To clear all operations related data (input, output as a well as overrides), click Clear ALL Operations Data.
Figure 1. River Operations
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Before you can begin forecasting, you must seed the model with available historical data (also known as "warming-up the model") using the Simulation toolbar:
- Choose Run w/Warm Up from the Select Analysis Type pop-up menu; and
- Click Configure.
This opens the Run w/Warm Up dialog (Figure 2).
Figure 2. Run w/Warm Up
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Assuming a daily time-step:
- The Start Date and End Date fields define the limits of the available historical data in your model;
- The Warm Up Start date is set to the beginning of your historical data but you can change this if you intend to limit the warm-up process to a shorter time span;
- The date for Today is set to the last day of your historical data but you can also adjust this field as appropriate. Assuming your historical data is up-to-date (yesterday was the last day of historical data), this value should normally be today’s date so any difference might indicate a need to verify that all data has been loaded correctly into the model; and
- The Forecast Length defaults to 90 days. You would usually set this to the maximum travel time associated with your normal operations.
The + button can be used to step the operations scenario forward in time, which allows you to move from one day’s operational scenario to the next. You can also specify the data source using the Input Set drop down menu.
The remaining fields summarise what will occur when you complete the warm-up process. Click OK, and then Begin Analysis (Run) to begin the warm-up process.
The Constituents tab gets enabled when constituents have been configured in a scenario (its operation is similar to the Constituents tab in a single analysis run).
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Once operations has been enabled, you can configure
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forecast input data
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under the
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relevant forecasting list item in
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a node's feature editor. For example, for the inflow node, choose Inflow Forecast under Additional Flow. Each of the parameters that are involved in creating forecasts handle input data differently.
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| This is different to the Forecasting list item, which relates to ordering for planning and operations models. |
The following forecast models extend the originally played in time series using a model. In the absence of a forecast model to generate forecast values, a default value is used, which is typically zero:
- Additional flow at the Inflow node;
- Demand at the Time Series demand model;
- Operating target, gauged releases, rainfall and evaporation for the Storage node.
The Unaccounted difference node and the Gauged Level unaccounted difference at the
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Forecast scenarios
storage node forecast unaccounted difference forecast the possible error. The default value in the absence of a forecast model is zero. The Unaccounted Difference is a time series computed during the historic phase of the run, and is the difference between the modelled value at a point in the system and the actual historic value which has been played in at that point. In the forecast phase, applying the forecast unaccounted difference (a positive value represents a gain; a negative value, a loss) is an attempt to compensate for the known over or under estimation inherent in the model.
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| Note: Unaccounted difference is named so because if the model were perfect, this would always be zero (the modelled value would match the actual values). In reality, the model does not simulate everything and this typically leads to the systematic over or under estimating of flows. |
For gauged releases forecast at the storage node, by default, the modelled releases are used by outlets, except where an override value has been provided, either by direct override (using the tabular editor) or by a forecast model. A storage outlet is a physical structure which has minimum and maximum release capabilities. The outlet release forecast/override can be any value, but the model cannot physically release any amount. The forecast/override values are therefore constrained at run-time. This is why the outlet releases each have two columns in the tabular editor, the first shows the modelled value that is actually released by the storage and the second shows the forecast/override. They will be different if the outlet release has been constrained. The second column is blank in the absence of any forecast/override values and in this case, the modelled values are used. Figure 3 shows an example of this. Note that from the 01/02/2011 onwards, the outlet release has been constrained.
Figure 3. Tabular Editor, forecasting, outlet release constrained
Forecast scenarios
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A collection of one or more forecasting models is known as a forecast scenario. You can define one or more scenarios for each node. For example, you might define "wet year", "dry year" and "normal year" scenarios, or variations that reflect your most optimistic or pessimistic expectations. To add a forecast scenario, right-click on the item you want to forecast in the relevant node's feature editor and choose Add Forecast Scenario (Figure
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4). You can choose the input set that will be associated with a particular forecast scenario. Right click on Forecast Scenario #<number>, then choose Add Forecast Model to add a model.
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| Note: Only one forecast model can be active at a point in time during the simulation. |
When more than one forecast model has been assigned to a forecast scenario, they are ordered from top to bottom in the hierarchical list. The model at the top of the list runs first. You can change the order of model run by dragging the forecast model to the required position in the list. For each model, you must also specify the number of time-steps it will be active for before moving onto the next model in the list. The last model in the list always has a Time Steps value of All Remaining and will be active for the remainder of the forecast period.
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| Forecast scenarios are unique to a node and must be configured individually for each node. |
Figure 3. Add Forecast Scenario dialog
Each forecast scenario that you create is placed in the Forecast Scenario pop-up menu and is then selected automatically. The controls in the Ops Forecast tab only affect the currently-selected forecast scenario. You can also apply a particular scenario forecast across all the scenario elements at a project level using Scenario tags. To edit a different forecast scenario, you must choose its name from the Forecast Scenario pop-up menu.
To rename an existing forecast scenario, first select the scenario that you wish to rename from the Forecast Scenario pop-up menu and then click Edit (above the Forecast Scenario pop-up menu). This re-opens the Add Forecast Scenario dialog (Figure 128). Enter a new name for your scenario and click OK.
To delete an existing forecast scenario, first select the scenario that you wish to delete from the Forecast Scenario pop-up menu and then click Remove (above the Forecast Scenario pop-up menu). The scenario is removed immediately without prompting for confirmation and the change can not be undone.
Forecasting models
Source supports the forecasting model types shown in Table 105, plus the ability to combine those models in an arbitrary order.
To add a forecasting model to the current forecast scenario, click Add (below the Forecast Scenario pop-up menu). This opens the Add New Forecast Model dialog (Figure 129):
Figure 129. Add New Forecast Model dialog
- Enter an appropriate name for your model into the Name field;
- Choose the appropriate model type from the Model Type pop-up menu; and
- Click OK.
Each forecasting model that you add to a forecast scenario becomes a sub-tab within the Ops Forecast tab. Feature Editor 77 has four sub-tabs showing that four forecasting models have been defined. When you create a new forecasting model, its sub-tab is created and becomes selected automatically.
Feature Editor 77. Inflow node (Ops Forecast, with models)
You can change both the name and the type of an existing forecasting model. To do either, select the sub-tab representing the model that you wish to adjust and then click Edit (below the Forecast Scenario pop-up menu). This re-opens the Add New Forecast Model dialog (Figure 129). Make the appropriate changes and click OK.
To delete an existing forecasting model, first select the sub-tab representing the model that you wish delete and then click Remove (below the Forecast Scenario pop-up menu). The forecasting model is removed immediately without prompting for confirmation and the change can not be undone.
Forecasting models are applied in the order reflected by the sub-tabs, beginning with the left-most sub-tab and moving to the right. To change the order in which a forecasting model is applied, first select the sub-tab that you wish to re-order and then use the < and > arrow buttons to move the sub-tab into the correct position.
Within each forecasting model, you have the choice of allowing the model to be applied to a fixed number of time-steps or all remaining time-steps. As forecasting models are applied, the first model that is encountered which applies to all remaining time-steps will be the final model to be executed. In other words, if you create more than one forecasting model in a scenario, you should define a fixed number of time-steps for all but the model represented by the right-most sub-tab.
To apply a forecasting model to an explicit number of time-steps:
- Select the sub-tab representing the forecasting model that you wish to adjust;
- Turn off All Remaining; and
- Set the Time Steps field to the appropriate number of time-steps.
Expression forecast
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Figure 4 shows the Forecast item for the Inflow node. Choose the forecast model you wish to specify by clicking the appropriate forecast model under Additional Flow Forecast (on the right). The forecast model that is active at the node is indicated by a green tick on the left of the model. In Figure 4, the Trend forecast model is the active model.
Figure 4. Inflow node, Operations forecasting
Figure 5. Storage Routing Link, Operations forecasting
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Forecasting models
Source supports the forecasting model types shown in Table 1.
Table 1. Forecast model types
Forecast model type | Description |
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| Average | Allows you to define the average over the last specified number of time-steps. |
Function | Allows you to define a function to return any value you choose for each time-step in the forecast period. For example:
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Monthly Average |
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Allows you to enter an average forecast value, in megalitres per day, to be applied for the whole of each month. You can either enter the monthly average values |
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manually, or import the values from a .CSV file formatted as shown |
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in Table |
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2. To trend from "today" to the monthly average, |
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enable the Trend to Value at Rate checkbox and enter a trend rate which is a real number greater than zero but less than one. The observed daily flow rate for the previous month and the number of days of the current month are used to determine the initial flow volume. | |
| Pulse | Allows a static forecast model that is applied on a specified date and has priority over other relative forecast models if enabled. The forecast pulse flow rate is entered under the Target Flow configuration, and the pulse start and end dates are specified with the date inputs. The rate of the rise and recession of the pulse is configured by the Rate sliders or can be entered directly as value. For example, the 0.6 Rate of the Pulse Rising indicates that at each time step there is an increase of 60% in the flow volume until the Target Flow is reached.. |
Time Series |
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To specify a forecast based on a time series, you must |
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Time series are assumed to conform with the structure shown |
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in Table |
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3. Note that any time-stamps contained in a time series are ignored. The observation in the first row of the time series is used for the first time-step of the forecast period, the observation in the second row for the second time-step, and so on, until either there are no more data rows in the time series or the simulation reaches the end of the forecast period. |
Trend |
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A single target value (either positive or negative) plus a recession rate. To specify a trend forecast, enter the target value in megalitres per day, and |
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use the slider to specify the trend rate, which is a real number greater than zero but less than one. |
Applying forecasts
Clicking Forecast (sel) executes the currently-selected forecast scenario. Clicking Forecast (all) executes all of the forecast scenarios that have been defined for the node.
Executing a forecast scenario is the equivalent of a run and produces results (see the Running scenarios chapter). Executing a forecast scenario also updates the both the Tabular Editor (Figure 184) and the Forecast Scenario Outputs tab (Feature Editor 78).
Feature Editor 78. Inflow node (Ops Forecast, visualisation)
Viewing forecasts
The results of executing one or more forecast scenarios can be viewed by switching to the Forecast Scenario Outputs tab (Feature Editor 78). The tab contains both tabular and graphical representations. The data produced by each forecasting scenario is represented by both a trace on the graph and a column in the table. You can use a combination of the table’s horizontal scroll bar or adjust the boundary between the table and graph to bring specific data columns into view.
To view the results of forecasts applied to multiple nodes in a scenario, switch to the Tabular Editor (Figure 184) and inspect the results. Refer to Using the Tabular Editor.
Adjusting forecasts
Cells containing forecast data can be adjusted or overridden by over-typing their values in either the data columns on the left of the Forecast Scenario Outputs tab, or in the Tabular Editor. Cells that are dependent on an adjustment automatically recalculate in the same manner as a spreadsheet.
Note that Source only stores one time series of forecast overrides for a project. You can not define one set of forecast overrides for your first forecast scenario, and a different set for your second forecast scenario.
You can access Figure 130 using
Table 105. Forecast model types
Forecast model type | Description |
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Expression | User defined arithmetic expressions |
Monthly Average | Daily average for the month in megalitres per day. |
Trend | A single target value (either positive or negative) plus a recession rate. |
Time Series | Supports the inclusion of forecast data from an external source. |
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Figure 6. Pulse Forecast Model
Table 2. Monthly average forecasting model (data file format)
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| 1 | Month | Forecast Value (ML/d) |
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month
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value
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Table
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Time series forecasting model (data file format)
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| 1..n | date | value |
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Viewing forecasts
The results of executing one or more forecast scenarios can be viewed using the Recording Manager or the tabular editor (to view and override individual values). Ensure that you enabled recording for the parameter that you are forecasting. For example, to forecast flow, enable recording of the Inflow attribute in the Recording Manager. Figure 5 shows an example of the output of a forecasted model. This forecasting scenario consists of two forecast models. A Trend forecast model is run for the first 10 time-steps and the remaining time-steps have a Function forecast model configured.