After you have created a new simulation or have opened an existing simulation, you are ready to make one of the alternatives active (if not already active) and have ResSim perform the computations.

Setting the Active Component

Once you have opened a Simulation, the simulation tree will show all of the selected Alternatives for the Simulation you have chosen.

The Active alternative of a simulation will be identified in the Simulation tree with bold text and its model schematic will be displayed in the map region. It will be computed if you press Compute in the Simulation Control Panel.

Most importantly, the Active alternative is editable. Only the Active alternative can be edited in the Simulation module. If you need to edit more than one alternative in your simulation, you must do so one at a time, making each alternative "active" in turn to make the desired changes. "Calibrating the Model and Editing Data" describes the ways you can edit the various elements of the active alternative.

To set the Active Alternative:

Computing the Simulation

After inputting all data and parameters as desired, you can compute a Simulation.

In the Simulation Control Panel of the main window of the Simulation Module, the simulation tree displays the current Simulation as a folder, beneath which is a list of the Alternatives associated with the Simulation. Also shown in the Simulation Control Panel is the time information associated with the Simulation.

To execute a Simulation, you must first set an Alternative as Active. Right-click on an Alternative in the Simulation Control Panel and, from the context menu, select Set as Active ("Figure: Simulation Control Panel Context Menu - Set Alternative As Active").

The name of the active Alternative appears in bold in the simulation tree and Compute becomes available. Also, the model schematic for the active Alternative will appear in the display area.

To compute a Simulation, either click Compute in the Simulation Control Panel or, in the simulation tree, right-click on the Alternative and select Compute from the context menu ("Figure: Simulation Control Panel Context Menu - Compute").


Figure: Simulation Control Panel Context Menu - Compute

When you compute a Simulation, a Compute window opens, as shown in "Figure: Compute Window". The Compute window provides Message Output that contains information regarding the status of each step of the computation process. The Progress Bar indicates the percentage of completion for each step. When the computation is finished, the Progress Bar is completely filled in and reads "100%" along with the message "Compute Complete" in the Message Bar of the Compute window.


Figure: Compute Window

If there are errors or any problems during the execution process, you can review the Message Output Text area of the compute window. The Compute Log can also provide information regarding any errors ("Viewing Compute Logs").

Click Close to close the Compute window.

As previously mentioned in "Menu Bar", there are two tabs available from the Tools Options menu that are specific to the Simulation Module. These two options are Simulation and ResSim Compute and are described below:

  • Simulation options—as shown in the figure below, you can choose to Reload Last Simulation on Startup, Restore Simulation Tree State, and/or indicate that the Compute Button Forces a Recompute.

    Figure: Simulation Module - Tools Menu - Options

  • ResSim Compute options—as indicated in "Figure: Simulation Module - Tools Menu - Options", there are default compute options that you can revise if needed. These options include: Minimum Number of Compute Passes (default = 2); Error Tolerance Factor for Storage Calculation (default = 0.00001); Maximum number of sub-steps for Storage Calculation (default = 200); a checkbox to indicate whether or not you want to Save Release to Guide Curve to DSS; and, a button to Edit Global ROC Options. If you change from these values and want to go back to the defaults, then you can click Reset Defaults.

    Figure: Simulation Module - Tools Menu - Compute

A Compute Pass refers to one ResSim program solution search moving from the upstream elements of the network to the downstream elements. The default is two passes. Certain system operation rules, such as system hydropower, automatically force four passes. A user may want to set the minimum number of passes to 3 or more if there are diversion elements in the network that are not performing correctly or that seem to have been ignored by upstream reservoirs.

  • The Storage Calculation refers to a ResSim storage integration approximation calculation performed across a computation step to assure the continuity principle is enforced over the outlet capacity range experienced during the timestep. If there are severe nonlinear shapes or discontinuities in the range of outlet capacities experienced during the timestep, then ResSim subdivides the time to better represent the average outflow during each time subdivision and therefore to better represent the storage at the end of the timestep. Storage calculation allows for a better simulation of small reservoirs subjected to large inflows and therefore large variations in outlet capacities during a timestep. If a small reservoir in a simulation has its storage oscillate unrealistically, increasing the error tolerance factor and/or the maximum number of sub steps may improve the behavior of the small reservoir.

  • For each time period, releases are determined that represent the amount of water that needs to be released in order to reach the reservoir's guide curve. By default, these releases are not stored to DSS. During analysis of the results, you may find it useful to know what these values were computed to be by selecting the Save Release to Guide Curve to DSS option.
    If the operation set contains reservoir rate of change rule(s) and downstream operation rule(s), you can indicate to include complex logic to consider the rate of change limits when determining the release needed for downstream operation by revising the options in the Global ROC Editor ("Figure: Global ROC Editor").


    Figure: Global ROC Editor