NEW IN RESSIM 3.5UPDATED IN RESSIM 4.0

ResSim Variants allow for variations of an alternative for use with standalone (default) and use with different program orders in CAVI and HEC-WAT, preserving the other aspects of the alternative. ResSim Variants were initially added to ResSim 3.4 and 3.5 to improve the ability to distinguish between inputs for a ResSim alternative in standalone compute and inputs used by a ResSim alternative being computed as part of a sequence of models, such as in CWMS CAVI or HEC-WAT. In ResSim 4.0, updates were made to the variants design to make it smoother for the user to manage alternatives. The description of Variants as used in ResSim 3.5 can be found here: ResSim Variants

ResSim Variants Definition

ResSim Variants are, very simply, different versions of the input time series information (known flows and lookback time series) used by an alternative, that can be selected when the model is being run in a CAVI or HEC-WAT compute environment.

Background

ResSim alternatives typically match a series of conditions in the model that define how the simulation should be performed - including (but not limited to) the timestep of the model, the input timeseries (boundary conditions), lookback values (initial conditions) and which operations sets each reservoir should use. When these alternatives were used in HEC-WAT and CWMS CAVI modeling, those programs would overwrite the timeseries with their own "model linking" information, specifying prior models (such as HEC-HMS or the HEC-WAT Hydrologic Sampler) that provide inputs to the ResSim model. As a work-around, users would create copies of the alternative for each set of inputs to be used, but this workaround then required updating all copies of that alternative when some other detail was changed. This created additional work and steps to review with some changes to the model. Variants were introduced as a way to map multiple input combinations to the same alternatives, eliminating the need for this duplication.

Variants in ResSim v4.0

If you were to open the same model from the Figure: Variants in ResSim v3.5 Alternative Editor the Alternative Editor Time Series tab would look like Figure: Alternative Editor in ResSim v4.0. By default, only the standalone ResSim will be displayed. This also applies to the Global Variable tab.

If a model has variants, the Variants menu drop down will appear when the user selects the Time-Series or Global Variables tab. From Figure: Variants drop-down menu, you can see that it lists all the Variants that were present in ResSim v3.5. The list will include all variants known by ResSim for the current alternative in the current context. The user can choose to add or remove individual or multiple variants. Selected variants to view will have a check box next to the variant name. The user can turn on and off the variants from the submenu. The user will not be able to turn off the ResSim default from the list, so this should never appear in this list. If more than one variant is selected to view, the variants will appear on subtabs as they did in ResSim v3.5.

In ResSim v3.5, DSS filenames and pathnames were stored in the .fits fi;e with each variant creating a copy of this file. This is no longer applicable to ResSim v4.0

The model linking editor was revised to now store the model linking information, while the variant .fits file only serves as a placeholder that helps during the time of compute. In newer versions of CWMS (v3.6) and WAT (v1.2), the pathnames and linkages are being stored in a .linkages file. For CWMS, this file is within the modelLinking folder within the cavi folder and for WAT, this file is within the modelLinking folder within the wat folder. The .fits files are written to at the time of compute. When a new compute is done for the same alternative, the .fits file will be overwritten. The description in the .fits file will include information on which variant was last run. With this new design, there is only one .fits file per alternative and per application. Assuming one alternative, this could reduce the number of .fits files to four (if there are CWMS and WAT models).

AlternativeName.fits (ResSim)
AlternativeNameObs.fits (ResSim)
AlternativeNameCWMS.fits
AlternativeNameWAT.fits

When viewing the CWMS and WAT variants in the Alternative Editor, the user can also hover above the tab and a pop up message will appear that states which variant was last passed through it. (Figure: Information about Time Series Input)

In addition to allowing users to turn Variants on and off, ResSim v4.0 provides users with an easy way to delete Variants. To delete Variant(s), the user needs to go to Alternative - Delete Variant... as shown in Figure: Delete Variants Menu

Once selected, the Delete Variants window will appear and users can choose to delete one or multiple variants at a time (Figure: Delete Variants Window). Older models will have .fits files that are carried with them and the user will be able to continue viewing them until deleted. When selecting a variant to delete, it will delete all files associated with that variant (.fits, .igv, etc). If the user deletes the CAVI or WAT variants, an new one will be created when a compute is run or when the user explicitly tells the MLE to save the linkages back to ResSim.

Variants in ResSim v3.5

HEC-ResSim creates a separate set of files for each of the variants that are required. By default, a set of these files are created for the "ResSim-Default" variant, which is the variant used during standalone computes. For software where ResSim runs as a compute plugin, such as the CWMS CAVI and HEC-WAT, the HEC-ResSim plugin for those programs uses a detail of those computes to create additional variants.

In HEC-ResSim 3.5, the plugins for the CWMS CAVI and HEC-WAT will use the program order name to define the additional variant names. For example, if a CWMS CAVI watershed has two program orders, one starting with ResSim called "ResSimOnly" and one starting with HMS and then running ResSim called "HMS+ResSim", both of these will get their own variants. Thus, if ResSim is being used with an external forecast in the CAVI, the input model linking for that forecast will be kept separate from the input model linking used for the HMS+ResSim run. For more information regarding the program order in CWMS, view the Program Order, CWMS users manual page. For the HEC-WAT, view the Program Order user manual page.

When accessing the model though the HEC-ResSim user interface, a set of tabs for each variant may be presented to the user on the Time-Series and Global Variable tabs. This additional row of tabs can be used to see all of the variants that have been set up for this model. These additional variants are created when the HEC-ResSim plugin for CWMS CAVI or HEC-WAT access the model linking for the model, so they may not show up until the model is edited in the CAVI or HEC-WAT interface.

The view of the ResSim Variants has evolved since they were first implemented as part of CWMS 3.0. Initially, variants were mostly hidden from view and only the variant needed in the current “context” (ResSim, CWMS, or HEC-WAT) was displayed (as the DSS pathname information) on the Time Series tab of the ResSim Alternative Editor. For example, if you launched ResSim in standalone, you would only see the ResSim Default variant for each alternative. However, if you launched ResSim from within the CAVI, the Time Series Tab of the Alternative editor would add a Variants menu to the Alternative Editor and would display, by default, the CWMS variant for the current context but you could view other variants by selecting them from the Variant menu.

After the release of CWMS 3.1.1, while addressing a few oversights in the implementation of variants in the CAVI's ResSim plugin and the CAVI’s Model linking editor, the display of the variants was made more visible. As of CWMS 3.2.1 and ResSim 3.5, if any ResSim alternative has at least one variant, the variants are shown on subtabs of the Time Series tab in the ResSim Alternative Editor, whether ResSim is launched in standalone or from the CAVI or WAT. Each Time Series subtab displays the name of the variant as the tab label. When possible, the current context (such as a CAVI forecast or HEC-WAT simulation) will cause the ResSim editor in those programs to select the relevant variant for that context.

Here is an example of a variant tabs for a ResSim alternative called “RSAlt1” that is used in a WAT run using a program order named “PO1-FRA”. (Figure: Variants in ResSim v3.5 Alternative Editor) You can see from this image that this model has many variants. There is also no straightforward way to delete variants.

Note: Observed data does not currently get revised due to model linking so there is currently no variant subtabs implemented for observed data tab. KNOWN LIMITATION