Creating an HEC-MetVue Model Alternative

HEC-MetVue Project File and Directory Structure

Settings within a HEC-MetVue Project file provide the base information for developing HEC-MetVue model alternatives in the CAVI. HEC-MetVue Project files follow the hierarchy: Project > Sessions > Map Windows.

Projects contain global settings.

Sessions are synonymous with model alternatives in the context of the CAVI (i.e. any Session in the Project file is also a model alternative in the CAVI).

Map Windows contain settings for the Input Data and Basin Average Maps.

Each watershed has a single HEC-MetVue Project, which contains one or more Sessions (each corresponding to a CAVI Model Alternative). Each Session should contain at least one Map Window, and the Map Windows within the Session will perform the data processing functions necessary for a forecast run. Since HEC-MetVue is a hydrometeorological data processor, it will likely need to process data for the Lookback and Forecast time windows separately. Therefore, creation of a Lookback and a Forecast Map Window for each dataset will likely be required. After creation of these Map Windows, input data should be loaded and any necessary basin average maps added.

If not already present in the watershed directory, HEC-MetVue will create the directory ./watershed/MetVue to house its settings when opening a watershed. Additionally, a Project file matching the watershed’s name will be created and opened, and a maps sub-directory will be created to house the basin average maps. The ./watershed/MetVue directory will also contain the HEC-MetVue model alternative files once they are created (with the .mvalt extension), which contains information about input files and output data.

For an tutorial on setting up an HEC-MetVue Project using the CAVI, see Creating an HEC-MetVue Project.

Importing Existing HEC-MetVue Projects

Importing of existing Project files may be performed if you have a pre-built project file with all the desired settings. During the import, each Session within the Project File will be converted into a Model Alternative. Through this process, the Project file will be copied into the ./watershed/MetVue directory with a file name matching the watershed. All basin average maps will be copied into the ./watershed/MetVue/maps directory, and all map files will become relatively pathed within the Project File. This will make the maps available for computes within the CAVI. Although maps are copied into the watershed directory, no HEC-MetVue data is copied. Copying of HEC-MetVue data is avoided because it could be very large and will likely be replaced through the extract process. Finally, a HEC-MetVue model alternative file will be created (with the .mvalt extension) for each Session within the Project file.

To import a MetVue Project:

1. Right-click on the MetVue icon in the Setup module and select Import. The Open MetVue Project File dialog will open.
   
2. Select the Project file you would like to import and click Open.
   

Creating HEC-MetVue Model Alternatives

HEC-MetVue supports the addition and deletion of Sessions and Map Windows in the watershed’s Project file. This allows for development of model alternatives within the automatically generated or imported Project file. This can be performed by launching the HEC-MetVue application in the CAVI (raindrop button on the Main Toolbar), then performing the necessary edits in the project tree. Once you have completed the necessary edits, close HEC-MetVue. Clicking on the HEC-MetVue node in the Setup module will refresh the Sessions and Map Windows. If Sessions were added, those will show up as new model alternatives. If Map Windows were added, those will show up in the MetVue alternative editor for the given model alternative. Similar to the Import process, a model alternative file will be created for each Session created in the Project file, and that model alternative file will contain the input data type and file/path information. As opposed to the Import process, the basin average maps will not be copied, and therefore it is recommended that all basin average maps are placed in the ./watershed/MetVue/maps directory and relative pathing turned on.

Editing HEC-MetVue Model Alternatives

You can edit HEC-MetVue model alternatives by right-clicking on the alternative node and selecting Edit Alternative. The MetVue Alternative Editor dialog will open. The editor has two tabs, Input Settings and Output settings.

Input Settings

The Input Settings tab identifies the Map Windows that will be used in the Forecast. In each row of the table, the user can specify if the Map Window applies to the Lookback, Forecast, or both. This controls the time window that the Map Window is asked to load data within the Modeling tab. Each Map Window used in a forecast must have at least one time window turned on.

The Basin Average Maps are used when computing basin average time series. Editing the basin average maps must be performed for each Map Window in the HEC-MetVue application. Changes to the Basin Average Maps performed in the HEC-MetVue application will appear in the MetVue Alternative Editor after closing and reopening the editor. When the mouse pointer is hovered over a row in this table, the path of the basin average map file is presented for verification purposes.

The Input Data section allows you to select the type of TIN/Grid Input (i.e. HEC-DSS, File, or MetVue Interp), define selection criteria for the input type, and specify your interval. The three options are summarized below:

• DSS - Selecting the HEC-DSS option allows you to see the pathname selection fields. These fields may be populated by manually entering text, or by clicking the Browse button and selecting a record in an existing HEC-DSS file. These settings will be used to select the pathname from the forecast.dss file based on the A, B, C, and F parts and the input duration.
• File - Selecting the file option allows you to select input files based on filename patterns and duration filtering.
• MetVue Interp - Selecting the MetVue Interp option allows specification of a MetVue Interp file. This allows you to specify the input data from point time series, which will then be interpolated onto a grid.

The TIN/Grid Input selection will be set during the import process, but may require additional editing if the settings are incomplete or incorrect. It is important to verify that each Map Window TIN/Grid Input matches the desired input data source. Additionally, any HEC-DSS paths are assumed to be located in the forecast.dss file once a forecast is created. The File and MetVue Interp options should be configured with relative pathnames to ensure proper loading when in the Modeling module.

If there are any errors with the setup, the Warnings box located at the bottom of the tab will contain notifications about what you need to change.

Output Settings

The Output Settings tab contains sections to specify the output datasets: the output dataset name, the output time interval, and three possible output data types (TIN File Generation, DSS Grid Outputs, and Time Series Generation).

The Output Data Selection table is located at the top of the Output Settings tab. This allows you to identify an output dataset and assign the Map Windows that will provide the lookback and forecast input data. The Lookback Map Window column will be populated with the Map Window specified for the lookback time window in the input settings, and the Forecast Map Window column will be populated with the Map Window specified for the forecast time window. If a single Map Window will be used for both the lookback and forecast, then that Map Window needs to have both time windows selected in the Input Settings tab. Each dataset needs to have a Name, Parameter and Unit specified. This determines how the program writes metadata for the output dataset.

The Output Time Interval is used to specify the time interval that the next model in the forecast sequence requires. As shown in the example above, MetVue will generate a 1-Hour dataset. If the input and output time intervals do not match, HEC-MetVue will aggregate/disaggregate/interpolate data from the input time interval to match the output time interval. Additionally, the Output Parameter Type may be altered. This will most like be PER-CUM for precipitation, and PER-AVG (for daily average) or INST-VAL (for sub-daily measurements) for temperature.

It is important to distinguish between Input Duration and Output Time Interval settings. In the Input Settings tab, with DSS as the selected input, records are filtered based on duration. Duration is the timespan of an individual grid ([end time]-[start time]). Alternatively, the Output Time Interval is the time difference between successive grids ([second grid start time]-[first grid start time]). For example, an input instantaneous temperature grid will have a duration of zero, but an output instantaneous temperature grid will have an interval greater than zero (i.e. 1Hour). In the case of non-instantaneous data (i.e. precipitation), the duration and interval will both be non-zero. In most cases, non-instantaneous grids will have an interval that equals its duration.

Output Extents allows you to define the spatial extents of the output data based on a shapefile. This ensures that HEC-MetVue is not creating unnecessarily large grids.

Three types of output data – TIN File Generation, DSS Grid Outputs, and Time Series Generation – can be specified. While all three types of output data may be generated in a single forecast run, it is advised that you only select necessary data because each output data type requires additional computation time and space within the forecast.dss file.

• TIN File Generation - allows you to save projected data to any gridded file output supported by HEC-MetVue. This option requires specification of the Write Provider, the projection of the output grid, and the output filename. Custom projection information can also be specified via the Add/Edit button.
• DSS Grid Outputs -  allows you to specify the record pathname to save the output data into, and these records will be saved into the forecast.dss file. These settings also allow the user to specify whether the output should be in the SHG or HRAP projection. 
• Time Series Generation -allows you to specify if basin-average time series will be generated, and allows for selection of the Sub-basin Name Column within the shapefiles, which is required for identifying the output pathname.

For most applications, it is expected that either DSS Grid Outputs or Time Series Generation will be used to pass data to HEC-HMS. For Time Series Generation, the default selection is “Name” for the Sub-Basin Name Column combo-box. That is the column in the shapefile that is expected to correspond to the HEC-HMS sub-basin name. If using Time Series Generation for a watershed in a Time Zone other than GMT, refer to Important HEC-MetVue Application Settings below for additional considerations.

You can access the QPF Trimming and Default Value Settings dialog from the Options button on the Output Settings tab. This dialog allows you to set QPF trimming and data filling options. QPF trimming provides the ability to set forecast precipitation to zero beyond a given lead time. Data filling for each output dataset is controlled in the Default Value Selection table, where each output dataset can be set to No Filling (leaves missing grids as missing), Default Value (creates an entire grid filled uniformly with the user-specified default value), or Closest Grid (duplicates the closest available grid in time). Once you have changed the settings, click Apply then OK to close the dialog.