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TR-20 models can be defined in WMS using the commands in the TR-20 menu and resulting dialogs.

The TR-20 model is included with all paid editions of WMS.

There are six steps in defining a TR20 model using WMS:

TR-20 Menu

The TR-20 menu, available in the Hydrologic Modeling module, contains the following commands:

  • Open TR-20 File – Brings up an Open dialog for importing files in the TR-20 file format.
  • Save TR-20 File – Saves the simulation in the TR-20 file format.
  • Run Simulation – Opens the TR-20 Input/Output dialog where simulation run parameters can be specified and the simulation run launched.
  • Read Solution – Brings up the Read TR-20 Solution dialog where the simulation solution file can be selected and imported.
  • Show Prince George's County Toolbox
  • Job Control – Opens the TR-20 Job Control dialog for setting parameters for the simulation run.
  • Edit Parameters – Opens the Edit TR-20 Parameters dialog for adding data to basins, outlets, and diversion.
  • Stochastic Modeling – Brings up the Stochastic Run Parameters dialog.
  • Run Stochastic Model – Opens the the Model Steering dialog to start the stochastic model run.

Create a Topologic Tree

In the absence of terrain data, this is done using the commands to build the tree in the Tree menu. When using the TIN, Map, or DEM modules to delineate a watershed and sub-basin boundaries, a topologic tree is automatically created. Diversions can not be created directly on a TIN or in the Map module, but must be created using the commands in the Tree menu.

Define Job Control Parameters

Job control parameters are used to define the time and length of a simulation, output diagnostic controls, and other miscellaneous items. Definition of these parameters is discussed in detail later in this chapter.

Edit Basin/Outlet/Reservoir/Diversion Data

Parameters for all sub-basin outlets, reach routes, reservoirs, and diversions (hydrograph stations) are entered/edited using the Edit TR20 Parameters dialog accessed from the TR-20 menu. This dialog displays current values and allows editing values for the currently selected hydrograph station.

Model Check

This step allows check ther TR20 data prior to performing an analysis. It reports errors such as zero area, undefined precipitation, etc. These errors should be corrected by returning to previous steps before actually trying to run TR20.

The Model Check command should be issued once all necessary TR20 data has been defined. It will report any possible errors/inconsistencies in the model so that corrections can be made prior to executing TR20. The list of checks made is not complete and just because no errors are reported does not ensure that a successful and/or accurate analysis will be completed. It's encouraged to report any additional checks that might be made while working through various problems.

Run TR-20

WMS creates TR-20 files compatible with any version of TR-20. However, a Windows (X-Windows on UNIX and MS-Windows on PC's) compiled version of TR-20 is distributed with WMS so that it can be run without leaving the WMS environment.

For an in depth description of the TR-20 runoff model itself, refer to the TR-20 User's Manual[1].

The version of TR-0 distributed with WMS can be run directly from WMS by using the Run Simulation command in the TR-20 menu. Before running a TR-20 simulation, run the model checker. The model checker will help identify serious and potential problems. These problems should be corrected before a successful run of TR-20 can be made.

The Run Simulation command will bring up a dialog allowing specifying three files which are necessary to run TR-20. The first file is the TR-20 input file. The second is an ASCII output file generated by TR-20. This output file can be used to extract specific results. It also contains important information which can be used to correct problems encountered when running TR-20. The third file will contain hydrograph results for basins and outlets. View these results by reading this file with the Open command from the Hydrographs menu.

Once these files have been defined and select OK, TR-20 will be executed. A separate window will appear and information about the TR-20 simulation will be reported. If running with Microsoft Windows, close this window when TR-20 terminates. On UNIX workstations the window closes automatically.

If TR-20 is not executed successfully when issuing this command then be sure that the path to the TR20.EXE file (tr20 for UNIX) is located in the same directory as the WMS executable file.

If TR-20 does not run to a successful completion, view the ASCII output file using the View File command in the File menu.

View Hydrographs

Once a TR20 simulation has been run, view resulting hydrographs using the commands in the Hydrographs menu. After viewing the hydrographs, if desired, repeat the previous steps in order to calibrate a model or look at different scenarios.

Reading Existing Files

WMS is capable of reading TR20 files created manually using a text editor or other program. However, there are a couple of problems which need to be considered, and may have to be altered either before or after reading in one of these files.

  • WMS reads analysis hydrograph results from the *.thy file. Many existing TR20 files will not specify output to this file and it may be necessary to define it for all hydrograph stations before being able to read in analysis results. This can be done by selecting all basins/outlets and bringing up the respecting output control dialog. Saving the TR20 file and running it will then create the *.thy file.
  • WMS will not read in TR20 files with more than one COMPUT record. Only one COMPUT record will be read in, and it will be the last COMPUT record in the file. If needing to make more than one computation, simply change the necessary input parameters in WMS, save the file, and run TR20 again.
  • WMS will not read in data from ALTER, DELETE, INSERT, IPEAKS, PEAKS, or DURINC records.
  • WMS adds basin, reservoir, outlet, reach, and diversion names in columns 73 through 78 of TR20 files. These names are not necessary to run TR20 or to read existing TR20 files into WMS.

If running into any other problems reading TR20 files, please contact the distributor WMS was purchased from.

Saving Files

Once a tree has been created and all of the necessary data entered, a TR20 input file can be generated by selecting the Save TR20 File command the TR20 menu. When writing the file, the proper order for computing, adding, and routing hydrographs is automatically determined. TR20 can be run without any further editing of the input file generated by WMS. Because WMS does not allow input for all TR20 options, it may be necessary to modify the file somewhat before execution. Hydrograph names must be defined in columns 73-80 of all RUNOFF, REACH, DIVERT, ADDHYD, and RESVOR, records and GRAPHICS must be defined in columns 61-68 of the JOB record before output of TR20 can be read back into WMS for display in the Hydrograph Window.

Existing files generated outside of WMS can be read it into WMS and a separate topological tree will automatically be generated for the watershed described in the file. Since WMS does not yet support all possible TR20 card types, there may be some incomplete information. However, the basic structure of the watershed will be created and all possible data will be retained. If multiple computations or runs of TR20 are specified in a single file, WMS will prompt for which one to use. With WMS only a single computation sequence may be defined. If additional computations are desired, the parameters can easily be changed within WMS and another run of TR20 made.

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