WMS:TR-20

TR20 models can be defined in WMS using the commands in the TR20 menu and resulting dialogs. There are six steps in defining a TR20 model using WMS:

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 TR20 menu. This dialog displays current values and lets you edit values for the currently selected hydrograph station.

Model Check

This step allows you to check your 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 you feel that all necessary TR20 data has been defined. It will report any possible errors/inconsistencies in your 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. We encourage you to report any additional checks that might be made as you work through various problems.

Run TR-20

WMS creates TR20 files compatible with any version of TR20. However, a Windows (X-Windows on UNIX and MS-Windows on PC's) compiled version of TR20 is distributed with WMS so that it can be run without leaving the WMS environment.

For an in depth description of the TR20 runoff model itself, refer to the TR20 User's Manual[1].

The version of TR20 distributed with WMS can be run directly from WMS by using the Run TR20 command in the TR20 menu. Before running a TR20 simulation, you should run the model checker. The model checker will help you identify serious and potential problems. These problems should be corrected before a successful run of TR20 can be made.

The Run TR20 command will bring up a dialog allowing you to specify 3 files which are necessary to run TR20. The first file is the TR20 input file. The second is an ASCII output file generated by TR20. 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 TR20. The third file will contain hydrograph results for basins and outlets. You can view these results by reading this file with the Open command from the Hydrographs menu.

Once these files have been defined and you select OK, TR20 will be executed. A separate window will appear and information about the TR20 simulation will be reported. If you are running with Microsoft Windows you must close this window when TR20 terminates. On UNIX workstations the window closes automatically.

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

If TR20 does not run to a successful completion you can view the ASCII output file using the View File command in the File menu.

View Hydrographs

Once a TR20 simulation has been run you can view resulting hydrographs using the commands in the Hydrographs menu. After viewing the hydrographs, you may wish to 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 you may need to define it for all hydrograph stations before you will be 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 you need 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 you run into any other problems reading TR20 files, please contact the distributor you purchased WMS 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 you for which one you want 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.

Related Topics

• Editing TR20 Parameters