Tutorials:9 Long-Term Simulations

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This tutorial is compatible with:

  • WMS Version 8.1 and later
  • GSSHA Version 3.0b and later

Disclaimer: GSSHA tutorial exercises do not represent real world conditions


Long-term simulations typically involve running several rainfall events along with the evapotranspiration model for weeks to months. There are two key parts to running a long-term simulation. The first is to set up the precipitation file, and the second is to set up the evapotranspiration model with its hydrometeorological (hmet for short) data.

Precipitation

A long-term event typically consists of multiple rainfall events, often with several rain gages. Multiple gage events can either be setup using WMS or using a handy Microsoft® Excel® spreadsheet. If you are only passingly familiar with Microsoft® Excel® it is recommended that you read Chapter 10, “Using Microsoft® Excel® to format GSSHA™ Data” first.

We will start by using a Microsoft® Excel® spreadsheet to set up a multiple-event, single gage precipitation file from some raw data.

Using the Format Precip Macro

  1. Navigate to the "Formatting Macros" folder.
  2. Open the Excel® file “format_precip_macro.xls” and enable macros, if prompted.
  3. Click on the worksheet titled “input_data”.
  4. Select columns “A” through “F”.
  5. Right-click on the columns and select “Format Cells…”
  6. In the “Format Cells” pop-up window select “Text” in the box below the word “Category”.
  7. Click “OK”.
  8. Use Notepad to open the file “precip_raw.txt”, located in the Precip_data folder.
  9. Select and copy the entire text file.
  10. Select cell “A1” on the input_data worksheet, then right-click and pick “Paste”
  11. Set up the data to match the format outlined on the “Instructions” worksheet of the spreadsheet (for help look at the instructions, or refer to Chapter 10 Using Microsoft® Excel® to format GSSHA™ Data.
  12. Follow the steps on the “Instruction” worksheet. (Use the default values. The coordinate for the gage is found in the Precip_formatted.txt file.)
  13. Once you have setup the data, click on the “Format precip data” button found on the “Instructions” worksheet”.
  14. Your formatted data is on the “Output_data” worksheet.

Hydrometeorological Data

Hydrometeorological data is used in GSSHA™ to determine how the soil moisture is affected by atmospheric conditions. The hydrometeorlogical data is used to drive the evapotranspiration model. In the following exercise we will create a file that contains all the hydrometeorological data for the same period as the precipitation data.

Using the Format Hmet Macro

  1. Open the Excel® file “Format_Hmet_macro.xls” from the Formatting_macros folder, and enable macros if prompted.
  2. Select the “Instructions” worksheet to learn how the data should be organized before it can be formatted for GSSHA™.
  3. To retrieve the raw data, open the Hmet raw data file called “Hmet_raw.xls” in the Hmet_data folder.
  4. Select the “KBLV_Scott worksheet and copy the appropriate columns of raw data to the “input_data1” worksheet of the format Hmet data macro.
  5. Select the worksheet “scott_radiation_2001” of the raw data file, and then copy the appropriate columns to the “input_data2” worksheet of the format Hmet data macro.
  6. Make sure that the “input_data1” and “input_data2” worksheets are organized as outlined on the “Instructions” worksheet, and then click the “Format Hmet data” button on the “Instructions” worksheet. (Note that the Instructions indicate that the data should be entered in cell A1. This is an error. The first row of data should be in cell A2.)
  7. The formatted data will be shown on the “output_data” worksheet.
  8. Save the “output_data” worksheet as a text file called “hmet.txt” in the folder you created earlier in the precipitation section.

Evapotranspiration

Now we will go back to WMS and set up the Long-term modeling data. First we need to set up the Job control options to turn on long-term mode.

If you are starting the tutorial from here, open the long_term.prj file found in the Finished Tutorial folder.

  1. Select GSSHA™| Job Control…
  2. Check the box next to "Long term simulation" in the GSSHA Job Control Parameters window.
  3. Click the Edit parameter... button and enter a value of 38.7696 for “Latitude”.
  4. Enter a value of 270.05 for “Longitude”.
  5. For “GMT” enter a value of –6.00.
  6. Enter 0.10 for “Minimum event discharge”.
  7. Make the “Soil moisture depth” equal to 0.5.
  8. Click on the folder icon to next to “HMET Data File” to browse for the Hmet text file you created with the “Format_Hmet_macro” spreadsheet. Navigate to the file and select it.
  9. Under “Format”, toggle on WES.
  10. Select OK.
  11. In the “Evapotranspiration” section of the window toggle “Penman Method”.
  12. In the Overland Flow Computation method combo box choose “ADE” instead of “Explicit.”
  13. Select OK.

    14. Next we need to set up the ET parameters.


  14. Select GSSHA™ | Map Tables…
  15. Click on the Evapotranspiration tab.
  16. In the drop down box next to “Using index map” select landuse, then click the “Generate IDs” button.
  17. Enter the values required for evapotranspiration using the following table, or you can find values from the appendix.

    18. Table 10. Values for the Evapotranspiration process.
    ID# Albedo Wilting Point (m3/m3) Vegetation Height (m) Vegetation Transmission Coefficient Canopy Stomatal Resistance (s/m)
    12 0.15 0.1 0.08 0.7 20
    15 0.22 0.1 0.1 0.5 20
    22 0.22 0.1 1 0.2 86
    42 0.2 0.1 17 0.15 100

  18. Click Done.

    19. Next we need to tell WMS to point to our precipitation file.


  19. Select GSSHA™ | Precipitation…
  20. Select Gage from the drop-down menu.
  21. Click the Import Gage File… button.
  22. Browse to the precipitation file, select it, and hit OK.

    23. Since we only have one gage, the rainfall data is spread out uniformly over the watershed. If we had more that one gage we would pick either Theissen Polygons or Inverse Distance weighted here in this dialog.


  23. Select Ok.

    24. We are ready to run now, but first we will want to change some output options. We will not want to output the data sets so frequently.


  24. Select GSSHA™ | Job Control...
  25. Click on the Output Control... button.
  26. In the Write frequency section of the dialog, change the Write Frequency to 60 (minutes).
  27. Select OK, OK.

    28. You are now ready to run a long-term simulation. Save the project, then run GSSHA™. This simulation may take some time to run to completion, and will run faster by selecting the Suppress screen printing option in the GSSHA Run Options dialog. You may view the simulation output by clicking the Abort button, selecting GSSHA | Read Solution and opening the sol_long_term.prj from the long_term_sol folder in the Finished_Tutorial directory.


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