Using NEXRAD Rainfall Data in an HEC-HMS

Using NEXRAD Rainfall Data in an HEC-HMS
v. 10.1
WMS 10.1 Tutorial
Spatial Hydrologic Modeling – Using NEXRAD
Rainfall Data in an HEC-HMS (MODClark) Model
Learn how to setup a MODClark model using distributed rainfall data
Objectives
Read an existing WMS watershed model. Finish defining the model input parameters, then use NEXRAD
(distributed radar rainfall) data for the model's precipitation. Compare the results from the NEXRAD
precipitation with a non-distributed precipitation method.
Prerequisite Tutorials

Spatial Hydrologic
Modeling – HEC-HMS
Distributed Parameter
Modeling with the
MODClark Transform
Required Components






Data
Drainage
Map
Hydrology
Hydrologic Models
2D Grid
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Time

30-60 minutes
© Aquaveo 2016
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Contents
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Contents ............................................................................................................................... 2
Introduction ......................................................................................................................... 2
Open an Existing WMS Project ......................................................................................... 2
Creating Landuse and Soil type Coverages ...................................................................... 3
Defining Model Parameters................................................................................................ 3
Defining Meteorological Data ............................................................................................ 5
Visualizing Meteorological Data ........................................................................................ 8
Saving the Model ................................................................................................................. 9
Running the Model.............................................................................................................. 9
Using Rainfall Hyetograph and Running the Model Again ............................................ 9
Introduction
In this tutorial see how the NEXRAD rainfall data can be used in an HEC-HMS
MODClark model. Begin with an existing WMS project file with a watershed already
delineated and build a MODClark model. Then use NEXRAD data for the precipitation.
Also compare the results from NEXRAD gridded precipitation method and user
hyetograph precipitation methods.
The data used for this tutorial can be downloaded from the WMS learning center of the
Aquaveo web site and can be unzipped to a folder called spatial on the computer.
3
Open an Existing WMS Project
Open a WMS project file for Park City watershed and keep building on it.
1. Select File | Open.
2. Locate the Hydrologic Models folder in the files for this tutorial. If needed,
download the tutorial files from www.aquaveo.com.
3. Browse and open the following file: \spatial\HMS\NEXRAD BaseProj.wms.
4. Save the project with a new name so that the original project remains
unchanged. Select File | Save As… and save the file as
spatial\HMS\NEXRAD\nexrad.wms.
5. Open the Hydrologic Modeling Wizard dialog by clicking the
button.
6. On the left side of the wizard dialog, click on the Select Model option as all
other processes have been performed.
7. Select the model to be HEC-HMS MODClark.
8. Click on Initialize Model Data.
9. Click Next on the wizard.
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© Aquaveo 2016
WMS TutorialsSpatial Hydrologic Modeling – Using NEXRAD Rainfall Data in an HEC-HMS (MODClark) Model
10. Enter the cell size of 90.
11. Click on the Create 2D Grid button.
12. Click OK to interpolate background elevation from DEM.
13. Click Next on the wizard.
14. Set the job control data (07/25/2007, 6:00:00 PM to 07/26/2007, 6:00:00
PM). Set the time interval to be 15 min.
15. Click on the Set Job Control Data button.
16. Click Next on the wizard.
4
Creating Landuse and Soil type Coverages
Here create two coverages, read in soil and land use data, and map these data to WMS
coverages.
1. Click on the Open button
next to Add shapefile: and open the file
spatial\RawData\ParkCity\Luse\salt_lake_city.shp. The land use shape
file is now added to the GIS Layers in the WMS Project Explorer.
2. Likewise, click on the Open button
next to Add shapefile: and open the
file spatial\RawData\ParkCity\SSURGO_Soil\Joinedsoil\ SSURGO_Soil.shp.
The soil type shape file is now added to the GIS Layers in the WMS
Project Explorer.
3. In the wizard, click on the Create Coverages… button to create land use
and soil coverages and map the corresponding shape file polygons to the
respective coverages. Navigate through the attribute mapping dialogs by
selecting Next, Next, and Finish in each dialog when prompted.
4. Click on Next in the modeling wizard.
5
Defining Model Parameters
1. Click the Compute GIS Attributes button which will open the Compute
HMS Loss Method Attributes dialog.
2. Toggle on SCS Curve Number.
3. Make sure that the soil type and land use coverages are mapped correctly.
4. Click on the Import button. Browse and open the file spatial\RawData\
scsland.txt.
5. Click OK to assign curve numbers to the grid from the land use and soil
data defined in this dialog. Notice that the Curve Number grid has been
added to the data tree under 2D Grid Data.
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© Aquaveo 2016
WMS TutorialsSpatial Hydrologic Modeling – Using NEXRAD Rainfall Data in an HEC-HMS (MODClark) Model
6. Click on the Edit Parameters button.
7. In the HMS Properties dialog, in the Display options portion of the dialog,
select the following

Loss Rate Method
o

Transform
o

Gridded SCS Curve Number
MODClark
Turning these options will add fields to the Properties area.
8. Set and/or fill in the following values in the rest of the fields:

Basin Area is computed by WMS

Make sure that the Loss Rate Method is Gridded SCS Curve
Number

Initial Abstraction Ratio = 0.2

Potential Retention Scale Factor = 1.0

Transform Method = MODClark
9. Click on the Compute… button under basin data. In the Basin Time
Computation dialog change Computation type to Compute Lag Time and
Method to SCS Method.
Notice the variables required for the SCS lag time equation listed in the box at the bottom
of the dialog. Although having computed a Curve Number grid, it’s still necessary to
enter a composite curve number value in the lag time equation
10. Check to make sure the CN variable in the Variables window is not 0.0. If
it is, click on the CN variable in the Variables window, enter a CN value of
72.46 in the Variable value edit field to the right of the window, then click
on any other variable in the Variables window so that the CN value gets
updated.
11. Check to make sure there are no zero values among the Lag Time variables
and click OK. See Figure 5-1.
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© Aquaveo 2016
WMS TutorialsSpatial Hydrologic Modeling – Using NEXRAD Rainfall Data in an HEC-HMS (MODClark) Model
Figure 5-1: Lag Time Variables for Basin Time Computation
12. Scroll all the way to the right and make sure that the Time of Concentration
(hr) and Storage Coefficient (hr) are calculated. WMS converts the lag
time to a time of concentration using the SCS equation.
13. Click OK.
14. Click Next.
6
Defining Meteorological Data
So far in all of the models being used either uniform intensity rainfall or SCS storm. Here
use NEXRAD RADAR rainfall data.
1. Click on the Define Precipitation button.
2. Select Gridded Precipitation for Precipitation Method.
Since there is not a DSS file for the precipitation grid, create it. First open the NEXRAD
files and convert them to DSS.
3. Click on Convert ASCII or XMRG files to DSS….
4. In the Convert Grids dialog that opens, make sure that the conversion
option is set to Arc/Info ASCII Grid to DSS.
5. Click the Add Files… button. Browse to spatial\RawData\ParkCity\
NEXRAD.
6. In the Open file browser, change the view menu to Details (Figure 6-1).
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© Aquaveo 2016
WMS TutorialsSpatial Hydrologic Modeling – Using NEXRAD Rainfall Data in an HEC-HMS (MODClark) Model
Figure 6-1: Change the view menu to Details
7. Click on the Type column label to sort the files by type.
8. Select the last time grid which is KMTX_NTP_20070726_0358.asc as
shown in Figure 6-2.
Figure 6-2: Select the last time grid first
9. Hold shift key and select first time grid which is
KMTX_NTP_20070725_1801.asc. Click Open.
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© Aquaveo 2016
WMS TutorialsSpatial Hydrologic Modeling – Using NEXRAD Rainfall Data in an HEC-HMS (MODClark) Model
10. In the Convert Grids dialog, make sure the Convert inches to millimeters
option is toggled off (Figure 6-3).
Figure 6-3: Convert Grids dialog
11. Click on the Browse button
and browse to the folder/file
spatial\HMS\NEXRAD\radarrain.dss (use the folder where the data used
in this tutorial is saved) and click Save. It is advisable to select a name that
is different than the HMS file (selecting a different name will separate the
gridded precipitation dss file from the project dss file and help keep the
files organized).
12. Set the Starting date to 7/25/2007 and the Starting time to 6:00 PM. Make
sure the time interval is set to 1 hour (60 min) and click OK.
13. After selecting OK, it will take some time to read and process the
precipitation files and save the gridded DSS file.
For more information on how this process is carried out, see
http://www.xmswiki.com/index.php?title=WMS:Radar_Rainfall
14. As soon as the saving process finishes, a prompt will appear to select a
program to view a summary showing the date/time and rainfall depth at
each time interval (Figure 6-4). Minimize this file—it is needed later on.
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© Aquaveo 2016
WMS TutorialsSpatial Hydrologic Modeling – Using NEXRAD Rainfall Data in an HEC-HMS (MODClark) Model
Figure 6-4: NEXRAD Radar Data summary report
15. Click OK.
7
Visualizing Meteorological Data
Before continuing, visualize the gridded rainfall data.
1. Select Close to close the wizard dialog.
2. Turn off the display of soil type and land use coverages as well as the GIS
layers by un-checking them in the data tree. This will help zoom into the
watershed area for better visualization.
3. Right-click on Rainfall Cumulative on the data tree under 2D Grid Data
and select Contour Options… Select Color Fill for the Contour Method.
Click OK.
4. Click on Rainfall Cumulative on the data tree under 2D Grid Data to make
sure that it is active.
5. Select the first time step in the properties window and with the down arrow
key on the keyboard, step through the time steps to see how the
precipitation varies.
There are two rainfall datasets, one is incremental and the other is cumulative. View the
incremental rainfall dataset in the same way the cumulative dataset was viewed. Choose
either dataset for creating the film loop.
6. In the 2D Grid Module
select Data | Film Loop… Specify the folder
where to save the animation, toggle off the option to Export to KMZ
(Google Earth) and click Next.
7. Under the option to Write to AVI file, make sure Rainfall Cumulative is
checked and that the option to write to a KMZ file is turned off for all
datasets. Turn off the option to Write the 2D Scattered Dataset to a KMZ
File.
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© Aquaveo 2016
WMS TutorialsSpatial Hydrologic Modeling – Using NEXRAD Rainfall Data in an HEC-HMS (MODClark) Model
8. Click Next
9. Click Finish
WMS may take a few moments to create and save the animation file. The animation will
start playing as soon as the saving process is complete. Try to visualize how rainfall is
changing over the watershed over time. Now continue working with the model.
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Saving the Model
1. Open the Hydrologic Modeling Wizard dialog again by clicking the
button.
2. Click Clean Up Model on the left side of the dialog.
3. Click on the Clean Up Model button. This button runs the operations that
are toggled on.
4. Click OK to accept the default values for stream redistribution.
5. In the model checker, fix any errors that may be listed, then click Done to
close the model checker.
6. Click Close to close the modeling wizard dialog.
7. Switch to the Hydrologic Modeling Module
Save HMS file.
and select HEC-HMS |
8. Save the HMS file as spatial\ HMS\NEXRAD\wmsexport.hms.
9
Running the Model
An HMS MODClark file has been successfully created for the Park City Watershed. Now
work inside the HMS interface.
1. Minimize the WMS window and open HEC-HMS 3.1 or later.
2. Select File | Open. Browse and open \spatial\HMS\NEXRAD\
wmsexport.hms. If the .hms file is not saved properly, open it from
\spatial\HMS\NEXRAD\finished \wmsexport.hms.
3. Run the model (sometimes run the model twice for the results to be active).
4. View the results.
10
Using Rainfall Hyetograph and Running the Model Again
1. Return to WMS.
2.
In Hydrologic Modeling Module
Parameters.
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select HEC-HMS | Meteorologic
© Aquaveo 2016
WMS TutorialsSpatial Hydrologic Modeling – Using NEXRAD Rainfall Data in an HEC-HMS (MODClark) Model
3. Change Precipitation Method to User Hyetograph and click on XY Series
button.
4. Open the summary file which was previously minimized and copy the
distribution from the summary file to Excel.
5. Make sure that the incremental/cumulative depths are in inches (if not use
conversion factor or 1 inch = 25.4mm to convert).
6. Copy and paste the time in minutes and the cumulative distribution into the
XY series editor (NOTE: WMS will accept a temporal rainfall distribution
that is either dimensional or dimensionless. If a dimensional distribution is
entered, WMS will normalize the curve and make it dimensionless before
applying the total rainfall depth to the distribution). Select OK.
7. Enter total rainfall depth (0.92 in. in this case).
8. Select OK.
9. Save the HMS project file.
10. Run HMS.
11. View the results and compare with the previous run.
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© Aquaveo 2016
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