Last Modified: 2023-12-11 08:57:44.831

Software Version

HEC-HMS version 4.11-beta.11 was used to create this example. You can open the example project with HEC-HMS v4.11 or a newer version.

Project Files

Download the initial project files here:


In this workshop, you will gain experience developing and calibrating one or more of the gridded snow accumulation and melt methods available in HEC-HMS. HEC-HMS version 4.11 has three gridded snow methods: Gridded Temperature Index, Gridded Hybrid, and Gridded Energy Budget. This workshop focuses on setting up a model application and calibrating using a subbasin-average snow water equivalent time series and observed streamflow time series.  Calibrating the model will aid in understanding how individual snowmelt model parameters impact the simulated snow accumulation and melt as well as runoff.  The required meteorologic components for each snowmelt model are shown in the table below.

MethodGridded Temperature IndexGridded Hybrid SnowGridded Energy Budget
SummaryUses air temperature as a proxy for available snowpack energyUses a radiation balance, rather than temperature, as a proxy for available snowpack energyPhysically-based energy and mass balance model
Required Meteorologic Components
Shortwave Radiation
Longwave Radiation
Wind Speed

Atmospheric Pressure
Relative Humidity


The following major tasks will serve as an outline for the workshop:

  1. Review the existing HEC-HMS project.
  2. Create a Meteorologic Model and parameterize the requisite methods.
  3. Create a new Basin Model, select a snow method, and parameterize the snow method.
  4. Create a Simulation and evaluate results.
  5. Repeat for additional snowmelt methods.

Study Area

In this tutorial group, the study area is designated as the Upper Truckee River watershed upstream of the USGS stream gage at South Lake Tahoe, CA.  The Upper Truckee River watershed is part of the larger Truckee River watershed.  The Truckee River originates as the Lake Tahoe outlet in California and flows approximately 105 miles north and east into Nevada.  Major population centers within the Truckee River watershed include the cities of Truckee, CA, Reno, NV, and Sparks, NV with a total population greater than 350,000 (as counted during the 2010 census).  While the Truckee River provides a major source of water for its nearby inhabitants, the river is also prone to significant flooding.  Substantial damage has occurred during large scale and widespread rain-on-snow flood events in 1996-1997, 2005-2006, and 2016-2017 (amongst others).  Numerous state and federal water supply and flood risk management projects have been constructed within this watershed.  Several major federally-constructed projects include Martis Creek, Prosser, Stampede, and Boca dams, as shown below.

Truckee River Watershed

The Truckee River watershed offers an excellent opportunity to investigate snowmelt modeling techniques within a real-world watershed that contains an extremely large amount of meteorological, snow, and river observation stations.  Approximately 50 active stream gages are maintained by the USGS while approximately 20 Snow Telemetry (SNOTEL) stations are maintained by the Natural Resources Conservation Service (NRCS).  The Upper Truckee River watershed encompasses an approximate 54 sq mi drainage area upstream of Lake Tahoe, as shown below.

Upper Truckee River Watershed

Elevations within the study area range from approximately 1175 ft to 2260 ft as referenced to the North American Vertical Datum of 1988 (NAVD88), as shown in the figure below.

Review Existing HEC-HMS Project

An HEC-HMS project named Upper_Truckee_River has already been created for you.  This HEC-HMS project contains a Basin Model named WY2017, a Control Specification named WY2017, two Time Series, several Grid Sets, and a Terrain.  As shown below, there is one subbasin element named UpTruckeeRv_S10 which is connected to a junction element named SouthLakeTahoe within the existing basin model.  This subbasin was originally delineated using terrain data downloaded from the USGS National Map Viewer.

WY2017 Basin Model

The subbasin element was configured to use a 2000-meter SHG Structured discretization, the Simple canopy method, the ModClark unit hydrograph transform method, and the Linear Reservoir baseflow method.  The previously-mentioned observed SWE and discharge time series were linked to the subbasin and junction elements as observed time series, respectively.


The time period spanning 01Oct2016 through 15Aug2017 will be simulated within this tutorial using a 1-hour time step.  The following data has been collected and imported to the existing HEC-HMS project for your use:

Data TypeSource
PrecipitationMulti-Radar/Multi-Sensor System (MRMS)
Air TemperatureReal-time Mesoscale Analysis (RTMA)
Shortwave RadiationInterpolated from point measurements at South Lake Tahoe Airport
Longwave RadiationInterpolated from point measurements at South Lake Tahoe Airport
WindspeedInterpolated from point measurements at South Lake Tahoe Airport
Atmospheric PressureInterpolated from point measurements at South Lake Tahoe Airport
Relative HumidityInterpolated from point measurements at South Lake Tahoe Airport
StreamflowSouth Lake Tahoe USGS gage
Snow Water Equivalent DepthSubbasin-Averaged Time Series from SNODAS data

Create a New Meteorologic Model and Parameterize

  1. Open the HEC-HMS project.
  2. Once the project opens, select Components | Meteorologic Model Manager | New....
  3. Enter WY2017 as the Name.  Click Create to finalize the creation of this new Meteorologic Model.
  4. In the Watershed Explorer, expand the Meteorologic Models folder and select the WY2017 node.
  5. Set the Unit System to U.S. Customary.
  6. Set the Replace Missing option to Set To Default.
  7. In the Component Editor, select each process, assign the appropriate grid, and parameterize the following methods as shown in the table below:


    Gridded Shortwave


    LongwaveGridded LongwaveInterp_Longwave
    PrecipitationGridded PrecipitationMRMS_corrected
    TemperatureGridded TemperatureRTMA
    WindspeedGridded WindspeedInterp_Windspeed
    PressureGridded PressureInterp_Pressure
    Dew PointGridded HumidityInterp_Humidity
    EvapotranspirationGridded Hamon0.0065
    Replace MissingSet to DefaultN/A

    Do not change the default Time Shift Method for any of the processes.

    Not all snow methods require the same meteorological boundary conditions.  However, if properly parameterized, the same Meteorologic Model can be used for all snow methods.

  8. Click the Save button.

Choose a Snow Method

Now that you have reviewed the existing HEC-HMS project and created a new Meteorologic Model, choose one of the following snow accumulation and melt methods to parameterize and calibrate. If time allows, select a second (or third) method to calibrate.

Option 1. Gridded Temperature Index: Upper Truckee River

Option 2. Gridded Hybrid: Upper Truckee River

Option 3. Gridded Energy Budget: Upper Truckee River