This tutorial was not designed to provide guidance for applying downscaled climate model projections to inform an analysis. Each Federal, State, and Local agency should follow agency specific guidance for including possible future climate change information in hydrologic analysis. This tutorial highlights tools in HEC-HMS that aid modelers in making use of gridded meteorologic datasets and utilizing the new Ensemble compute option to organize many simulations. 

This section combines a couple of steps that show you how to convert the CMIP5 climate projection datasets into a format HEC-HMS can use and set up meteorologic models. 

Convert Historical Livneh and Downscaled CMIP5 Climate Projection Datasets to HEC-DSS Format

The HEC-HMS Gridded Data Import tool was used to convert the Livneh and CMIP5 Climate Projection datasets from NetCDF format to HEC-DSS format. The following steps demonstrate the process of converting data formats.  

  1. Open HEC-HMS and select the File | Import | Gridded Data | Importer menu option to open the Gridded Data Import Wizard.
  2. Choose one of the NetCDF files. 
  3. Choose one of the Variables. In the example below, the "pr" precipitation variable is selected.
  4. As shown in the figure below, a Clipping datasource was selected. This step is highly recommended to keep the file size reduced. The clipping dataset was created by exporting a subbasin shapefile from the HEC-HMS project. The subbasins were merged into one bounding polygon and then buffered by 1000 feet. The SHG projection was selected by clicking the world button and choosing SHG as the selected projection. Notice a target cell size was not selected in the figure below. The original data's cell size is preserved when no target cell size is specified in the Gridded Data Import Wizard. Finally, the Bilinear resampling option was selected. 
  5. Select a Destination DSS file to save the gridded data.
  6. The final step in the Gridded Data Import Wizard is critical. The program will correctly define the C-part pathname, DSS Units, and DSS Data Type for you. You do not need to override these setting when importing data from the Downscaled CMIP3 and CMIP5 Climate and Hydrology Projection website used for this example. You can use the other DSS pathname parts to define the watershed and data source. (The HEC-HMS gridded data tools includes a Sanitizer tool than can be used to screen gridded data values. For example, missing or value greater than a specified threshold could be set to 0 to prevent simulations from aborting.)
  7. The temperature data provided from the Downscaled CMIP3 and CMIP5 Climate and Hydrology Projection website included the daily minimum and maximum temperatures. The evapotranspiration and snowmelt option in HEC-HMS require an air temperature estimate at regular time intervals. The minimum and maximum temperature data was processed using the Grid to Point tool (available in HEC-HMS from Tools | Data | Grid to Point) to compute the watershed average time-series. Then the minimum and maximum time series were averaged (using HEC-DSSVue) to generate an average temperature time-series. As shown in the following sections, the watershed average temperature time-series were interpolated to gridsets using the terrain data and a lapse rate.

This step took approximately 2 hours to complete. You can see all gridsets and time-series in the …\Success_Dam_ensemble\data directory.

Create Gridsets and Time-Series Gages in the HEC-HMS Project

HEC-HMS Precipitation gridsets were created for each of the CMIP5 Climate Projection and Livneh precipitation boundary condition. As described above, the subbasin average daily average temperature was computed. The subbasin average temperature data was loaded into the HEC-HMS model as temperature gages. 

The following steps describe how the precipitation gridsets and temperature time-series were added to the HEC-HMS project. It is a suggested practice to store all gridded and time-series data in your project’s data folder.

  1. Open the Grid Data Manager and create a Precipitation gridset.
  2. Open the Component Editor for the precipitation gridset. As shown below, a description was entered, the Single Record HEC-DSS Data Sources selected, a DSS file selected, and a pathname was selected. This step was duplicated for all 10 CMIP5 Climate Projection and Livneh datasets. 
  3. Open the Time-Series Data Manager and create a Temperature gage.
  4. Open the Component Editor for the temperature time-series gage. As shown below, a description was entered, the Single Record HEC-DSS Data Sources selected, a DSS file selected, and a pathname was selected. The watershed (total project watershed) centroid elevation (3985 feet, 1214.6 meters) and latitude and longitude coordinates were entered. This step was duplicated for all 10 CMIP5 Climate Projection and Livneh datasets.
  5. The following figure shows the Watershed Explorer and the Precipitation Gridsets and Temperature Gages folders expanded. 

This step took approximately 30 minutes to complete.

Create Meteorologic Models in the HEC-HMS Project

The calibrated basin model was used for all simulations using the CMIP5 Climate Projection datasets. A separate meteorologic model was configured for each of the CMIP5 Climate Projection datasets and for the Livneh dataset.

The following steps describe how meteorologic models were added to the HEC-HMS project.

  1. Open the Meteorologic Model Manager and add a new meteorologic model to the project. Set the precipitation, temperature, and evapotranspiration methods for the meteorologic model. The following figure shows the CMIP5-1a meteorologic model (uses precipitation and temperature from the access 1-0 climate model). The meteorologic model was configured to use the Gridded Precipitation, Interpolated Temperature, and Gridded Hamon methods.
  2. Open the Gridded Precipitation component editor and choose the appropriate precipitation gridset. The following figure shows the Gridded Precipitation component editor for the CMIP5-1a meteorologic model. Notice the CMIP5-1a gridset is selected.
  3. Open the Interpolated Temperature component editor and enter the required information. The following figure shows the Interpolated Temperature component editor for the CMIP5-1a meteorologic model. Notice the CMIP5-1a basin average temperature gage is selected. The gage's elevation and geographic location were defined in the time-series gage component editor. The program will create an interpolated temperature grid using the terrain model defined in the basin model and a Lapse Rate of -3 Degrees F per 1000 vertical feet.
  4. Open the Gridded Hamon component editor. You can edit the default Hamon Coefficient. The program will use the interpolated temperature gridset when computing the potential evapotranspiration for each grid cell in the basin model. The following figure shows the Gridded Hamon component editor for the CMIP5-1a meteorologic model. The same Hamon Coefficient was used for all meteorologic models.
  5. The following figure shows all meteorologic models added to the example project. 

This step took approximately 30 minutes to complete.

Continue to Calibrate the Basin Model to Historical Data using Daily Precipitation and Temperature Dataset.