WMS:GSSHA

Gridded Surface Subsurface Hydrologic Analysis (GSSHA) is a two-dimensional finite difference rainfall/runoff model. A finite difference grid is used to establish the computational domain and parameters for surface runoff. The GSSHA model is fully coupled with hydraulic stream flow/routing models. Parameters for stream channels are defined using arcs and then mapped to the appropriate underlying grid cells.

Features of GSSHA include 1D stream flow and infiltration, 2D overland flow and groundwater, and full coupling between the groundwater, shallow soils, streams, and overland flow. "Sediment and constituent fate and transport are simulated in the shallow soils, overland flow plane, and in streams and channels. GSSHA can be used as an episodic or continuous model where soil surface moisture, groundwater levels, stream interactions, and constituent fate are continuously simulated. The fully coupled groundwater to surface-water interaction allows GSSHA to model basins in both arid and humid environments."

The GSSHA model can be added to a paid edition of WMS.

GSSHA Menus

There are two GSSHA menus in WMS:

• When in the Map module, the GSSHA menu is available when a GSSHA coverage is selected. See here for more details.
• When in the 2D Grid module, the main GSSHA menu is available. See here for more details.

Cell Properties

The 2D grid cell properties include an I,J location and a scalar or index map value. The scalar or index map value is associated with the currently selected dataset in the Project Explorer and can be edited in the Properties Window. The I,J location can be viewed but not edited in the Properties Window. The 2D grid contours are a way of visualizing the spatial variation of the scalar or index map values for the selected dataset.

GSSHA Model Check

GSSHA Model Check dialog

The GSSHA Model Check dialog lists potential problems with the GSSHA model. It is accessed by selecting GSSHA | Model Check... while in the 2D Grid module. The model check runs through the input data for a GSSHA simulation and looks for obvious inconsistencies and problems with the model. The model check will find logical problems, but will not identify values that are outside of plausible ranges.

An example of a problem that the model checker would not find is if a stream arc has a pit that pools water. Examples of potential problems that will be identified by the model check:

• An index map has one or more cells whose ID is "0" (which is not allowed in GSSHA).
• A specified process that has an ID with parameters whose values are "0.00" (which indicates an incomplete entry).

Clicking on a specific warning or error will open a dialog that will allow the potential problem to be fixed, if needed.

At the bottom of the dialog are three buttons:

• Help – Opens this article in a web browser.
• Done – Closes the GSSHA Model Check dialog.
• Print – Opens a Choose name of output file dialog. Enter the desired File name and click Save to export the model check information to a text file.

GSSHA Run Options

GSSHA Run Options dialog

The GSSHA Run Options dialog lists options for running the GSSHA model. It is accessed by selecting GSSHA | Run GSSHA... while in the 2D Grid module.

The following sections and options are found in this dialog:

• Location section – Lists the GSSHA project file that will be run. Click to open a Save GSSHA Project File dialog. Select the desired project, or enter a new File name and click Save to close the Save GSSHA Project File dialog.
• Options section – The following options can be turned on or off:
  • Suppress screen printing –
  • Save file before running –
  • Pause GSSHA window after running –

At the bottom of the dialog are the following buttons:

• OK – Saves the changes and opens the Model Wrapper dialog.
• Cancel – Cancels the GSSHA model run and closes the GSSHA Run Options dialog.