User:Jcreer/SMS: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 SMS.

Building a GSSHA Simulation

[[File:|thumb|250 px|Example of a GSSHA simulation in the Project Explorer]]

Creating a GSSHA Simulation in SMS requires several components. These components include:

• a 2D UGrid
• a GSSHA boundary conditions coverage

While the project can contain multiple UGrids, only one UGrid can be attached to each GSSHA simulation. The 2D UGrid must follow certain rules that include square cells, not rotated, and numbered the in the way required by GSSHA. The GSSHA 2D UGrid tool can be used to created this UGrid.

To create a GSSHA simulation:

1. Right-click on an empty space in the Project Explorer, or right-click on " Project" in the Project Explorer, and select New Simulation | GSSHA.

When the simulation has been initially created, the selected UGrid can be linked to the simulation.