| This contains information about functionality available starting at GMS version 10.4.
The content may not apply to other versions.
The Soil-Water-Balance (SWB) model has been developed by USGS to allow estimates of potential recharge to be made quickly and easily.
Four gridded datasets are required:
- Hydrologic soil group
- land use/land cover
- Available soil-water capacity
- Surface-water flow direction
In addition to gridded land-surface data the model requires tabular daily climatological data (daily precip (inches), average air temperature [F], max air temp [F], min air temp [F]). Additional data may be required depending on model options:
- daily average wind speed (m/s),
- daily average relative humidity (%),
- daily max relative humidity (%),
- daily percentage of possible sunshine (%).
Finally a lookup table must be supplied to assign curve numbers, interception values, rooting depths, and maximum daily recharge values.
Creating an SWB Simulation
To create an SWB simulation, do the following:
A new "Simulation Data" item will appear in the Project Explorer, along with a "SWB Simulations" item and a new simulation item. Right-clicking on the "SWB Simulations" item also has a New Simulation command that allows adding additional SWB simulations to the project.
- Delete – Removes the simualation item.
- Duplicate Creates a copy for the simulation, including all parameters set in the model control.
- Rename – Allows changing the name of the simulation item.
- Model Control – Opens the Model Control dialog where the model run parameters are set.
- Model Check – Looks for potential errors in the model setup. Brings up the Model Checker dialog if issues are discovered.
- Export SWB – Generates files used in the model run.
- Launch SWB – Starts the SWB model run and opens the Simulation Run Queue dialog.
- Save, Export, and Launch SWB – Combines several other commands together. First, it saves the project file, then exports files for the model run, and finally launches the SWB model run.
- Properties – Opens the Properties dialog which displays the simulation properties and allows adding notes.
SWB Output Files
After running the model, SWB will generate several output files.
- Recharge daily statistics – Contains the minimum, maximum, and mean values for all major components of the water balance for all grid cells in the model on a given day.
- Recharge daily report – Contains values representing the individual daily values summed over the entire model multiplied by the conversion factor.
- Recharge annual statistics – Contains mean values representing the annual sum of daily mean values.
- Log file – Contains a report of the processes performed during the model run.
- Grid and image files – Based on the selected optional output variables in the model control.
GMS – Groundwater Modeling System
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