The Soils Menu allows input for soil characteristics.

Input files for initial temperature and moisture profiles and boundary conditions at the bottom of the soil profile may either be created by the user interface or supplied by the user, in which case the interface will prompt the user for the location of these input files. If desired, the user interface will optionally extend the depth of the profile to 4 meters where soil temperature may be assumed constant. In this case, the user interface will artificially create additional simulation depths down to 4 meters. Temperature at this bottom depth is estimated from the specified annual average air temperature. Initial water content to 4 meters is assumed equal to the deepest input water content.

Albedo of Dry Soil

Solar Reflection (albedo) of dry soil. Valid range: 0.1 - 0.5

Albedo of Wet Soil

Solar Reflection (albedo) of wet soil. Valid range: 0.1 - 0.5

Lower Boundary Condition for Heat Flow Two options are available for temperature at the lower soil boundary:

1) Assume constant soil temp at 4 meter depth: The user interface will extend the specified simulation depths down to 4 meters and assume a constant temperature.

Average Annual Air Temp: The nearly constant soil temperature at a depth of 4 m can be approximated by the average annual air temperature. Valid range -20 to +30 C.

2) Soil temperatures from user file: The user can specify a varying temperature at the lower boundary in an input soil temperature file.

Soil Temperatures File: Path and filename of the user-supplied soil temperature file. The format for the user-supplied soil temperature file is described in the SHAW Users Manual.

Lower Boundary Condition for Water Flow Several options are available for specifying moisture conditions at the lower soil boundary.

1) Assume constant water content at 4 meter depth: This option is available only if user chooses "Assume constant soil temp at 4 meter depth" for the Lower Boundary Condition for Heat Flow. Water content at 4 m is assumed equal to the deepest input water content in the "Enter Simulation Depths" screen.

2) Water flux calculated assuming gravity flow: Water flow out the lower boundary will be due to gravity flow based the simulated water content. (This is referred to as a dimensionless unit gradient.)

3) Soil water content from user file: The user can specify a varying water content at the lower boundary in an input soil temperature file. This option is available only if user chooses "Soil temperatures from user file" for the Lower Boundary Condition for Heat Flow.

Soil Water Content File: Path and filename of the user-supplied soil water content file. The format for the user-supplied soil temperature file is described in the SHAW Users Manual