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United States Department of Agriculture

Agricultural Research Service

SHAW History
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Check this page for information on updates, new releases, and corrections to the SHAW model. Future modifications expected for SHAW include provisions for saturated soil conditions and presence of a water table.

The following gives a brief history of the various versions of the SHAW model. Check on the version of the model you have been using.

SHAW 2.3 (Released 2/97)

Modifications:

  • Corrections made to maintain solute balance when large infiltration events penetrate multiple soil layers. (Released 10/19/2004; program compiled to force model to pause at end of simulation before window is closed)
  • Corrections made to prevent ice content from being set to zero when initial soil temperature profile has sub-freezing temperatures. (Released 3/9/2004)
  • Modifications made to calculation of soil thermal conductivity to correct problems reported by Kennedy and Sharratt, Soil Science 163(8):636-645. (version 2.3.6, released 9/30/2003)
  • Improper array dimension introduced by the modification of 5/25/2001 was corrected (Released 10/19/2001).
  • Inaccuracies due to limitations of Green-Ampt infiltration equation when wetting front enters a layer of much higher conductivity were corrected (version 2.3.5, released 5/25/2001).
  • Numerical problems asociated with very small root densities in an individual soil layer were corrected.
  • Convergence of canopy layers was improved and interception of snow within the canopy was included (version 2.3.4, released 6/2000).
  • Soil profile can have as many as 50 soil layers (version 2.3.3, released 5/1999).
  • Executable created using newer compiler which allows faster runtimes (version 2.3.2, released 1/1999).
  • Structure of model changed to facilitate coupling with other models.
  • Residue layer can have a single residue node (rather than a minimum of two).
  • Program was modified to be more transferrable to other Fortran compilers by incorporating SAVE statements in many of the subroutines (implemented 4/98, version 2.3.1).

Known bugs:

  • Model incorrectly calculated refreezing of snowmelt water precolating through snowpack (fixed 9/30/2003, version 2.3.6
  • Numerical instabilities encountered with extremely tall (>20m) plant canopy (fixed 5/99, version 2.3.3).
  • Errors in water balance with longer time steps under certain conditions of rapid snowmelt and disappearance of snowpack (fixed 2/99).
  • Overestimation of water vapor transfer in soil layers with 0% clay content (fixed 1/99, version 2.3.2).
  • Inaccurate water balance and transpiration if roots extend beyond half of the depth of the soil profile (fixed 3/97)
  • Slight inconsistency in water balance experienced during freezing with high levels of solutes (fixed 4/97).
  • Option for specifying NSP < 0 no longer works
  • Program cannot be started on day 1, hour 0.

SHAW 2.2 (Released 6/96)

Modifications:

  • Corrections implemented to allow for complete sublimation of snow pack
  • Corrections implemented for infiltration events which extend beyond soil profile

SHAW 2.1 (Released 11/95)

Modifications:

  • Warning issued when old output files are to be over-written

Limitations:

  • Problems encountered if infiltration event extends beyond soil profile

Known bugs:

  • Errors in solute leaching calculations when large infiltration events penetrated multiple soi layers created errors in solute balance (fixed 10/19/2004)
  • Inaccurate water balance and transpiration if roots extend beyond half of the depth of the soil profile
  • Run-time errors if sublimation is sufficient to consume all of snow pack within a time step (likely to occur only daily time steps)
  • Inaccurate water balance and transpiration if roots extend beyond half of the depth of the soil profile
  • Slight inconsistency in water balance experienced during freezing with high levels of solutes

SHAW 2.0 (Released 6/95)

Modifications:

  • More control over output
    Input requirements changed (and hopefully simplified)
  • more parameters hard-coded in the model
  • Development of user interface
  • Incorporation of plant canopy and transpiration, including provisions for changing plant canopy characteristics

Limitations:

  • User not allowed to write over old output files
  • Problems encountered if infiltration event extends beyond soil profile

Known bugs:

  • No adequate control of output for water flow between nodes (fixed 11/95)
  • Run-time errors encountered when clay content equals zero (fixed 11/95)
  • Inaccurate water balance and transpiration if roots extend beyond half of the depth of the soil profile
  • Slight inconsistency in water balance experienced during freezing with high levels of solutes

SHAW 1.xx

Limitations:

  • User interface not available
  • Input simplified in later versions
  • No daily weather input or daily time steps in early versions
  • No plant canopy in early versions
  • Problems encountered if infiltration event extends beyond soil profile

Known bugs:

  • Incorrect value for heat capacity of soil hard-coded in model (fixed 9/90)
  • Incorrect calculation of azimuth and solar angles for certain parts of the year (fixed 10/94)

Last Modified: 4/15/2008
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