1. General Model Information

Name: Simultaneous Heat and Water model

Acronym: SHAW

Main medium: terrestrial
Main subject: hydrology
Organization level: ecosystem
Type of model: compartment model, partial differential equations (1D)
Main application:
Keywords: frozen soil, heat transfer, water transfer, solute transfer, infiltration, evapotranspiration, runoff, surface energy balance


Gerald N. Flerchinger
Northwest Watershed Research Center
800 Park Blvd, Suite 105
Boise, ID 83712
Phone: 208-422-0716
Fax: 208-334-1502
email: gflerchi@nwrc.ars.usda.gov
Homepage: http://www.ars.usda.gov/pandp/people/people.htm?personid=1752


Gerald N. Flerchinger


The SHAW (Simultaneous Heat and Water) model is a one-dimensional physical-process model which simulates detailed heat, water and solute movement through the vegetative cover, snow, residue cover and soil. The model enables detailed simulation of water and energy flux at the atmospheric-soil interface and within the soil profile, and includes the effects of vegetation, snow, residue cover and soil freezing. The model was developed by Gerald N. Flerchinger in Boise, Idaho. (Flerchinger, 1991)

The model requires:

Model outputs are hourly and daily predictions of evapotranspiration, transpiration, soil frost depth, snow depth, runoff, surface energy balance and soil profiles of temperature, water, ice and solutes.

The model has been validated by comparing model output with measured soil temperatures, soil water and energy budgets, snowmelt and frost depths at numerous sites around the world.

Author of the abstract:


II. Technical Information

II.1 Executables:

Operating System(s): Distribution of the model and source code includes a DOS executable; the source code is transferrable to any system with a Fortran compiler.
see download page at www.nwrc.ars.usda.gov

II.2 Source-code:

Programming Language(s): FORTRAN

II.3 Manuals:

see download page at www.nwrc.ars.usda.gov

II.4 Data:

III. Mathematical Information

III.1 Mathematics

Weather conditions above the upper boundary and soil conditions at the lower boundary define heat and water fluxes into the system. Water and heat flux at the surface boundary include absorbed solar radiation, long-wave radiation exchange, and turbulent transfer of heat and vapor. A layered system is established through the plant canopy, snow, residue and soil, with each layer represented by a node. Equations governing heat and water flux through the plant canopy, snow, residue and soil layers are written in implicit finite difference form and solved using an iterative Newton-Raphson technique. Iterations are continued until successive approximations are within a prescribed tolerance.

III.2 Quantities

III.2.1 Input

Input to the SHAW model includes: General site information includes slope, aspect, latitude, and surface roughness parameters. Residue or litter properties include residue loading, thickness of the residue layer, percent cover and albedo. Input soil parameters are bulk density, saturated conductivity, coefficients for the matric potential-water content relation, and albedo-water content relation.

III.2.2 Output

IV. References

References for the SHAW model are available in pdf format at ftp.nwrc.ars.usda.gov

V. Further information in the World-Wide-Web

VI. Additional remarks

Last review of this document by: T. Gabele: 08. 07. 1997 -
Status of the document:
last modified by Joachim Benz Mon Dec 12 16:00:55 CET 2005

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