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Global Change Master Directory (GCMD)
UNSATCHEM - Software Package for Simulating Water, Heat, Carbon Dioxide and Solute Movement in One-Dimensional Variably Saturated Media
Entry ID: USDA_ARS_UNSATCHEM


Summary
Abstract: UNSATCHEM is a software package for simulating water, heat, carbon dioxide and solute movement in one-dimensional variably saturated media. The software consists of the UNSCHEM (version 2.0) computer program, and the UNSATCH interactive graphics-based user interface. The UNSCHEM program numerically solves the Richards' equation for variably-saturated water flow and convection-dispersion type equations for heat, carbon dioxide and solute transport. The flow equation incorporates a sink term to account for water uptake by plant roots. The heat transport equation considers transport due to conduction and convection with flowing water. Diffusion in both liquid and gas phases and convection in the liquid phase are considered as CO2 transport mechanisms. The CO2 production model is described. The major variables of the chemical system are Ca, Mg, Na, K, SO4, Cl, NO3, H4SiO4, alkalinity, and CO2. The model accounts for equilibrium chemical reactions between these components such as complexation, cation exchange and precipitation-dissolution. For the precipitation-dissolution of calcite and dissolution of dolomite, either equilibrium or multicomponent kinetic expressions are used which include both forward and back reactions. Other dissolution-precipitation reactions considered include gypsum, hydromagnesite, nesquehonite, and sepiolite. Since the ionic strength of soil solutions can vary considerably with time and space and often reach high values, both modified Debye-Huckel and Pitzer expressions were incorporated into the model as options to calculate single ion activities.

The program may be used to analyze water and solute movement in unsaturated, partially saturated, or fully saturated porous media. The flow region may be composed of nonuniform soils. Flow and transport can occur in the vertical, horizontal, or a generally inclined direction. The water flow part of the model can deal with prescribed head and flux boundaries, boundaries controlled by atmospheric conditions, as well as free drainage boundary conditions. The governing flow and transport equations are solved numerically using finite differences and Galerkin-type linear finite element schemes, respectively.

Related URL
Link: DOWNLOAD SOFTWARE
Description: Access the UNSATCHEM software package (registration required).

ISO Topic Category
FARMING
CLIMATOLOGY/METEOROLOGY/ATMOSPHERE
ENVIRONMENT
GEOSCIENTIFIC INFORMATION


Access Constraints
User registration is required before downloading the software package.


Keywords
Models
Solute Movement
Water Movement
Heat Movement
Carbon Dioxide Movement


Personnel
DONALD LOUIS SUAREZ
Role: TECHNICAL CONTACT
Phone: (951) 369-4816
Fax: (951) 342-4962
Email: dsuarez at ussl.ars.usda.gov
Contact Address:
George E. Brown, Jr. Salinity Laboratory
450 West Big Springs Road
USDA, ARS
City: Riverside
Province or State: CA
Postal Code: 92507-4617
Country: USA


TYLER B. STEVENS
Role: SERF AUTHOR
Phone: 301-851-8113
Email: Tyler.B.Stevens at nasa.gov
Contact Address:
5700 Rivertech Court
City: Riverdale
Province or State: MD
Postal Code: 20737
Country: USA


Publications/References
Simunek, J., D. L. Suarez, and M. Sejna. 1996. The UNSATCHEM Software Package for Simulating One-Dimensional Variably Saturated Water Flow, Heat Transport, Carbon Dioxide Production and Transport, and Solute Transport with Major Ion Equilibrium and Kinetic Chemistry, Version 2.0. Research Report No. 141, USDA-ARS U. S. Salinity Laboratory, Riverside, California.
Extended Metadata Properties
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Creation and Review Dates
SERF Creation Date: 2011-05-11
SERF Last Revision Date: 2018-09-13



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