**CHEMFLO
Screening Model for Flow and Transport in Soils**

**Version 1.30 - August 1989**

**CHEMFLO is a one-dimensional
screening level model for simulation of the movement of water and chemicals
in unsaturated soils. Water movement is described using Richards equation. The
equation describing the movement of chemicals includes advective and dispersive
transport, first-order decay in the liquid and solid phase, zero-order production
or decay, and linear equilibrium adsorption (using a retardation coefficient.
These equations are solved using the finite difference method. The model handles
three types of boundary conditions for flow. At the upper boundary, the conditions
may be constant potential, constant flux, mixed type condition, or rainfall.
The latter condition is a mixed type with the given flux equal to the rainfall
rate and the given head equal to zero. For a finite soil system, the conditions
at the lower boundary may be: constant potential, constant flux, or mixed type.
Results of the water model can be displayed in the form of graphs of water content,
matrix potential, driving force, conductivity, and flux density of water versus
distance or time. Graphs of concentration and flux density of chemical as functions
of distance or time can also be displayed. Cumulative fluxes of water and chemical
and total mass of chemical in the soil can be displayed as functions of time.
**

** The program has a menu driven
preprocessor for data input and editing. It produces output in both tabular
and graphical formats. Public domain CHEMFLO is distributed on DOS-formatted
disks containing executable image and example data sets. The user's manual includes
data input instructions and example problems. **

**SYSTEM REQUIREMENTS **

** Intel 80i86 based computer, 640
Kb RAM, about 1 Mb free disk space, and CGA or EGA graphics; math co-processor
recommended. **

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TO DOWNLOAD FREEWARE**

*Developers:
D.L. Nofziger, K. Rajender, S.K. Nayudu, and P.Y. Su (Oklahoma State Univ.)
for U.S. EPA*