United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA/600/S8-89/076 Dec. 1989
£EPA Project Summary
CHEMFLO: One-Dimensional
Water and Chemical
Movement in Unsaturated Soils
D. L. Nofziger, K. Rajender, Sivaram K. Nayudu, and Pei-Yao Su
This user's guide serves the
purpose of instructing the user in the
execution of a software package
CHEMFLO for simulating water and
chemical movement in unsaturated
soils. The guide should allow easy
access to information critical to the
development of an understanding of
the transport and fate of chemicals
for point and non-point sources.
This Project Summary was devel-
oped by EPA's Robert S. Kerr Envi-
ronmental Research Laboratory, Ma,
OK, to announce key findings of the
research project that Is fully docu-
mented in a separate report of the
same title (see Protect Report order-
Ing Information at back).
Introduction
Understanding the movement of water
and chemicals into and through soils is of
great importance in managing, utilizing,
and protecting our natural resources.
These processes are very dynamic,
changing dramatically over time and
space. Soil properties, chemical prop-
erties, and water and chemical appli-
cation rates interact in complex ways
within the soil system to determine the
direction and rate of movement of these
materials. Researchers have worked
many years to understand the physical
and chemical mechanisms responsible
for the movement of these materials.
They have developed mathematical
models describing these processes and
compared the predictions of these
models with field and laboratory meas-
urements. The resulting mathematical
models form a basis for predicting the
behavior of water and chemicals in soils.
The full manual describes a software
system designed to enable persons to
define water and chemical movement
systems, to solve the mathematical
models, and to display the results of the
simulations in graphical and tabular
forms. This software expands on that of
Nofziger1 by reducing limitations in
simulating water movement, adding
chemical movement, and expanding the
graphical and tabular output options. The
manual describes the mathematical
models used in the software and their
limitations. The computer hardware and
software required are then described.
Simulations for several flow systems are
included as the use of the software is
described. Other features of the software
are then illustrated. Finally, a set of
numerical experiments is included. These
experiments are designed to illustrate
flow and transport in different types of
soil systems and to enable users to
assess the importance of different soil
properties and other physical and chem-
ical parameters upon water and chemical
movement.
The software is intended for use by
students, regulators, consultants, scien-
tists, and persons involved in managing
water and chemicals in soil who are
interested in understanding unsaturated
flow and transport processes. A limited
amount of technical terminology is used
in the software and manual, but the user
need not understand the mathematics of
the model in order to effectively use the
software. As is the case in any model, the
user is urged to become familiar with the
limitations of the model and to assess
their significance for the situation of
interest before using it for decision
making.
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Conclusions
An interactive software system was
developed to enable decision-makers,
regulators, policy-makers, scientists, con-
sultants, and students to simulate the
movement of water and chemicals in
unsaturated soils. Water movement is
modeled using Richards2 equation.
Chemical transport is modeled by means
of the convection-dispersion equation.
These equations are solved numerically
for one-dimensional flow and transport
using finite differences. Results of the
water model can be displayed in the form
of graphs of water content, matric
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.
Tabular outputs are also available. The
full manual presents the mathematical
equations and the numerical techniques
used in the software. Limitations of the
model are presented. Instructions for
installing the software on your computer
are given along with illustrations of its
use. Finally, a set of numerical exper-
iments are presented to enable the user
to gain an understanding of the dynamic
processes involved in water movement
and chemical transport in soils. The
software was written for use with IBM
compatible microcomputers with 640 K
bytes of random access memory, twJ
floppy disk drives or one floppy disk and
one fixed disk, or CGA, EGA, or VGA
graphics cards, and an 80x87 math
coprocessor.
References
1. Nofziger, D. L. 1985. Interactive simu-
lation of one-dimensional watei
movement in soils: user's guide
University of Florida, Institute of Fooc
and Agricultural Sciences, Cir. 675
56pp.
2. Richards, L. A. 1931. Capillary con
duction of liquids through porou
mediums. Physics 1:318-333.
D. L Nofziger, K. Rajender, Sivaram K. Nayudu, and Pei-Yao Su are with Oklahoma
State University, Stillwater, OK 74078.
Joseph R. Williams is the EPA Project Officer (see below).
The complete report, entitled "CHEMFLO: One-Dimensional Water and Chemical
Movement in Unsaturated Soils," (Order No. PB 90-126 020/AS; Cost: $23.00,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
Ada, OK 74820
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Penalty for Private Use $300
EPA/600/S8-89/076
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