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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 EPA/600/S8-89/076
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