1. General Model Information
Name: Estimating transport parameters from laboratory or field tracer experiments
Acronym: CXTFIT
Main medium: terrestrial
Main subject: hydrology
Organization level: ecosystems
Type of model: partial differential equations (1D)
Main application:
Keywords: parameter estimation, parameter identification, transport parameters, solute transport, tracer, nonlinear least-squares optimisation, inverse problem, inverse modeling, convection-dispersion equation, analytical solution, nonequilibrium transport, stochastic transport, stream tube model,Levenberg-Marquardt-algorithm
Contact:
N. Toride
U. S. Salinity Laboratory, USDA, ARS
450 West Big Springs Road
Riverside, CA 92507-4617
Tel.: (909)369-4850
Fax.. (909)342-4964
email: titan@citrus.ucr.edu
Walter Russell
U.S. Salinity Laboratory
USDA, ARS
450 West Big Springs Road
Riverside, CA 92507-4716Tel: 909-369-4850
FAX: 909-342-4964
email: wrussell@ussl.ars.usda.gov
Author(s):
Toride, N., Leij, F.J., Parker, J.C., van Genuchten M.ThUSDA, ARS, Riverside, CA
Abstract:
Successful predictions of the fate and transport of solutes in the subsurface hinges on the availability of
accurate transport parameters. CXTFIT 2.0 is a update and extension of the CXTFIT code of Parker and
van Genuchten (1984) for estimating solute transport parameters using a nonlinear least-squares
parameter optimization method. The program may be used to solve the inverse problem by fitting
mathematical solutions of theoretical transport models, based upon the the convection-dispersion
equation (CDE), to experimental results. This approach allows parameters in the transport models to be
quantified. The program may also be used to solve the direct or forward problem to determine the
concentration as a function of time and /or position.
Three different one-dimensional transport models are included: (i) the conventional CDE; (ii) the chemical
and physical nonequilibrium CDE; and (iii) a stochastic stream tube model based upon the local-scale
CDE with equilibrium or nonequilibrium adsorption. The two independent stochastic parameters in the
stream-tube model are the pore water velocity, and either the dispersion coefficient, the distribution
coefficient, or the nonequilibrium rate parameter. These pairs of stochastic parameters are described with
a bivariate lognormal probability density function (pdf).
II. Technical Information
II.1 Executables:
Operating System(s):
II.2 Source-code:
Programming Language(s): ANSI standard FORTRAN 77 The source code is available upon request from the authors, please email:jsimunek@ussl.ars.usda.gov or : wrussell@ussl.ars.usda.gov The program comes with a user manual giving adetailed description of the computer program, including the subroutines used toevaluate the analytical solutions for optimizing model parameters. Input andoutput files for all major problems are also included in the manual.
II.3 Manuals:
(see Source-code)
II.4 Data:
(see Source-code)
III. Mathematical Information
III.1 Mathematics
III.2 Quantities
III.2.1 Input
III.2.2 Output
IV. References
Toride, N., Leij, F.J., van Genuchten M.Th., 1995.The CXTFIT code for estimating transport parameters from laboratory or field tracer experiments, Version 2.0. Research Report No. 137, 121 p., U.S. Salinity Laboratory, USDA, ARS, Riverside, California.
Parker, J.C., van Genuchten M.Th., 1984.Determining transport parameters from laboratory or field tracer experiments, Bull. 84-3, Va. Agric.Exp.St., Blacksburg.
V. Further information in the World-Wide-Web
VI. Additional remarks
Last review of this document by: T. Gabele : 7. 7. 1997 -
Status of the document:
last modified by
Tobias Gabele Wed Aug 21 21:44:41 CEST 2002