1. General Model Information

Name: RETention Curve Computer Code

Acronym: RETC

Main medium: terrestrial
Main subject: hydrology
Organization level: ecosystem
Type of model: static-algebraic equations
Main application: simulation/optimisation tool
Keywords: data processing tool, unsaturated, soil, hydraulic properties, hydraulic functions, hydraulic conductivity, retention, characteristic,parameter estimation, prediction, unimodal, pore size distribution, Mualem, Burdine, van Genuchten, parametric models


Walter Russell
U.S. Salinity Laboratory
450 West Big Springs Road
Riverside, CA 92507-4716

Tel: 909-369-4850
FAX: 909-342-4964
Email: to wrussell@ussl.ars.usda.gov


Van Genuchten M.Th


The program permits the prediction of the unsaturated soil hydraulic functions assuming known values of the hydraulic parameters in unimodal retention and hydraulic conductivity models (the forward or direct problem), or to estimate the hydraulic functions from observed soil water retention and/or hydraulic conductivity/diffusivity data. It includes the parametric equations of Brooks-Corey and van Genuchten, which are used in conjunction with the VAN GENUCHTEN (1980) analytical solutions to the theoretical pore size distribution models of Mualem and Burdine to predict unsaturated hydraulic conductivity from observed soil water retention data. Can be used in a forward mode and in a parameter fitting mode. When fitting analytical models simultaneously to observed water retention and hydraulic conductivity data, the program permits weighing of measured data and estimates the parameter l (pore interaction index) in the Mualem model. Several examples are presented to illustrate a variety of program options.

The program comes with a user manual giving detailed information about the computer program along with instructions for data input preparation and listings of sample input and output files. A listing of the source code is also provided.

II. Technical Information

II.1 Executables:

Operating System(s): DOS The program and manual are available upon request from: Walter Russell ,USDA, ARS, Riverside/CA please mail to wrussell@ussl.ars.usda.gov The DOS-Binaries Ver 1.1 1994( Source code included) can be downloaded from

II.2 Source-code:

Programming Language(s): FORTRAN(see Executables)

II.3 Manuals:

The Documentation can be downloaded from

II.4 Data:

(see Executables)

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

III.2.1 Input

III.2.2 Output

IV. References

van Genuchten, M.T. 1980. A Closed-form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils. Soil Sci. Soc. J. 44:892-898.
van Genuchten, M. Th., F. J. Leij, and S. R. Yates. 1991
The RETC Code forQuantifying the Hydraulic Functions of Unsaturated Soils, Version 1.0.
EPA Report 600/2-91/065, U.S. Salinity Laboratory, USDA, ARS, Riverside, California.

V. Further information in the World-Wide-Web

VI. Additional remarks

Last review of this document by: T. Gabele: 08. 07. 1997 -
Status of the document:
last modified by Joachim Benz Tue Nov 19 15:42:11 CET 2002

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