VGPest3
Description
This program estimates the 3 parameters (a,n,r) for the van Genuchten's Mualem soil-water characteristic curve formula by using the optimization subroutine LMDIF1 from the math library MINPACK (Argonne National Laboratory). VGPest3 reads the Soil and Water Characteristic Curve (SWCC) laboratory values, water content (, cm3/cm3) vs suctions (h, -cm water) and calculates the parameters such as:
- θ_c(h) = θr + (θs-θr)×[1+(a.h)^n]^(-m); m = 1 -1/n (1)
and then calculates the unsaturated conductivity curve as:
- θ_c(h) - θr
Se = ---------------- (2)
θs - θr
- Kr(Se) = Ku/Ks = Se^0.5 [1-(1-Se^(1/m))^m]^2 (3)
where:
- θ(h), θ_c(h) = Measured and predicted water contents
Se(i,2) = effective saturation (j = 2) for each pressure step (j = 1)
SWCC(i,2) = Water content (j = 2) for each suction step (j = 1)
θs, θr, θr_c = Saturated and Residual water content (_c = predicted)
Ks (cm/h) = Saturated hydraulic conductivity.
Program Usage & Output
The program runs in DOS mode and is written in Fortran (main engine) and C++ (interface). Command line UNIX and DOS versions are available from the authors.
Unpack the contents of the ZIP package on a directory. To run the program write "vg" at the command line and a graphical interfase will open in the screen. Follow instructions as given. The program allows to select the initial parameters for the optimization. After convergence is reached, the program shows the results on a graphic mode.
Input File Example
Before starting the program the input file must be written. The program input is contained in the input file swcc.in written in ASCII format. The user should edit this file replacing the contents with the values from the case to analyze. Please notice that this file must be saved in ACSII format for the program to run properly. This is a sample input file:
Title (30 characters max): | "Lysimeter Soil 2-35cm 28/4/94" | ||
alpha,n,r: | 1.000 | 1.000 | 0.1 |
Ks(cm/h): | 4.8 | ||
(hi,θi); NOTE: For i=1 → (0,θs): | 0. | 0.475108 | |
3.81 | 0.442734 | ||
13.81 | 0.401439 | ||
28.81 | 0.372662 | ||
53.81 | 0.343165 | ||
103.81 | 0.315827 | ||
203.81 | 0.292086 | ||
403.81 | 0.274101 | ||
15000 | 0.2056 |
Program License
This program is distributed as Freeware/Public Domain under the terms of GNU-License. If the program is found useful the authors ask that acknowledgment is given to its use in any resulting publication and the authors notified. The source code is available from the authors upon request:
- Rafael Muñoz-Carpena
Professor, Hydrology & Water Quality
Department of Agricultural
& Biological Engineering
University of Florida
P.O. Box 110570
287 Frazier Rogers Hall
Gainesville, FL 32611-0570
(352) 392-1864 x287
622-1864 x287 (Suncom)
(352) 392-4092 (fax)
carpena@ufl.edu
- Dr. Javier Álvarez-Benedí
Researcher
S.I.D.T.A., Valladolid
Apdo 172
47080 Valladolid (Spain)
+34-983-414435
+34-983-414780 (fax)
javier@iq.cie.uva.es
© Copyright 1996 Rafael Muñoz-Carpena & Javier Álvarez-Benedí
This page was last updated on July 13, 2019.