1. General Model Information

Name: Soil WAter and CROP production model

Acronym: SWACROP


Main medium: terrestrial
Main subject: hydrology
Organization level: ecosystem
Type of model: partial differential equations (finite differences,1D)
Main application:
Keywords: unsaturated zone, soil evaporation, soil water, crop production, soil water flow, potato, wheat, maize, grass, irrigation, drainage

Contact:

International Ground Water Modeling Center at the Colorado School of Mines

Ir. J.G. Wesseling
DLO Winand Staring Centre (SC-DLO)
Dept. of Agrohydrology
P.O.Box 125
6700 AC Wageningen
THE NETHERLANDS
Tel. +31.317.474313
Fax +31.317.424812
Email: wesseling@sc.agro.nl

Author(s):

Wesseling, J.G., P. Kabat, B.J. v.d. Broek & R. A. Feddes

Abstract:

SWACROP (Soil WAter and CROP production model) is a transient one-dimensional finite difference model for simulation of the unsaturated zone. It incorporates the process of water uptake by roots. The soil profile is divided into several layers (containing one or more compartments of variable thickness) having different physical properties. The partial differential equation for flow in the unsaturated system is solved using an implicit finite difference scheme. An explicit linearization of the hydraulic conductivity (K) and soil water capacity (C) is used. Knowing the initial conditions (i.e. water content or pressure head distribution profile) and top and bottom boundary conditions, the system of equations for all the compartments is solved for each (variable) time step by applying the so-called Thomas tridiagonal algorithm. The integration procedure within each time step allows calculation of all water balance terms for each time period selected. For the top boundary, data on rainfall, potential soil evaporation, and potential transpiration are required. When the soil system remains unsaturated, one of three bottom boundary conditions can be used: pressure head, zero flux, or free drainage. When the lower part of the system remains saturated, one can either give the ground-water level or the flux through the bottom of the system as input. In the latter case, the ground-water level is computed. The rate of vegetation growth, both potential and actual can be simulated in the crop growth submodel which is linked to the main water model in a dynamic way. This submodel supplies information about the vegetation characteristics to the main water model throughout the simulation period. However, both models can be run separately.

The SWACROP 2.02 model is derived from SWATRE which was in turn derived from the SWATR model. The SWACROP 2.02 model is actually an update of the SWATRE model. The SWATR and SWATRE models are no longer available under those names.


II. Technical Information

II.1 Executables:

Operating System(s): The program runs in batch mode. Example data sets are provided, which can be copied and edited with a text editor for individual problems. Results are saved in text files. SWACROP is distributed on 5" HD or 3" DD DOS-formatteddiskettes containing source code, executable image, a graphical analysis package for the water balance, and example data sets. The user's manual contains installation instructions, a list of symbols used, and various paperscovering the theory and applications of SWACROP.

SYSTEM REQUIREMENTS Available from:
IGWMC office in Golden, Colorado by phone, fax, mail, and e-mail.
Contact: IGWMC: http://www.mines.edu/research/igwmc/

II.2 Source-code:

Programming Language(s): FORTRAN-77

II.3 Manuals:

Wesseling, J.G., P. Kabat, B.J. v.d. Broek & R.A. Feddes, 1992. SWACROP, version 2.02.Documentation package IGWMC-FOS 45. Distribution by International Ground Water ModellingCentre (IGWMC - Delft), c/o Institute of Applied Geoscience, P.O.Box 285, 2600 JA Delft, TheNetherlands.

II.4 Data:



III. Mathematical Information


III.1 Mathematics


III.2 Quantities

Theta (volume moisture content), pressure head, hydraulic conductivity, groundwater level, daily and total biomass. Physical and hydrological soil properties, crop characteristics (soil cover, leaf area

III.2.1 Input

Physical and hydrological soil properties, crop characteristics (soil cover, leaf areaindex, crop height etc.), daily meteorological data, drainage and irrigation specific data. Flow rate through profile, state variables, crop rate and state variables.

III.2.2 Output

Flow rate through profile, state variables, crop rate and state variables.
Time interval of simulation: 1 day.
Basic spatial unit: m2 to field level.


IV. References

SWATR:
Feddes, R.A., P.J. Kowalik and H. Zaradny, 1978. Simulation of field water use and cropyield. Simulation Monograph. Pudoc-DLO, Wageningen, The Netherlands. 189 pp.

SWATRE:
Belmans, C., J.G. Wesseling and R.A. Feddes, 1993. Simulation model of the water balance of acropped soil: SWATRE. Journal of Hydrology 63 (1983) 3/4: 271-286

SWACROP:

Kabat, P., B.J. van den Broek & R.A. Feddes, 1992. SWACROP: A Water Management and CropProduction Simulation Model. SWACROP: Un modele de simulation pour la queation d'eau et laproduction des cultures. ICID Bulletin 1992, Vol. 41, no. 2. 61-84

Wesseling, J.G., P. Kabat, B.J. v.d. Broek & R.A. Feddes, 1992. SWACROP, version 2.02.Documentation package IGWMC-FOS 45. Distribution by International Ground Water ModellingCentre (IGWMC - Delft), c/o Institute of Applied Geoscience, P.O.Box 285, 2600 JA Delft, TheNetherlands.

Kabat, P., B.J. van den Broek, B. Marshall, J. Vos & H. van Keulen (Editors), 1994. Modelling andparameterization of the soil-plant-atmosphere system: A Comparison of Potato Growth Models.450 pp.

Faria, R.T., C.A. Madramootoo, J. Boisvert & S.O. Prasher, 1992. A comparison of the versatile soilmoisture budget and SWACROP models in Brazil. ASAE paer no. 922114, Summer Meeting 1992,N.C., U.S.A., 30 pp.

Clemente, R.S., R. de Jong, H.N. Hayhoe, W.D. Reynolds & M. Hares, 1994. Testing and comparisonof three unsaturated soil water flow models. Agricultural Water Management 25 (1994): 135-152

Zepp, H. & A. Belz, 1994. Sensitivity and problems in modelling soil moisture conditions. J. of Hydrology 131 (1992) 227-238

V. Further information in the World-Wide-Web


VI. Additional remarks


Last review of this document by: J. Bierwirth: Nov 7 2000 -
Status of the document:
last modified by Tobias Gabele Wed Aug 21 21:44:50 CEST 2002

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