1. NAME AND TITLE
SESOIL: Code System to Calculate One-Dimensional Vertical Transport for the Unsaturated Soil Zone.
Oak Ridge National Laboratory, Oak Ridge, Tennessee.
Wisconsin Department of Natural Resources, Madison, Wisconsin.
3. CODING LANGUAGE AND COMPUTER
Fortran 77; IBM PC's and compatibles. (C00629IBMPC03)
4. NATURE OF PROBLEM SOLVED
SESOIL, as an integrated screening-level soil compartment model, is designed to simultaneously model water transport, sediment transport, and pollutant fate. SESOIL is a one-dimensional vertical transport model for the unsaturated soil zone. Only one compound at a time can be considered. The model is based on mass balance and equilibrium partitioning of the chemical between different phases (dissolved, sorbed, vapor, and pure). The SESOIL model was designed to perform long-term simulations of chemical transport and transformations in the soil and uses theoretically derived equations to represent water transport, sediment transport on the land surface, pollutant transformation, and migration of the pollutant to the atmosphere and groundwater. Climatic data, compartment geometry, and soil and chemical property data are the major components used in the equations. SESOIL was developed as a screening-level model, utilizing less soil, chemical, and meteorological values as input than most other similar models. Output of SESOIL includes time-varying pollutant concentrations at various soil depths and pollutant loss from the unsaturated zone in terms of surface runoff, percolation to the groundwater, volatilization, and degradation. The version of SESOIL in RSICC's collection runs stand alone and is functionally equivalent to the version in the RISKPRO system distributed and supported by General Sciences Corporation. The February 1995 release corrected an error that caused the code to fail when average monthly air temperature was -10C and includes an improved iteration procedure for the mass balance equations in the model. In June 1996 a minor change was made to the Fortran source file to correct erroneous values which were sometimes written to the printed output for the user-specified, pollutant mass input table. In October 2003, a minor correction was made to the source; and the program was recompiled with Compaq Visual Fortran 6.6 Update A.
5. METHOD OF SOLUTION
The processes modeled by SESOIL are categorized into three cycles: hydrology, sediment, and pollutant transport. Each cycle is a separate sub-model within the SESOIL code. The hydrologic cycle is one-dimensional, considers vertical movement only, and focuses on the role of soil moisture in the soil compartment. The hydrologic cycle is an adaptation of the water balance dynamics theory of Eagleson (1978) and can be described as a dimensionless analytical representation of water balance in the soil column. An iteration technique is used to solve the mass balance equations in the hydrologic cycle. The sediment cycle is optional; it can be turned on or off by the user. If used, SESOIL employs the theoretical sediment yield model EROS (Foster et al., 1980), which considers the basic processes of soil detachment, transport, and deposition. The pollutant fate cycle focusses on the various chemical transport and transformation processes which may occur in the soil and uses calculated results form the hydrologic and sediment washload cycles. The ultimate fate and distribution of the contaminant is controlled by the processes interrelated by a mass balance equation for each soil layer (compartment) that is specified by the user. An iteration procedure is used to solve each equation. The soil compartment is a cell extending from the surface through the unsaturated zone to the upper level of the saturated soil zone, also referred to as the aquifer or groundwater table.
6. RESTRICTIONS OR LIMITATIONS
As many years as desired can be specified for computation using the model. Available storage for the output file is the only limitation in this regard.
Care should be taken when applying SESOIL to sites with large vertical variation in soil properties since the hydrologic cycle assumes a homogeneous soil profile.
7. TYPICAL RUNNING TIME
As an example, a ten-year simulation that includes all four layers with three sublayers per layer requires approximately 5.5 minutes to run and about 250000 bytes of storage on an IBM compatible 486 PC (50 mhz). The sample problem ran in a few seconds on a Pentium IV 1.4GHz.
8. COMPUTER HARDWARE REQUIREMENTS
SESOIL runs on IBM PC or compatible.
9. COMPUTER SOFTWARE REQUIREMENTS
The included PC executable was created on a Pentium 4 under Windows 2000 with the Compaq Visual Fortran Version 6.6 Update A compiler using default compiler options. The executable runs under Windows2000 and XP.
a: Included in documentation:
D. M. Hetrick, "Instructions for Running Stand-Alone SESOIL Code," (October 1993).
D. M. Hetrick, "Background Information on February 1995 Modifications to SESOIL," (January 21, 1994).
D. M. Hetrick, S. J. Scott, with M. J. Barden "The New SESOIL User's Guide," PUBL-SW-200-93 (Revision 1.6) (August 1994).
b: Background information:
Editors M. Bonazountas, D. M. Hetrick, E. Calabrese, and P. Kostecki, “SESOIL in Environmental Fate and Risk Modeling,” Amherst Scientific Publishers (1997).
M. Bonazountas and J. Wagner (Draft), "SESOIL: A Seasonal Soil Compartment Model." Arthur D. Little, Inc., Cambridge, MA, prepared for the U.S. Environmental Protection Agency, Office of Toxic Substances, (1981, 1984). (Available through National Technical Information Service, publication PB86-112406).
P. S. Eagleson, "Climate, Soil, and Vegetation," Water Resources Research 14(5):705-776, (1978).
G. R. Foster, L. J. Lane, J. D. Nowlin, J. M. Laflen, and R. A. Young, "A Model to Estimate Sediment Yield from Field-Sized Areas: Development of Model," Purdue Journal No. 7781 (1980).
11. CONTENTS OF CODE PACKAGE
The referenced documents in 10a. and a self-extracting, compressed Windows file are transmitted on CD. The package contains documentation, source code, sample input and output data, and a Windows executable.
12. DATE OF ABSTRACT
August 1994, February 1995, September 1995, July 1996, October 2003.
KEYWORDS: HYDRODYNAMICS; MICROCOMPUTER