STANMOD

Criterion

Explanation

General Description

Analytical solution to the subsurface convective-diffusion equation for solute transport

Model Domain

Soil and groundwater

Developer

United States Department of Agriculture (USDA)

Hardware computing requirements

For use on Windows machines

Code language

All computational programs are written in FORTRAN, and the graphical interface is in MS Visual C++.

Original application

A Windows-based software package for simulating solute transport in porous media using analytical solutions of the convection-dispersion equation. The suite of analytical models includes models for one-dimensional and multi-dimensional transport.

Public/proprietary and cost

Public; No cost

Physically or empirically based

Physically based.

Mathematical methods used

STANMOD includes several models:

The 3DADE model solves the direct problem (i.e., the concentration is calculated as a function of time and space for specified model parameters), and the indirect (inverse) problem in which the program estimates selected parameters by fitting one of the analytical solutions to specified experimental data.

In the N3DADE code, analytical solutions for three-dimensional equilibrium solute transport in the subsurface pertain to selected cases of three-dimensional solute transport during steady, unidirectional water flow in porous media having uniform flow properties.
Solute transport terms in the equation are:

• Solute movement by convection
• Solute movement by dispersion
• Solute retardation
• First-order decay
• Zero-order production

STNAMOD uses the analytical solutions to the one-dimensional convective dispersion equation described in Toride et al (1993).

Input data requirements

User creates input data through the Project Manager module. New projects are given a name and assigned to a Workspace (any existing, accessible subdirectory). Input data requirements include groundwater flow related parameters (hydraulic conductivity, storativity), and solute transport related parameters (dispersitivity, porosity, initial pore water concentration, adsorption-related and decay- and production-related parameters).  

Outputs

The post-processing unit consists of simple x-y plots for graphical presentation of the results and a dialog window that displays an ASCII output file.

Pre-processing and post-processing tools

ASCII text outputs can easily be brought into Excel.

Representation of uncertainty

The model does not have built-in uncertainty representation. This can be assessed for each specific case using sensitivity analysis.

Prevalence

Widely used for studying vadose zone flow and transport processes, including for agricultural application. STANMOD has used in the Delta to simulate DOC transport in Twitchell Island cores (Deverel et al. 2017).

Ease of use for public entities

Readily available and easy to use

Ease of obtaining information and availability of technical support

Support for problems with the model code, or suggestions for improvement can be submitted to:
U. S. Salinity Laboratory
USDA, ARS
450 West Big Springs Road
Riverside, CA 92507
E-mail: jsimunek@ussl.ars.usda.gov, rvang@ussl.ars.usda.gov

Source code availability

Source code is not readily available. The executable file is available at:

Status of model development

Version 2.0 completed for use in 2000

Challenges for integration