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United States Department of Agriculture

Agricultural Research Service

Title: Development and Applications of the HYDRUS and STANMOD Software Packages, and related codes

item Simunek, Jirka
item Van Genuchten, Martinus
item Sejna, Miroslav

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2007
Publication Date: 5/1/2008
Publication URL:
Citation: Simunek, J., Van Genuchten, M.T., Sejna, M. 2008. Development and Applications of the HYDRUS and STANMOD Software Packages, and related codes. Vadose Zone Journal. Vol 7:587-600

Interpretive Summary: Solving problems involving water flow and contaminant transport in the subsurface requires appropriate modeling tools consistent with the application. While certain problems may be described using relatively simple analytical models, other problems require more sophisticated one- or multidimensional numerical models that simulate fluid flow, solute transport, and a range of biogeochemical reactions. To have the flexibility in optimally addressing general as well as site-specific problems, one may thus need a toolbox containing a variety of computer codes of varying complexities. A large number of such computer tools have been developed jointly by the U.S. Salinity Laboratory (USSL) and the University of California, Riverside (UCR) over a period of about 30 years, and released to the public. In this paper we summarize the most pertinent of these computer programs and discuss several applications. Our main focus is initially on the numerical HYDRUS models, their predecessors, and various modifications and extensions that resulted from the work of several groups of developers in the USA, the Czech Republic, Israel, The Netherlands and Belgium. However, we also summarize several other modeling tools that were developed in close collaboration between USSL and UCR, such as the CXTFIT and STANMOD codes for analytical transport modeling, as well as additional software and databases (e.g., RETC, Rosetta, and UNSODA) for analyzing the unsaturated soil hydraulic properties. Most of the modeling tools and databases are in the public domain. A CD containing the various codes and manuals is freely available from USSL. Most codes can also be downloaded freely from both the HYDRUS website (, and the USSL site ( The programs cover a large number of processes, from relatively simple one-dimensional solute transport problems to multidimensional flow and transport applications at the field scale, including relatively complex problems involving a range of biogeochemical reactions. The models are important tools to better predict the fate and transport of agricultural and other contaminants in the subsurface.

Technical Abstract: Mathematical models have become indispensable tools for studying vadose zone flow 43 and transport processes. In this paper we review the history of development, the main processes involved, and selected applications of HYDRUS and related models and software packages developed collaboratively by several groups in the USA, the Czech Republic, Israel, Belgium, and the Netherlands. Our main focus is on modeling tools developed jointly by the U.S. Salinity Laboratory (USSL) of the USDA, Agricultural Research Service, and the University of California Riverside (UCR). This collaboration over the past three decades has resulted in the development of a large number of numerical (e.g., HYDRUS-1D, HYDRUS-2D, HYDRUS (2D/3D), HP1) as well as analytical (e.g., CXTFIT and STANMOD) computer tools for analyzing water flow and/or solute transport processes in soils and groundwater. The research also produced additional programs and databases (e.g., RETC, Rosetta, UNSODA) for quantifying the unsaturated soil hydraulic properties. All of the modeling tools, with the exception of HYDRUS-2D and HYDRUS (2D/3D), are in the public domain and can be downloaded freely from several websites.

Last Modified: 08/17/2017
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