Development and Applications of the HYDRUS and STANMOD Software Packages and Related Codes

TLDR

Mathematical models are indispensable for studying vadose zone flow and transport processes. The study reviews the history, key processes, and selected applications of HYDRUS and related models developed by international collaborations. The collaboration produced a suite of numerical and analytical tools—such as SWMS_2D, HYDRUS‑1D/2D/3D, HP1, CXTFIT, and STANMOD—and databases like RETC, Rosetta, and UNSODA for analyzing water flow, solute transport, and unsaturated soil hydraulic properties, most of which are freely available.

Abstract

Mathematical models have become indispensable tools for studying vadose zone flow and transport processes. We reviewed 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 United States, the Czech Republic, Israel, Belgium, and the Netherlands. Our main focus was on modeling tools developed jointly by the U.S. Salinity Laboratory of the USDA, Agricultural Research Service, and the University of California, Riverside. This collaboration during the past three decades has resulted in the development of a large number of numerical [e.g., SWMS_2D, HYDRUS‐1D, HYDRUS‐2D, HYDRUS (2D/3D), and HP1] as well as analytical (e.g., CXTFIT and STANMOD) computer tools for analyzing water flow and solute transport processes in soils and groundwater. The research also produced additional programs and databases (e.g., RETC, Rosetta, and UNSODA) for quantifying 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.