Developments and applications of the HYDRUS computer software packages since 2016

Abstract

The HYDRUS codes have become standard tools for addressing many soil, agricultural, environmental, and hydrological problems requiring the evaluation of various subsurface physical, chemical, and biological processes. There are now many thousands of HYDRUS users worldwide, with thousands of applications of the HYDRUS models appearing in the peer-reviewed literature. In this manuscript, we provide an overview of the capabilities of the most recent Version 5 of HYDRUS, focusing primarily on features implemented since 2016. We briefly describe the standard HYDRUS model and its standard and nonstandard specialized add-on modules that significantly expand the capabilities of the software packages. The standard add-on modules include HPx, UNSATCHEM, Wetland, Furrow, PFAS, COSMIC, DPU, SLOPE Cube, and Particle Tracking. Recent developments of the HYDRUS Package for MODFLOW are also described, along with additional capabilities incorporated into the graphical user interface supporting HYDRUS. Also discussed are new or improved options to simulate the fate and transport of environmental isotopes, multi-cropping systems, compensated root water uptake, and hydraulic redistribution within the rootzone, which will be implemented in upcoming add-on modules. Another objective is to review selected applications of the HYDRUS models, such as evaluations of various irrigation, low-impact development (LID), and managed aquifer recharge (MAR) schemes.