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item Van Genuchten, Martinus
item Bradford, Scott

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 8/1/2005
Publication Date: 10/1/2005
Citation: Simunek, J., Van Genuchten, M.T., Bradford, S.A., Lenhard, R.J. 2005. New Features of HYDRUS-1D, Version 3.0. In: S. Torkzaban and S. Majid Hassanizadeh (eds.), Proceedings of Workshop on HYDRUS Applications, p. 86-89, October 19, 2005, ISBN 90-39341125, Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands.

Interpretive Summary: Computer models are increasingly used to predict the fate and transport of agricultural chemicals (salts, pesticides, pathogenic microorganisms, nutrients, heavy metals) in soils and groundwater, and to study alternative soil and water management practices aimed at reducing soil and groundwater pollution while optimizing crop yield. One such model is the windows-based HYDRUS-1D software package for simulating water, heat and solute movement in the unsaturated zone between the soil surface and the groundwater table. This program considers unsaturated flow, water uptake by plant roots, transpiration by a crop, evaporation from the soil surface, solute adsorption by the soil’s solid phase, and solute degradation, among many other processes. This paper summarizes several new features that were included in a new version 3.0 that was released in May 2005. One important new feature if the simulation of preferential flow of water and dissolved constrituents through the unsaturated zone using a hierarchy of modules of increasing compexity. These modules consider the presence of immobile water, exchange of water or solutes between soil macropores and the soil matrix (made up of micropores), and possible water flow and solute transport in both the macropores and micropores. Another new feature is compensated root water uptake to allow increased uptake of water by plant roots in those parts of the soil root zone that are relatively wet (and hence subject to less water stress). The new version also has several options to simulate the transport of viruses, bacteria, and colloids in soils. The transport equations for this purpose include provisions for kinetic attachment/detachment of colloids or pathogens to the solid phase, physical straining of colloid particles by the solid phase, and possible accumulation at air-water interfaces when the soil becomes unsaturated. The model provides theoretical and applied scientists and engineers with a much-needed tool for predicting water and chemical transport in the subsurface.

Technical Abstract: This paper briefly summarizes new features in version 3.0 of HYDRUS-1D, released in May 2005, as compared to version 2.1. The new features are a) new approaches to simulate preferential and nonequilibrium water flow and solute transport, b) a new hysteresis module that avoids the effects of pumping, c) compensated root water uptake, d) options to simulate the transport of viruses, bacteria, and colloids, e) carbon dioxide production and transport, and f) geochemical transport of major ions.