Modeling Nonequilibrium Flow and Transport Processes Using HYDRUS

Abstract

means, electronic or mechanical, including photocopying, recording, or any informa on storage and retrieval system, without permission in wri ng from the publisher. S S : V Z M Accurate process-based modeling of nonequilibrium water fl ow and solute transport remains a major challenge in vadose zone hydrology. Our objec ve here was to describe a wide range of nonequilibrium fl ow and transport modeling approaches available within the latest version of the HYDRUS-1D so ware package. The formula ons range from classical models simula ng uniform fl ow and transport, to rela vely tradi onal mobile-immobile water physical and two-site chemical nonequilibrium models, to more complex dual-permeability models that consider both physical and chemical nonequilibrium. The models are divided into three groups: (i) physical nonequilibrium transport models, (ii) chemical nonequilibrium transport models, and (iii) physical and chemical nonequilibrium transport models. Physical nonequilibrium models include the Mobile-Immobile Water Model, Dual-Porosity Model, Dual-Permeability Model, and Dual-Permeability Model with Immobile Water. Chemical nonequilibrium models include the One Kine c Site Model, the Two-Site Model, and the Two Kine c Sites Model. Finally, physical and chemical nonequilibrium transport models include the Dual-Porosity Model with One Kine c Site and the Dual-Permeability Model with Two-Site Sorp on. Example calcula ons using the diff erent types of nonequilibrium models are presented. Implica ons for the formulaon of the inverse problem are also discussed. The many diff erent models that have been developed over the years for nonequilibrium fl ow and transport refl ect the mul tude of o en simultaneous processes that can govern nonequilibrium and preferen al fl ow at the fi eld scale.

A review of model applications for structured soils: a) Water flow and tracer transport

“…TRANSMIT (Hutson and Wagenet, 1995) is another similar three-region 1D model. HYDRUS-1D (Šimůnek et al, 1998, 2005, 2008aŠimůnek and van Genuchten, 2008) describes water, heat, and solute movement in the vadose zone. The latest version includes a variety of SPM, MIM, and DPM approaches; the more frequently used MIM and DPM are again based on DUAL (Gerke and van Genuchten, 1993).…”

“…The PF model concepts are only briefly explained here. For details, the reader is referred to recent review articles by Šimůnek et al (2003), Gerke (2006), Jarvis (2007), and Šimůnek and van Genuchten (2008). Here, the emphasis is on the applications of such models in describing experimental observations.…”

Ecological risks of polycyclic musk in soils irrigated with reclaimed municipal wastewater

“…Terrestrial organisms, wheat (Triticum aetivum L), earthworm (Eisenia fetida), and springtail (F. candida) are selected as the target organisms in the assessment due to the sufficiency of toxicological data about those three terrestrial species and their universality in soil environment. Long-term accumulation of HHCB and AHTN in soil is simulated using HYDRUS-1D, a water and solute fate and transport software package (Simunek and Van Genuchten, 2008).…”

The HPx software for multicomponent reactive transport during variably-saturated flow: Recent developments and applications

“…Water flow in its most general form is described using a dual-porosity formulation of the Richards equation (Šimůnek and van Genuchten, 2008):…”