Submitted to: Vadose Zone Journal
Publication Type: Review article
Publication Acceptance Date: 1/22/2008
Publication Date: 5/1/2008
Publication URL: www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2243.pdf
Citation: Simunek, J., Bradford, S.A. 2008. Vadose Zone Modeling: Introduction and Importance. Vadose Zone Journal. Vol 7:581-586 Interpretive Summary: This manuscript reviews models for simulating water flow and pollution transport in unsaturated soils. In particular, this review covers papers that were included in a special issue of Vadose Zone Journal on Modeling Vadose Zone Processes. The special issue is divided into two parts. In the first part of the special issue authors of some of the most widely used models for simulating various flow and transport processes in unsaturated soils discuss their latest developments or specific applications of their codes. The following models were covered in this part of the special issue: HYDRUS, MODFLOW-SURFACT, STOMP, SWAP, TOUGH2, and VS2DI. In the second part of the special issue authors working on modeling various processes or problems in the subsurface provided review papers or have described a specific model application. Contributions considered the following topics: colloid and colloid-facilitated contaminant transport, reactive biogeochemical transport, multiphase flow and remediation, modeling surface-subsurface interactions, preferential and nonequilibrium flow and transport, salt leaching under subsurface drip irrigation, spatially distributed water fluxes, subsurface flow in constructed wetlands, and inverse modeling.
Technical Abstract: Many models of varying degree of complexity and dimensionality have been developed during the past several decades to quantify the basic physical and chemical processes affecting water flow and pollutant transport in the unsaturated zone and these models are now increasingly being used for a wide range of applications in research and management of natural subsurface systems. Modeling approaches range from relatively simple analytical and semi-analytical models, to more complex numerical codes that permit consideration of a large number of simultaneous nonlinear processes. While analytical and semi-analytical solutions are still used for relatively simple applications, the ever-increasing power of personal computers, and the development of more accurate and numerically stable solution techniques have given rise to the much wider use of numerical models in recent decades