Citation:

Williams*, J R., Y. Ouyang, J. S. Chen, AND V. Ravi. ESTIMATION OF INFILTRATION RATE IN THE VADOSE ZONE: APPLICATION OF SELECTED MATHEMATICAL MODELS - VOLUME II. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-97/128b (NTIS 98-147317), 1998.

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Description:

Movement of water into and through the vadose zone is of great importance to the assessment of contaminant fate and transport, agricultural management, and natural resource protection. The process of water movement is very dynamic, changing dramatically over time and space. Infiltration is termed as the initial process of water movement into the vadose zone through the soil surface. Knowledge of the infiltration process is prerequisite for managing soil water flux, and thus the transport of contaminants in the vadose zone. Although a considerable amount of research has been devoted to the investigation of water infiltration in unsaturated soils, these investigation have primarily focused on scientific research aspects. An overall evaluation of infiltration models in terms of their application to various climatic characteristics, soil physical and hydraulic properties, and geological conditions has not been done. Specifically, documentation of these type models has been limited and, to some extent, non existent for the purpose of demonstrating appropriate site-specific application. This document attempts to address this issue by providing a set of water infiltration models which have the flexibility of handling a wide variety of hydrogeologic, soil, and climate scenarios. More specifically, the purposes of this document are to: (1) categorize infiltration models presented based on their intended use; (2) provide a conceptualized scenario for each infiltration model that includes assumptions, limitations, boundary conditions, and applications; (3) provide guidance for model selection for site-specific scenarios; (4) provide a discussion of input parameter estimation; (5) present example application scenarios for each model and, (6) provide a demonstration of sensitivity analysis for selected input parameters. Six example scenarios were chosen as illustrations for applications of the infiltration models with one scenario for each model. The intention of these scenarios is to provide applications guidance to users for these models to various field conditions. Each model application scenario includes the problem setup, conceptual model, input parameters, and results and discussion.

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