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78 Models of Water Flow and Solute Transport in the Unsaturated Zone

Part 6. Soils

  1. Jirka Šimůnek

Published Online: 15 APR 2006

DOI: 10.1002/0470848944.hsa080

Encyclopedia of Hydrological Sciences

Encyclopedia of Hydrological Sciences

How to Cite

Šimůnek, J. 2006. Models of Water Flow and Solute Transport in the Unsaturated Zone. Encyclopedia of Hydrological Sciences. 6:78.

Author Information

  1. University of California, Department of Environmental Sciences, Riverside, CA, US

Publication History

  1. Published Online: 15 APR 2006


A large number of models for simulating water flow and solute transport in the unsaturated zone are now increasingly being used for a wide range of applications in both research and management. Modeling approaches range from relatively simple analytical and semianalytical solutions, to complex numerical codes. While analytical and semianalytical solutions are still popular for some applications, the ever-increasing power of personal computers and the development of more accurate and numerically stable solution techniques have motivated much wider use of numerical codes in recent decades. The wide use of numerical models is also significantly enhanced by their availability in both the public and commercial domains, and by the development of sophisticated graphics-based interfaces that can tremendously simplify their use.

In this paper I focus mainly on numerical models, give a brief history of their development, and discuss some of the more often used numerical techniques including relatively efficient matrix solvers that now are available for multidimensional models. Names and web addresses of some of the more popularly used numerical codes simulating vadose zone processes are also provided. Finally, some typical problems in which the numerical codes have been applied are identified.


  • unsaturated zone;
  • water flow;
  • solute transport;
  • matrix solvers;
  • numerical modeling