Introduction: The movement of moisture and the simultaneous transfer of water and
solutes in unsaturated porous media are problems of practical interest in
ground water hydrology and soil physics. A large fraction of the water
falling as rain on the land surfaces of the earth moves through unsaturated
zone of soil during the subsequent processes of infiltration, drainage,
evaporation, and absorption of soil -water by plant roots. A soil profile
is characteristically nonuniform in its properties, nonisothermal, and may
be nonrigid. Microorganisms and the roots of higher plants are a part of
the system. This region is characterized by cylic fluctuation of water
content as water is removed from the soil profile by evaportranspiration
and replenished by recharge, irrigation, or rainfall.
In unsaturated porous media the problem of movement and retention
of water may be approached from (1) the molecular, (2) the microscopic,
or (3) the macroscopic standpoint. In the molecular viewpoint theories
of the mechanisms of flow and retention in terms of the behavior of water
molecules are devised. At microscopic level a theory of flow treating
the fluid in pores as a continuum and applying the principles of continuum
mechanics to understand the detailed behavior of fluid within the pores
is developed. The complicated pore geometry and consequent impossibility
of specifying the boundary conditions on flow, preclude any practical
progress by this appraoch. Since the behavior of individual molecules and
the distributions of fluid velocity and pressure cannot be observed in
porous media, a macroscopic theory of flow is needed. In the macroscopic approach, all variables are treated continuous
functions of time and space. Velocity, pressure, and other variables
are assumed as point functions. Thus, any theory of water transport to
be useful must be developed to the point of describing the transfer of
water on the macroscopic level. The coefficients of transport such as
permeability and diffusivity can be defined microscopically.
In many investigations which involve the transport of pesticides
and fertilizes along with water , the simultaneous movement of water and
solutes is of primary concern. These pollutants when mixed with water
move in the unsaturated soil and finally join the region of saturated soil or water table, resulting in the contamination of fresh water existing
below the water table.
The scope of this report is to review the available literature, that
may be categorized into two parts; one, the movement of water in unsaturated
soil, and the other, the simultaneous movement of water and solutes
in unsaturated soil. The papers, reviewed in this report, pertain to the
theoretical study, laboratory study and field study on the two problems.
At the end, an appendix appears which lists the references, categorizing
the kind of study by various investigators.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/610643 |
| Date | 05 1900 |
| Creators | Tyagi, Avdhesh K. |
| Publisher | Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ) |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | Technical Report |
| Source | Provided by the Department of Hydrology and Water Resources. |
| Rights | Copyright © Arizona Board of Regents |
| Relation | Technical Reports on Hydrology and Water Resources, No. 9 |
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