In this paper a nonlinear boundary value problem which arises in an unsaturated flow with extraction is studied. A reciprocal transformation and the Hopf-Cole transformation are employed to transform the nonlinear boundary value problem into a moving boundary problem for which the Fourier series solution is obtained.

The forecast of unsaturated water flow has the important significance in atmosphere science, pedology, agricultural engineering, environment engineering and ground water dynamics, etc.

The process of surface and ground water flow, such as atmospheric precipitation, evaporation and transpiration, surface's water leakage, absorption of roots and ground water flow, etc, all can be taken as unsaturated water flow .

UNSATCHEM is a simulation software for 1-D variably saturated water flow and multicomponent solute transport with chemical reactions. UNSATCHEM was applied to simulate the processes of cation exchange with solute transfer. The results showed that UNSATCHEM could successfully simulate the multicomponent solute transport processes that accompany chemical reactions.

Unsteady saturated-unsaturated flow to horizontal drains

As compared to the previous studies, the unique features of this study were to include unsaturated flow effect and to provide the physical basis and quantification for the >amp;lt;Cs(t)>amp;gt;->amp;lt;Cq(t)>amp;gt; relationship.

Unsaturated flow with heterogeneous soil surfaces in the field scale is an outstanding issue in hydrologic modeling.

The results from the upscaling of one-dimensional vertical unsaturated flow model are compared with extensive sets of Monte-Carlo simulations for several degrees of the heterogeneity in soil surfaces.

The method also applies to inhomogeneous media, and to cases with a partial unsaturated flow.

In this paper two variation rates, K/θ and h2/Z2,are introduced in a time difference scheme of the equation of unsaturated soil water flow movement. It is considered that the two rates may show highly nonlinear characteristics of unsaturated flow movement of soil water near the abrupt interfaces of soil layers and near the sharp wetting fronts of soil water flow. The time difference equation derived from unsaturated flow equation can be approximated by Galerkin finite element or finite difference method for...

In this paper two variation rates, K/θ and h2/Z2,are introduced in a time difference scheme of the equation of unsaturated soil water flow movement. It is considered that the two rates may show highly nonlinear characteristics of unsaturated flow movement of soil water near the abrupt interfaces of soil layers and near the sharp wetting fronts of soil water flow. The time difference equation derived from unsaturated flow equation can be approximated by Galerkin finite element or finite difference method for space coordinate derivatives.

The general equation of transfer function model (TFM) developed by Jury et al is simplified in this paper and a simplified equation of TFM is introduced suitable for studying the salt movements under infiltration. The travel time probability distribution function P(t) and its density function g(t-t'), describing salt movements through soil layers of 0-60cm, are obtained from the simplified equation for irrigation water with different salinities in the field. Some parameters such as average travel time t of salt,...

The general equation of transfer function model (TFM) developed by Jury et al is simplified in this paper and a simplified equation of TFM is introduced suitable for studying the salt movements under infiltration. The travel time probability distribution function P(t) and its density function g(t-t'), describing salt movements through soil layers of 0-60cm, are obtained from the simplified equation for irrigation water with different salinities in the field. Some parameters such as average travel time t of salt, average velocity v in pores, average water content of movable water θm, describing the charateristics of unsaturated water movement and convection transport of salt in soil layers are obtained. Some theoretical shortcomings in this research are also pointed out.

The features of natural soil profile of rice field and the significances of steady flow rate in the profile for the growth of rice, water management of rice fields, planning and designing of drainage project and evaluation of agricultural ecosystem are discussed. The criteria for forming unsaturated flow between the least permeable layer (plowgh pan or clayey soil) and subsoil are presented based on Darcy's general equation. After introducing the Gardner's model, in which hydraulic conductivity exponentially...

The features of natural soil profile of rice field and the significances of steady flow rate in the profile for the growth of rice, water management of rice fields, planning and designing of drainage project and evaluation of agricultural ecosystem are discussed. The criteria for forming unsaturated flow between the least permeable layer (plowgh pan or clayey soil) and subsoil are presented based on Darcy's general equation. After introducing the Gardner's model, in which hydraulic conductivity exponentially relates to negative soil water pressure, into Darcy's equation, the author presents analytical equations for calculating steady flow rate through the profile and for calculating pressure distributions within two unsaturated zones. The calculated flow rate and pressure distribution based on the analytical equations presented in the paper agree well with the field experimental data appeared in reference [5]. The conclusions and equations in this paper can be applied to analyze any problems of coexistence of saturated and unsaturated flow in three-layer soils.