Alachlor Transport during Transient Water Flow in Unsaturated Soils

2002 ◽  
Vol 66 (6) ◽  
pp. 1773-1783 ◽  
Author(s):  
H. M. Selim ◽  
L. Zhou ◽  
S. K. Xue
Keyword(s):  
Water Flow ◽  
Unsaturated Soils

Acoustic Tomography Applied to Water Flow in Unsaturated Soils

2004 ◽  
Vol 3 (1) ◽  
pp. 288
Author(s):  
Andreas Blum ◽  
Ivo Flammer ◽  
Thomas Friedli ◽  
Peter Germann
Keyword(s):  
Water Flow ◽  
Unsaturated Soils ◽  
Acoustic Tomography

Historical development of soil-water physics and solute transport in porous media

2007 ◽  
Vol 7 (1) ◽  
pp. 59-66 ◽  
Author(s):  
D.E. Rolston
Keyword(s):  
Porous Media ◽  
Hydraulic Conductivity ◽  
Solute Transport ◽  
Soil Water ◽  
20Th Century ◽  
Water Flow ◽  
Unsaturated Soils ◽  
Transport Processes ◽  
Transport In Porous Media ◽  
Unsaturated Hydraulic Conductivity

The science of soil-water physics and contaminant transport in porous media began a little more than a century ago. The first equation to quantify the flow of water is attributed to Darcy. The next major development for unsaturated media was made by Buckingham in 1907. Buckingham quantified the energy state of soil water based on the thermodynamic potential energy. Buckingham then introduced the concept of unsaturated hydraulic conductivity, a function of water content. The water flux as the product of the unsaturated hydraulic conductivity and the total potential gradient has become the accepted Buckingham-Darcy law. Two decades later, Richards applied the continuity equation to Buckingham's equation and obtained a general partial differential equation describing water flow in unsaturated soils. For combined water and solute transport, it had been recognized since the latter half of the 19th century that salts and water do not move uniformly. It wasn't until the middle of the 20th century that scientists began to understand the complex processes of diffusion, dispersion, and convection and to develop mathematical formulations for solute transport. Knowledge on water flow and solute transport processes has expanded greatly since the early part of the 20th century to the present.

Water flow in unsaturated soils subjected to multiple infiltration events

2020 ◽  
Vol 57 (3) ◽  
pp. 366-376
Author(s):  
Xiaokun Hou ◽  
Sai K. Vanapalli ◽  
Tonglu Li
Keyword(s):  
Water Content ◽  
Water Flow ◽  
Unsaturated Zone ◽  
Unsaturated Soils ◽  
Water Infiltration ◽  
Wetting Front ◽  
Influx Rate ◽  
The Relationship ◽  
Stable Zone

In this paper, water flow in a 4 m height column with an unsaturated soil that is subjected to multiple infiltration events for a 62 day period is investigated. One-dimensional (1D) numerical analysis is also undertaken to analyze the flow, extending the seepage theory for unsaturated soils. Results highlight the formation of two wetting fronts; namely, wetting front I and wetting front II that are induced by the first and subsequent infiltration events, respectively. There is a stable zone where the water content is approximately constant; it forms between the two fronts. A conceptual model of the suction profile is proposed for interpreting in situ water flow by dividing the unsaturated zone into four distinct zones; namely, active, steady, transition, and capillary fringe zones. This division is helpful for providing a rational explanation of water flow in different zones. Novel contributions from this study include a relationship between the hydraulic properties in the steady zone and the flow velocity, which is determined by an average influx rate. In addition, the rate of groundwater recharge can also be estimated using the average influx rate. Results of the present study are useful to understand and interpret the relationship between water infiltration and suction or water content profile in the unsaturated zone as well as variation of groundwater table level.

Acoustic Tomography Applied to Water Flow in Unsaturated Soils

2004 ◽  
Vol 3 (1) ◽  
pp. 288-299 ◽  
Author(s):  
Andreas Blum ◽  
Ivo Flammer ◽  
Thomas Friedli ◽  
Peter Germann
Keyword(s):  
Water Flow ◽  
Unsaturated Soils ◽  
Acoustic Tomography

Water movement in unsaturated soils as influenced by gypsum

Soil Research ◽  
1972 ◽  
Vol 10 (1) ◽  
pp. 25 ◽  
Author(s):  
ML Sharma
Keyword(s):  
Cation Exchange ◽  
Water Flow ◽  
Unsaturated Soils ◽  
Water Movement ◽  
Mean Diffusivity ◽  
Distilled Water ◽  
Exchangeable Sodium ◽  
Flow Properties ◽  
High Concentration ◽  
The Third

Three soils varying in texture and exchangeable sodium were treated either with distilled water or with a gypsum solution of 10 or 30 m-equiv./l. concentration and their water-flow properties, diffusivity (D), capillary conductivity (K), and weighted mean diffusivity (D) determined. Invariably the treatment of soils with gypsum resulted in increased D and K, the increases being more pronounced near saturation and declining with desaturation. The soil with the highest clay content and exchangeable sodium percentage (ESP) responded most. For the three soils, at the end of the third wetting and draining cycle the highest increase in D and K varied from about 3 to 15 times while D increased by a factor of 2 to 7.5. Wetting and draining cycles resulted in decreased D for all soils when distilled water was used, but only for two soils when 10 or 30 m-equiv. solutions were used. In the soil most responding to gypsum D was slightly increased with increasing number of wetting and draining cycles when gypsum solutions were used. This was due probably to rebuilding of structure by cation exchange, which was lost by slaking and dispersion during the first wetting and draining cycle. The electrolyte concentration of flowing solution did not significantly affect the water flow properties provided that the slaking and dispersion were reduced by a solution of high concentration during the process of cation exchange. At the end of the third wetting and draining cycle, 30 m-equiv. solution gave about 1.7 times higher D compared to 10 m-equiv. for the high clay, high exchangeable sodium soil. This was probably because initial structural loss caused by the first wetting and draining with 10 m-equiv. was not fully regained during subsequent wetting and draining.

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