Evaporation and Water Redistribution in Layered Unsaturated Soil Profiles

The mechanisms controlling surface evaporation and water redistribution in layered, unsaturated soil profiles are of particular interest for the design of soil covers for landfills and mine waste (e.g., tailings) where layering of texturally contrasting soils is common. Evaporation and water redistribution were observed in laboratory tests of three layered soil columns (sand overlying silt, silt overlying sand, and multiple sand and silt layers), with two homogeneous soil columns (sand or silt) serving as controls. Changes in water storage were monitored along with changes in potential and actual evaporation with time. Near continuous monitoring of temperature along the columns was also conducted. The hydraulic properties of the sand and silt were measured but also verified through simulations of the homogeneous sand and silt columns. These optimized parameters were then used to simulate the layered columns. Layered columns with silt at the surface had more evaporation than homogeneous soil columns of either sand or silt. Changes in water storage in the columns with sand at the surface occurred primarily within the surficial sand layer without drawing water from deeper in the column. Columns with silt at surface drew water for evaporation from sand layers deeper within the column. Numerical modeling of the columns was able to reproduce the observed changes in evaporation rates and water content for all layered soil columns. The laboratory and simulation studies illustrated the strong influence that textural layering may have on water dynamics in soil profiles under evaporative conditions.

[1]  Soil Water Retention and Conductivity When Vapor Flow Is Important , 2003 .

[2]  Philip G. Bruch.  Laboratory study of evaporative fluxes in homogeneous and layered soils , 1993 .

[3]  G. Salvucci,et al.  Evaporation from Porous Media in the Presence of a Water Table , 2010 .

[4]  Robert Horton,et al.  Simultaneous Transfer of Heat, Water, and Solute in Porous Media: I. Theoretical Development , 1992 .

[5]  D. Fredlund,et al.  The effect of soil suction on evaporative fluxes from soil surfaces , 1997 .

[6]  J. Carrera,et al.  Modeling evaporation processes in a saline soil from saturation to oven dry conditions , 2011 .

[7]  W. O. Willis.  Evaporation from Layered Soils in the Presence of a Water Table 1 , 1960 .

[8]  D. Hellwig.  Evaporation of water from sand, 4: The influence of the depth of the water-table and the particle size distribution of the sand , 1973 .

[9]  Design of a composite soil cover for an experimental waste rock pile near Newcastle, New Brunswick, Canada , 1993 .

[10]  Shmuel Assouline,et al.  Characteristic lengths affecting evaporative drying of porous media. , 2008, Physical review. E, Statistical, nonlinear, and soft matter physics.

[11]  M. J. Fayer,et al.  UNSAT-H Version 3.0:Unsaturated Soil Water and Heat Flow Model Theory, User Manual, and Examples , 2000 .

[12]  J. Šimůnek,et al.  Water and Vapor Movement with Condensation and Evaporation in a Sandy Column , 2009 .

[13]  G. Wilson,et al.  Evaluation of the saturated–unsaturated groundwater conditions of a thickened tailings deposit , 1993 .

[14]  John A. Cherry,et al.  REDUCTION OF ACID GENERATION IN MINE TAILINGS THROUGH THE USE OF MOISTURE-RETAINING COVER LAYERS AS OXYGEN BARRIERS , 1989 .

[15]  J. Gowing,et al.  Evaporative flux from a shallow watertable: The influence of a vapour–liquid phase transition , 2006 .

[16]  Bridget R. Scanlon,et al.  Numerical Analysis of Coupled Water, Vapor, and Heat Transport in the Vadose Zone , 2005 .

[17]  John R. Nimmo,et al.  Modeling of soil water retention from saturation to oven dryness , 1994 .

[18]  Y. Mualem.  A New Model for Predicting the Hydraulic Conductivity , 1976 .

[19]  J. Bonnet.  THE NATURE OF LATERIZATION AS REVEALED BY CHEMICAL, PHYSICAL, AND MINERALOGICAL‐STUDIES OF A LATERITIC SOIL PROFILE FROM PUERTO RICO , 1939 .

[20]  M. Prat,et al.  A study on slow evaporation of liquids in a dual-porosity porous medium using square network model , 2009 .

[21]  M. J. Fayer,et al.  Modified Soil Water Retention Functions for All Matric Suctions , 1995 .

[22]  Marc Prat,et al.  Percolation model of drying under isothermal conditions in porous media , 1993 .

[23]  M. Aubertin,et al.  The behavior of inclined covers used as oxygen barriers , 2003 .

[24]  Infiltration and drainage processes in multi-layered coarse soils , 2011 .

[25]  J. R. Philip,et al.  Moisture movement in porous materials under temperature gradients , 1957 .

[26]  D. Or,et al.  Evaporation from layered porous media , 2010 .

[27]  Craig H. Benson,et al.  Field Evaluation of Alternative Earthen Final Covers , 2001 .

[28]  E. E. Miller,et al.  The temperature dependence of isothermal moisture vs. potential characteristics of soils. , 1986 .

[29]  Robert Horton,et al.  Soil Heat and Water Flow With a Partial Surface Mulch , 1987 .

[30]  Influence of textural layering on field capacity of coarse soils , 2011 .

[31]  A. Adamson.  Physical chemistry of surfaces , 1960 .

[32]  T. L. Jones,et al.  Enhancement of thermal water vapor diffusion in soil , 1984 .

[33]  Kosuke Noborio,et al.  Two‐Dimensional Model for Water, Heat, and Solute Transport in Furrow‐Irrigated Soil: II. Field Evaluation , 1996 .

[34]  Kosuke Noborio,et al.  Two‐Dimensional Model for Water, Heat, and Solute Transport in Furrow‐Irrigated Soil: I. Theory , 1996 .

[35]  Tarek Abichou,et al.  Field water balance of landfill final covers. , 2004, Journal of environmental quality.

[36]  Van Genuchten,et al.  A closed-form equation for predicting the hydraulic conductivity of unsaturated soils , 1980 .