Determination of water content in drying soils: incorporating transition from liquid phase to vapour phase

In arid and semi-arid environments, soil profiles often exhibit a liquid–vapour displacement known as evaporation front characterised by a critical matric potential (ψme) or water content (θe) located somewhere inside the unsaturated zone above a watertable (WT). The objective of this study was to determine the θe including the range of water content (θ) in the transition zone from liquid to vapour both theoretically and experimentally for different soil textures under saline and non-saline WTs. Characteristic shapes of water content and salt concentration profiles were the criteria to obtain θe experimentally, and the θ–diffusivity relationship was used to compute the θe and θ range in the transition zone. Measured θe values of 0.05 and 0.12 m3/m3 under non-saline WT and 0.07 and 0.15 m3/m3 under saline WT were in agreement with the computed values of 0.05 and 0.10 m3/m3 for sandy loam and clay loam soils, respectively. The model calculates roughly the same θe for saline and non-saline conditions. Besides experimental soils, θe and range of θ in the transition zone were calculated for silty loam and coarse sand. The lighter the soil texture, the smaller is θe and the steeper the transition zone. The results were further compared with those calculated by different authors.

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Determination of critical soil water content and matric potential for wind erosion

Journal of Soils and Sediments ◽

10.1007/s11368-010-0281-8 ◽

2010 ◽

Vol 11 (2) ◽

pp. 209-220 ◽

Cited By ~ 11

Author(s):

Kristine Bolte ◽

Peter Hartmann ◽

Heiner Fleige ◽

Rainer Horn

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Wind Erosion ◽

Matric Potential

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Determination of the Boundaries of the Compressible Strata When Conducting Engineering Surveys

Proceedings of Southwest State University ◽

10.21869/2223-1560-2020-24-3-79-87 ◽

2020 ◽

Vol 24 (3) ◽

pp. 79-87

Author(s):

K. O. Dubrakova ◽

V. A. Solodilova

Keyword(s):

Sandy Loam ◽

Physical And Mechanical Properties ◽

Fine Sand ◽

Coarse Sand ◽

Adequate Accuracy ◽

Practical Standpoint ◽

The Cost ◽

The Given ◽

Main Influence

Purpose of research. Errors and inaccuracies in the preparation of deliverables based on the results of engineering surveys which are an integral and important part of the design and estimate documentation, can lead to irreversible consequences and significantly reduce the life of buildings and structures. The main difficulty in investigating soil physical and mechanical properties at a construction site is to determine the depth of excavation. This is due to the fact that an increase in the calculated depth leads to the increase in the cost of work, and its decrease leads to the risk of inaccuracies and errors in the design of foundations of buildings and structures. In accordance with the current regulatory documents, the excavation depth during soil investigation should be 1-2 meters below the boundary of the compressible strata. The condition on the basis of which the specified boundary is determined is provided. The development of a technique that allows determining the depth of the compressible strata at the stage of engineering surveying with adequate accuracy is an important task from a practical standpoint. Methods. Determining natural stress Ϭzg,0 as the product of foundation depth d and the specific gravity of the soil above the base ɣ′ІІ, , taking into account the fact that the average pressure tends to the value of the estimated resistance of the soil, it is shown that physical-mechanical structure of the base soil exerts the main influence on the parameters of the compressible strata, and correspondingly, to the excavation depth value. In this case, the stresses transferred by the foundation of a building or structure have an indirect effect. Results. The maximum values of the depth of excavation for engineering and geological surveying for tight coarse sand, medium density and fineness sand, and fine sand and sandy loam are determined. Conclusion. It is concluded that the given technique allows determining the depth of excavation during engineering and geological surveying with an adequate accuracy.

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In-situ determination of soil water retention curves in heterogeneous soil profiles with a novel dielectric tube sensor for measuring soil matric potential and water content

Journal of Hydrology ◽

10.1016/j.jhydrol.2021.126829 ◽

2021 ◽

pp. 126829

Author(s):

Song Yu ◽

Qiang Xu ◽

Xianglin Cheng ◽

Yang Xiang ◽

Yufan Zhu ◽

...

Keyword(s):

Water Content ◽

Water Retention ◽

Soil Profiles ◽

Soil Matric Potential ◽

Soil Water Retention ◽

Matric Potential ◽

Dielectric Tube ◽

Heterogeneous Soil

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Influence of soil matric potential on 14C exudation from fungal propagules

Canadian Journal of Botany ◽

10.1139/b87-284 ◽

1987 ◽

Vol 65 (10) ◽

pp. 2084-2089 ◽

Cited By ~ 5

Author(s):

A. B. Filonow ◽

D. K. Arora

Keyword(s):

Water Content ◽

Sandy Loam ◽

Macrophomina Phaseolina ◽

Sandy Loam Soil ◽

Soil Matric Potential ◽

Clay Loam ◽

Clay Loam Soil ◽

Matric Potential ◽

Fungal Propagules ◽

Loam Soil

The influence of soil matric potential (ψm) on 14C exudation from labeled fungal propagules incubated in two soils over 5 days was determined, using tensiometers set at 0, −50, −100, and −200 mbar ψm (1 bar = 100 kPa). In general, 14C exudation to soil (as a percent of initial label) tended to be greatest at 0 mbar and decreasing ψm. In a sandy loam soil, the range of 14C exudation from conidia of Bipolaris victoriae or sclerotia of Macrophomina phaseolina was 18.4–20.9 or 4.4–5.5% at 0 mbar. At −200 mbar, it was 5.5–6.0 or 1.2–1.7%, respectively. In a clay loam soil at 0 mbar, conidia of B. victoriae or B. sorokiniana lost 17.6–19.9 or 7.3–9.2%, respectively, of total 14C label as exudate. At −200 mbar 14.6 or 5.9–7.2% was lost, respectively. Sclerotia of M. phaseolina lost 5.1–5.7% 14C-labeled exudate to the clay loam soil at 0 mbar and 4.3–4.6% at −200 mbar. 14C exudation at ψm less than saturation was about 2–3 times greater in the clay loam soil than in the sandy loam soil. Calculated ratios of evolved 14CO2/total 14C-labeled exudate were lowest at 0 mbar and increased as ψm decreased, suggesting that oxygen availability and soil water content as regulated by ψm were related to soil respiratory utilization of exudate.

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Effect of watertable depth on evaporation and salt accumulation from saline groundwater

Soil Research ◽

10.1071/sr04051 ◽

2005 ◽

Vol 43 (5) ◽

pp. 565 ◽

Cited By ~ 46

Author(s):

D. A. Rose ◽

F. Konukcu ◽

J. W. Gowing

Keyword(s):

Transition Zone ◽

Soil Profile ◽

Arid Regions ◽

Capillary Flow ◽

Sandy Loam ◽

Upward Movement ◽

Evaporation Front ◽

Evaporative Demand ◽

Saline Groundwater ◽

Rate Of Evaporation

When the evaporative demand is greater than the ability of the soil to conduct water in the liquid phase, the soil profile above a watertable exhibits a liquid−vapour discontinuity, known as the evaporation front, that affects the depth of salinisation and the rate of evaporation. We conducted experiments on a sandy loam with shallow saline watertables under high isothermal evaporative demand (24 mm/day), monitoring rates of evaporation from the soil and upward movement of groundwater, and observing profiles of soil water and salinity over periods of up to 78 days. Three zones were distinguished in the soil profile: a zone of liquid flow above the watertable, a zone of vapour flow close to the surface, and an intermediate transition zone in which mixed liquid−vapour flow occurred. The vapour-flow zone above the evaporation front appeared after a few days and progressed downward to depths of 40, 60, and 120 mm, while eventual steady-state rates of evaporation were 1.3, 1.1, and 0.3 mm/day for watertable depths of 300, 450, and 700 mm, respectively. Salts mainly accumulated in the transition zone, suggesting that the depth of the evaporation front should be a criterion to locate and prevent salinisation as a result of capillary flow from a watertable in arid regions.

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Spatial Variability of Soil Water and Evapotranspiration

Hydrology Research ◽

10.2166/nh.1986.0018 ◽

1986 ◽

Vol 17 (4-5) ◽

pp. 261-268 ◽

Cited By ~ 5

Author(s):

S. Hansen ◽

H. E. Jensen

Keyword(s):

Spatial Variability ◽

Physical Properties ◽

Water Content ◽

Soil Water ◽

Sandy Loam ◽

Coarse Sand ◽

Soil Physical Properties ◽

Climatic Conditions ◽

Field Variability ◽

Soil Water Profiles

Spatial variability in evapotranspiration from a crop covered field exposed to homogeneous climatic conditions is partly caused by field variability in soil physical properties and partly by field variability in pertinent crop properties. The present paper presents an analysis of the spatial variability in soil water content and evapotranspiration for two 0.5 ha grass fields of different soil texture, viz. a coarse sand and a sandy loam. Soil physical properties and soil water profiles were determined 1 m apart at 16 points systematically located in each field. The analysis of soil water profiles in relation to soil physical properties indicates an appreciable variability within a range of 1 m. For this reason a relatively simple model was used to simulate the variability pattern of the evapotranspiration, taking into account the variability in plant available water content. The results of the simulations are compared with the evapotranspiration patterns determined on the basis of a short term water balance.

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Spatial Variability of Physical Parameters and Processes in Two Field Soils

Hydrology Research ◽

10.2166/nh.1991.0020 ◽

1991 ◽

Vol 22 (5) ◽

pp. 275-302 ◽

Cited By ~ 7

Author(s):

K. Høgh Jensen ◽

J. C. Refsgaard

Keyword(s):

Hydraulic Conductivity ◽

Solute Transport ◽

Water Content ◽

Numerical Solutions ◽

Sandy Loam ◽

Solute Concentration ◽

Coarse Sand ◽

Richards Equation ◽

Physical Parameters ◽

Field Site

Natural field systems exhibit a large degree of soil heterogeneity which affects the movement of water and solutes and thus leads to highly varying observations of water content and solute concentration. To investigate this problem comprehensive field investigation programs were carried out at two field sites in Denmark representing two different soil types, a coarse sand and a sandy loam, respectively. The field investigations included collection of soil samples for analysis of textural composition, retention, and hydraulic conductivity, measurements of water content and suction, and measurements of radioactive tracer concentration, all carried out at a number of positions within the two field sites. Models for one-dimensional vertical unsaturated flow and solute transport were applied to the two field sites, and the simulation results were compared to field measurements of water content, suction and solute concentration. This paper describes results from model simulations in individual soil profiles, while the variability issues at field scale are described in the two accompanying papers. The modelling approach was based on numerical solutions to Richards' equation for water flow and the convection-dispersion equation (CDE) for solute transport. The model results from the coarse sand field site compared relatively well to measurements of water content, suction, and concentration except for the upper soil layer (∼ 10 cm depth) where the measured water contents appeared to be somewhat uncertain. Due to the neglecting of hysteresis and macropore flow (by-pass) in the model the measured retention curves (drainage based) and the hydraulic conductivity functions at the sandy loam field site had to he modified empirically through the calibration procedure in order to match the measurements.

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Simulation of the rainfall runoff process using a hysteretic infiltration redistribution model

Soil Research ◽

10.1071/sr9750133 ◽

1975 ◽

Vol 13 (2) ◽

pp. 133 ◽

Cited By ~ 7

Author(s):

KK Watson ◽

SJ Lees

Keyword(s):

Water Content ◽

Soil Profile ◽

Sandy Loam ◽

Water Status ◽

Surface Flux ◽

Numerical Approach ◽

Initial Water Content ◽

Initial Water ◽

Rainfall Events

The significance of the soil profile and its accompanying water status in deterministic catchment models is discussed in relation to the current use of the soil-store concept. An alternative numerical approach is described in which the movement of water into and through the soil profile (together with the determination of runoff volumes) is continuously monitored during any pattern of rainfall and non-rainfall events. A significant component in the approach is the use of a comprehensive domain-type hysteresis model for the analysis of infiltration-redistribution sequences. The simulation is illustrated by using a rainfall hyetograph of 7 h duration (including one non-rainfall period of 1 h) as the flux input into a homogeneous profile of a sandy loam of uniform initial water content. The time-dependent relationships of rate of surface flux, depression storage and runoff volume are calculated for the duration of the hyetograph period. Profiles of water content are also presented.

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