scholarly journals Mixed formulation for an easy and robust numerical computation of sorptivity

2021 ◽  
Author(s):  
Laurent Lassabatere ◽  
Pierre-Emmanuel Peyneau ◽  
Deniz Yilmaz ◽  
Joseph Pollacco ◽  
Jesús Fernández-Gálvez ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Pressure ◽  
Pressure Head ◽  
Mixed Formulation ◽  
Water Infiltration ◽  
Degree Of Saturation ◽  
Soil Water Retention ◽  
Initial Water ◽  
Hydraulic Diffusivity ◽  
Water Contents

Abstract. Sorptivity is one of the most important parameters for the quantification of water infiltration into soils. Parlange (1975) proposed a specific formulation to derive sorptivity as a function of the soil water retention and hydraulic conductivity functions, as well as initial and final soil water contents. However, this formulation requires the integration of a function involving the hydraulic diffusivity, which may be undefined or present numerical difficulties that cause numerical misestimations. In this study, we propose a mixed formulation that scales sorptivity and splits the integrals into two parts: the first term involves the scaled degree of saturation while the second involves the scaled water pressure head. The new mixed formulation is shown to be robust and well-suited to any type of hydraulic functions - even with infinite hydraulic diffusivity or positive air-entry water pressure heads - and any boundary condition, including infinite initial water pressure head, h → −∞.

scholarly journals Water and salt transport in daily irrigated root zone.

1987 ◽  
Vol 35 (3) ◽  
pp. 395-406
Author(s):  
C. Dirksen
Keyword(s):  
Soil Water ◽  
Water Uptake ◽  
Gamma Ray ◽  
Root Zone ◽  
Root Water Uptake ◽  
Salt Transport ◽  
Soil Water Retention ◽  
Transport Models ◽  
Leaching Fraction ◽  
Water Contents

With closed, high-frequency irrigation systems, the water supply can be tailored to the instant needs of plants. To be able to do this optimally, it is necessary to understand how plants interact with their environment. To study water uptake under a variety of non-uniform conditions in the root zone, lucerne was grown in laboratory soil columns with automated gamma ray attenuation, tensiometer and salinity sensor equipment to measure soil water contents, pressure potentials and osmotic potentials, respectively. The columns were irrigated with water of different salinity at various frequencies and leaching fractions. This paper presents results obtained in a column irrigated daily with water of conductivity 0.33 S/m (h0 = -13.2 m) at a target leaching fraction of 0.08. This includes the drying and wetting patterns under daily irrigations in deficit and excess of evapotranspiration, respectively. After 230 days the salination of the column had still not reached a steady state. Salinity increased rapidly with depth and root water uptake was shallow for the deep-rooting lucerne. Water and salt transport under daily irrigation cannot be described without taking hysteresis of soil water retention into account. The data presented are suitable for testing various water uptake models, once numerical water and salt transport models of the required complexity are operational. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Soil-water characteristics of compacted sandy and cemented soils with and without vegetation

2015 ◽  
Vol 52 (9) ◽  
pp. 1331-1344 ◽  
Author(s):  
W.M. Yan ◽  
Guanghui Zhang
Keyword(s):  
Soil Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Rapid Development ◽  
Characteristic Curve ◽  
Degree Of Saturation ◽  
Material Density ◽  
Water Characteristics ◽  
Field And Laboratory Conditions ◽  
Humidity Monitoring

Experiments were undertaken to study the soil-water characteristics of compacted sandy soil (SS) and cemented soil (CS) in field and laboratory conditions. The influence of vegetation and material density on the development of negative pore-water pressure (PWP) and degree of saturation (Sr) in the studied materials was investigated. The field planting experiments demonstrated a promising survival rate of Schefflera heptaphylla in both types of material, while the (SS) promoted better growth of the seedlings than the cemented one. In the field study, PWP and Sr of the compacted SS responded noticeably and promptly to natural drying–wetting cycles. However, the responses in the CS were relatively mild. When subjected to the same drying–wetting cycles, PWP responded more slowly and to a smaller magnitude compared with that of the uncemented counterpart. In addition, Sr changed little in CS. An increase in the density of the SS promoted rapid development of negative PWP, while an opposite trend was observed for CS. Attempts have been made to explain the observations from the perspectives of material permeability and change in water content during a drying period in both soil types. Furthermore, in SS, the development of PWP (with a measurement limit of −90 kPa) was minimally affected by the presence of vegetation, while vegetation noticeably helped the development of negative PWP in CS. Bounds of the soil-water characteristic curve (SWCCs) of the studied materials were presented based on estimates from the drying and wetting scanning curves derived from the field monitoring. A corresponding laboratory study was carried out in an environmental chamber with controllable temperature and humidity. Monitoring results from the laboratory agreed qualitatively with those obtained from the field.

scholarly journals Examining the effect of pore size distribution and shape on flow through unsaturated peat using computed tomography

2009 ◽  
Vol 13 (10) ◽  
pp. 1993-2002 ◽  
Author(s):  
F. Rezanezhad ◽  
W. L. Quinton ◽  
J. S. Price ◽  
D. Elrick ◽  
T. R. Elliot ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Hydraulic Conductivity ◽  
Pore Structure ◽  
Pore Size ◽  
Soil Water ◽  
Water Pressure ◽  
Peat Soil ◽  
Pressure Head ◽  
Peat Soils ◽  
Unsaturated Hydraulic Conductivity

Abstract. The hydraulic conductivity of unsaturated peat soil is controlled by the air-filled porosity, pore size and geometric distribution as well as other physical properties of peat materials. This study investigates how the size and shape of pores affects the flow of water through peat soils. In this study we used X-ray Computed Tomography (CT), at 45 μm resolution under 5 specific soil-water pressure head levels to provide 3-D, high-resolution images that were used to detect the inner pore structure of peat samples under a changing water regime. Pore structure and configuration were found to be irregular, which affected the rate of water transmission through peat soils. The 3-D analysis suggested that pore distribution is dominated by a single large pore-space. At low pressure head, this single large air-filled pore imparted a more effective flowpath compared to smaller pores. Smaller pores were disconnected and the flowpath was more tortuous than in the single large air-filled pore, and their contribution to flow was negligible when the single large pore was active. We quantify the pore structure of peat soil that affects the hydraulic conductivity in the unsaturated condition, and demonstrate the validity of our estimation of peat unsaturated hydraulic conductivity by making a comparison with a standard permeameter-based method. Estimates of unsaturated hydraulic conductivities were made for the purpose of testing the sensitivity of pore shape and geometry parameters on the hydraulic properties of peats and how to evaluate the structure of the peat and its affects on parameterization. We also studied the ability to quantify these factors for different soil moisture contents in order to define how the factors controlling the shape coefficient vary with changes in soil water pressure head. The relation between measured and estimated unsaturated hydraulic conductivity at various heads shows that rapid initial drainage, that changes the air-filled pore properties, creates a sharp decline in hydraulic conductivity. This is because the large pores readily lose water, the peat rapidly becomes less conductive and the flow path among pores, more tortuous.

scholarly journals Investigation into water retention behaviour of deformable soils

2013 ◽  
Vol 50 (2) ◽  
pp. 200-208 ◽  
Author(s):  
Simon Salager ◽  
Mathieu Nuth ◽  
Alessio Ferrari ◽  
Lyesse Laloui
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Retention ◽  
Void Ratio ◽  
Degree Of Saturation ◽  
Retention Data ◽  
Soil Water Retention ◽  
Retention Behaviour ◽  
Wide Range ◽  
Water Retention Behaviour

The paper presents an experimental and modelling approach for the soil-water retention behaviour of two deformable soils. The objective is to investigate the physical mechanisms that govern the soil-water retention properties and to propose a constitutive framework for the soil-water retention curve accounting for the initial state of compaction and deformability of soils. A granular soil and a clayey soil were subjected to drying over a wide range of suctions so that the residual state of saturation could be attained. Different initial densities were tested for each material. The soil-water retention curves (SWRCs) obtained are synthesized and compared in terms of water content, void ratio, and degree of saturation, and are expressed as a function of the total suction. The studies enable assessment of the effect of the past and present soil deformation on the shape of the curves. The void ratio exerts a clear influence on the air-entry value, revealing that the breakthrough of air into the pores of the soil is more arduous in denser states. In the plane of water content versus suction, the experimental results highlight the fact that from a certain value of suction, the retention curves corresponding to different densities of the same soil are convergent. The observed features of behaviour are conceptualized into a modelling framework expressing the evolution of the degree of saturation as a function of suction. The proposed retention model makes use of the theory of elastoplasticity and can thus be generalized into a hysteretic model applicable to drying–wetting cycles. The calibration of the model requires the experimental retention data for two initial void ratios. The prediction of tests for further ranges of void ratios proves to be accurate, which supports the adequacy of formulated concepts.

Soil Physical Properties of Tied Ridges in the Sudan Savannah of Burkina Faso

1988 ◽  
Vol 24 (3) ◽  
pp. 375-384 ◽  
Author(s):  
N. R. Hulugalle ◽  
M. S. Rodriguez
Keyword(s):  
Physical Properties ◽  
Soil Temperature ◽  
Bulk Density ◽  
Soil Water ◽  
Water Retention ◽  
Clay Content ◽  
Soil Physical Properties ◽  
Water Infiltration ◽  
Soil Water Retention ◽  
Maize Varieties

SUMMARYThe soil physical properties of tied ridges were measured in a trial, established in 1983, comparing three treatments: handhoe cultivation and planting on the flat; planting directly without any cultivation on tied ridges constructed the previous year; and handhoe cultivation and remoulding of tied ridges constructed the previous year. Two maize varieties and two management levels were used. The soil properties monitored were particle size distribution, penetro-meter resistance in the surface 20 mm, bulk density, water infiltration, soil water retention and soil temperature.Soil physical properties were affected mainly by the type of seedbed. Clay content in the surface 0.05 m was greater with tied ridging, with that in the furrows being higher than that in the ridge slopes. Daily maximum soil temperature was greatest in the flat planted plots and in the ridge slopes of the tied ridged plots. Penetrometer resistance at a soil water content of 0.05 kg kg−1 was greater in the tied ridged plots. Cumulative infiltration after 2 h was greatest with flat planting. The bulk density of ridge slopes in tied ridged plots was less than that in the furrows and in the flat planted plots. Soil water retention was greatest in the furrows of the tied ridged plots. Clay content was the major factor determining all the soil physical properties measured.

Prediction of evaporation with the CONSEVB simulation-model - an experimental evaluation

Soil Research ◽  
1994 ◽  
Vol 32 (1) ◽  
pp. 45
Author(s):  
HP Cresswell ◽  
DJ Painter ◽  
KC Cameron
Keyword(s):  
Soil Moisture ◽  
Soil Temperature ◽  
Simulation Model ◽  
Water Content ◽  
Soil Water ◽  
Cost Benefit ◽  
Initial Water ◽  
Input Parameters ◽  
Moisture Characteristic ◽  
Water Contents

The CONSERVB simulation model was evaluated by comparing predictions of evaporation, net radiation, and water and temperature profiles with measured values from a bare, tilled soil in New Zealand conditions. No model calibration was used whatsoever. The assessment included tests of the sensitivity of output to variations (uncertainty) in input parameters. On 18 of the 24 days simulated, evaporation was within 0.5 mm day-1 of the measured means, although that represented less than 20% error on only 6 days. The mean difference between measured and simulated surface soil temperature for the two drying cycles was 1.2 and 1.3�C; most of this error occurred in warm conditions around noon each day. Simulated soil temperature at 0.05 m exceeded measured values during the warmest parts of the day and fell below them at night. Soil temperature prediction was sensitive to the air temperature and solar radiation climatic inputs. Evaporation prediction was sensitive to initial profile water contents, to the soil moisture characteristic and to the unsaturated hydraulic conductivity inputs. An increase in the water content at each matric potential step in the soil moisture characteristic input by a factor of 1.10 resulted in an increase in simulated cumulative evaporation of over 40%. For the prediction of evaporation and soil water content, field effort in the measurement of the soil hydraulic properties and initial water contents (where simulations are short) for model parameterization is likely to give the highest cost-benefit. Very accurate determinations of these input parameters and functions are required for model evaluation. Given the sensitivities, and the uncertainties associated with measurement and prediction of model input parameters, the predictions from CONSERVB have large uncertainties associated with them. Field-measured values of cumulative evaporation were within the range of variation in predicted values that resulted from uncertainty in determination of initial soil water contents alone. CONSERVB is more applicable to an operations research modelling approach than to prediction of evaporation and surface water contents in specific conditions.

scholarly journals Responses of Soil Infiltration to Water Retention Characteristics, Initial Conditions, and Boundary Conditions

Land ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 361
Author(s):  
Lesheng An ◽  
Kaihua Liao ◽  
Chun Liu
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Retention ◽  
Constant Pressure ◽  
Pressure Head ◽  
Estimation Methods ◽  
Initial Water Content ◽  
Initial Water ◽  
Cumulative Infiltration ◽  
Retention Characteristics

(1) Background: Simulation of soil water infiltration process and analysis of its influencing factors are important for water resources management. (2) Methods: In this study, the relative contributions of the soil water retention characteristics (SWRC) estimation, initial water content, and constant pressure head at upper boundary to the cumulative infiltration under various soil conditions were quantified based on the 1-D Richards’ equation and 900 scenarios. Scenario simulations were performed for two SWRC estimation methods (Jensen method and Rosetta); three different initial water contents (0.15, 0.20, and 0.25 cm3/cm3); five different constant pressure heads (0.5, 1, 2, 4, and 8 cm); and thirty soil samples with varying texture and bulk density. (3) Results: Rosetta representing the drying branch of the SWRC yielded higher simulated cumulative infiltration compared with the Jensen method representing the wetting branch of the SWRC. However, the Jensen method–predicted cumulative infiltration fluxes matched well with the measured values with a low RMSE of 0.80 cm. (4) Conclusions: The relative contribution of the SWRC estimation method to cumulative infiltration (19.1–72.2%) was compared to that of constant pressure head (14.0–65.5%), and generally greater than that of initial water content (2.2–29.9%). Findings of this study have practical significance for investigating the transport of water, nutrients, and contaminants in the unsaturated zone.

Influence of active aluminium oxides on water movement in soils

Soil Research ◽  
1969 ◽  
Vol 7 (3) ◽  
pp. 325 ◽  
Author(s):  
CK Tweneboah ◽  
JW Kijne ◽  
DJ Greenland
Keyword(s):  
Sodium Chloride ◽  
Soil Water ◽  
Water Retention ◽  
Water Movement ◽  
Soil Water Retention ◽  
Water Diffusivity ◽  
The Stability ◽  
Soil Pores ◽  
Water Contents ◽  
Soil Water Contents

Active aluminium oxides were removed from several soils by treatment with 0.5M calcium chloride or lM sodium chloride at pH 1.5. Soil-water retention and soil-water diffusivity were determined and contrasted with the values for these properties obtained after treatment with neutral salts. The changes resulting from the removal of aluminium oxides were relatively small in calcium saturated systems, but in sodium saturated systems soil-water diffusivity was drastically reduced by the prior removal of aluminium oxides. The results are discussed in terms of the influence of aluminium oxides on the stability of soil pores at different soil-water contents.

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