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Yves Coquet - One of the best experts on this subject based on the ideXlab platform.
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Estimating Saturated Hydraulic Conductivity from Surface Ground-Penetrating Radar Monitoring of Infiltration
arXiv: Geophysics, 2013Co-Authors: Emmanuel Léger, Albane Saintenoy, Yves CoquetAbstract:In this study we used Hydrus-1D to simulate water infiltration from a ring infiltrometer. We generated water content profiles at each time step of infiltration, based on a particular value of the Saturated Hydraulic Conductivity while knowing the other van Genuchten parameters. Water content profiles were converted to dielectric permittivity profiles using the Complex Refractive Index Method relation. We then used the GprMax suite of programs to generate radargrams and to follow the wetting front using arrival time of electromagnetic waves recorded by a Ground-Penetrating Radar (GPR). Theoretically, the depth of the inflection point of the water content profile simulated at any infiltration time step is related to the peak of the reflected amplitude recorded in the corresponding trace in the radargram. We used this relationship to invert the Saturated Hydraulic Conductivity for constant and falling head infiltrations. We present our method on synthetic examples and on two experiments carried out on sand. We further discuss the possibility of estimating two other van Genuchten parameters, n and \alpha, in addition to the Saturated Hydraulic Conductivity.
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Saturated Hydraulic Conductivity determined by on ground mono-offset Ground-Penetrating Radar inside a single ring infiltrometer
arXiv: Geophysics, 2013Co-Authors: Emmanuel Léger, Albane Saintenoy, Yves CoquetAbstract:In this study we show how to use GPR data acquired along the infiltration of water inside a single ring infiltrometer to inverse the Saturated Hydraulic Conductivity. We used Hydrus-1D to simulate the water infiltration. We generated water content profiles at each time step of infiltration, based on a particular value of the Saturated Hydraulic Conductivity, knowing the other van Genuchten parameters. Water content profiles were converted to dielectric permittivity profiles using the Complex Refractive Index Method relation. We then used the GprMax suite of programs to generate radargrams and to follow the wetting front using arrival time of electromagnetic waves recorded by a Ground-Penetrating Radar (GPR). Theoretically, the 1D time convolution between reflectivity and GPR signal at any infiltration time step is related to the peak of the reflected amplitude recorded in the corresponding trace in the radargram. We used this relation ship to invert the Saturated Hydraulic Conductivity for constant and falling head infiltrations. We present our method on synthetic examples and on two experiments carried out on sand soil. We further discuss on the uncertainties on the retrieved Saturated Hydraulic Conductivity computed by our algorithm from the van Genuchten parameters.
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vertical variation of near Saturated Hydraulic Conductivity in three soil profiles
Geoderma, 2005Co-Authors: Yves Coquet, P Vachier, C LabatAbstract:Abstract Hydraulic Conductivity is an important parameter of water and solute transport in soils. Hydraulic Conductivity is known to be highly variable in space, but its dependence on soil horizonation has seldom been explored. We measured the near-Saturated Hydraulic Conductivity of three soils located in the Centre of France, a Neoluvisol, a Calcisol, and a Calcosol (according to the “Referentiel Pedologique”), using tension disc infiltrometry. The Reynolds and Elrick's multipotential technique has been applied to the steady state infiltration kinetics measured at potentials −1.5, −0.6, −0.3, −0.1 and −0.05 kPa to derive the Hydraulic Conductivity values. Each horizon of the three soil profiles has been characterised at least once at three locations 50-cm apart from each other on a flat surface prepared within the same access pit. Some horizons have been characterised on a second occasion in other access pits opened at nearly 10 m from the previous ones. On average, Hydraulic Conductivity values increased from 1.3×10−7 m/s at −1.5 kPa to 2.5×10−6 m/s at −0.3 kPa. Saturated Hydraulic Conductivity varied between 3.6×10−6 m/s for the ploughed layer of the Calcosol and 4.9×10−3 m/s for the Calcosol substrate (C horizon). The various horizons of the Neoluvisol had Hydraulic Conductivity values which were not significantly different from each other, except the ploughed layer which had lower Hydraulic Conductivity values than the underlying horizons. The tilled layers of the Calcisol and the Calcosol also had lower Hydraulic Conductivity values than their respective underlying cambic horizons. Further, the Hydraulic Conductivity of the tilled layer of the Calcosol was lower than that of the tilled layers of the Calcisol and the Neoluvisol. This difference was attributed to the effect of different tillage systems, the Calcosol being superficially tilled while the Calcisol and Neoluvisol were ploughed each year. The structural S cambic horizons of the Calcisol and Calcosol had similar Hydraulic conductivities but lower than their respective substrate (limestone).
Nicholas Jarvis - One of the best experts on this subject based on the ideXlab platform.
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upscaling soil Saturated Hydraulic Conductivity from pore throat characteristics
Advances in Water Resources, 2017Co-Authors: Behzad Ghanbarian, Allen G Hunt, Todd H Skaggs, Nicholas JarvisAbstract:Abstract Upscaling and/or estimating Saturated Hydraulic Conductivity K sat at the core scale from microscopic/macroscopic soil characteristics has been actively under investigation in the hydrology and soil physics communities for several decades. Numerous models have been developed based on different approaches, such as the bundle of capillary tubes model, pedotransfer functions, etc. In this study, we apply concepts from critical path analysis, an upscaling technique first developed in the physics literature, to estimate Saturated Hydraulic Conductivity at the core scale from microscopic pore throat characteristics reflected in capillary pressure data. With this new model, we find K sat estimations to be within a factor of 3 of the average measured Saturated Hydraulic conductivities reported by Rawls et al. (1982) for the eleven USDA soil texture classes.
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post tillage evolution of structural pore space and Saturated and near Saturated Hydraulic Conductivity in a clay loam soil
Soil & Tillage Research, 2017Co-Authors: Maria Sandin, Nicholas Jarvis, John Koestel, Mats LarsboAbstract:Abstract Soil structure varies considerably with time in agricultural soils, as a result of complex interactions between soil management (i.e. tillage and traffic) and site-specific environmental factors. The resulting temporal variations in soil Hydraulic properties significantly affect the soil water balance (e.g. partitioning between infiltration and runoff), but are still poorly understood. Thus, post-tillage decreases in Saturated and near-Saturated Hydraulic conductivities have been frequently observed, although the underlying changes in the properties of the structural pore-space have not been studied. We used X-ray tomography to quantify the temporal changes in the volume, size distribution and connectivity of structural pores in the harrowed layer of a conventionally-tilled agricultural field over one growing season. We also determined the extent to which these properties could explain temporal variations in Saturated Hydraulic Conductivity measured on the same samples and near-Saturated Hydraulic conductivities measured in the field with tension disc infiltrometers. Early-season rainfall events caused significant decreases in the imaged porosity in the uppermost 5 mm of soil within one month of harrowing and also at 2.5–5 cm depth but only for pores >0.5 mm in diameter. Measurements of critical pore diameter showed that the sample-scale connectivity of these pores was very limited at all times. Temporal changes in the pore network characteristics were reflected in the field measurements of near-Saturated Hydraulic Conductivity, but not in Saturated Hydraulic Conductivity measured in the laboratory. Saturated Hydraulic Conductivity was, however, correlated (Spearman ρ = 0.50) with the connectivity probability which is a measure of global pore space connectivity. Large spatial variation combined with a small sample size limited our ability to quantify temporal variations in the soil structural pore-space. Increased automation of image processing would enable greater replication and therefore enhance the utility of X-ray tomography as a technique for investigating the properties of the structural pore space.
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indirect estimation of near Saturated Hydraulic Conductivity from readily available soil information
Geoderma, 2002Co-Authors: Nicholas Jarvis, Per Atle Olsen, Kalman Rajkai, W D Reynolds, Laura Zavattaro, M Mcgechan, M Mecke, Binayak P Mohanty, P B Leedsharrison, Diederik JacquesAbstract:Application of process-based water flow and solute transport models is often hampered by insufficient knowledge of soil Hydraulic properties. This is certainly true for dual- or multi-porosity models that account for non-equilibrium flow of water in macropores, where the Saturated ‘matrix’ Hydraulic Conductivity is a particularly critical parameter. Direct measurement is possible, but this is impractical for larger scale studies (i.e. catchment or regional), where estimation methods (pedotransfer functions) are usually required. This paper presents pedotransfer functions for Hydraulic Conductivity at a pressure head of � 10 cm, K10, based on measurements of near-Saturated Hydraulic Conductivity made with tension infiltrometers in 70 soil horizons at 37 different sites in
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near Saturated Hydraulic Conductivity in soils of contrasting texture measured by tension infiltrometers
Soil Science Society of America Journal, 1995Co-Authors: Nicholas Jarvis, Ingmar MessingAbstract:Soil structure is known to strongly affect water flow and solute transport, yet little information is available concerning soil Hydraulic properties close to saturation. This study reports detailed measurements of near-Saturated Hydraulic Conductivity in undisturbed field soils. Steady-state infiltration rates from tension infiltrometers were measured at the surface of six tilled soils of contrasting texture ranging from loamy sand to silty clay. Hydraulic conductivities (K) at supply pressure heads (h) in the range from -100 mm to zero were obtained using Wooding's solution For infiltration from a circular source. The paired K,h data were summarized using the technique of functional normalization with three alternative models of K(h): a single exponential function (Gardner's model), a two-line exponential model, and the Mualem-van Genuchten model. The commonly used single exponential model was found to be inappropriate in all cases. Both the two-line exponential and Mualem-van Genuchten models satisfactorily described the data, with the former performing marginally better for five of the six soils. In the supply pressure head range -100 mm to zero, K increased by three to four orders of magnitude in the finer textured soils and by about two orders of magnitude in two sandy soils. Estimates of field-Saturated Hydraulic Conductivity (K fs ) were largest in the fine-textured soils, presumably because of the influence of continuous surface-vented macropores. Spatial variability in measured K(h) was small to moderate for all soils. Predicting unSaturated K from soil water release data using K fs as a matching point was shown to result in serious overestimations
Ahmed Arab - One of the best experts on this subject based on the ideXlab platform.
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effect of fines content and void ratio on the Saturated Hydraulic Conductivity and undrained shear strength of sand silt mixtures
Environmental Earth Sciences, 2013Co-Authors: Mostefa Belkhatir, Tom Schanz, Ahmed ArabAbstract:The Hydraulic Conductivity represents an important indicator parameter in the generation and redistribution of excess pore pressure of sand–silt mixture soil deposits during earthquakes. This paper aims to determine the relationship between the undrained shear strength (liquefaction resistance) and the Saturated Hydraulic Conductivity of the sand–silt mixtures and how much they are affected by the percentage of low plastic fines (finer than 0.074 mm) and void ratio of the soil. The results of flexible wall permeameter and undrained monotonic triaxial tests carried out on samples reconstituted from Chlef river sand with 0, 10, 20, 30, 40, and 50 % non-plastic silt at an effective confining pressure of 100 kPa and two initial relative densities (D r = 20, 91 %) are presented and discussed. It was found that the undrained shear strength (liquefaction resistance) can be correlated to the fines content, intergranular void ratio and Saturated Hydraulic Conductivity. The results obtained from this study reveal that the Saturated Hydraulic Conductivity (k sat) of the sand mixed with 50 % low plastic fines can be, in average, four orders of magnitude smaller than that of the clean sand. The results show also that the global void ratio could not be used as a pertinent parameter to explain the undrained shear strength and Saturated Hydraulic Conductivity response of the sand–silt mixtures.
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Effect of fines content and void ratio on the Saturated Hydraulic Conductivity and undrained shear strength of sand–silt mixtures
Environmental Earth Sciences, 2013Co-Authors: Mostefa Belkhatir, Tom Schanz, Ahmed ArabAbstract:The Hydraulic Conductivity represents an important indicator parameter in the generation and redistribution of excess pore pressure of sand–silt mixture soil deposits during earthquakes. This paper aims to determine the relationship between the undrained shear strength (liquefaction resistance) and the Saturated Hydraulic Conductivity of the sand–silt mixtures and how much they are affected by the percentage of low plastic fines (finer than 0.074 mm) and void ratio of the soil. The results of flexible wall permeameter and undrained monotonic triaxial tests carried out on samples reconstituted from Chlef river sand with 0, 10, 20, 30, 40, and 50 % non-plastic silt at an effective confining pressure of 100 kPa and two initial relative densities (D r = 20, 91 %) are presented and discussed. It was found that the undrained shear strength (liquefaction resistance) can be correlated to the fines content, intergranular void ratio and Saturated Hydraulic Conductivity. The results obtained from this study reveal that the Saturated Hydraulic Conductivity (k sat) of the sand mixed with 50 % low plastic fines can be, in average, four orders of magnitude smaller than that of the clean sand. The results show also that the global void ratio could not be used as a pertinent parameter to explain the undrained shear strength and Saturated Hydraulic Conductivity response of the sand–silt mixtures.
Behzad Ghanbarian - One of the best experts on this subject based on the ideXlab platform.
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upscaling soil Saturated Hydraulic Conductivity from pore throat characteristics
Advances in Water Resources, 2017Co-Authors: Behzad Ghanbarian, Allen G Hunt, Todd H Skaggs, Nicholas JarvisAbstract:Abstract Upscaling and/or estimating Saturated Hydraulic Conductivity K sat at the core scale from microscopic/macroscopic soil characteristics has been actively under investigation in the hydrology and soil physics communities for several decades. Numerous models have been developed based on different approaches, such as the bundle of capillary tubes model, pedotransfer functions, etc. In this study, we apply concepts from critical path analysis, an upscaling technique first developed in the physics literature, to estimate Saturated Hydraulic Conductivity at the core scale from microscopic pore throat characteristics reflected in capillary pressure data. With this new model, we find K sat estimations to be within a factor of 3 of the average measured Saturated Hydraulic conductivities reported by Rawls et al. (1982) for the eleven USDA soil texture classes.
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sample dimensions effect on prediction of soil water retention curve and Saturated Hydraulic Conductivity
Journal of Hydrology, 2015Co-Authors: Behzad Ghanbarian, Vahid Taslimitehrani, Guozhu Dong, Yakov A PachepskyAbstract:Summary Soil water retention curve (SWRC) and Saturated Hydraulic Conductivity (SHC) are key Hydraulic properties for unSaturated zone hydrology and groundwater. Not only the SWRC and SHC measurements are time-consuming, but also their results are scale dependent. Although prediction of the SWRC and SHC from available parameters, such as textural data, organic matter, and bulk density have been under investigation for decades, up to now no research has focused on the effect of sample dimensions on the soil Hydraulic properties pedotransfer functions development. The main purpose here is investigating sample internal diameter and height (or length) effects on the prediction of the soil water retention curve and the Saturated Hydraulic Conductivity. We, therefore, develop pedotransfer functions using a novel approach called contrast pattern aided regression (CPXR) and consider the sample dimensions as input variables. Two datasets including 210 and 213 soil samples with known sample dimensions were extracted from the UNSODA database to develop and evaluate pedotransfer functions for the SWRC and SHC, respectively. The 10-fold cross-validation method is applied to evaluate the accuracy and reliability of the proposed regression-based models. Our results show that including sample dimensions, such as sample internal diameter and height (or length) could substantially improve the accuracy of the SWRC and SHC pedotransfer functions developed using the CPXR method.
Volker Hennings - One of the best experts on this subject based on the ideXlab platform.
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accuracy of the Saturated Hydraulic Conductivity prediction by pedo transfer functions compared to the variability within fao textural classes
Geoderma, 1996Co-Authors: Olaf Tietje, Volker HenningsAbstract:Abstract Saturated Hydraulic Conductivity is one of the key parameters for water transport models in the unSaturated zone. Several attempts have been made to estimate this parameter from available soil data as e.g. particle size distribution, bulk density, and organic matter content. All of these estimation methods (pedo-transfer functions) exhibit large differences between the predicted and the measured Saturated Hydraulic conductivities, because they calculate the Saturated Hydraulic Conductivity as a deterministic physical parameter. In this study the Saturated Hydraulic Conductivity is defined as a lognormally distributed random variable, the (geometric) mean and standard deviation of which depend on the texture. The confidence limits of the geometric mean and standard deviation of the measured Saturated Hydraulic Conductivity within the FAO textural classification scheme are presented. Due to the lognormal distribution the ratio of the predicted and the measured Saturated Hydraulic Conductivity (error ratio) is statistically analyzed within the FAO textural classes using the database of the Lower Saxony Soil Information System. For some pedo-transfer functions the geometric mean error ratio is near one, but the geometric standard deviation of the error ratio is generally large and within the investigated textural classes has nearly the same value as the geometric standard deviation of the measured Saturated Hydraulic Conductivity. This indicates that the pedo-transfer function approach is useful to predict Saturated Hydraulic Conductivity, if mean and standard deviation are considered.
