Capillary pressure-dependent anisotropy of layered unsaturated soils

2010 ◽  
Vol 90 (2) ◽  
pp. 319-329 ◽  
Author(s):  
J. Zhu ◽  
D. Sun
Keyword(s):  
Hydraulic Conductivity ◽  
Transfer Function ◽  
Bulk Density ◽  
Capillary Pressure ◽  
Soil Texture ◽  
Unsaturated Soils ◽  
Particle Diameter ◽  
Hydraulic Parameters ◽  
Conductivity Anisotropy ◽  
Shape Factors

This paper presents an approach based on a conceptualization of combining the neural network based pedo-transfer function (PTF) results with the thin layer concept to explore capillary-pressure-dependent anisotropy in relation to soil texture and soil bulk density. The effects of capillary pressure (or saturation degree) on the hydraulic conductivity anisotropy of unsaturated soils are still poorly understood. The main objective is to examine how anisotropy characteristics are related to the relationships between hydraulic parameters and the basic soil attributes such as texture and bulk density. The hydraulic parameters are correlated with the texture and bulk density based on the pedo-transfer function (PTF) results. It is demonstrated that non-monotonic behavior of the unsaturated soil anisotropy in relation to the capillary pressure is only observed when the saturated hydraulic conductivity and the shape parameter are both related to the particle diameter. Therefore, it is suggested that this behavior is mainly due to the coupled dependence of the layer saturated hydraulic conductivities and the shape factors on the texture and bulk density. The results illustrate that the inter-relationships of soil texture, bulk density, and hydraulic properties may produce vastly different characteristics of anisotropic unsaturated soils.Key words: Anisotropy, unsaturated soils, capillary pressure-dependent

scholarly journals A global data set of soil hydraulic properties and sub-grid variability of soil water retention and hydraulic conductivity curves

2017 ◽  
Vol 9 (2) ◽  
pp. 529-543 ◽  
Author(s):  
Carsten Montzka ◽  
Michael Herbst ◽  
Lutz Weihermüller ◽  
Anne Verhoef ◽  
Harry Vereecken
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Texture ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Climate Models ◽  
Hydraulic Parameters ◽  
Soil Hydraulic Properties ◽  
Soil Water Retention ◽  
Data Set ◽  
Global Data

Abstract. Agroecosystem models, regional and global climate models, and numerical weather prediction models require adequate parameterization of soil hydraulic properties. These properties are fundamental for describing and predicting water and energy exchange processes at the transition zone between solid earth and atmosphere, and regulate evapotranspiration, infiltration and runoff generation. Hydraulic parameters describing the soil water retention (WRC) and hydraulic conductivity (HCC) curves are typically derived from soil texture via pedotransfer functions (PTFs). Resampling of those parameters for specific model grids is typically performed by different aggregation approaches such a spatial averaging and the use of dominant textural properties or soil classes. These aggregation approaches introduce uncertainty, bias and parameter inconsistencies throughout spatial scales due to nonlinear relationships between hydraulic parameters and soil texture. Therefore, we present a method to scale hydraulic parameters to individual model grids and provide a global data set that overcomes the mentioned problems. The approach is based on Miller–Miller scaling in the relaxed form by Warrick, that fits the parameters of the WRC through all sub-grid WRCs to provide an effective parameterization for the grid cell at model resolution; at the same time it preserves the information of sub-grid variability of the water retention curve by deriving local scaling parameters. Based on the Mualem–van Genuchten approach we also derive the unsaturated hydraulic conductivity from the water retention functions, thereby assuming that the local parameters are also valid for this function. In addition, via the Warrick scaling parameter λ, information on global sub-grid scaling variance is given that enables modellers to improve dynamical downscaling of (regional) climate models or to perturb hydraulic parameters for model ensemble output generation. The present analysis is based on the ROSETTA PTF of Schaap et al. (2001) applied to the SoilGrids1km data set of Hengl et al. (2014). The example data set is provided at a global resolution of 0.25° at https://doi.org/10.1594/PANGAEA.870605.

scholarly journals Capillary pressure–saturation curves of thin hydrophilic fibrous layers: effects of overburden pressure, number of layers, and multiple imbibition–drainage cycles

2019 ◽  
Vol 89 (23-24) ◽  
pp. 4906-4915 ◽  
Author(s):  
Amir Hossein Tavangarrad ◽  
S. Majid Hassanizadeh ◽  
Rodrigo Rosati ◽  
Luigi Digirolamo ◽  
Martinus Th van Genuchten
Keyword(s):  
Porous Media ◽  
Hydraulic Conductivity ◽  
Capillary Pressure ◽  
Unsaturated Soils ◽  
Measured Data ◽  
Text Data ◽  
Overburden Pressure ◽  
Number Of Layers ◽  
Thin Porous Media ◽  
Data Points

Unsaturated fluid flow in thin porous media depends on hydraulic properties, such as the capillary pressure, P c, as a function of saturation, S. We measured this relationship for two different types of compressible thin hydrophilic fibrous layers under varying conditions. Among other factors, we changed the number of layers and the overburden pressure (i.e. the confined solid pressure applied on top of the sample) imposed on one layer or a stack of layers. Applying an overburden pressure drastically affected the [Formula: see text] curves. However, increasing the number of fibrous layers had little impact on the capillary pressure–saturation curves. We also investigated the effect of multiple imbibition–drainage cycles on the [Formula: see text] data. Measured data points were used to find general expressions for the [Formula: see text] relationships of compressible thin porous media. Existing quasi-empirical correlations used in vadose zone hydrology, notably expressions by van Genuchten (Van Genuchten MTh. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci Soc Am J 1980; 44: 892-898) and Durner (Durner W. Hydraulic conductivity estimation for soils with heterogeneous pore structure. Water Resour Res 1994; 32: 211–223) for single- and dual-porosity media, respectively, were employed to fit the measured data points.

Evaluation of some selected soil properties of a drip irrigated tomato field at different moisture regimes in South-Western Nigeria

2021 ◽  
Vol 6 (2) ◽  
Author(s):  
E.O. Ogundipe
Keyword(s):  
Organic Matter ◽  
Hydraulic Conductivity ◽  
Soil Properties ◽  
Bulk Density ◽  
Soil Texture ◽  
Organic Matter Content ◽  
Infiltration Rate ◽  
Matter Content ◽  
Saturated Hydraulic Conductivity ◽  
Tomato Field

Soil properties are important to the development of agricultural crops. This study determined some selected soil properties of a drip irrigated tomato (Lycopersicon esculentum M.) field at different moisture regime in South-Western Nigeria. The experiment was carried out using Randomized Complete Block Design with frequency and depth of irrigation application as the main plot and sub-plot, respectively in three replicates. Three frequencies (7, 5 and 3 days) and three depths equivalent to 100, 75 and 50% of water requirement were used. Undisturbed and disturbed soil samples were collected from 0-5, 5-10, 10-20 and 20-30 cm soil layers for the determination of some soil properties (soil texture, organic matter content, bulk density, infiltration rate and saturated hydraulic conductivity) were determined using standard formulae. Soil Water Content (SWC) monitoring was conducted every two days using a gravimetric technique. The soil texture was sandy loam for all the soil depths; average value of soil organic matter was highest (1.8%) in the 0-5 cm surface layer and decreased with soil depth; the soil bulk density value before and after irrigation experiment ranged from 1.48 and 1.73 g/cm3 and 1.5 and 1.76 g/cm3, respectively; there was a rapid reduction in the initial infiltration and final infiltration rate. Saturated hydraulic conductivity show similar trend although the 20-30 cm layer had the lowest value (50.84 mm/h); the SWC affect bulk density during the growing season. The study showed that soil properties especially bulk density and organic matter content affect irrigation water movement at different depth..

Reducing non-uniqueness of inverting bimodal soil Kosugi hydraulic parameters

2021 ◽  
Author(s):  
Jesús Fernández-Gálvez ◽  
Joseph Pollacco ◽  
Stephen McNeill ◽  
Sam Carrick ◽  
Linda Lilburne ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Water ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Water Pressure ◽  
Full Range ◽  
Inverse Modelling ◽  
Residual Soil ◽  
Hydraulic Parameters ◽  
The Matrix

<p>Hydrological models use soil hydraulic parameters to describe the storage and transmission of water in soils. Hydraulic parameters define the water retention, <em>θ(ψ)</em>, and the hydraulic conductivity, <em>K(θ)</em>, functions. These functions are usually obtained by fitting experimental data to the corresponding θ(ψ) and K(θ) functions. The drawback of deriving the hydraulic parameters by inverse modelling is that they suffer from equifinality or non-uniqueness, and the optimal hydraulic parameters are non-physical (Pollacco <em>et al.</em>, 2008). To reduce the non-uniqueness, it is necessary to invert the hydraulic parameters simultaneously from observations of both<em> θ(ψ)</em> and <em>K(θ</em>), and ensure the measurements cover the full range of <em>θ</em> from fully saturated to oven dry, which requires expensive, labour-intensive measurements.  </p><p>We present a novel procedure to derive a unique, physical set of bimodal or dual permeabilityKosugi hydraulic functions,<em> θ(ψ)</em> and <em>K(θ)</em>, from inverse modelling. The Kosugi model was chosen given its parameters have direct physical meaning to the soil pore-size distribution. The challenge of using bimodal functions is they require double the number of parameters (Pollacco <em>et al.</em>, 2017), exacerbating the problem of non-uniqueness. To address this shortcoming, we<strong> (1) </strong>derive residual soil water content from the matrix Kosugi standard deviation, <strong>(2) </strong>derive macropore hydraulic parameters from the soil water pressure boundary between macropore and matrix, and <strong>(3)</strong> dynamically constraint the matrix Kosugi hydraulic parameters. We successfully reduce the number of hydraulic parameters to optimize and constrain the hydraulic parameters without compromising the fit of the <em>θ(ψ)</em> and <em>K(θ)</em> functions.</p><p>The robustness of the methodology is demonstrated by deriving the hydraulic parameters exclusively from<em> θ(ψ)</em> and <em>K<sub>s</sub></em>data, enabling satisfactory prediction of <em>K(θ)</em> without having measured K(θ) data. Moreover, having a reduced number of hydraulic parameters that are physical allows an improved characterization of hydraulic properties of soils prone to preferential flow, which is a fundamental issue regarding the understanding of hydrological processes.</p><p> </p><p><strong>References</strong></p><p>Pollacco, J.A.P., Ugalde, J.M.S., Angulo-Jaramillo, R., Braud, I., Saugier, B., 2008. A linking test to reduce the number of hydraulic parameters necessary to simulate groundwater recharge in unsaturated soils. Adv Water Resour 31, 355–369. https://doi.org/10.1016/j.advwatres.2007.09.002</p><p>Pollacco, J.A.P., Webb, T., McNeill, S., Hu, W., Carrick, S., Hewitt, A., Lilburne, L., 2017. Saturated hydraulic conductivity model computed from bimodal water retention curves for a range of New Zealand soils. Hydrol. Earth Syst. Sci. 21, 2725–2737. https://doi.org/10.5194/hess-21-2725-2017</p>

What is the optimal level of soil organic matter in tropical climates to prevent soil degradation?

2020 ◽  
Author(s):  
Christian Guzman ◽  
Tigist Tebebu ◽  
Fasikaw Zimale ◽  
Tammo Steenhuis
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
Hydraulic Conductivity ◽  
Bulk Density ◽  
Soil Texture ◽  
Fine Particles ◽  
Penetration Resistance ◽  
Optimal Level ◽  
Soil Penetration Resistance ◽  
Lower Bulk Density

<p>Land degradation emerges when a critical component of productive land begins to diminish beyond a threshold. In tropical soils, organic matter may vary depending on the local climatic conditions and production of litter and organic materials and furthermore drastic changes in land use may be responsible for changes in organic matter which coincides with soil physical changes. In two research regions in mountainous (sub) humid conditions, organic matter was measured alongside surface and profile characteristics. In the Ethiopian Highlands, we measured organic matter, soil penetration resistance, soil texture, pH, and bulk density in three land use classifications (native forests, pasture lands, croplands).  In this region, soil in cropped regions and pasturelands had organic matter roughly below 4 %, had greater soil penetration resistance, lower pH (more acidic), and had greater bulk density. Soils in the native forests had organic matter roughly between the range of 4% to 12 % with lower soil penetration resistance, higher pH (less acidic) and lower bulk density.</p><p>The soils were investigated in the Andean region of the southwest of Colombia were analyzed for organic matter, hydraulic conductivity, soil texture, pH, and bulk density across two main land use classifications (native- and regenerated-forests and cultivated and pastureland). Soils in the cropped and pasturelands had organic matter around 4.8%, with low saturated hydraulic conductivity, greater fraction of fine particles, lower pH (more acidic), and greater bulk density. Soils in the native and regenerated forest cover had organic matter between 5 to 7%, with greater saturated hydraulic conductivity, lower fraction of fine particles, higher pH (less acidic), and a lower bulk density. While a universal optimal level of soil organic matter may not be applicable across various tropical regions, there are distinct changes that are consistent when organic matter falls below a regional threshold including increased compaction, acidity, and shifting of soil texture.  </p>

scholarly journals A global data set of soil hydraulic properties and sub-grid variability of soil water retention and hydraulic conductivity curves

2017 ◽  
Author(s):  
Carsten Montzka ◽  
Michael Herbst ◽  
Lutz Weihermüller ◽  
Anne Verhoef ◽  
Harry Vereecken
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Texture ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Climate Models ◽  
Hydraulic Parameters ◽  
Soil Hydraulic Properties ◽  
Soil Water Retention ◽  
Data Set ◽  
Global Data

Abstract. Agroecosytem models, regional and global climate models, as well as numerical weather prediction models require adequate parameterization of soil hydraulic properties. These properties are fundamental for describing and predicting water and energy exchange processes at the transition zone between solid Earth and Atmosphere, and regulate evapotranspiration, infiltration, and runoff generation. Hydraulic parameters describing the soil water retention (WRC) and hydraulic conductivity (HCC) curves are typically derived from soil texture via pedotransfer functions (PTFs). Resampling of those parameters for specific model grids is typically performed by different aggregation approaches such a spatial averaging and the use of dominant textural properties or soil classes. These aggregation approaches introduce uncertainty, bias and parameter inconsistencies throughout spatial scales due to nonlinear relationships between hydraulic parameters and soil texture. Therefore, we present a method to scale hydraulic parameters to individual model grids and provide a global data set that overcomes the mentioned problems. The approach is based on Miller-Miller scaling that fits the parameters of the WRC through all sub-grid WRCs to provide an effective parameterization for the grid cell at model resolution; at the same time it preserves the information of sub-grid variability of the water retention curve by deriving local scaling parameters. Based on the Mualem van Genuchten approach we also derive the unsaturated hydraulic conductivity from the water retention functions, thereby assuming that the local parameters are also valid for this function. In addition, via the Miller-Miller scaling parameter lambda, information on global sub-grid scaling variance is given that enables modellers to improve dynamical downscaling of (regional) climate models or to perturb hydraulic parameters for model ensemble output generation. The present analysis is based on the ROSETTA PTF of Schaap et al. (2001) applied to the SoilGrids1km data set of Hengl et al. (2014). The example data set is provided at a global resolution of 0.25° at DOI:10.1594/PANGAEA.870605 (DOI registration in progress, so far the data can be accessed under https://doi.pangaea.de/10.1594/PANGAEA.870605).

Spatial Variation of Aquifer Parameters from Coastal Aquifers of Sindhudurg District, Maharashtra Using Pore-water Resistivity and Bulk Resistivity

2018 ◽  
Vol 1 (1) ◽  
pp. 28-40
Author(s):  
Suneetha Naidu ◽  
Gautam Gupta
Keyword(s):  
Hydraulic Conductivity ◽  
Pore Water ◽  
Coastal Aquifers ◽  
Hydraulic Parameters ◽  
Formation Factor ◽  
Bulk Resistivity ◽  
Good Correspondence ◽  
Aquifer System ◽  
Transverse Resistance ◽  
Water Resistivity

Estimation of hydraulic parameters in coastal aquifers is an important task in groundwater resource assessment and development. An attempt is made to estimate these parameters using geoelectrical data in combination with pore-water resistivity of existing wells. In the present study, 29 resistivity soundings were analysed along with 29 water samples, collected from the respective dug wells and boreholes, in order to compute hydraulic parameters like formation factor, porosity, hydraulic conductivity and transmissivity from coastal region of north Sindhudurg district, Maharashtra, India. The result shows some parts of the study area reveal relatively high value of hydraulic conductivity, porosity and transmissivity. Further, a negative correlation is seen between hydraulic conductivity and bulk resistivity. The hydraulic conductivity is found to vary between 0.014 and 293 m/day, and the transmissivity varied between 0.14 and 11,722 m2/day. The transmissivity values observed here are in good correspondence with those obtained from pumping test data of Central Ground Water Board. These zones also have high aquifer thickness and therefore characterize high potential within the water-bearing formation. A linear, positive relationship between transverse resistance and transmissivity is observed, suggesting increase in transverse resistance values indicate high transmissivity of aquifers. These relations will be extremely vital in characterization of aquifer system, especially from crystalline hard rock area.

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