New pedotransfer function (“CRC”) for the prediction of unsaturated soil hydraulic conductivity using soil water retention data

Abstract. Few parametric expressions for the soil water retention curve are suitable for dry conditions. Furthermore, expressions for the soil hydraulic conductivity curves associated with parametric retention functions can behave unrealistically near saturation. We developed a general criterion for water retention parameterizations that ensures physically plausible conductivity curves. Only 3 of the 18 tested parameterizations met this criterion without restrictions on the parameters of a popular conductivity curve parameterization. A fourth required one parameter to be fixed. We estimated parameters by shuffled complex evolution (SCE) with the objective function tailored to various observation methods used to obtain retention curve data. We fitted the four parameterizations with physically plausible conductivities as well as the most widely used parameterization. The performance of the resulting 12 combinations of retention and conductivity curves was assessed in a numerical study with 751 days of semiarid atmospheric forcing applied to unvegetated, uniform, 1 m freely draining columns for four textures. Choosing different parameterizations had a minor effect on evaporation, but cumulative bottom fluxes varied by up to an order of magnitude between them. This highlights the need for a careful selection of the soil hydraulic parameterization that ideally does not only rely on goodness of fit to static soil water retention data but also on hydraulic conductivity measurements. Parameter fits for 21 soils showed that extrapolations into the dry range of the retention curve often became physically more realistic when the parameterization had a logarithmic dry branch, particularly in fine-textured soils where high residual water contents would otherwise be fitted.

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The influence of microplastic on soil hydraulic properties

10.5194/egusphere-egu2020-9337 ◽

2020 ◽

Author(s):

Patrizia Hangele ◽

Katharina Luise Müller ◽

Hannes Laermanns ◽

Christina Bogner

Keyword(s):

Hydraulic Conductivity ◽

Soil Water ◽

Hydraulic Properties ◽

Water Retention ◽

Pore Space ◽

Water Retention Curve ◽

Soil Hydraulic Properties ◽

Soil Water Retention ◽

Soil Hydraulic Conductivity ◽

Soil Hydraulic

The need to study the occurrence and effects of microplastic (MP) in different ecosystems has become apparent by a variety of studies in the past years. Until recently, research regarding MP in the environment has mainly focused on marine systems. Within terrestrial systems, studies suggest soils to be the biggest sink for MP. Some studies now started to explore the presence of MP in soils. However, there is a substantial lack of the basic mechanistic understanding of the behaviour of MP particles within soils.This study investigates how the presence of MP in soils affects their hydraulic properties. In order to understand these processes, experiments are set up under controlled laboratory conditions as to set unknown influencing variables to a minimum. Different substrates, from simple sands to undisturbed soils, are investigated in soil cylinders. MP particles of different sizes and forms of the most common plastic types are applied to the surface of the soil cylinders and undergo an irrigation for the MP particles to infiltrate. Soil-water retention curves and soil hydraulic conductivity are measured before and after the application of MP particles. It is hypothesised that the infiltrated MP particles clog a part of the pore space and should thus reduce soil hydraulic conductivity and change the soil-water retention curve of the sample. Knowledge about the influence of MP on soil hydraulic properties are crucial to understand transport and retention of MP in soils.

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Using neural networks to predict soil water retention and soil hydraulic conductivity

Soil and Tillage Research ◽

10.1016/s0167-1987(98)00070-1 ◽

1998 ◽

Vol 47 (1-2) ◽

pp. 37-42 ◽

Cited By ~ 125

Author(s):

M Schaap

Keyword(s):

Neural Networks ◽

Hydraulic Conductivity ◽

Soil Water ◽

Water Retention ◽

Soil Water Retention ◽

Soil Hydraulic Conductivity ◽

Soil Hydraulic

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Parametric soil water retention models: a critical evaluation of expressions for the full moisture range

10.5194/hess-2016-168 ◽

2016 ◽

Author(s):

Raneem Madi ◽

Gerrit Huibert de Rooij ◽

Henrike Mielenz ◽

Juliane Mai

Keyword(s):

Hydraulic Conductivity ◽

Soil Water ◽

Water Retention ◽

Retention Data ◽

General Criterion ◽

Soil Water Retention ◽

Retention Curve ◽

Special Cases ◽

Conductivity Curve ◽

Soil Hydraulic

Abstract. Of the many parametric expressions for the soil water retention curve, only a few are suitable for the dry 15 range. Furthermore, expressions for the soil hydraulic conductivity curves associated with these retention functions can exhibit non-physical behavior near saturation. We developed a general criterion that needs to be met by soil water retention parameterizations to ensure physically plausible hydraulic conductivity curves. Only three of the 18 tested parameterizations did not impose any restrictions on the parameters of the most popular conductivity curve parameterization, which includes three functions as special cases. One other retention function required one 20 conductivity parameter to be fixed. We employed the Shuffled Complex Evolution parameter estimation method with the objective function tailored to various observation methods normally used to obtain retention curve data. We fitted the four parameterizations with physically plausible conductivities as well as the most widely used parameterization. We then compared the performance of the resulting 12 combinations of retention curve and conductivity curve in a 25 numerical study with 999 days of semi-arid atmospheric forcing applied to unvegetated, uniform, 1-m freely draining columns for four textures. Choosing different parameterizations had a minor effect on evaporation, but cumulative bottom fluxes varied by up to an order of magnitude between them. This highlights the need for a careful selection procedure for the parameterization of the soil hydraulic properties that ideally does not only rely on goodness-of-fit to static soil 30 water retention data but also on observations of the hydraulic conductivity curve made during dynamic flow conditions.

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Calculation of soil hydraulic conductivity from soil--water retention relationships

10.2172/4318607 ◽

1973 ◽

Cited By ~ 1

Author(s):

A.E. Reisenauer

Keyword(s):

Hydraulic Conductivity ◽

Soil Water ◽

Water Retention ◽

Soil Water Retention ◽

Soil Hydraulic Conductivity ◽

Soil Hydraulic

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Method for Quick Prediction of Hydraulic Conductivity and Soil-Water Retention of Unsaturated Soils

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198118798486 ◽

2018 ◽

Vol 2672 (52) ◽

pp. 108-117 ◽

Cited By ~ 1

Author(s):

Shaoyang Dong ◽

Yuan Guo ◽

Xiong (Bill) Yu

Keyword(s):

Finite Element ◽

Hydraulic Conductivity ◽

Soil Properties ◽

Soil Water ◽

Unsaturated Soil ◽

Unsaturated Soils ◽

Hydraulic Properties ◽

Water Retention ◽

Characteristic Curve ◽

Soil Water Retention

Hydraulic conductivity and soil-water retention are two critical soil properties describing the fluid flow in unsaturated soils. Existing experimental procedures tend to be time consuming and labor intensive. This paper describes a heuristic approach that combines a limited number of experimental measurements with a computational model with random finite element to significantly accelerate the process. A microstructure-based model is established to describe unsaturated soils with distribution of phases based on their respective volumetric contents. The model is converted into a finite element model, in which the intrinsic hydraulic properties of each phase (soil particle, water, and air) are applied based on the microscopic structures. The bulk hydraulic properties are then determined based on discharge rate using Darcy’s law. The intrinsic permeability of each phase of soil is first calibrated from soil measured under dry and saturated conditions, which is then used to predict the hydraulic conductivities at different extents of saturation. The results match the experimental data closely. Mualem’s equation is applied to fit the pore size parameter based on the hydraulic conductivity. From these, the soil-water characteristic curve is predicted from van Genuchten’s equation. The simulation results are compared with the experimental results from documented studies, and excellent agreements were observed. Overall, this study provides a new modeling-based approach to predict the hydraulic conductivity function and soil-water characteristic curve of unsaturated soils based on measurement at complete dry or completely saturated conditions. An efficient way to measure these critical unsaturated soil properties will be of benefit in introducing unsaturated soil mechanics into engineering practice.

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PREDICTION OF HYDRAULIC CONDUCTIVITY FROM SOIL WATER RETENTION DATA

Soil Science ◽

10.1097/00010694-198509000-00004 ◽

1985 ◽

Vol 140 (3) ◽

pp. 184-188 ◽

Cited By ~ 15

Author(s):

T. TALSMA

Keyword(s):

Hydraulic Conductivity ◽

Soil Water ◽

Water Retention ◽

Retention Data ◽

Soil Water Retention

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The role of biochar particle size and hydrophobicity in improving soil hydraulic properties

10.5194/egusphere-egu21-4117 ◽

2021 ◽

Author(s):

Ifeoma Edeh ◽

Ondřej Mašek

Keyword(s):

Particle Size ◽

Hydraulic Conductivity ◽

Soil Water ◽

Hydraulic Properties ◽

Water Retention ◽

Sandy Loam ◽

Particle Sizes ◽

Soil Hydraulic Properties ◽

Soil Water Retention ◽

Soil Hydraulic

The physical properties of biochar have been shown to dramatically influence its performance as a soil amendment. Biochar particle size is one of key parameters, as it controls its specific surface area, shape, and pore distribution. Therefore, this study assessed the role of biochar particle size and hydrophobicity in controlling soil water movement and retention. Softwood pellet biochar in five particle size ranges (>2 mm, 2 &#8211; 0.5 mm, 0.5 &#8211; 0.25 mm, 0.25 &#8211; 0.063mm and <0.063 mm) was used for the experiment. These particle sizes were tested on 2 soil types (sandy loam and loamy sand) at four different application rates (1, 2, 4 and 8%).&#160; Our results showed that biochar hydrophobicity increased with decreasing biochar particle size, leading to a reduction in its water retention capacity. The effect of biochar on soil hydraulic properties varied with different rate of application and particle sizes. With increasing rate of application, water retention increased while hydraulic conductivity decreased. Water content at field capacity, permanent wilting point, and the available water content increased with increasing biochar particle size. The soil hydraulic conductivity increased with decreasing particle sizes apart from biochar particles <0.063mm which showed a significant (p&#8804;0.05) decrease compared to the larger particle sizes. The results clearly showed that both biochar intra-porosity and inter-porosity are important factors affecting soil hydraulic properties. Biochar interpores affected mainly hydraulic conductivity, both interpores and intrapores controlled soil water retention properties. Our results suggest that for a more effective increase in soil water retention in sandy loam and loamy sand, the use of hydrophilic biochar with high intra-porosity is recommended.

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