Influence of water content and soil properties on unsaturated hydraulic conductivity of some red and black soils

1979 ◽  
Vol 142 (1) ◽  
pp. 99-108 ◽  
Author(s):  
D. Bhatnagar ◽  
Y. Nagarajarao ◽  
R. P. Gupta
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Properties ◽  
Water Content ◽  
Unsaturated Hydraulic Conductivity ◽  
Influence Of Water

Hyphal colonization of Rhizophagus irregularis increases unsaturated hydraulic conductivity of a loamy sand distant from roots

2021 ◽  
Author(s):  
Michael Bitterlich ◽  
Richard Pauwels
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Hydraulic Properties ◽  
Volumetric Water Content ◽  
Rhizophagus Irregularis ◽  
Loamy Sand ◽  
Soil Hydraulic Properties ◽  
Unsaturated Hydraulic Conductivity ◽  
Soil Hydraulic ◽  
Root Exclusion

<p>Hydraulic properties of mycorrhizal soils have rarely been reported and difficulties in directly assigning potential effects to hyphae of arbuscular mycorrhizal fungi (AMF) arise from other consequences of AMF being present, i.e. their influence on growth and water consumption rates of their host plants that both also influence soil hydraulic properties.</p><p>We assumed that the typical nylon meshes used for root-exclusion experiments in mycorrhizal research can provide a dynamic hydraulic barrier. It is expected that the uniform pore size of the rigid meshes causes a sudden hydraulic decoupling of the enmeshed inner volume from the surrounding soil as soon as the mesh pores become air-filled. Growing plants below the soil moisture threshold for hydraulic decoupling would minimize plant-size effects on root-exclusion compartments and allow for a more direct assignment of hyphal presence to modulations in soil hydraulic properties.</p><p>We carried out water retention and hydraulic conductivity measurements with two tensiometers introduced in two different heights in a cylindrical compartment (250 cm³) containing a loamy sand, either with or without the introduction of a 20 µm nylon mesh equidistantly between the tensiometers. Introduction of a mesh reduced hydraulic conductivity across the soil volumes by two orders of magnitude from 471 to 6 µm d<sup>-1</sup> at 20% volumetric water content.</p><p>We grew maize plants inoculated or not with Rhizophagus irregularis in the same soil in pots that contained root-exclusion compartments while maintaining 20% volumetric water content. When hyphae were present in the compartments, water potential and unsaturated hydraulic conductivity increased for a given water content compared to compartments free of hyphae. These differences increased with progressive soil drying.</p><p>We conclude that water extractability from soils distant to roots can be facilitated under dry conditions when AMF hyphae are present.</p><p> </p>

scholarly journals A numerical study on the effect of salinity on stability of an unsaturated railway embankment under rainfall

2020 ◽  
Vol 195 ◽  
pp. 01004
Author(s):  
Ali Kolahdooz ◽  
Hamed Sadeghi ◽  
Mohammad Mehdi Ahmadi
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Water ◽  
Water Retention ◽  
Numerical Study ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Unsaturated Hydraulic Conductivity ◽  
Influence Of Water ◽  
Dispersive Soils

Dispersive soils, as one of the main categories of problematic soils, can be found in some parts of the earth, such as the eastern-south of Iran, nearby the Gulf of Oman. One of the most important factors enhancing the dispersive potential is the existence of dissolved salts in the soil water. The main objective of this study is to explore the influence of water salinity on the instability of a railway embankment due to rainfall infiltration. In order to achieve this goal, the embankment resting on a dispersive stratum is numerically modeled and subjected to transient infiltration flow. The effect of dispersion is simplified through variations in the soil-water retention curve with salinity. The measured water retention curves revealed that by omitting the natural salinity in the soil-water, the retention capability of the soil decreases; therefore, the unsaturated hydraulic conductivity of the soil stratum will significantly decline. According to the extensive decrease in the hydraulic conductivity of the desalinated materials, the rainfall cannot infiltrate in the embankment and the rainfall mostly runs off. However, in the saline embankment, the infiltration decreases the soil suction; and consequently, the factor of safety of the railway embankment decreases.

Estimation of hydraulic conductivity of unsaturated soils using a geotechnical centrifuge

2002 ◽  
Vol 39 (3) ◽  
pp. 684-694 ◽  
Author(s):  
D N Singh ◽  
Sneha J Kuriyan
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Soil Sample ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Soil Hydraulic Conductivity ◽  
Centrifuge Testing ◽  
Geotechnical Centrifuge ◽  
Silty Soil ◽  
Unsaturated Hydraulic Conductivity

A saturated silty soil sample is centrifuged in a geotechnical centrifuge to create an unsaturated state. The change in water content of the soil sample is recorded at different points along the length of the sample to obtain the water-content profile, which is then used to obtain the unsaturated hydraulic conductivity of the soil sample. These hydraulic conductivity values are compared with those obtained and reported by previous researchers by conducting accelerated falling-head tests on this soil sample in a centrifuge. The study demonstrates the use of centrifugation techniques to obtain hydraulic conductivities of unsaturated soils.Key words: silty soil, saturated soil, unsaturated soil, hydraulic conductivity, centrifuge testing.

scholarly journals Spatial distribution of argan tree influence on soil properties in southern Morocco

SOIL ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 511-524
Author(s):  
Mario Kirchhoff ◽  
Tobias Romes ◽  
Irene Marzolff ◽  
Manuel Seeger ◽  
Ali Aït Hssaine ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Seedling Survival ◽  
Drip Line ◽  
Soil Parameters ◽  
Wind Drift ◽  
Argan Tree ◽  
Unsaturated Hydraulic Conductivity

Abstract. The endemic argan tree (Argania spinosa) populations in southern Morocco are highly degraded due to overbrowsing, illegal firewood extraction and the expansion of intensive agriculture. Bare areas between the isolated trees increase due to limited regrowth; however, it is unknown if the trees influence the soil of the intertree areas. Hypothetically, spatial differences in soil parameters of the intertree area should result from the translocation of litter or soil particles (by runoff and erosion or wind drift) from canopy-covered areas to the intertree areas. In total, 385 soil samples were taken around the tree from the trunk along the tree drip line (within and outside the tree area) and the intertree area between two trees in four directions (upslope, downslope and in both directions parallel to the slope) up to 50 m distance from the tree. They were analysed for gravimetric soil water content, pH, electrical conductivity, percolation stability, total nitrogen content (TN), content of soil organic carbon (SOC) and C/N ratio. A total of 74 tension disc infiltrometer experiments were performed near the tree drip line, within and outside the tree area, to measure the unsaturated hydraulic conductivity. We found that the tree influence on its surrounding intertree area is limited, with, e.g., SOC and TN content decreasing significantly from tree trunk (4.4 % SOC and 0.3 % TN) to tree drip line (2.0 % SOC and 0.2 % TN). However, intertree areas near the tree drip line (1.3 % SOC and 0.2 % TN) differed significantly from intertree areas between two trees (1.0 % SOC and 0.1 % TN) yet only with a small effect. Trends for spatial patterns could be found in eastern and downslope directions due to wind drift and slope wash. Soil water content was highest in the north due to shade from the midday sun; the influence extended to the intertree areas. The unsaturated hydraulic conductivity also showed significant differences between areas within and outside the tree area near the tree drip line. This was the case on sites under different land usages (silvopastoral and agricultural), slope gradients or tree densities. Although only limited influence of the tree on its intertree area was found, the spatial pattern around the tree suggests that reforestation measures should be aimed around tree shelters in northern or eastern directions with higher soil water content or TN or SOC content to ensure seedling survival, along with measures to prevent overgrazing.

euptfv2: updated hydraulic pedotransfer functions for Europe

2021 ◽  
Author(s):  
Brigitta Szabó ◽  
Melanie Weynants ◽  
Tobias Weber
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Properties ◽  
Water Content ◽  
Hydraulic Properties ◽  
Field Capacity ◽  
Pedotransfer Functions ◽  
Predictor Variables ◽  
Soil Hydraulic Properties ◽  
Matric Potential ◽  
Soil Hydraulic

<p>We present improved European hydraulic pedotransfer functions (PTFs) which now use the machine learning algorithm random forest and include prediction uncertainties. The new PTFs (euptfv2) are an update of the previously published euptfv1 (Tóth et al., 2015). With the derived hydraulic PTFs soil hydraulic properties and van Genuchten-Mualem model parameters can be predicted from easily available soil properties. The updated PTFs perform significantly better than euptfv1 and are applicable for 32 predictor variables combinations. The uncertainties reflect uncertainties from the considered input data, predictors and the applied algorithm. The euptfv2 includes transfer functions to compute soil water content at saturation (0 cm matric potential head), field capacity (both -100 and -330 cm matric potential head) and wilting point (-15,000 cm matric potential head), plant available water content computed with field capacity at -100 and -330 cm matric potential head, saturated hydraulic conductivity, and Mualem-van Genuchten parameters of the moisture retention and hydraulic conductivity curves. The influence of predictor variables on predicted soil hydraulic properties is explored and suggestions to best predictor variables given.</p><p>The algorithms have been implemented in a web interface (https://ptfinterface.rissac.hu) and an R package (https://doi.org/10.5281/ZENODO.3759442) to facilitate the use of the PTFs, where the PTFs’ selection is automated based on soil properties available for the predictions and required soil hydraulic property.</p><p>The new PTFs will be applied to derive soil hydraulic properties for field- and catchment- scale hydrological modelling in European case studies of the OPTAIN project (https://www.optain.eu/). Functional evaluation of the PTFs is performed under the iAqueduct research project.</p><p> </p><p>This research has been supported by the Hungarian National Research, Development and Innovation Office (grant no. KH124765), the János Bolyai Research Scholarship of the Hungarian Academy of Sciences (grant no. BO/00088/18/4), and the German Research Foundation (grant no. SFB 1253/12017). OPTAIN is funded by the European Union’s Horizon 2020 Program for research and innovation under Grant Agreement No. 862756.</p>

Finite formulation for the computation of sorptivity

2020 ◽  
Author(s):  
Pierre-Emmanuel Peyneau ◽  
Laurent Lassabatere ◽  
Joseph Pollacco ◽  
Jesús Fernández-Gálvez ◽  
Borja Latorre ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Water Retention ◽  
Water Pressure ◽  
Pressure Head ◽  
Concentration Function ◽  
Point Of View ◽  
Water Infiltration ◽  
Unsaturated Hydraulic Conductivity ◽  
Flux Concentration

<p>Soil sorptivity is one of the key hydraulic parameters for modelling water infiltration into soil. It quantifies the capacity of a soil to infiltrate water by capillarity. Several formulations, based on various models, have been proposed to compute it from the water retention and the unsaturated hydraulic conductivity functions. All these formulations use the integration of the product of either the hydraulic conductivity or diffusivity function with the flux concentration function. The integration can be performed either over an interval of water pressure head or water content, yielding two equal values. However, the expression of the integral as a function of water pressure head may involve a huge or even infinite interval, which can be numerically difficult to handle. In opposite, the expression of the integral as a function of water content involves the integration of a diverging function (diffusivity) over a large interval, which is also troublesome from a numerical point of view. In this paper, we provide a new expression for sorptivity by cutting the integral in two parts, in order to involve only the integration of a finite function over a finite interval. The dependency of the integral on the flux concentration function is also investigated.</p>

scholarly journals Determining the Unsaturated Hydraulic Conductivity of Remoulded Loess with Filter Paper Method and Soil Column Seepage Test

2021 ◽  
Author(s):  
Wenwu Chen ◽  
Quanquan Jia ◽  
Peng Liu ◽  
Yanmei Tong
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Filter Paper ◽  
Characteristic Curve ◽  
Soil Column ◽  
Volumetric Water Content ◽  
Experimental Results ◽  
Paper Test ◽  
Unsaturated Hydraulic Conductivity ◽  
The One

Abstract Loess is very widely distributed, and the unsaturated hydraulic conductivity of loess is related to many engineering issues. In order to determine the unsaturated hydraulic conductivity of remolded loess more conveniently and at a lower cost, filter paper test and soil column seepage test were carried out. The results indicate that in the one-dimensional soil column seepage process, the unsaturated hydraulic conductivity of loess increases with the increase of the volumetric water content, and as the seepage time continues, the unsaturated hydraulic conductivity of loess at different depths gradually becomes uniform. The changes in the microstructure indicate that the collapsible settlement will occur during the seepage process, which will reduce the unsaturated hydraulic conductivity of the underlying loess to a certain extent. Compared with the experimental results, the soil hydraulic conductivity curve (SHCC) obtained by the van Genuchten-Mualem model (VG-M model) underestimates the magnitude of unsaturated hydraulic conductivity in the part with a low volumetric water content (< 20%). and the Childs ༆ Collis-George model (CCG model) has more consistent results with the experimental results because it is based on more segments of the soil-water characteristic curve (SWCC).

Application of the Groenevelt - Grant soil water retention model to predict the hydraulic conductivity

Soil Research ◽  
2010 ◽  
Vol 48 (5) ◽  
pp. 447 ◽  
Author(s):  
C. D. Grant ◽  
P. H. Groenevelt ◽  
N. I. Robinson
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Water Retention ◽  
Soil Water Retention ◽  
Retention Model ◽  
Unsaturated Hydraulic Conductivity ◽  
Incomplete Gamma Functions ◽  
Relative Water ◽  
Van Genuchten Model ◽  
Conductivity Function

We outline several formulations of the Groenevelt–Grant water retention model of 2004 to show how it can be anchored at different points. The model is highly flexible and easy to perform multiple differentiations and integrations on. Among many possible formulations of the model we choose one anchored solely at the saturated water content, θs, to facilitate comparison with the van Genuchten model of 1980 and to obtain a hydraulic conductivity function through analytical integration: where, k0, k1, and n are fitting parameters. We divided this formulation by θs to obtain the relative water content, θr(h), and inverted the function to produce a form required for integration, namely: in which the parameter β is introduced to accommodate both the ‘Burdine’ and ‘Mualem’ models. The integrals are identified as incomplete gamma functions and are distinctly different from the incomplete beta functions embodied in the van Genuchten–Mualem models. Rijtema’s data from 1969 for 20 Dutch soils are used to demonstrate the procedures involved. The water retention curves produced by our Groenevelt–Grant model are virtually indistinguishable from those produced by the van Genuchten model. Relative hydraulic conductivities produced by our Mualem and Burdine models produced closer estimates of Rijtema’s measured values than those produced by the van Genuchten–Mualem model for 19 of his 20 soils. This work provides an alternative to the widely used van Genuchten–Mualem approach and represents a preamble for the, as yet unsatisfactory, treatment of the tortuosity component of the unsaturated hydraulic conductivity function.

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