Extending established soil hydraulic property models by non-capillary water: A comprehensive model performance test

2021 ◽  
Author(s):  
Tobias L. Hohenbrink ◽  
Andre Peters ◽  
Sascha C. Iden ◽  
Wolfgang Durner
Keyword(s):  
Hydraulic Properties ◽  
Water Retention ◽  
Performance Test ◽  
Model Performance ◽  
Model System ◽  
Water Retention Curve ◽  
Comprehensive Model ◽  
Capillary Water ◽  
Retention Curve ◽  
Soil Hydraulic

<p>Understanding and describing the hydrologic function of soils requires adequate models of soil hydraulic properties. Established models for hydraulic properties implicitly assume that water flow occurs only in completely filled soil pores. This simplification is questionable in cases where soils become dry.  Lab measurements have repeatedly shown that under dry conditions, water retention and hydraulic conductivity are dominated by water in thin films. Today, there are some modelling approaches that take into account this so-called non-capillary water. One of these is the simple Peters-Durner-Iden model system (PDI), which extends any basic model of capillary retention and conductivity by a non-capillary counterpart. In the original form, this requires one additional fitting parameter to characterize the magnitude of non-capillary conductivity. Peters et al. (2021) have recently updated the model system (PDIc) to predict the non-capillary conductivity from the water retention curve without increasing the number of adjustable parameters compared to the established models.</p><p>In this contribution we present a comprehensive model performance test of the established capillary models, the original PDI model, and the new PDIc model. The performance test is based on a data collection of soil hydrological variables measured at 500 undisturbed soil samples. The collection contains soil water retention and conductivity data, determined in the laboratory by the evaporation method, supplemented by dew point method data and measurements of saturated conductivity. For each data set we estimated the soil hydraulic parameters for any combination of the three basic models: van Genuchten with m=1-1/n, van Genuchten with a free parameter m, and Fredlund & Xing and the three considerations of non-capillary water: not considered (no PDI), PDI, and PDIc.</p><p>The results showed that the most flexible basic functions generally yielded the best model fits. For example, the Fredlund & Xing model outperformed the two van Genuchten models. Considering non-capillary water by the PDI model system also clearly increased the model performance. The root mean squared errors (RMSE) for the fits of both the retention and the conductivity curve were clearly reduced in the order from no PDI to PDIc to PDI. Remarkably, the PDIc model generally achieved better fits than the established models although it has exactly the same free parameters.</p><p> </p><p>References<br>Peters, A., T.L. Hohenbrink, S.C. Iden, and W. Durner. A simple model to predict hydraulic conductivity in medium to dry soil from the water retention curve. Geophysical Research Abstracts Vol. 23, EGU21-8717, 2021.</p>

Testing an infiltrometer methodology to investigate water impact effects on both soil sealing and hydraulic properties of a loam soil under conventional tillage and no-tillage

2020 ◽  
Author(s):  
Mirko Castellini ◽  
Simone Di Prima ◽  
Anna Maria Stellacci ◽  
Massimo Iovino ◽  
Vincenzo Bagarello
Keyword(s):  
Hydraulic Conductivity ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Soil Management ◽  
Water Retention Curve ◽  
Soil Hydraulic Properties ◽  
Retention Curve ◽  
Soil Sealing ◽  
Loam Soil ◽  
Soil Hydraulic

<p>Testing new experimental procedures to assess the effects of the drops impact on the soil sealing formation is a main topic in soil hydrology.</p><p>In this field investigation, the methodological approach proposed first by Bagarello et al. (2014) was extended to account for a greater soil infiltration surface (i.e., about 3.5 times higher), a higher range and number of heights of water pouring and to evaluate the different impact on soil management. For this purpose, the effects of three water pouring heights (low, L=3 cm; medium, M=100 cm; high, H=200 cm) on both no-tilled (NT) and conventionally tilled (CT) loam soil were investigated by Beerkan infiltration runs and using the BEST-procedure of data analysis to estimate the soil hydraulic properties.</p><p>Final infiltration rate decreased when perturbing runs (i.e., M and H) were carried out as compared with the non-perturbing (L) ones (by a factor of 1.5-3.1 under NT and 3.4-4.4 under CT). Similarly, the water retention scale parameter, h<sub>g</sub>, increased (i.e., higher in absolute terms) by a factor 1.6-1.8 under NT and by a factor 1.7 under CT. Saturated hydraulic conductivity, K<sub>s</sub>, changed significantly as a function of the increase of water pouring height; regardless of the soil management, perturbing runs caused a reduction in soil permeability by a factor 5 or 6. Effects on hydraulic functions (i.e., soil water retention curve and hydraulic conductivity function), obtained with the BEST-Steady algorithm, were also highlighted. For instance, differences in water retention curve at fixed soil pressure head values (i.e., field capacity, FC, and permanent wilting point, PWP) due to perturbing and non-perturbing runs, were estimated as higher under NT (3.8%) than CT (3.4%) for FC, and equal to 2.1% or 1.6% for PWP.</p><p>Main results of this investigation confirm that a recently tilled loamy soil, without vegetation cover, can be less resilient as compared to a no-tilled one, and that tested water pouring heights methodology looks promising to mimic effects of high energy rainfall events and to quantify the soil sealing effects under alternative management of the soil.</p><p><strong>Acknowledgments</strong></p><p>The work was supported by the project “STRATEGA, Sperimentazione e TRAsferimento di TEcniche innovative di aGricoltura conservativA”, funded by Regione Puglia–Dipartimento Agricoltura, Sviluppo Rurale ed Ambientale, CUP: B36J14001230007.</p><p><strong> </strong><strong>References</strong></p><p>Bagarello, V., Castellini, M., Di Prima, S., Iovino, M. 2014. Soil hydraulic properties determined by infiltration experiments and different heights of water pouring. Geoderma, 213, 492–501. https://doi.org/10.1016/j.geoderma.2013.08.032</p>

Experiments and interpretations on unsaturated hydraulic properties using water retention tests based on the membrane in Korea

2020 ◽  
Author(s):  
Seboong Oh ◽  
Sungjin Kim ◽  
Kwang Ik Son
Keyword(s):  
Unsaturated Soils ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Void Ratio ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Huge Amount ◽  
Retention Curve ◽  
Hydraulic Behavior

<p>In unsaturated soils, the soil water retention curve (SWRC) is most important in the fundamental hydraulic properties. In order to measure SWRCs through an alternative method in Korea, high air entry disks were replaced by micro membranes. Micro membranes are thin in which the air entry value is around 100kPa. Tests with the membrane are fast to reduce the duration of infiltration through the high air entry disk.</p><p>The water retention curves using the membrane were compared with the data using high air entry disks from the volumetric pressure plate extractor and Tempe pressure cell for samples of various sites. As a result, the SWRCs using the membrane were very similar for most cases and the micro membrane was verified as a useful tool to measure SWRCs.</p><p>The unsaturated hydraulic behavior could be measured easily using the membrane than ceramic disks and the huge amount of data could have been obtained in Korea. Using DB of SWRCs, the hydraulic properties were interpreted based on the parameters of the van Genuchten SWRC model. The void ratio and density are correlated to SWRCs under the same classification soil.</p><p><strong>Acknowledgements</strong> This research is supported by grant from Korean NRF (2019R1A2C1003604) and MOE (79608), which are greatly appreciated.</p>

Predicting water retention curves of fine texture soils from particle size distribution

2020 ◽  
Author(s):  
Joseph Pollacco ◽  
Jesús Fernández-Gálvez ◽  
Sam Carrick
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Pore Space ◽  
Water Retention Curve ◽  
Soil Hydraulic Properties ◽  
Retention Curve ◽  
Soil Particles

<p>Indirect methods for estimating soil hydraulic properties from particle size distribution have been developed due to the difficulty in accurately determining soil hydraulic properties, and the fact that particle size distribution is one piece of basic soil physical information normally available. The similarity of the functions describing the cumulative distribution of particle size and pore size in the soil has been the basis for relating particle size distribution and the water retention function in the soil. Empirical and semi-physical models have been proposed, but these are based on strong assumptions that are not always valid. For example, soil particles are normally assumed to be spherical, with constant density regardless of their size; and the soil pore space has been described by an assembly of capillary tubes, or the pore space in the soil matrix is assumed to be arranged in a similar way regardless of particle size. However, in a natural soil the geometry of the pores may vary with the size of the particles, leading to a variable relation between particle radius and pore radius.</p><p> </p><p>The current work is based on the hypothesis that the geometry of the pore size and the void ratio depends on the size of the soil particles, and that a physically based model can be generalised to predict the water retention curve from particle size distribution. The rearrangement of the soil particles is considered by introducing a mixing function that modulates the cumulative particle size distribution, while the total porosity is constrained by the saturated water content.</p><p> </p><p>The model performance is evaluated by comparing the soil water retention curve derived from laboratory measurements with a mean Nash–Sutcliffe model efficiency a value of 0.92 and a standard deviation of 0.08. The model is valid for all soil types, not just those with a marginal clay fraction.</p>

Impact of plant roots and soil organisms on soil micromorphology and hydraulic properties

Biologia ◽  
2006 ◽  
Vol 61 (19) ◽  
Author(s):  
Radka Kodešová ◽  
Vít Kodeš ◽  
Anna Žigová ◽  
Jiří Šimůnek
Keyword(s):  
Pore Structure ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Water Retention Curve ◽  
Soil Organisms ◽  
Soil Hydraulic Properties ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve ◽  
The Impact

AbstractA soil micromorphological study was performed to demonstrate the impact of soil organisms on soil pore structure. Two examples are shown here. First, the influence of earthworms, enchytraeids and moles on the pore structure of a Greyic Phaeozem is demonstrated by comparing two soil samples taken from the same depth of the soil profile that either were affected or not affected by these organisms. The detected image porosity of the organism-affected soil sample was 5 times larger then the porosity of the not-affected sample. The second example shows macropores created by roots and soil microorganisms in a Haplic Luvisol and subsequently affected by clay coatings. Their presence was reflected in the soil water retention curve, which displayed multiple S-shaped features as obtained from the water balance carried out for the multi-step outflow experiment. The dual permeability models implemented in HYDRUS-1D was applied to obtain parameters characterizing multimodal soil hydraulic properties using the numerical inversion of the multi-step outflow experiment.

Soil-water retention curve model for fine-grained soils accounting for void ratio-dependent capillarity

2021 ◽  
Author(s):  
Jiangu Qian ◽  
Zhiqiang Lin ◽  
Zhenhao Shi
Keyword(s):  
Volume Change ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Void Ratio ◽  
Water Retention Curve ◽  
Capillary Water ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve ◽  
Fine Grained

This paper presents a soil-water retention curve (SWRC) model for fine-grained soils. Compared with existing studies, the proposed model accounts for the distinct roles of the volume change of soils on capillarity and adsorption mechanisms. The capillary water is described by a relation that includes the characteristics of the pore-size distributions as parameters, while the absorbed water is modeled by a novel proposition that both considers the phenomenon of capillary condensation and allows for the decoupling between the degree of capillary and adsorptive saturation. Based on this feature, the void ratio effects are considered in a way in which they only affect capillary water, i.e., consistent with how volume change influences soil microstructures. The relative contributions of void ratio effects and hydraulic hysteresis on the path- and history-dependence of SWRC in Sr-s-e space for deformable unsaturated soils are examined. The significance of discriminating the effects of volume change on capillary and adsorptive water is illustrated by applying the SWRC model to computing the shear strength of unsaturated soils with different void ratios. The model performance is assessed by comparing against test data reported for four types of fine-grained soils and that tested for natural loess in this work.

scholarly journals Further tests of the HYPROP evaporation method for estimating the unsaturated soil hydraulic properties

2018 ◽  
Vol 66 (2) ◽  
pp. 161-169 ◽  
Author(s):  
Camila R. Bezerra-Coelho ◽  
Luwen Zhuang ◽  
Maria C. Barbosa ◽  
Miguel Alfaro Soto ◽  
Martinus Th. van Genuchten
Keyword(s):  
Hydraulic Conductivity ◽  
Unsaturated Soil ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Measurement Techniques ◽  
Richards Equation ◽  
Water Retention Curve ◽  
Soil Hydraulic Properties ◽  
Evaporation Method ◽  
Soil Hydraulic

AbstractMany soil, hydrologic and environmental applications require information about the unsaturated soil hydraulic properties. The evaporation method has long been used for estimating the drying branches of the soil hydraulic functions. An increasingly popular version of the evaporation method is the semi-automated HYPROP©measurement system (HMS) commercialized by Decagon Devices (Pullman, WA) and UMS AG (München, Germany). Several studies were previously carried out to test the HMS methodology by using the Richards equation and the van-Genuchten-Mualem (VG) or Kosugi-Mualem soil hydraulic functions to obtain synthetic data for use in the HMS analysis, and then to compare results against the original hydraulic properties. Using HYDRUS-1D, we carried out independent tests of the HYPROP system as applied to the VG functions for a broad range of soil textures. Our results closely agreed with previous findings. Accurate estimates were especially obtained for the soil water retention curve and its parameters, at least over the range of available retention measurements. We also successfully tested a dual-porosity soil, as well as an extremely coarse medium with a very high van Genuchtennvalue. The latter case gave excellent results for water retention, but failed for the hydraulic conductivity. In many cases, especially for soils with intermediate and highnvalues, an independent estimate of the saturated hydraulic conductivity should be obtained. Overall, the HMS methodology performed extremely well and as such constitutes a much-needed addition to current soil hydraulic measurement techniques.

scholarly journals Artificial Neural Networks for Predicting the Water Retention Curve of Sicilian Agricultural Soils

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1431 ◽  
Author(s):  
Alessandro D’Emilio ◽  
Rosa Aiello ◽  
Simona Consoli ◽  
Daniela Vanella ◽  
Massimo Iovino
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Soil Water ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Water Retention Curve ◽  
Retention Data ◽  
Soil Hydraulic Properties ◽  
Retention Curve ◽  
Artificial Neural

Modeling soil-water regime and solute transport in the vadose zone is strategic for estimating agricultural productivity and optimizing irrigation water management. Direct measurements of soil hydraulic properties, i.e., the water retention curve and the hydraulic conductivity function, are often expensive and time-consuming, and represent a major obstacle to the application of simulation models. As a result, there is a great interest in developing pedotransfer functions (PTFs) that predict the soil hydraulic properties from more easily measured and/or routinely surveyed soil data, such as particle size distribution, bulk density (ρb), and soil organic carbon content (OC). In this study, application of PTFs was carried out for 359 Sicilian soils by implementing five different artificial neural networks (ANNs) to estimate the parameter of the van Genuchten (vG) model for water retention curves. The raw data used to train the ANNs were soil texture, ρb, OC, and porosity. The ANNs were evaluated in their ability to predict both the vG parameters, on the basis of the normalized root-mean-square errors (NRMSE) and normalized mean absolute errors (NMAE), and the water retention data. The Akaike’s information criterion (AIC) test was also used to assess the most efficient network. Results confirmed the high predictive performance of ANNs with four input parameters (clay, sand, and silt fractions, and OC) in simulating soil water retention data, with a prediction accuracy characterized by MAE = 0.026 and RMSE = 0.069. The AIC efficiency criterion indicated that the most efficient ANN model was trained with a relatively low number of input nodes.

scholarly journals Effect of Chia Seed Mucilage on the Rhizosphere Hydraulic Characteristics

2021 ◽  
Vol 13 (6) ◽  
pp. 3303
Author(s):  
Faisal Hayat ◽  
Mohanned Abdalla ◽  
Muhammad Usman Munir
Keyword(s):  
Hydraulic Conductivity ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Numerical Models ◽  
Chemical Properties ◽  
Water Retention Curve ◽  
Soil Drying ◽  
Retention Curve ◽  
Unsaturated Hydraulic Conductivity ◽  
Chia Seed

The rhizosphere is one of the major components in the soil–plant–atmosphere continuum which controls the flow of water from the soil into roots. Plant roots release mucilage in the rhizosphere which is capable of altering the physio-chemical properties of this region. Here, we showed how mucilage impacted on rhizosphere hydraulic properties, using simple experiments. An artificial rhizosphere, treated or not with mucilage, was placed in a soil sample and suction was applied to mimic the negative pressure in plant xylem. The measured water contents and matric potential were coupled with numerical models to estimate the water retention curve and hydraulic conductivity. A slower loss of water was observed in the treated scenario which resulted in an increase in water retention. Moreover, a slightly lower hydraulic conductivity was initially observed in the treated scenario (8.44 × 10−4 cm s−1) compared to the controlled one in saturated soil. Over soil drying, a relatively higher unsaturated hydraulic conductivity was observed. In summary, we demonstrated that mucilage altered the rhizosphere hydraulic properties and enhanced the unsaturated hydraulic conductivity. These findings improve our understanding of how plants capture more water, and postulate that mucilage secretion could be an optimal trait for plant survival during soil drying.

scholarly journals Soil physical and hydraulic properties in the Donato stream basin, RS, Brazil. Part 2: Geostatistical simulation

2019 ◽  
Vol 23 (9) ◽  
pp. 675-680
Author(s):  
Tirzah M. Siqueira ◽  
José A. S. Louzada ◽  
Olavo C. Pedrollo ◽  
Nilza M. dos R. Castro ◽  
Marquis H. C. de Oliveira
Keyword(s):  
Soil Water ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Geostatistical Simulation ◽  
Sequential Gaussian Simulation ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve ◽  
Gaussian Simulation

ABSTRACT Geostatistical simulation has been the most promising and used technique for the analysis of uncertainties of soil physical and hydraulic properties, with high spatial heterogeneity. This study carried out a stochastic analysis of saturated hydraulic conductivity (Ksat) and soil water retention curve parameters in the Donato stream basin, located in the municipality of Pejuçara, in the state of Rio Grande do Sul, Brazil, with geographic coordinates between 28º 25’ 34” S and 53º 40’ 30” W, and 28º 24’ 50” S and 53º 41’ 30” W, 590 m of altitude. Soil samples were collected during the period from August to November of 2012. Sequential Gaussian simulation technique was used to generate 100 random fields of each variable. The results showed great uncertainties for Ksat and the parameter α of the soil water retention curve. The uncertainties between the percentiles 5 and 95% for Ksat indicated values from 24 to 44 cm d-1, and for the parameter α, the uncertainties could be estimated from 0.622 to 1.122 cm-1.

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