The Development of a One-Parameter Model for the Soil-Water Characteristic Curve in Loess Gully Regions

2012 ◽  
Vol 256-259 ◽  
pp. 488-493
Author(s):  
Xiao Yu Song ◽  
Huai You Li ◽  
Wen Juan Shi
Keyword(s):  
Soil Water ◽  
Hydraulic Properties ◽  
Characteristic Curve ◽  
Soil Samples ◽  
Soil Hydraulic Properties ◽  
Logarithmic Model ◽  
Soil Water Characteristic Curve ◽  
Soil Water Characteristic Curves ◽  
Best Fit ◽  
Gardner Model

It is important to understand soil hydraulic properties in order to predict the movement of water and solutes such as pollutants. To this end, 55 soil samples were collected from different areas of the Nanxiaohegou basin and used to generate soil-water characteristic curves. These were then fitted using the power-, exponential-, and logarithmic versions of the Gardner model; the logarithmic model yielded the best fit overall. The logarithmic model was further simplified to yield a one-parameter model for estimating the soil-water characteristic curve within the basin, and it was demonstrated that the value of the single parameter is dependent on the topography and usage of the land.

scholarly journals Performance Evaluation of Four-Parameter Models of the Soil-Water Characteristic Curve

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Siti Jahara Matlan ◽  
Muhammad Mukhlisin ◽  
Mohd Raihan Taha
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Data Sets ◽  
Modified Model ◽  
Soil Water Characteristic Curve ◽  
Geoenvironmental Engineering ◽  
Wide Range ◽  
Soil Water Characteristic Curves ◽  
Model Equations ◽  
Exponential Variable

Soil-water characteristic curves (SWCCs) are important in terms of groundwater recharge, agriculture, and soil chemistry. These relationships are also of considerable value in geotechnical and geoenvironmental engineering. Their measurement, however, is difficult, expensive, and time-consuming. Many empirical models have been developed to describe the SWCC. Statistical assessment of soil-water characteristic curve models found that exponential-based model equations were the most difficult to fit and generally provided the poorest fit to the soil-water characteristic data. In this paper, an exponential-based model is devised to describe the SWCC. The modified equation is similar to those previously reported by Gardner (1956) but includes exponential variable. Verification was performed with 24 independent data sets for a wide range of soil textures. Prediction results were compared with the most widely used models to assess the model’s performance. It was proven that the exponential-based equation of the modified model provided greater flexibility and a better fit to data on various types of soil.

Measurement of soil hydraulic properties of structured and repacked soils

2021 ◽  
Author(s):  
Urša Pečan ◽  
Luka Žvokelj ◽  
Jure Ferlin ◽  
Vesna Zupanc ◽  
Marina Pintar
Keyword(s):  
Soil Water ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Soil Samples ◽  
Measuring System ◽  
Soil Hydraulic Properties ◽  
Soil Water Retention ◽  
Undisturbed Soil ◽  
Soil Hydraulic ◽  
Low Tension

<p>Soil hydraulic properties provide important information about soil behavior under unsaturated and saturated conditions. Often sampling of undisturbed soils is not possible and soil samples have to be repacked for laboratory analysis. The HYPROP® measuring system (METERgroup, Munich, Germany) is a convenient method for determination of soil water retention characteristics and unsaturated hydraulic conductivity of undisturbed soil samples. It measures the matric potential of the saturated and drying soil sample using two tensiometers placed at different depths. Although the tensiometers are based on a new design that theoretically withstands cavitation at higher tension values, they are still considered to operate in the low tension range. Since soil water retention properties in the low tension range are strongly influenced by soil structure and pore size distribution, we were interested in the changes in hydraulic properties when measured on disturbed and then repacked samples, and undisturbed soil samples. Therefore, we investigated the soil hydraulic properties of three different soil types using the evaporation method on undisturbed and repacked samples. The results provide important insights for the interpretation of the results when the collection of undisturbed samples is not possible, and for designing laboratory experiments with repacked soils.</p>

Experimental Study on Soil Water Characteristic Curve of Compacted Unsaturated Soil

2010 ◽  
Vol 168-170 ◽  
pp. 1285-1288
Author(s):  
Dong Lin Wang
Keyword(s):  
Soil Water ◽  
Influencing Factors ◽  
Unsaturated Soils ◽  
Stress Condition ◽  
Characteristic Curve ◽  
External Stress ◽  
Method Of Least Squares ◽  
Soil Water Characteristic Curve ◽  
Triaxial Apparatus ◽  
Soil Water Characteristic Curves

Soil water characteristic curve is one of important topics of unsaturated soils. Pressure plate extractor and GDS unsaturated triaxial apparatus are used to study influencing factors including types of soils and net mean stress. Through method of least-squares, Fredlund five-parameter model were employed to fit soil-water characteristic curves. The results show that model provided a satisfactory fit to the experimental data. Through an analysis of influencing factors, we find that not only physical condition of samples but also external stress condition can affect the shape of soil water characteristic curve.

Statistical assessment of soil-water characteristic curve models for geotechnical engineering

2001 ◽  
Vol 38 (6) ◽  
pp. 1297-1313 ◽  
Author(s):  
W Scott Sillers ◽  
Delwyn G Fredlund
Keyword(s):  
Soil Water ◽  
Akaike Information Criterion ◽  
Characteristic Curve ◽  
Information Criterion ◽  
Soil Suction ◽  
Data Sets ◽  
Empirical Equations ◽  
Soil Water Characteristic Curve ◽  
The Relationship ◽  
Best Fit

A number of empirical equations have been proposed for the soil-water characteristic curve. A nonlinear, least squares method was used to determine best-fit parameters for several empirical equations that were best-fit to 230 water content versus soil suction data sets. In addition, two proposed correction methods to accommodate high soil suctions up to 1 000 000 kPa were applied to the various soil-water characteristic curve equations. The data sets of water content versus soil suction were arranged into one of the USDA soil classifications based on their relative amounts of sand, silt, and clay (only eight soil classifications had sufficient data for later analysis). The quality of fit for each model was compared using the Akaike Information Criterion. A series of conclusions were arrived at regarding (i) the relationship between two- and three-parameter equations, (ii) the relationship between exponential and sigmoidal type equations, and (iii) the value of correction factors for the high soil suction range.Key words: soil-water characteristic curve, unsaturated soil, soil suction, regression analysis, SWCC models, Akaike Information Criterion.

scholarly journals Spatial variability of the parameters of soil-water characteristic curves in gravel-mulched fields

2019 ◽  
Vol 20 (1) ◽  
pp. 231-239
Author(s):  
Wenju Zhao ◽  
Taohong Cao ◽  
Zongli Li ◽  
Yu Su ◽  
Zhiwei Bao
Keyword(s):  
Spatial Variability ◽  
Soil Water ◽  
Water Retention ◽  
Characteristic Curve ◽  
Model Parameters ◽  
Soil Hydraulic Properties ◽  
Geostatistical Methods ◽  
Classical Statistics ◽  
Van Genuchten Model ◽  
Soil Water Characteristic Curves

Abstract Knowledge of the soil-water characteristic curve (SWCC) and its spatial variability is essential for many agricultural, environmental, and engineering applications. We analyzed the spatial variability of the parameters of SWCC in gravel-mulched fields using classical statistics and geostatistical methods. Soil samples were collected from the layer in 64 evenly distributed 1 × 1 m quadrats 4 m apart, center to center. SWCC in the gravel-mulched fields could be fitted well by both the van Genuchten and Brooks–Corey models, but the fit was better with the van Genuchten model. The type of fitting three parameters was tested. The model parameters θs and n of each type of soil were weakly variable, and α was moderately variable. The results indicate that the gravel-mulched field has better water retention, and the water retention effect of the new gravel-mulched fields is most obvious. The spatial variation of the parameters in SWCC can therefore be used to infer soil hydraulic properties, which is important for simplifying the calculation of SWCC and quantitatively determining the retention of soil water and for managing the capacity of soil to retain water in gravel-mulched fields in arid regions.

Measurement of soil-water characteristic curves for fine-grained soils using a small-scale centrifuge

2002 ◽  
Vol 39 (5) ◽  
pp. 1209-1217 ◽  
Author(s):  
R M Khanzode ◽  
S K Vanapalli ◽  
D G Fredlund
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Characteristic Curve ◽  
Small Scale ◽  
Characteristic Curves ◽  
Pressure Plate ◽  
Soil Water Characteristic Curve ◽  
Fine Grained ◽  
Soil Water Characteristic Curves ◽  
Plate Apparatus

Considerably long periods of time are required to measure soil-water characteristic curves using conventional equipment such as pressure plate apparatus or a Tempe cell. A commercially available, small-scale medical centrifuge with a swinging type rotor assembly was used to measure the soil-water characteristic curves on statically compacted, fine-grained soil specimens. A specimen holder was specially designed to obtain multiple sets of water content versus suction data for measuring the soil-water characteristic curve at a single speed of rotation of the centrifuge. The soil-water characteristic curves were measured for three different types of fine-grained soils. The three soils used in the study were processed silt (liquid limit, wL = 24%; plasticity index, Ip = 0; and clay = 7%), Indian Head till (wL = 35.5%, Ip = 17%, and clay = 30%), and Regina clay (wL = 75.5%, Ip = 21%, and clay = 70%). The soil-water characteristic curves for the above soils were measured in 0.5, 1, and 2 days, respectively, using the centrifuge technique for suction ranges from 0 to 600 kPa. Time periods of 2, 4–6, and 16 weeks were required for measuring the soil-water characteristic curves for the same soils using a conventional pressure plate apparatus. There is reasonably good agreement between the experimental results obtained by the centrifuge and the pressure plate methods. The results of this study are encouraging as soil-water characteristic curves can be measured in a reduced time period when using a small-scale centrifuge.Key words: unsaturated soils, soil-water characteristic curve, centrifuge technique, soil suction, matric suction, water content.

Investigating structural stability using the soil water characteristic curve

2002 ◽  
Vol 42 (3) ◽  
pp. 291 ◽  
Author(s):  
K. Barlow ◽  
D. Nash
Keyword(s):  
Soil Water ◽  
Soil Structure ◽  
Agricultural Land ◽  
Characteristic Curve ◽  
Soil Cores ◽  
Undisturbed Soil ◽  
Soil Water Characteristic Curve ◽  
Soil Water Characteristic Curves ◽  
Intact Soil Cores ◽  
The Stability

Soil physical properties, including infiltration, strength, water storage and aeration, affect the productivity of agricultural land. This paper investigated the stability of soil structure to chemical disruption, using the soil water characteristic curve. The soil water characteristic was determined twice on intact soil cores of an acidic mesotrophic, red Ferrosol (Gn4.11) and an acidic, eutrophic, grey Dermosol (Gn4.51). Saturated NaCl or deionised water was used to wet the soil cores between each determination. Despite the variability associated with undisturbed soil cores, significant differences were detected in the soil water characteristic curves both within and between soil types. The ability to detect differences in the soil structure of the Ferrosol and Dermosol, both Emerson class 8, suggests this technique could be used to determine the chemical stability of soils with minimal mechanical disruption of the structure.

The hydrology of Vertosols used for cotton production: II. Pedotransfer functions to predict hydraulic properties

Soil Research ◽  
2006 ◽  
Vol 44 (5) ◽  
pp. 479 ◽  
Author(s):  
R. W. Vervoort ◽  
B. Minasny ◽  
S. R. Cattle
Keyword(s):  
Linear Regression ◽  
Bulk Density ◽  
Soil Water ◽  
Hydraulic Properties ◽  
Characteristic Curve ◽  
Total Carbon ◽  
Pedotransfer Functions ◽  
Cotton Production ◽  
Total Carbon Content ◽  
Soil Water Characteristic Curve

Using a range of earlier published results and a recently published dataset, pedotransfer functions (PTFs) were developed to predict some hydraulic properties of Vertosols. A fitting approach using neural networks was employed with good results to predict the soil water characteristic curve. The developed functions are complex due to the large numbers of parameters, but moisture contents are predicted to within 5%. Other PTFs to predict the moisture content at the drained upper limit (DUL) and lower limit (LL), and bulk density in the normal shrinkage curve, were developed using multiple linear regression. The PTFs to predict the soil water characteristic curve, DUL and LL, and the bulk density in the normal shrinkage zone were mainly based on total clay, sand, and silt contents and bulk density, with minor contributions of ECEC and total carbon content. PTFs for unsaturated hydraulic conductivities were also developed using multi-linear regression and were mainly dependent on silt contents and ESP values. The mean error in these predictions was 2.76 mm/h, which is reasonable for predictions at the field and farm scale where inherent soil variability can cause larger variation. The developed PTFs can be used to predict parameters needed in crop modelling tools such as OZCOT to simulate cotton development on Vertosols. Some further examples of the use of the PTFs for management of irrigation are given.

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