Modelling soil water retention to identify management influence on soil pore characteristics (original) (raw)
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PREDICTION OF SOIL WATER RETENTION PROPERTIES BY USING OF ARYA-PARIS MODEL
14th SGEM GeoConference on WATER RESOURCES. FOREST, MARINE AND OCEAN ECOSYSTEMS, 2014
The soil water retention curve or the soil water content-matric potential relationship expresses the capacity of soils to store water for plant growth, which is a very important soil property for irrigation and hydrological modelling. Due to relatively long time involved in the determination of water retention curves, there is an increasing interest for models that estimate this property from simple taxonomic data (soil particle size distribution, bulk density, organic matter and other basic properties). Among these models is the Arya -Paris approach, which is based on the similarity between the shapes of particle size distribution and soil water retention curves. In this paper the model of Arya -Paris was used for assessing the water retention curve using soil texture and bulk density data. Arya-Paris model with α values calculated was applied to evaluate pairs of θ (soil water content) -ψ (matric potential). The van Genuchten equation was then used to estimate the water retention curve in the analyzed soils. Two soil types (Rendzic Leptosol and Calcaro-calcic Kastanozem) located in the Dobrogea area from SE of Romania were analyzed. Parameters of the van Genuchten equation, θr, θs, α, n were evaluated using the pairs of values θψ calculated by Arya-Paris model. Van Genuchten equation was then used to assess some parameters that have agronomical significance. Optimum soil water content and soil matric potential for soil workability correspond to the inflection point of the soil water retention curve. Depending on the characteristics of the soil water retention curve at the inflection point the soil physical quality index, S was calculated.
Relationship between soil water retention model parameters and structure stability
EURASIAN JOURNAL OF SOIL SCIENCE (EJSS), 2016
Studying and modeling the effects of soil properties and management on soil structure and near saturation water retention is vital for the development of effective soil and water conservation practices. The contribution of soil intrinsic properties and extrinsic conditions to structure stability was inferred, in quantitative terms, from changes in water retention curves near saturation (low matric potential, 0-50 cm, macropores > 60 µm) that were obtained by the high energy moisture characteristic (HEMC) method. The S-shaped water retention curves were characterized by the modified van Genuchten model that provided: (i) the model parameters α and n, which represent the location of the inflection point and the steepness of the water retention curve, respectively; and (ii) the soil structure index, SI=VDP/MS, where VDP is the volume of drainable pores, and MS is the modal suction. Model parameters, claculated by the soil-HEMC model, were related to soil properties and hence soil water retention properties were linked to measured characteristics in several field and laboratory experiments. Soil SI increased exponentially with the increase in α and the decrease in n, while the relationship between SI and α/n was linear. An improved description of the water retention and its link to pore and apparent aggregate size distribution, by using the model parameters α and n, could potentially assist in the selection of management practices for obtaining the most suitable type of soil structure depending on the desired soil function.
A conceptual model of the soil water retention curve
Water Resources Research, 1998
A conceptual model based on the assumption that soil structure evolves from a uniform random fragmentation process is proposed to define the water retention function. The fragmentation process determines the particle size distribution of the soil. The transformation of particles volumes into pore volumes via a power function and the adoption of the capillarity equation lead to an expression for the water retention curve. This expression presents two fitting parameters only. The proposed model is tested on water retention data sets of 12 soils representing a wide range of soil textures, from sand to clay. The agreement between the fitted curves and the measured data is very good. The performances of the model are also compared with those of the two-parameter models of van Genuchten [1980] and Russo [1988] for the water retention function. In general, the proposed model exhibits increased flexibility and improves the fit at both the high and the low water contents range.
Comparing the Applicability of Soil Water Retention Models
2016
Recently, the public has become more aware of the environmental problems facing our planet today. Underground water pollution is one of these problems, and it requires serious attention. As a result, many studies have been performed to examine the movement of water within soil. These studies present many new models for determining soil water retention rates. It is essential that these models be investigated for accuracy and applicability. This study attempts to analyze three of these well-known water retention models: Campbell, Saxton, and Huston-Cass. To analyze these models, the pressure plate test (ASTM C199-09) was performed on soil samples with different soil textures and from different geographical locations within the country of Iran. Using these results, the general applicability of each model was measured using the 1:1 slope line correlation method. In addition, the accuracy and applicability of each model was measured by calculating the Root Mean Square Error (RMSE) and th...
Relationship between soil structure and water retention properties in a residual compacted soil
Engineering Geology, 2016
Soil structure, especially the soil pore size distribution, is a fundamental property that describes the hydro-mechanical behavior of soils. The volume change behavior, shear strength, water retention capacity and hydraulic conductivity of soil are controlled by the pore size distribution. However, research on soil structure has been limited due to the associated expenses and specialized instruments, such as environmental scanning electron microscopes and mercury intrusion porosimeters (MIPs). In this study, the relationship between the soil water retention curve (WRC) along a drying path and the pore size distribution obtained through an MIP method was reviewed. The WRC for a compacted tropical soil was converted into a soil air injection curve and then used to estimate the pore size density (PSD) function. Relative to the data collected from MIP methods, the results showed an acceptable prediction of the PSD function based on a soil air injection curve. Finally, a series of adjustments to the air injection curve were performed to improve the accuracy of the PSD prediction based on the water retention curve.
Empirical models for estimating water retention curves in soil in Janaúba-MG, Brazil
Idesia (Arica), 2012
Retention curves describe water dynamics in the soil and represent the relationship between the energy of water retention and moisture content. Several empirical models of water retention curve settings in the soil are analyzed (Van Genuchten-VG, Brooks & Corey BC, Bruce & Luxmore-BL and Driessen-D). Deformed soil samples were collected at 10 sites per plot; a compound sample was established with 36 plots between October and November 2007, at depths 0-20 cm and 20-40 cm in the Irrigation District of Gorutuba in Janaúba MG, Brazil. Tensions used for tests were 10, 30, 100, 500 and 1500 kPa. Soil Water Retention Curve software was employed to obtain the parameters of the empirical equations. The performance of empirical models was obtained by the index suggested by Camargo & Sentelhas, coupled to estimate standard error, standard deviation and coefficient of variation. The results showed that the VG model had the best performance compared to the other models tested for data on water retention in the soil. The BC model had the most unsatisfactory performance.
Pedotransfer functions developed especially for predicting soil-water retention for tropical soils are very scarce and the existing ones still need improvement. The aims of this work were to create a consistent database about the physical properties of the Brazilian savanna tropical soils and to develop specific pedotransfer functions for estimating their soil-water retention characteristics. The soil database, which consisted of soil-water retention curves and related soil-physical characteristics, came from 413 locations and various depths, totalizing 1401 soil layers. Two non-linear models were proposed to estimate the four parameters of the van Genuchten equation, used to describe soil-water retention curves. The performance of the proposed models was statistically evaluated and their estimation efficiency was compared with the Tomasella's pedotransfer function considered as a reference for Brazilian soils. The soil database generated in the scope of this study is quite representative of the Brazilian savanna region. The success in predicting soil-water retention curve by using the herein developed pedotransfer functions was about 70%, which is much higher than the percentage of success obtained by Tomasella's model level 1 (20%) for the same soil database.
Soil porous system changes quantified by analyzing soil water retention curve modifications
Soil & Tillage Research, 2008
Soil water retention curves (SWRC) relate soil water pressure head (h) to soil water content (θ) and can also be used to find information regarding soil pore distribution. To analyze SWRCs in relation to pore size distribution (PSD), changes due to wetting and drying (W-D) cycles were studied in three different tropical soils (Geric Ferralsol, GF; Eutric Nitosol, EN;
Study on Soil Moisture Retention Function for the Indian Forested Hillslope Soils
2013
Pedotransfer functions (PTFs) are one of the widely used tools to predict the soil water retention curves (SWRC). The objective of this study was to develop and validate point and parametric PTF models based on nonlinear regression technique using the different set of predictors such as particle-size distribution, bulk density, porosity and organic matter content. Soil samples were collected from different elevations at different depths in forested hillslope area of Pavanje river basin that lies in coastal area of Karnataka, India. The point PTF models estimated retention points at 33, 100, 300, 500, 1000, and 1500 kPa pressure heads and the parametric PTF models estimated the van Genuchten and Brooks-Corey retention parameters. The data were evaluated with the root mean square error (RMSE), mean error (ME), and coefficient of determination (R^2) between the measured and predicted water contents. The prediction of soil water retention curve using PTFs by point estimation method for ...