نتایج جستجو برای: soil hydraulic functions

تعداد نتایج: 692333  

2002
K. Kosugi

The scaling theory approach has been widely used as an effective method to describe the variation of soil hydraulic properties. In conventional scaling, reference retention curves and scaling factors are determined from minimization of residuals. Most previous studies have shown that scaling factors are lognormally distributed. In this study, we derived physically based scaling factors, assumin...

2010
Andrew S. Gregory Nigel R.A. Bird W. Richard Whalley Peter Matthews

To understand the hydraulic properties of soils, accurate prediction of unsaturated hydraulic conductivity is needed which is commonly derived from the soil water release characteristic. In fine-textured soils the modified Mualem-van Genuchten (MMVG) function has been used extensively to predict the change in relative conductivity with changes in matric potential, but this assumes that the soil...

Journal: :journal of agricultural science and technology 2010
a. keyhani d. wulfsohn

a pressure-based coupled heat and mass transfer model was used to simulate temperature and soil suction in a drying process within a clay soil column. closed form functions were used for all parameters needed in the governing equations. model predictions were compared with experimental data using the mean relative percentage deviation method. thermocouples and mini-gypsum blocks were used t...

2009
D. D. Bosch

Steady-state and transient one-dimensional unsaturated flow in vertically stratified porous media are examined. Saturated hydraulic conductivity and the alpha parameter of the exponential hydraulic conductivity function were assumed to vary from soil layer to soil layer. The use of effective unsaturated hydraulic conductivity to compute matric potential in the soil profile is demonstrated. Resu...

1997
Jinqi Zhang Jim Yeh

An iterative geostatistical inverse approach is developed to estimate conditional effective unsaturated hydraulic conductivity parameters, soil-water pressure head, and degree of saturation in heterogeneous vadose zones. This approach is similar to the classical cokriging technique, and it uses a linear estimator that depends on covariances and cross covariances of unsaturated hydraulic paramet...

2014
Ranmalee Bandara Jeffrey P. Walker Christoph Rüdiger

Soil moisture is a key variable that controls the exchange of water and energy fluxes between the land surface and the atmosphere. However, the temporal evolution of soil moisture is neither easy to measure nor monitor at large scales because of its high spatial variability. This is mainly a result of the local variation in soil properties and vegetation cover. Thus, land surface models are nor...

ژورنال: علوم آب و خاک 2012
بیژن خلیل‌مقدم, , جهانگرد محمدی, , حبیب خداوردی‌لو, , سیروس دهقانی بانیانی, , شجاع قربانی دشتکی, ,

Saturated hydraulic conductivity (Kfs) and macroscopic capillary length of soil pores are important hydraulic properties for water flow and solute transport modeling. Measuring these parameters is tedious, time consuming and expensive. One way is using indirect methods such as Pedotransfer functions (PTFs). The objective of this research was to develop some PTFs for estimating saturated hydraul...

2012
Zilong Wang Qiuxiang Jiang Qiang Fu Tianxiao Li

The identification of freezing-thawing soil hydraulic properties is the basis and key problem of studying soil water movement. Current identifying methods of the properties have many limitations, such as big error, high uncertainty and low operability. Thus, the identifying method of freezingthawing soil hydraulic properties was researched in the research. The estimating parameters of soil free...

2014
Keith R. Daly Sacha J. Mooney Malcolm J. Bennett Neil M. J. Crout Saoirse R. Tracy

Short title for page headings: Influence of the rhizosphere on soil hydraulic properties 16 17 Short statement: Using non-destructive imaging techniques and numerical modelling we 18 quantify differences in hydraulic and structural properties of bulk and rhizosphere soil for 19 sand and clay loam soils. 20 21 22 2 1. Abstract 23 Understanding the dynamics of water distribution in soil is crucia...

2007
L. Ma P. Heilman L. R. Ahuja T. Meade R. S. Kanwar

Process-based agricultural system models require detailed description of soil hydraulic properties that are usually not available. The objectives of this study were to evaluate the sensitivity of model simulation results to variability in measured soil hydraulic properties and to compare simulation results using measured and default soil parameters. To do so, we measured soil water retention cu...

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