نتایج جستجو برای: soil hydraulic functions

تعداد نتایج: 692333  

2007
Raghavendra B. Jana Binayak P. Mohanty

Soil hydraulic properties are needed in globaland regionalscale circulation models for hydrologic and climate forecasting. They are also necessary in pointand nonpoint-source contaminant transport models. Prediction accuracy of these models is highly dependent on the quality of the model parameters. Collecting the required soil hydraulic parameters by direct measurement at any model grid scale ...

1999
Jiřı́ Šimůnek Radka Kodešová Molly M. Gribb Martinus T. van Genuchten

Data obtained from modified cone penetrometer experiments were used to estimate the hysteretic soil hydraulic properties with a parameter estimation technique which combined a numerical solution of the Richards equation with Marquardt-Levenberg optimization. The modified cone penetrometer was designed to inject water into a soil through a cylindrical screen, measure the infiltration rate with t...

Journal: :آب و خاک 0
فاطمه مسکینی ویشکائی محمود شعبانپور شهرستانی ناصر دوات گر

abstract the saturated hydraulic conductivity (ks) is an important physical property of soil. the direct measurement of this property in soils is a difficult and time consuming process. pedotransfer functions (ptfs) provide an alternative by estimating soil parameters from more readily available soil data. the objective of this study is to determine effective factors on soil hydraulic conductiv...

2005
C. J. Matthews J. H. Knight F. J. Cook R. D. Braddock

Analytical solutions for non-steady flow are an important aspect of mathematical modeling in all fields of computational science. An analytical solution provides an exact solution for a specific (simplified) test case, which then can be used to test and verify numerical solutions. Within soil physics, there has been a multitude of analytical solutions that model transient flow through onedimens...

2004
L. F. F. Moreira A. M. Righetto V. M. de A. Medeiros

Hydrological modeling of the unsaturated soil zone fluxes allows the transfer processes simulation through the hydrological active soil zone. The pedotransfer functions (FTP) are useful tools in the modeling process. They contain analytical functions derived through statistic optimization process using a large amount of soil information data. This paper aims to analyze the level of reliability ...

2009
Navin K. C. Twarakavi Jirka Šimůnek M. G. Schaap

[1] In the past, texture-based classification of soils has been used for grouping soils in variably saturated water flow and solute transport studies. Classification of soils becomes especially important for large-scale studies where the spatial and temporal variability in the hydraulic properties of soils exceeds the field sampling capabilities. Although soiltexture-based classification has be...

Journal: :آب و خاک 0
مرتضی صادقی بیژن قهرمان

abstract scaling methods, which are based on similar media theory, are used to simplify the statistic description of soil spatial variations. to simulate the water flow in heterogeneous soils, simultaneous scaling of soil hydraulic functions, including soil water retention and unsaturated hydraulic conductivity functions, is highly desirable. in the similar media theory, the simultaneous scalin...

Journal: :تحقیقات آب و خاک ایران 0
پریسا مشایخی دانشجوی دکتری/دانشگاه شهرکرد شجاع قربانی دشتکی هیئت علمی محمدرضا مصدقی هیات علمی/دانشگاه صنعتی اصفهان حسین شیرانی هیات علمی/دانشگاه حضرت ولی عصر رفسنجان مهدی پناهی هیات علمی/موسسه تحقیقات خاک و آب کرج محمدرضا نوری هیات علمی/دانشگاه شهرکرد

in this study, hydrus2d/3d software was used to estimate the hydraulic parameters of van genuchten-mualem model via inverse modeling using double-ring infiltrometers data in 3 different soil textures. nine scenarios of inverse modeling (divided in three groups) were considered with different number (5, 4 and 3) of fitted hydraulic parameters for optimization. in the first group, simulation was ...

2008
Binayak P. Mohanty

39 S oil hydraulic parameters are essential input to most hydrologic and climatic models (Mohanty et al., 2002; Mohanty and Zhu, 2007). Th ey are used to defi ne the hydraulic characteristics of the soil vital in modeling soil moisture and fl ux in the unsaturated zone near the land–atmosphere boundary. At the scale of model applications, it is very important to defi ne the appropriate paramete...

2005
Marcel G. Schaap

The unsaturated soil hydraulic properties are often described using Mualem–van Genuchten (MVG) type analytical functions. Recent studies suggest several shortcomings of these functions near saturation, notably the lack of second-order continuity of the soil water retention function at saturation and the inability of the hydraulic conductivity function to account for macroporosity. We present a ...

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