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...

A piezometric head method is proposed to estimate the impermeable layer depth used in drain spacing formulae. The method was tested and compared with soil texture changes and the US Bureau of Reclamation (USBR, 1978) criterion of impermeable layer being one with hydraulic conductivity one tenth to one fifth that of the weighted hydraulic conductivity of the upper layers. The proposed method, wh...

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 ...

Soil moisture plays a key role in most environmental processes, as evaporation and transpiration are heavily dependent on soil moisture variability. While it is one of the few important hydrological variables that can be directly observed, the high spatial and temporal variability makes it difficult to measure globally or even regionally. Reliance is therefore placed on land surface models to p...

introduction: soil hydraulic conductivity is considered as one of the most important hydraulic properties in water and solutionmovement in porous media. in recent years, variousmodels as pedo-transfer functions, fractal models and scaling technique are used to estimate the soil saturated hydraulic conductivity (ks). fractal models with two subset of two (solid and pore) and three phases (solid,...

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 ...

There are applications of barrier technology where the variability in hydraulic conductivity from point to point in the barrier, in addition to the average hydraulic conductivity of the barrier, is important. Throughout this chapter, the following application will be referred to in order to demonstrate this point: use of a circumferential soil-bentonite cutoff wall to completely enclose a conta...