... ) and K sat , observed soil moisture in the field, and soil hydraulic properties from the UNSODA database. Our study indicates, however, that the homogeneous-medium assumption commonly used to effectively describe a heterogeneous system may fail to closely represent a highly heterogeneous (layered) soil...

...) , synthetic soils and numerical experiments were used to test the TCT concept. In this research, two data sets, one from the UNSODA database ( Leij et al., 1996 ; Nemes et al., 2001 ), but originally measured by Laliberte (1966) for natural soils, and the other from a numerical experiment by Bear et al...

..., respectively. In 2008, Šimůnek et al. (2008b) described the entire history of the development of the various HYDRUS programs and related models and tools such as STANMOD, RETC, ROSETTA, UNSODA, UNSATCHEM, HP1, and others. The objective of this manuscript is to review selected capabilities of HYDRUS that have...

... the suction head and packing state. Our results showed that the model can adequately predict the SMC as measured in 80 soils selected from the UNSODA database. It was also shown that the proposed model provides better predictions of SMC than the AP or HP models. The model underestimates the moisture content...

... processes in soils and groundwater. The research also produced additional programs and databases (e.g., RETC, Rosetta, and UNSODA) for quantifying unsaturated soil hydraulic properties. All of the modeling tools, with the exception of HYDRUS-2D and HYDRUS (2D/3D), are in the public domain and can...

...F ig . 1. Textural distribution of 137 soils from the UNSODA database ( Nemes et al., 2001 ) used in model development: sandy (sand and loamy sand), loamy (sandy loam, loam, silt loam, and silt), and clayey (sandy clay loam, silty clay loam, clay loam, sandy clay, silty clay, and clay) soils. ...

...-entry pressure ( h s ) into the water retention curve. Analysis of the UNSODA soil hydraulic database revealed an optimal value of −4 cm for h s , more or less independent of soil texture. The modified model uses a pressure dependent piece-wise linear correction to ensure that deviations between...

... and nonlinearity of the employed parametric models, the algorithm is suited to generate a useful description of parameter uncertainty and its antithesis, parameter identifiability. A set of measured water retention characteristics of the UNSODA database ( Leij et al., 1996 ) spanning a wide range of soil textures...

...Fig. 2. Variation in textural composition of samples in the different databases used to fit the van Genuchten–Mualem (VGM) parameterization and to develop pedotransfer functions (PTFs). M7 refers to UNSODA, and M9 refers to the Ahuja database ( Schaap and Leij, 1998a ). M8 ( Schaap and Leij...

...Fig. 7. (a) Scatterplot of data selected using particle size criteria in the UNSODA database; (b) mean water retention curve (red line) with confidence interval (dashed blue line) obtained with an experimental approach from weathered granite samples and compared with predictions of particle size...

.... The proposed model was tested against 20 sets of experimental data obtained from the Unsaturated Soil Hydraulic Database (UNSODA) ( Leij et al., 1996 ) and other literature ( Lebeau and Konrad, 2010 ). We present the results from nine soils, which ranged from coarse sand to sandy clay, as illustrative examples...

... ones. cdf, cumulative distribution function cmf, cumulative mass fraction FPS, fully penetrable spheres pdf, probability density function TIS, totally impenetrable spheres UNSODA, Unsaturated Soil Hydraulic Database O ne of the fundamental soil hydraulic properties is the water...

... . doi:10.1029/91WR01550 Leij F.J. Alves W.J. van Genuchten M.Th. Williams J.R. . 1996 . The UNSODA unsaturated soil hydraulic database, version 1.0, EPA Rep . EPA/600/R-96/095, EPA National Risk Management Laboratory, G-72 , Cincinnati, OH . Lessoff S.C. Indelman P...

... ), UNSODA ( Leij et al., 1996 ), and RAWLS databases. It contains water retention parameters for 2134 soil samples and saturated hydraulic conductivity K s for 1306 samples. Schaap and Leij (1998) tabulated mean values of these parameters for 12 USDA soil classes. Comparative simulations...

... Genuchten, 1988 ; Schaap and Leij, 1998 ). Schaap and Leij (1998) developed hierarchical neural network–based PTFs to predict parameters in the retention function of van Genuchten (1980) and the saturated hydraulic conductivity, K s . Three large databases (i.e., RAWLS, AHUJA, and UNSODA [ Leij et al...

...) as calculated from data in the UNSODA database ( Leij et al., 1996 ). The range of saturated water contents and bulk densities were chosen from UNSODA data for sandy loam soils. In the preliminary analysis, the uniform distribution of θ i ( Table 1 ) was used as the sampling distribution for θ in Eq. [6...

... were generated by the SWAP model using the available soil hydraulic parameters from the UNSODA database ( Leij et al., 1999 ) in a forward mode. For Case 3, several field sites at Brown, IL, Walnut Creek (WC 11–14), IA, and Lubbock, TX, were selected for the validation studies as shown in Fig. 2 . We...