Unsaturated Soil Hydraulic Database Research Articles

Estimating Saturated Hydraulic Conductivity Using Genetic Programming

Saturated hydraulic conductivity (Ks) is one of the key parameters in modeling solute and water movement in the vadose zone. Field and laboratory measurement of Ks is time consuming, and hence is not practical for characterizing the large spatial and temporal variability of Ks As an alternative to direct measurements, pedotransfer functions (PTFs), which estimate Ks from readily available soil data, are being widely adopted. This study explores the utility of a promising data‐driven method, namely, genetic programming (GP), to develop PTFs for estimating Ks from sand, silt, and clay contents and bulk density (Db). A data set from the Unsaturated Soil Hydraulic Database (UNSODA) was considered in this study. The performance of the GP models were compared with the neural networks (NNs) model, as it is the most widely adopted method for developing PTFs. The uncertainty of the PTFs was evaluated by combining the GP and the NN models, using the nonparametric bootstrap method. Results from the study indicate that GP appears to be a promising tool for developing PTFs for estimating Ks The better performance of the GP model may be attributed to the ability of GP to optimize both the model structure and its parameters in unison. For the PTFs developed using GP, the uncertainty due to model structure is shown to be more than the uncertainty due to model parameters. Moreover, the results indicate that it is difficult, if not impossible, to achieve better prediction and less uncertainty simultaneously.

Unsaturated Soil Hydraulic Database of Hungary: HUNSODA

Databases with information on soils often constitute a basic source of information for studies in production agriculture, environmental engineering, and remote sensing. A new, searchable, relational database of soil physical and hydrophysical properties has been developed for Hungarian soils. The database is stored in MS-Access format. The database is compatible with most of the popular software and can be run on a personal computer as well as on computer networks. It currently stores data of 840 soil horizons, 576 having soil hydraulic data, measured using nationally and internationally accepted standard methodology. An outline of the structure and the contents of HUNSODA, as well as a basic guide to its operation has been given. Developing this database may enhance the ability of Hungarian soil scientists to address many more environmental issues of concern, however, further expansion of the database is recommended. Additional data can easily be included in the database. Expansion of the database may help in making it more widely applicable.

Description of the unsaturated soil hydraulic database UNSODA version 2.0

Quantifying water flow and chemical transport in the vadose zone typically requires knowledge of the unsaturated soil hydraulic properties. The UNsaturated SOil hydraulic DAtabase (UNSODA) was developed to provide a source of unsaturated hydraulic data and some other soil properties for practitioners and researchers. The current database contains measured soil water retention, hydraulic conductivity and water diffusivity data as well as pedological information of some 790-soil samples from around the world. A first MS-DOS version of the database was released in 1996. It has been applied in numerous studies. In this paper, we describe the second version (UNSODA V2.0) for use with Microsoft Access-97®11Trade names are provided for the benefit of the reader and do not imply an endorsement by the authors or their organizations.. The format and structure of the new database have been modified to provide additional and more convenient options for data searches, to provide compatibility with other programs for easy loading and downloading of data, and to allow users to customise the contents and look of graphical output. This paper reviews the structure and contents of the database as well as the operations that can be performed on the different data types in UNSODA V2.0. The use and application of the new database are illustrated with two examples. The retrieval of data is briefly illustrated, followed by a more detailed example regarding the interpolation of soil particle-size distribution data obtained according to different national definitions of particle-size classes. The interpolation procedure, which is based on finding similar particle-size distribution curves from a large European data set, also performed well for soils that originate from other geographical areas.