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United States Department of Agriculture

Agricultural Research Service

Title: Pedotransfer Functions: Bridging the Gap Between Available Basic Soil Data and Missing Soil Hydraulic Data: Their Development, Uncertainty and Practical Use in Modelling

Authors
item Wosten, J - ALTERRA GREEN WORLD RES
item Pachepsky, Yakov
item Rawls, Walter

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 2001
Publication Date: September 1, 2001
Citation: WOSTEN, J.H.M., PACHEPSKY, Y.A., RAWLS, W.J. PEDOTRANSFER FUNCTIONS: BRIDGING THE GAP BETWEEN AVAILABLE BASIC SOIL DATA AND MISSING SOIL HYDRAULIC DATA: THEIR DEVELOPMENT, UNCERTAINTY AND PRACTICAL USE IN MODELING. JOURNAL OF HYDROLOGY. V. 251. P. 123-150.

Interpretive Summary: Water retention and hydraulic conductivity are crucial input parameters in any modelling study on water and solute transport in soils. Because of inherent temporal and spatial variability in these hydraulic characteristics a large number of samples is often required to properly characterize areas of land. Hydraulic characteristics can be obtained from direct laboratory and field measurements, however, these measurements are time consuming and costly. It is beneficial to analyse existing databases of measured soil hydraulic characteristics to relate hydraulic properties to readily available soil data. In many cases, resulting relationships, called also pedotransfer functions, proved to be excellent tools for predicting the hydraulic properties. However, a comprehensive review on this topic, that can serve as a reference to both developers and users of pedotransfer functions, has not yet been published. This paper presents such a review. Data sources, modern development methods based on the data mining, and applications are presented using the international experience. The list of references encompasses the most important international literature. Both the current state of pedotransfer functions and existing problems of derivation and use are addressed. Examples are presented to illustrate the relative efficiency of existing approaches. The role of databases in pedotransfer function discovering and testing is underscored. Discussion and conclusions show the trends and needs of the pedotransfer function development and use.

Technical Abstract: Water retention and hydraulic conductivity are crucial input parameters in any modelling study on water and solute transport in soils. Because of inherent temporal and spatial variability in these hydraulic characteristics a large number of samples is often required to properly characterize areas of land. Hydraulic characteristics can be obtained from direct laboratory and field measurements, however, these measurements are time consuming and costly. It is beneficial to analyse existing databases of measured soil hydraulic characteristics to relate hydraulic properties to readily available soil data. In many cases, resulting relationships, called also pedotransfer functions, proved to be excellent tools for predicting the missing information. Examples are presented of different equations describing hydraulic characteristics and of pedotransfer functions used to predict parameters in these equations. Grouping of data prior to pedotransfer function development is discussed as well as the use of different soil properties as predictors. In addition to regression analysis, new techniques such as artificial neural networks, group method of data handling and regression tree algorithm are increasingly being used for pedotransfer function development. The development of pedotransfer functions is demonstrated by describing a practical case study. Examples are presented of application of the pedotransfer function approach for other purposes than prediction of hydraulic characteristics. Accuracy and reliability of pedotransfer functions are discussed. Accounting for inherent uncertainty in pedotransfer functions is illustrated. Finally, a number of conclusions are formulated.

Last Modified: 11/27/2014
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