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United States Department of Agriculture

Agricultural Research Service

Title: Use of Soil Survey Information for Determining Soil Hydraulic Parameters for Hydrologic Modeling

item Rawls, Walter
item Pachepsky, Yakov

Submitted to: Federal Interagency Hydrologic Modeling Conference
Publication Type: Proceedings
Publication Acceptance Date: August 1, 2002
Publication Date: July 28, 2002
Citation: Rawls, W.J., Pachepsky, Y.A. 2002. Use of soil survey information for determining soil hydraulic parameters for hydrologic modeling [CD-ROM]. Federal Interagency Hydrologic Modeling Conference.

Technical Abstract: Knowledge of hydraulic properties is a key element in hydrologic modeling. Laboratory and field methods for determining soil hydraulic properties are time consuming and expensive. Average soil hydraulic properties developed in the early 1980's according to soil texture are commonly used in models; however, pedotransfer functions which are procedures to relate basic soil properties such as texture, organic matter, bulk density, etc to properties that are rarely measured on a routine basis such as soil-water retention and saturated/unsaturated hydraulic conductivity are now readily available. Pedotransfer functions (PTF's) which predict various soil hydraulic properties (water retention and hydraulic conductivity) based on various levels of soil survey information were developed by applying regression tree analysis to the NRCS national soils data base. The qualitative information used in the pedotransfer functions were USDA soil texture classes, structure, grade, size and shape classes, dry and moist consistency classes and stickness and plasticity classes. Topographic features, organic matter and taxonomic units which are subjectively estimated in the field and are part of every soil profile description appear to be useful predictors of soil hydraulic properties.

Last Modified: 4/22/2015
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