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United States Department of Agriculture

Agricultural Research Service

Title: On Pedotransfer Functions, Soil Structure, and Dual-Porosity/dual-Permeability Modeling

Authors
item Van Genuchten, Martinus
item Schaap, Marcel - UC RIVERSIDE, CA

Submitted to: Soil Science Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 2003
Publication Date: October 20, 2003
Citation: Van Genuchten, M.T., Schaap, M. 2003. On pedotransfer functions, soil structure, and dual-porosity/dual-permeability modeling. (CD-ROM). Soil Science Society of America Annual Meeting. Abstracts. Denver, CO. Nov. 2-6, 2003.

Technical Abstract: Process-based descriptions of preferential flow generally invoke dual-porosity or dual-permeability models which assume that the soil consists of two interacting pore regions, one associated with the macropore or fracture network, and one with micropores inside soil aggregates or rock matrix blocks. Dual-permeability models arise when water flow occurs in both the fracture and matrix domains. Application of these models requires estimates of the hydraulic properties of the fracture pore network, the matrix region, or some composite of these. Measurements of the composite properties can be obtained using a combination of tension infiltrometer and more traditional methods. Evidence from field measurements suggests that the fracture conductivity is generally about one order of magnitude larger than the matrix conductivity at saturation. Using neural network analysis of a large unsaturated soil hydraulic database (UNSODA) we found similar differences. Moreover, the air-entry value of the fracture hydraulic conductivity was found to be at about 3 or 4 cm. This information should help greatly in quantifying the constitutive relationships of dual-permeability models.

Last Modified: 8/27/2014
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