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Project Summary. THE RETC CODE FOR QUANTIFYING THE HYDRAULIC FUNCTIONS OF UNSATURATED SOILS
Citation:
van Genuchten, M. T., F. J. Leij, AND S. R. Yates. Project Summary. THE RETC CODE FOR QUANTIFYING THE HYDRAULIC FUNCTIONS OF UNSATURATED SOILS. U.S. Environmental Protection Agency, Washington, DC, EPA/600/S2-91/065, 1992.
Impact/Purpose:
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Description:
This summary describes the RETC computer code for analyzing the soil water retention and hydraulic conductivity functions of unsaturated soils. These hydraulic properties are key parameters in any quantitative description of water flow into and through the unsaturated zone of soils. The program uses the parametric models of Brooks-Corey and van Genuchten to represent the soil water retention curve, and the theoretical pore-size distribution models of Mualem and Burdine to predict the unsaturated hydraulic conductivity function from observed soil water retention data. Some of the analytical expressions used for quantifying the soil water retention and hydraulic conductivity functions are presented. A brief review is also given of the nonlinear least-squares parameter optimization method used for estimating the unknown coefficients in the hydraulic models. The program may be used to predict the hydraulic conductivity from observed soil water retention data assuming that an estimate of the saturated hydraulic conductivity is available. The program also permits one to fit analytical functions simultaneously to observed water retention and hydraulic conductivity data, or to predict the hydraulic curves from specified model parameters, If no retention and conductivity data are available. The actual report, summarized here, serves as both a user manual and reference document.