%0 Journal Article
%T Soil Water Retention Modeling Using Pedotransfer Functions
%A R. K. Jaiswal
%A T. Thomas
%A R. V. Galkate
%A Jaivir Tyagi
%J ISRN Civil Engineering
%D 2013
%R 10.1155/2013/208327
%X The unsaturated hydraulic functions are key input data in numerical models of vadose zone processes. The direct measurement of soil moisture at different suction heads requires detailed analysis of soil samples with sophisticated instruments which can be replaced with the help of pedotransfer functions (PTFs) which are empirical relationships between the soil hydraulic properties and the more easily obtainable basic soil properties. The CalcPTF software has been used to compute the parameters of the most commonly used models of Brooks and Corey (BC) and Van Genuchten (VG) from PTFs for determination of soil water retention curves on seventeen sites in the commands of Benisagar and Rangawan reservoirs in Chhatarpur district (MP), India. The parameters of sixteen PTFs have been estimated and results have been compared with observed data using root mean square error (RMSE), coefficient of determination (R2), , and graphical representation. The PTF of BC model suggested by Rawls and Brakensiek, 1985 (BC-RB), has been found to be the best-fit PTF for sites 1, 2, 5, 6, 10, 11, 14, 15, and 17, where BC model by Saxton et al., 1986 (BC-SEL), can be used for modeling the soil moisture for sites 3, 4, 9, 12, and 16. It may be concluded that the PTF suggested by Rawls and Brakensiek, 1985 (BC-RB), or Saxton et al., 1986 (BC-SEL), can be used for computation of soil moisture retention curves in the region. 1. Introduction The common conceptual models for unsaturated flow often rely on the oversimplified representation of medium pores as a bundle of cylindrical capillaries and assume that soil water pressure head is attributed to capillary forces only and ignores the adsorptive surface forces. Hence, it is often assumed that aqueous flow is negligible when a soil is near or at residual water content ( ). The reason for the finite value of is that the dominant historical water-content measurements were in the wet range, and the typical soil water retention models assumed asymptotic behavior at low water content values. It is generally treated as a fitting parameter. Hence, an effective saturation is often defined as with being water content and the saturated water content [1]. To use the model, additional parameters must be known to quantify the contribution of film flow. Several functions have been proposed to empirically describe the soil water retention curve. These models were based on Rechards equation for flow of water in saturated or partly saturated soil. One of the most popular functions has been the equation given by Brooks and Corey in 1964 (BC) [2] which
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