Description Usage Arguments Details Value Author(s) References See Also Examples
This is a four-parameter function to determine water retention hydraulic parameters contained in the van Genuchten water retention model
1 | SSvgm4(input, Thr, Ths, alp, nscal)
|
input |
Suction potential/head as contained in the x-column of the xy water retention table or data |
Thr |
This is the residual moisture content. It's the moisture content when suction potential is very high (almost at the drying point) |
Ths |
This is the saturated moisture content. It's the moisture content when suction potential is very low (almost at the saturation point) |
alp |
It's natural logarithm of the inverse of air-entry potential or bubbling pressure |
nscal |
This is a parameter or index for the pore-size distribution |
Van Genuchten model is a type of self-starting nonlinear curve fitting model for fitting water retention characteristics using experimental data. In this model, the restriction of m=1-1/n has been imposed on the water retention characteristics. Air-entry potential = exp(alp). If warnings are given during the estimation process, try to increase the iteration limit using control function. Sometimes the warnings can be suppressed using (warn=-1)/ignored since they do not terminate the process
A list of objects returned by standard R regression functions such as nls and lm
Christian Thine Omuto
van Genuchten MT. 1980. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Science Society of America Journal 44: 892-898
SSomuto, Brook, Campbel
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