SSomuto: 'Omuto' Water Retention Model

In HydroMe: Estimating Water Retention and Infiltration Model Parameters using Experimental Data

'Omuto' Water Retention Model

Description

This is a four- parameter function to determine water retention hydraulic parameters contained in a bimodal pore-size distribution developed by Omuto. The parameters are for the first and second compartments

Usage

SSomuto(input, Ths1, alp1, Ths2, alp2)

Arguments

input	Suction potential/head as contained in the x-column of the xy water retention table or data
Ths1	This is saturated moisture content in the first compartment of a bimodal pore-size distribution water retention characteristics
alp1	This is the inverse of air-entry potential in the first compartment of a bimodal pore-size distribution water retention characteristics
Ths2	This is saturated moisture content in the second compartment of a bimodal pore-size distribution water retention characteristics
alp2	This is the inverse of air-entry potential in the second compartment of a bimodal pore-size distribution water retention characteristics

Details

Omuto model is a self-starting biexponential model for nonlinear curve fitting model to water retention data. 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

Value

A list of objects returned by standard R regression functions such as nls and lm

Note

This function can also be used to fit water retention characteristics for a grouped dataset as well as with mixed-effects modelling

Author(s)

Christian Thine Omuto

References

Omuto CT. 2009. Biexponential model for water retention characteristics. Geoderma 149:235-242

See Also

SSvgm, SSgard

Examples

data(isric)
isric1 <- isric[1:32,]
library(nlme)
omuto <- nlsList(y ~ SSomuto(x,ths1,alp1,ths2,alp2) | Sample,  isric1)
omuto.nlme <- nlme(omuto)## for fitting mixed-effects models
summary(omuto.nlme)

HydroMe documentation built on May 29, 2024, 9:35 a.m.