MV: Mualem van Genuchten model

In melwey/euptf: Hydraulic pedotransfer functions for Europe

Mualem van Genuchten model

Description

Evaluates Mualem van Genuchten model describing the soil moisture retention and hydraulic conductivity curve as a function of the suction head h (L) or the water content theta (L^3 L^-3)

Usage

MV(par, h = NULL, theta = NULL)

Arguments

par	vector of parameters of the (Mualem-)van Genuchten model: c(thr,ths,alp,n,m,K0,L), with thr the residual water content,ths the saturated water content, alp (L^(-1)), n (-) and m (-) shape parameters. K0 (L T^(-1)) is the hydraulic conductivity at h=0 and L a shape parameter (-). If only the retention curve is needed, K0 and L can be omitted. If the conductivity is needed, m should be equal to 1-1/n.
h	vector of suction heads at which the model is to be evaluated. If NULL, theta must be provided.
theta	vector of water content at which the model is to be evaluated. If NULL, h must be provided.

Details

The van Genuchten model is defined as:

Se = (theta - thr)/(ths - thr) = (alp * h^n)^(-m)

Provided that m=1-1/n, it can be coupled with the Mualem model as:

K = K0 * (Se)^L * (1-(1-Se^(1/m))^m)^2

Value

A data frame with length(h) rows with columns:

h	provided as arguments or calculated as a function of theta
theta	provided as argument or calculated as a function of h
Se	relative saturation
K	soil hydraulic conductivity (LT^(-1)

Warning

The pedotransfer functions in this package use the following units:

Length:	centimeter
Time:	day
Mass:	gram

Author(s)

M. Weynants

References

Van Genuchten, M. T. (1980). A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Science Society of America Journal, 44, 89-98.

See Also

predict.ptf

Examples

mvg <- MV(par=c(0.02,0.45,0.02,3.5,1-1/3.5,150,0.5),h=10^(seq(0,5,by=0.1)))
par(mfrow=c(2,1))
plot(theta ~ h, data = mvg, log = "x")
plot(K ~ h, data = mvg, log = "xy")

melwey/euptf documentation built on Sept. 17, 2022, 3:35 a.m.