| Kr_theta {soilphysics} | R Documentation |
Unsaturated Hydraulic Conductivity as a function of water content
Description
A closed-form analytical expressions for calculating the relative unsaturated hydraulic conductivity as a function of soil water content based on van Genuchten's water retention curve.
Usage
Kr_theta(theta, thetaS, thetaR, n, Ks, f=0.5)
Arguments
theta |
The volumetric water content (m^3/m^3). |
thetaS |
The volumetric water content at the saturation (m^3/m^3). |
thetaR |
The volumetric residual water content (m^3/m^3). |
n |
The shape parameter in van Genuchten's formula. |
Ks |
Saturated hydraulic conductivity (e.g. cm/day). |
f |
The pore-connectivity parameter. Default 0.5 [Mualem, 1976]. |
Value
numeric, the value of unsaturated hydraulic conductivity.
Author(s)
Renato Paiva de Lima <renato_agro_@hotmail.com>
References
Guarracino, L. (2007). Estimation of saturated hydraulic conductivity Ks from the van Genuchten shape parameter alpha. Water Resources Research, 43(11).
Van Genuchten, M. T. (1980). A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Science Society of America Journal 44(5):892-898.
Mualem, Y. (1976). A new model for predicting the hydraulic conductivity of unsaturated porous media. Water Resour. Res. 43(11): 513-522,
Examples
# EXAMPLE 1
Kr_theta(theta=0.45,thetaS=0.5,thetaR=0.15,
n = 2, Ks = 1.06*10^2, f=0.5)
# EXAMPLE 2
thetaS <- 0.50
thetaR <- 0.15
theta <- seq(thetaS, thetaR, len=50)
y <- Kr_theta(theta=theta,thetaS=thetaS,thetaR=thetaR,
n = 2, Ks = 1.06*10^2, f=0.5)
# Just for this example, we are removing the "0" value
# for plotting the graph in log scale, sence log10(0) results in "-Inf"
Kr <- y[-50]
w <- theta[-50]
plot(x=w,y=Kr,xlab=expression(theta~(m^3~m^-3)),
ylim=c(0.001,100), log="y",yaxt='n',
ylab="", xlim=c(0.15,0.50))
mtext(expression(K[r] ~ (cm~d^-1)), 2, line=2)
ax <- c(0.001, 0.01, 0.1, 1, 10, 100)
axis(2,at=ax, labels=ax)
# End (not run)