Kr_theta | R Documentation |
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.
Kr_theta(theta, thetaS, thetaR, n, Ks, f=0.5)
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]. |
numeric, the value of unsaturated hydraulic conductivity.
Renato Paiva de Lima <renato_agro_@hotmail.com>
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,
# 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)
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