Kr_theta: Unsaturated Hydraulic Conductivity as a function of water...

Description Usage Arguments Value Author(s) References Examples

View source: R/Kr_theta.R

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

1
Kr_theta(theta, thetaS, thetaR, alpha, 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).

alpha

The scale parameter of the van Genuchten's model (hPa^-1).

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

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
# EXEMPLE 1
Kr_theta(theta=0.45,thetaS=0.5,thetaR=0.15, 
         alpha = 0.02, n = 2, Ks = 1.06*10^2, f=0.5)

# EXEMPLE 2
thetaS <- 0.50
thetaR <- 0.15
theta <- seq(thetaS, thetaR, len=50)
y <- Kr_theta(theta=theta,thetaS=thetaS,thetaR=thetaR, 
             alpha = 0.02, 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)

soilphysics documentation built on Jan. 13, 2021, 7:06 p.m.