soilwater5 {soilphysics} | R Documentation |
Soil Water Retention, based on the modified van Genuchten's formula
Description
Function to calculate the soil water content based on the modified van Genuchten's formula, as suggested by Pierson and Mulla (1989):
\theta = \theta_R + (\theta_S - \theta_R)(1 + (\alpha x)^n)^{-m} + b_0 + b_1 x + b_2 * x^2
Usage
soilwater5(x, theta_R, theta_S, alpha, n, m = 1 - 1/n, b0, b1, b2)
Arguments
x |
the matric potential. |
theta_R |
the residual water content. |
theta_S |
the water content at saturation. |
alpha |
a scale parameter of the van Genuchten's formula. |
n |
a shape parameter in van Genuchten's formula. |
m |
a shape parameter in van Genuchten's Formula. Default is |
b0 |
a parameter added to the van Ganuchten's formula. |
b1 |
a parameter added to the van Ganuchten's formula. |
b2 |
a parameter (of quadratic term) added to the van Ganuchten's formula. |
Value
The the soil water content or the saturation index (a value between 0 and 1).
Author(s)
Anderson Rodrigo da Silva <anderson.agro@hotmail.com>
References
Pierson, F.B.; Mulla, D.J. (1989) An Improved Method for Measuring Aggregate Stability of a Weakly Aggregated Loessial Soil. Soil Sci. Soc. Am. J., 53:1825–1831.
See Also
Examples
soilwater5(x = 20, theta_R = 0.2735, theta_S = 0.478, alpha = 0.1029,
n = 9.45, b0 = 0.2278, b1 = -0.0165, b2 = 0.000248)
curve(soilwater5(x, theta_R = 0.2735, theta_S = 0.478, alpha = 0.1029,
n = 9.45, b0 = 0.2278, b1 = -0.0165, b2 = 0.000248),
from = 0, to = 40,
ylab = "Water content",
xlab = "Matric potential")
# End (Not run)