OFEST: The Offin Estimation of Soil Transfer parameters
In gowusu/vadose: The estimation of saturated hydraulic conductivity and soil water retention Curves in the vadose zone

Description Usage Arguments Details Value Author(s) References See Also Examples

This function uses philip or sw with lass3, ksat and vg to estimate water retention and hydraulic conductivity curves. See datails below.

OFEST(data = NULL, time, I, n = NULL, m = "b", pb = 1.2, tho = 0.169,
  thr = 0, ths = NULL, theta = NULL, PSD = NULL, Ks = NULL,
  h = seq(0, 1500, by = 5), model = "philip", type = "nonlinear",
  hg = "BEST", K = "BC")

## Default S3 method:
OFEST(data = NULL, time, I, n = NULL, m = "b",
  pb = 1.2, tho = 0.169, thr = 0, ths = NULL, theta = NULL,
  PSD = NULL, Ks = NULL, h = NULL, model = "philip",
  type = "nonlinear", hg = "BEST", K = "BC")

group.OFEST(data = NULL, time, I, n = NULL, m = "b", pb = 1.2,
  tho = 0.169, thr = 0, ths = NULL, theta = NULL, PSD = NULL,
  Ks = NULL, h = NULL, model = "all", type = "nonlinear", hg = "BEST",
  group, plot = TRUE, hlog = NULL, klog = NULL, layout = c(2, 2),
  opar = par(mar = c(2, 2, 1.8, 2)))

cal.OFEST(data = NULL, time, I, n = NULL, m = "b", pb = c(1, 1.8, 0.1),
  tho = c(0.01, 0.8, 0.05), thr = c(0, 0.2, 0.05), ths = NULL,
  theta = NULL, PSD = NULL, Ks = NULL, hg = "BEST", h = NULL,
  model = "all", type = "nonlinear", group = NULL)

gof.OFEST(x = NULL, obs = NULL, est = NULL, P = NULL)

## S3 method for class 'OFEST'
coef(object, ...)

## S3 method for class 'OFEST'
predict(object, h = NULL, ...)

## S3 method for class 'OFEST'
plot(x, main = NULL, xlab = "Water Content", ylab = "",
  ylab2 = "", layout = NULL, hlog = NULL, klog = NULL,
  kcol = "darkgreen", col = c("blue", "red", "darkgreen", "gold"),
  units = c("s", "mm"), mfrow = c(2, 2), type = "all", legend = TRUE,
  opar = par(mar = c(2, 2, 1.5, 2)), ...)

`data`	dataframe. It can contain data with column names of "time" and "I"
`time`	character or numeric. The name of time variable in the dataframe. If the "data" parameter contains "time", this will be ignored. The unit must be in seconds.
`I`	character or numeric. The name of cumulative infiltration variable in the dataframe. If the "data" parameter contains "I", this will be ignored. The unit must be in millimetres [mm].
`n`	numeric. A shaping parameter for water retention curve. This can be calibrated. If the parameter "PSD" is not set NULL `lass3` will be automatically used to estimate it.
`m`	character. The water retention curve condition. It takes either "b" for Burdine condition or "m" for Mualem condition.
`pb`	numeric. Bulk density[g cm^-3]. This can be calibrated.
`tho`	numeric. initial volumetric soil water content. This can be calibrated.
`thr`	numeric. Residual volumetric soil water content. This can be calibrated.
`ths`	numeric. The saturated soil water content [m3/m3].
`theta`	The measured soil water content[m3m-3] at the modelled pressure levels. It is used to check the fitness of the model.
`PSD`	dataframe. Particle Size Distribution. A dataframe of two columns. The first column should be labeled "D" in the range of 0.001 to 2 mm. The second column should be named as "fr" i.e.' the fraction of Diameter. The range should be 0-1.
`Ks`	saturated hydraulic conductivity
`h`	list. The range of metric head desired or measured [mm].
`model`	character. Either "philip" or "sw" (Swartzendruber) or "valiantzas" or "brutsaert". The model for estimation of sorptivity (S) and hydraulic conductivity (Ks).
`type`	character. Whether "linear" or "nonlinear" philip based equation to be applied.
`hg`	character "rawls" or "BEST" bubbling capillary pressure algorithm. It takes either Rawls (1993) as in Dingman(2002) or BEST
`K`	character. The type of hydraulic conductivity model. It takes "BC" for Brooks and Corey (1964) and VG for van Genuchten (1980).
`group`	character. The name of the group variables if the data is from different areas.
`plot`	whether a plot should be performed.
`hlog`	TRUE or FALSE. Whether metric potential should be log transformed
`klog`	TRUE or FALSE. Whether hydraulic conductivity should be log transformed
`layout`	plot layout
`x`	a return object of the function.
`obs`	Observed data
`est`	Estimated or modelled data
`P`	Number of Parameters
`object`	Model output object
`...`	Any other graphical parameter
`main`	Title of the plot
`xlab`	x label of the plot
`ylab`	y label of the plot
`ylab2`	y label of the second plot (K)
`kcol`	colour of hydraulic conductivity
`col`	Color of the plot
`units`	Units of the plot
`mfrow`	The graphical layout of the plots
`legend`	A legend of the plot

The function first estimates sorptivity and Ks from 3D or early part of vertical cumulative infiltration data with philip or sw or valiantzas or brutsaert. Second, lass3 is used to estimate pore-size parameters, e.g. n, b. Mualem or Burdine condition is applied to estimate m parameter of van Genuchten hydraulic conductivity curve. Third, a bubbling capillary pressure hb is estimated with Ks and S. Fourth, van Genuchten (1980) water retention curve and hydraulic conductivity are estimated. Finally, the predicted infiltration rate (q) is estimated.

For the output of PSD see lass3. For the output of goodness of fit tests see gof.OFEST. In the case of cal.OFEST the output can be assesed with mod object. The return parameters can be assessed with coef.OFEST. The predicted soil water can be assessed with predict.OFEST

Ks saturated hydraulic conductivity [LT^-1]
S Sorptivity [LT^-0.5]
mod_theta,mod_thetal,mod_thetay,mod_thetab: The estimated soil water content at different metric potentials
theta: The observed soil water content at different metric potentials
K: The unsaturated hydraulic conductivity [LT^-1]
hg: bubbling capillary pressure [L]
q: infiltration rates [LT^-1]

George Owusu

Swartzendruber, D. (1987). A quasi-solution of Richards equation for the downward infiltration of water into soil. Water Resour Res, 23, 809-817.
Philip, J. R. (1957). The theory of infiltration:Sorptivity and algebraic infiltration equations. Soil Science, 84, 257-264.
Brutsaert, W. (1977). Vertical infiltration in dry soil. Water Resour. Res., 13, 363-368.
Valiantzas, J. D. (2010). New linearized two-parameter infiltration equation for direct determination of conductivity and sorptivity. Journal of Hydrology, 387. doi: 10.1016/j.jhydrol.2009.12.049
Rawls, W. J., Ahuja, L. R., Brakensiek, D. L., & Shirmohammadi, A. (1993). Infiltration and Soil Water Movement. In D. Maidment (Ed.), Handbook of Hydrology: McGraw-Hill Education.
Dingman, S. L. (2002). Physical Hydrology: Prentice-Hall.
van Genuchten, M. T. (1980). A Closed-form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils1. Soil Sci. Soc. Am. J., 44(5), 892-898. doi: 10.2136/sssaj1980.03615995004400050002x
Brooks, R. H., & Corey, A. T. (1964). Hydraulic properties of porous medium Hydrology Paper (Vol. 3): Colorado State University.

BEST

psd=read.csv(system.file("ext","sys","psd.csv",package="vadose"))
hf=read.csv(system.file("ext","sys","h.csv",package="vadose"))
data=read.csv(system.file("ext","sys","exampleBEST.csv",package="vadose"))
ofin1<-OFEST(data=data,time="time",I="I",h=hf$h,PSD=psd)
pred=predict(ofin1)
coefficients=coef(ofin1)
plot(ofin1,type="h")
plot(ofin1,type="all")
plot(ofin1,type="all",hlog=TRUE,klog=TRUE,kcol="green")

#with measured theta
ofin2<-OFEST(data=data,time="time",I="I",h=hf$h,PSD=psd,model="sw",theta=ofin1$mod_theta)
print(gof.OFEST(ofin2))
ofin1$K
## Not run: 
#calibration
ofin2.cal<-cal.OFEST(data=data,time="time",I="I",h=hf$h,PSD=psd,model="sw",theta=ofin1$mod_theta)
coef2=coef(ofin2.cal)
predict=predict(ofin2.cal,h=500)
 
## End(Not run)