SWC {SoilHyP}

Soil water content

Description

Calculates the volumetric soil water content for a corresponding suction/pressure head (th(suc)) for unimodal or bimodal van Genuchten (vG), Peters-Durner-Iden (PDI) and Brooks and Corey (bc) (only unimodal) parameterisation.

Usage

SWC(
  suc,
  par.shp = c(ths = 0.9, thr = 0, alfa = 0.02, n = 2),
  FUN.shp = "vg",
  modality = "uni",
  suc.negativ = TRUE
)

Arguments

suc

Suction/pressure heads. Negative if suc.negativ = TRUE

par.shp

named parameter in list or vector

FUN.shp

Funktion for soil hydraulic properties (vG, PDI or bc) (see details)

modality

pore size distribution ('uni' or 'bi')

suc.negativ

set TRUE if suction/pressure heads are negative and FALSE if positive

Details

FUN.shp:

vG: van Genuchten (uni or bimodal) (vGM is working aswell)
PDI: Peters-Durner-Iden with saturation function of van Genuchten (uni or bimodal)
bc: Brooks and Corey (unimodal)

par.shp (vG and PDI):

ths [-]: saturated water content
thr [-]: residual water content
alfa [1/L]: van Genuchten shape parameter
n [-]: van Genuchten shape parameter
m [-]: shape parameter (m = 1-(1/n) if missing)

par.shp (additional for 'PDI'):

h0 [L]: suction at water content of 0 (i.e. oven dryness) (h0 = 10^6.8 if missing, corresponding to oven dryness at 105°C (Schneider and Goss, 2012))

par.shp (additional for bimodal (modality = 'bi')):

w2 [-]: weigthing between pore space distributions
alfa2 [1/L]: van Genuchten parameter alfa for second pore space distribution
n2 [-]: van Genuchten parameter n for second pore space distribution
m2 [-]: shape parameter (m2 = 1-(1/n2) if missing)

par.shp (BC):

ths [-]: saturated water content
thr [-]: residual water content
alfa [1/L]: inverse of the air-entry value or bubbling pressure
lambda [-]: pore size distribution index

PDI:
theta(h) = (ths - thr) * Scap(h) + thr * Sad(h)
Scap: Rescaled capillary saturation function
Sad: Relative saturation function for adsorbed water

input for FUN.shp and modality works for upper- and lowercase letters

Value

volumetric water content theta (th) [L³/L³]

Author(s)

Ullrich Dettmann

References

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.

Durner, W. (1994). Hydraulic conductivity estimation for soils with heterogeneous pore structure. Water Resources Research, 30(2), 211-223.

Peters, A. (2013). Simple consistent models for water retention and hydraulic conductivity in the complete moisture range. Water Resour. Res. 49, 6765–6780. physics-a review. Vadose Zone J. http://dx.doi.org/10.2136/vzj2012.0163.

Iden, S., Durner, W. (2014). Comment to Simple consistent models for water retention and hydraulic conductivity in the complete moisture range by A. Peters. Water Resour. Res. 50, 7530–7534.

Peters, A. (2014). Reply to comment by S. Iden and W. Durner on Simple consistent models for water retention and hydraulic conductivity in the complete moisture range. Water Resour. Res. 50, 7535–7539.

Schneider, M., & Goss, K. U. (2012). Prediction of the water sorption isotherm in air dry soils. Geoderma, 170, 64-69.

Brooks, R.H., and A.T. Corey (1964): Hydraulic properties of porous media. Hydrol. Paper 3. Colorado State Univ., Fort Collins, CO, USA.

See Also

Ku Sat

Examples

# --------------------------------------------
#  Unimodal van Genuchten
# --------------------------------------------
SWC(suc = seq(1, 1000, by = 1), par.shp = c(ths = 0.4, thr = 0, alfa = 0.02, n = 1.5),
FUN.shp = c('vG'), modality = 'uni', suc.negativ = FALSE)
# --------------------------------------------
#  Bimodal van Genuchten
# --------------------------------------------
SWC(suc = seq(1, 1000, by = 1),
par.shp = c(ths = 0.4, thr = 0, alfa = 0.02, n = 2, w2 = 0.2, alfa2 = 1, n2 = 10),
FUN.shp  = c('vG'), modality = c('bi'), suc.negativ = FALSE)
# --------------------------------------------
#  Unimodal PDI
# --------------------------------------------
SWC(suc = seq(1, 1000, by = 1), par.shp = list(ths = 0.4, thr = 0, n = 1.6, alfa = 0.02),
FUN.shp = c('pdi'), modality = c('uni'), suc.negativ = FALSE)
# --------------------------------------------
#  Brooks and Corey (BC) (only unimodal)
SWC(suc = seq(1, 1000, by = 1), par.shp = list(ths = 0.4, thr = 0, lambda =  0.211, alfa = 0.1),
FUN.shp = c('bc'), modality = c('uni'), suc.negativ = FALSE)
# --------------------------------------------