Relative saturation function for adsorptive water storage described by a piecwise linear function (Iden and Durner, 2014).
Sad(suc, par.shp, modality = c("uni"), suc.negativ = TRUE)Suction/pressure heads. Negative if suc.negativ = TRUE
named parameter of soil hydraulic properties in list or vector (see details)
pore size distribution ('uni' or 'bi')
set TRUE if suction/pressure heads are negative and FALSE if positive
additional for bimodal (modality == 'bi'): alfa2 [1/L]: van Genuchten parameter alfa for second pore space distribution n2 [-]: van Genuchten parameter n for second pore space distribution
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<U+2013>7534.
Schneider, M., & Goss, K. U. (2012). Prediction of the water sorption isotherm in air dry soils. Geoderma, 170, 64-69.